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Recomend dual band VHF / UHF antenna for two radios
I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting.
One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master antenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH |
Recomend dual band VHF / UHF antenna for two radios
On 3/11/2015 6:02 PM, Tom W3TDH wrote:
I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master an tenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Tom, There are a number of good antennas around. The problem is not going to be the antenna, though - it will be separating the two radios. If you transmit on one while both are connected to the antenna, you'll blow the front end of the other. You'll need either a coax switch/relay or some kind of filters to ensure one does not get into the other. And even though we're talking VHF and UHF, good filers which will provide the separation you need yet not degrade the signal you want are expensive. If you're only talking one frequency, maybe a couple of sets of duplexers will work - one set for each band. Of course, rf detecting coax switches will work - but you also then need to ensure that both don't try to transmit at the same time - one or both will be transmitting into an open circuit (depending on how you wire them up). -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Recomend dual band VHF / UHF antenna for two radios
On 3/11/2015 5:02 PM, Tom W3TDH wrote:
I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master antenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Hi, Tom - I did some quick, crude modelling of a vertically-polarized half-wave (J-Pole) and it seems to have a pattern about as good on 70cm as on 2M. There is a bit more energy radiated about 50 degrees above the horizon on 70cm, but there seems to be plenty left at about 1.5 degrees (about 6.5dBi). I assumed an antenna height of 20 feet. If it were me, I would try the J-Pole. However, you need to consider how much time and effort it would take to change to a different antenna if you are not happy. 73, John N1JLS |
Recomend dual band VHF / UHF antenna for two radios
In article ,
Tom W3TDH wrote: The other radio will be a UHF D-STAR hotspot. Tom- What kind of range are you trying to achieve with the hotspot? The little antenna that came with a UHF DVAP covers my property fairly well, just sitting on a table. I connected it to a Larsen dual-band mag-mounted antenna stuck on top of a filing cabinet, and get about a half mile range when mobile. The DVAP puts out about a tenth of a Watt. I suspect it can hear the 50 Watt mobile a lot further away. If you want range, consider taking the DVAP with you and connecting to the internet through a cellular modem or telephone. I'm considering getting a D-HAP, which holds everything but the radio and the cellular connection. http://www.portableuniversalpower.com/dhap/ 73, Fred K4DII |
Recomend dual band VHF / UHF antenna for two radios
On Thursday, March 12, 2015 at 12:20:57 PM UTC-4, Fred McKenzie wrote:
In article , Tom W3TDH wrote: The other radio will be a UHF D-STAR hotspot. Tom- What kind of range are you trying to achieve with the hotspot? The little antenna that came with a UHF DVAP covers my property fairly well, just sitting on a table. I connected it to a Larsen dual-band mag-mounted antenna stuck on top of a filing cabinet, and get about a half mile range when mobile. The DVAP puts out about a tenth of a Watt. I suspect it can hear the 50 Watt mobile a lot further away. If you want range, consider taking the DVAP with you and connecting to the internet through a cellular modem or telephone. I'm considering getting a D-HAP, which holds everything but the radio and the cellular connection. http://www.portableuniversalpower.com/dhap/ 73, Fred K4DII Fred I must confess that I am a little up in the air on the D-STAR hot spot issues. The hot spot is part of a club project that I would be hosting at my home. The club is using Motorola M120 radios at the low end of their power output which is around Twenty Five Watts I believe. The effort is intended to cover as much of our service area as is practical with Seventy Centimeter D-STAR coverage. The strange thing is that I am not a D-STAR user. I use the clubs centrally located analog repeater for my UHF coverage needs. I'm only hosting the local node in order to support the club effort. Tom Horne W3TDH |
Recomend dual band VHF / UHF antenna for two radios
On Wednesday, March 11, 2015 at 7:11:14 PM UTC-4, Brian Reay wrote:
Tom W3TDH wrote: I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master antenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Diamond do a number of other antennas similar to the x30, essentially longer, with more gain. I would suggest you look at their website and pick one to match you budget, acceptable profile, etc. It may be worth investing in another tribander, you may just want the third band in the future and it will save another negotiation with Senior Management. Or you could take my approach and have an XYL who is licensed ;-) 73 Brian G8OSN/W8OSN Brian Thank you for the second tribander idea. I do not now have a 220 MHz base antenna. So using a tribander instead of a dual band antenna will add that additional bands worth of capability to me base station. Since I am very heavily involved in local EMCOMM preparation that is a very worthwhile thing to do. It must be a good day because I learned something new. -- Tom Horne W3TDH |
Recomend dual band VHF / UHF antenna for two radios
On Wednesday, March 11, 2015 at 8:15:54 PM UTC-4, Jerry Stuckle wrote:
On 3/11/2015 6:02 PM, Tom W3TDH wrote: I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master an tenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Tom, There are a number of good antennas around. The problem is not going to be the antenna, though - it will be separating the two radios. If you transmit on one while both are connected to the antenna, you'll blow the front end of the other. You'll need either a coax switch/relay or some kind of filters to ensure one does not get into the other. And even though we're talking VHF and UHF, good filers which will provide the separation you need yet not degrade the signal you want are expensive. If you're only talking one frequency, maybe a couple of sets of duplexers will work - one set for each band. Of course, rf detecting coax switches will work - but you also then need to ensure that both don't try to transmit at the same time - one or both will be transmitting into an open circuit (depending on how you wire them up). -- ================== Remove the "x" from my email address Jerry, AI0K ================== Jerry I am going to declare myself lost on this one so please be patient. I had though I had addressed these issues when I said I was using a DCI Dual Band Filter and Diplexer. Is the DCI combination filter and diplexer insufficient to protect the two radios from each other? DCI claimed it would be. The model number is DCI-146-444-DX-DB. The web sight were it is listed is http://www.dci.ca/?Section=Products&SubSection=Amateur. If I need to add Duplexers it is practical to do because the mobile ones available used are manageable money. If there is a real chance for damage in the event of simultaneous transmission then I will need to add circulators and dummy loads to the output of both radios. That will end up being a little pricy. -- Tom Horne W3TDH |
Recomend dual band VHF / UHF antenna for two radios
In article ,
Tom W3TDH wrote: Thank you for the second tribander idea. I do not now have a 220 MHz base antenna. So using a tribander instead of a dual band antenna will add that additional bands worth of capability to me base station. Since I am very heavily involved in local EMCOMM preparation that is a very worthwhile thing to do. It must be a good day because I learned something new. My home base-station antenna is a Comet CX-333 (2m/220/440), with a triplexer in the shack (Kenwood TS-2000 for 2m and 440, and a Kenwood I-forget-what for 220). It seems to work very much as one would expect. No complaints at all. |
Recomend dual band VHF / UHF antenna for two radios
"Tom W3TDH" wrote in message ... I am going to declare myself lost on this one so please be patient. I had though I had addressed these issues when I said I was using a DCI Dual Band Filter and Diplexer. Is the DCI combination filter and diplexer insufficient to protect the two radios from each other? DCI claimed it would be. The model number is DCI-146-444-DX-DB. The web sight were it is listed is http://www.dci.ca/?Section=Products&SubSection=Amateur. If I need to add Duplexers it is practical to do because the mobile ones available used are manageable money. If there is a real chance for damage in the event .of simultaneous transmission then I will need to add circulators and dummy loads to the output of both radios. That will end up being a little pricy. That DCI should be plenty to protect the two rigs. You may have a desense on the 440 receiver if it on a near 3 rd harmonic of the 144 transmiter. It won't be enough to cause any damage, just enough to block the 440 receiver. |
Recomend dual band VHF / UHF antenna for two radios
On 3/12/2015 2:06 PM, Tom W3TDH wrote:
On Wednesday, March 11, 2015 at 8:15:54 PM UTC-4, Jerry Stuckle wrote: On 3/11/2015 6:02 PM, Tom W3TDH wrote: I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master an tenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Tom, There are a number of good antennas around. The problem is not going to be the antenna, though - it will be separating the two radios. If you transmit on one while both are connected to the antenna, you'll blow the front end of the other. You'll need either a coax switch/relay or some kind of filters to ensure one does not get into the other. And even though we're talking VHF and UHF, good filers which will provide the separation you need yet not degrade the signal you want are expensive. If you're only talking one frequency, maybe a couple of sets of duplexers will work - one set for each band. Of course, rf detecting coax switches will work - but you also then need to ensure that both don't try to transmit at the same time - one or both will be transmitting into an open circuit (depending on how you wire them up). Jerry I am going to declare myself lost on this one so please be patient. I had though I had addressed these issues when I said I was using a DCI Dual Band Filter and Diplexer. Is the DCI combination filter and diplexer insufficient to protect the two radios from each other? DCI claimed it would be. The model number is DCI-146-444-DX-DB. The web sight were it is listed is http://www.dci.ca/?Section=Products&SubSection=Amateur. If I need to add Duplexers it is practical to do because the mobile ones available used are manageable money. If there is a real chance for damage in the event of simultaneous transmission then I will need to add circulators and dummy loads to the output of both radios. That will end up being a little pricy. -- Tom Horne W3TDH Tom, You said you were using a diplexer, but didn't specify which one. Many of the cheap ones are OK for receive, but can't handle any significant amount of transmit power. The DCI will handle 200 watts, so unless you're planning on exceeding that, you should be OK. It's loss specifications are pretty reasonable, also. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Recomend dual band VHF / UHF antenna for two radios
In article ,
"Ralph Mowery" wrote: "Tom W3TDH" wrote in message ... I am going to declare myself lost on this one so please be patient. I had though I had addressed these issues when I said I was using a DCI Dual Band Filter and Diplexer. Is the DCI combination filter and diplexer insufficient to protect the two radios from each other? DCI claimed it would be. The model number is DCI-146-444-DX-DB. The web sight were it is listed is http://www.dci.ca/?Section=Products&SubSection=Amateur. If I need to add Duplexers it is practical to do because the mobile ones available used are manageable money. If there is a real chance for damage in the event .of simultaneous transmission then I will need to add circulators and dummy loads to the output of both radios. That will end up being a little pricy. That DCI should be plenty to protect the two rigs. You may have a desense on the 440 receiver if it on a near 3 rd harmonic of the 144 transmiter. It won't be enough to cause any damage, just enough to block the 440 receiver. I agree that you are not likely to damage a radio. The common duplexer (or triplexer) is often used to connect a single multi-band antenna to multiple connectors of a multi-band radio, which is essentially multiple radios in a single package. The difference between this and what you are planning, is that the multi-band radio is usually not used for simultaneous reception and transmission. Or at least you would accept some desensitization if it occurred. You can choose frequencies such that the third harmonic of the Two Meter frequency is not in the IF passband of the 440 receiver, but you are likely have overloading of the receiver's broad front end. (You may also have some overloading of the Two Meter radio due to the amount of power involved.) That said, go ahead and try it. It may work well enough to meet your needs. If it does not work out, the alternative is a "real" repeater. One advantage of a repeater, is that local users can hear each other. With your Hot Spot, local users are talking simplex. 73, Fred K4DII |
Recomend dual band VHF / UHF antenna for two radios
Fred McKenzie wrote:
I agree that you are not likely to damage a radio. The common duplexer (or triplexer) is often used to connect a single multi-band antenna to multiple connectors of a multi-band radio, which is essentially multiple radios in a single package. The difference between this and what you are planning, is that the multi-band radio is usually not used for simultaneous reception and transmission. Or at least you would accept some desensitization if it occurred. You can choose frequencies such that the third harmonic of the Two Meter frequency is not in the IF passband of the 440 receiver, but you are likely have overloading of the receiver's broad front end. (You may also have some overloading of the Two Meter radio due to the amount of power involved.) I have heard this "armchair theorist" story many times, but I have never experienced this problem with my 3-band Diamond and matching triplexer. Sure I hear the harmonics full-scale when tuned that way, but never any overloading let alone damage. Maybe it is only a problem when using QRO. I think it is more warranted to warn against collinear antennas that get shipped in two parts. The connection is the weak point in the antenna. Unfortunately it appears that for a 6/2/70 tribander it is the only option. Normally they fail within a couple of years. Also on the high bands there is severe fading in windy conditions because the entire antenna bends too much. My 2/70/23 tribander is in one piece and it does not have those defects. |
Recomend dual band VHF / UHF antenna for two radios
On Thursday, March 12, 2015 at 11:41:23 PM UTC-4, Fred McKenzie wrote:
In article , "Ralph Mowery" wrote: "Tom W3TDH" wrote in message ... I am going to declare myself lost on this one so please be patient. I had though I had addressed these issues when I said I was using a DCI Dual Band Filter and Diplexer. Is the DCI combination filter and diplexer insufficient to protect the two radios from each other? DCI claimed it would be. The model number is DCI-146-444-DX-DB. The web sight were it is listed is http://www.dci.ca/?Section=Products&SubSection=Amateur. If I need to add Duplexers it is practical to do because the mobile ones available used are manageable money. If there is a real chance for damage in the event ..of simultaneous transmission then I will need to add circulators and dummy loads to the output of both radios. That will end up being a little pricy. That DCI should be plenty to protect the two rigs. You may have a desense on the 440 receiver if it on a near 3 rd harmonic of the 144 transmiter.. It won't be enough to cause any damage, just enough to block the 440 receiver. I agree that you are not likely to damage a radio. The common duplexer (or triplexer) is often used to connect a single multi-band antenna to multiple connectors of a multi-band radio, which is essentially multiple radios in a single package. The difference between this and what you are planning, is that the multi-band radio is usually not used for simultaneous reception and transmission. Or at least you would accept some desensitization if it occurred. You can choose frequencies such that the third harmonic of the Two Meter frequency is not in the IF passband of the 440 receiver, but you are likely have overloading of the receiver's broad front end. (You may also have some overloading of the Two Meter radio due to the amount of power involved.) That said, go ahead and try it. It may work well enough to meet your needs. If it does not work out, the alternative is a "real" repeater. One advantage of a repeater, is that local users can hear each other. With your Hot Spot, local users are talking simplex. 73, Fred K4DII Fred As I already said I am not totally conversant with D-STAR. I was under the impression that the persons participating in any given QSO could hear each other over the access point they were using. I had pictured it as somewhat akin to the remote receivers on our club's analog FM repeater in that the other users on the QSO would hear the conversation over the repeaters output. Our D-STAR repeater is located in Germantown and I do not actually know what it's effective range is. We operate six different sites with four repeaters, four remote receivers with radio links back to the analog two meter repeater, and two APRS digipeaters. In addition to those sites we will have several members hosting D-STAR hot spots in order to fill in the edges of our service area that are outside the effective receive range of portable radios. Those using mobile or base station radio will, hopefully, be able to raise the repeater without resorting to one of the hot spots We can make changes to the location of the various elements of our repeater system including the location of the D-STAR repeater itself if that is needed to allow all users to hear the conversation. On the harmonic de-sensing issue I can purchase a DCI low pass filter that cuts off at 160MHz if that becomes a problem. It would be inserted between the two meter radio and the filter/diplexer so that the harmonic would not reach the diplexer at all. Part of this question affects operations well beyond my home location. The county ARES unit is gearing up to support hospital emergency communications in our area. Our first client hospital purchased an Icom IC-7100 transceiver for the hospital station. If that remains the only transmitter at the hospital's EOC then the use of directly connected multi band antennas will work fine. But if the hospital discovers that it needs more than one mode or frequency to be used at the same time then our team will have to devise a Diplexing setup in order to keep the two radios from clobbering each other. I could see them needing both local tactical voice and medium range digital at the same time in a real disaster situation. In the Mid Atlantic region the most common natural disaster with region wide effects are severe ice storms. Since I moved to three land in 1980 we have had three such storms that have wiped out communications infrastructure over wide portions of our region. It usually takes at least a week to get all of the wires and fibers back up in the air. Were about fifteen years out from our last bad one so we're about due. The hospitals have learned that continuing to operate when it is very difficult to talk to anyone that is not on campus is more than challenging. That's why I think they are going to want more than one communications pathway available to them and nothing carries long documents as quickly and accurately as digital. Thanks again for taking the time to help on this. -- Tom Horne W3TDH |
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You have too many of the same band antenna's concentrated in one place. No matter how hard you try, they aren't going to play nice with each other. I read 14 posts and no one gave an even close right answer to your question. The answer is that you need to construct a tower, no less than 100', near your house in order to even try to do what you wish to do. Even then, you will need feet of separation vertically in order to get the antenna's to play nice with each other. Your SWR is going to be all messed up, because you have too many of the same antenna's in the same proximity. The only good 6 / 2 / 70 cm antenna that I could recommend would be the Diamond v2000. This is the only antenna that I am aware of that has a decent amount of gain - if you want to call it that, along with being semi resonant on all three bands. What you are doing is back-feeding everything that you transmit back into the receive of the front ends of all of the radios in your shack when any one radio transmits. Unless it is in your budget to replace all those radios on a semi annual schedule, you will eventually experience that each of those transceivers will eventually become deaf. I have seen filters promoted in QST that allows two operators on two different bands to share a beam antenna with two transceivers, as long as each transceiver stays on it's band it is ok. But there is a hell of a difference between 20 meters - 14 MHz - CW and 40 meters Phone. Even though 70 cm is not a harmonic of 2m, and even though there is a heck of a disparity between 440 MHz and 146 MHZ there is always going to be problems when dealing with FM, and Digital modes. I have to take your wife's side on this one! Tell your club to go out and buy an acre of ground and put up a transmitter and a tower and put their packet and their D-Star crap on their tower, and then you can tune to their tower frequency if you so choose. You are killing not only all of your transceivers by what you are trying to do, but you are diminishing the range at which you yourself can operate... If you can hear other repeaters / more than 20 miles away though all of that RF noise you have created, you will be lucky.. It doesn't matter if the radios are all turned on or off, as long as they are connected to the coax / antenna, they are still going to experience front end overload. |
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Recomend dual band VHF / UHF antenna for two radios
My replies are in line with information you have offered in order to help me in keeping my responses organized.
On Friday, March 13, 2015 at 10:13:04 PM UTC-4, Channel Jumper wrote: Tom W3TDH;836715 Wrote: I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master antenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Tom, You have too many of the same band antenna's concentrated in one place. No matter how hard you try, they aren't going to play nice with each other. I read 14 posts and no one gave an even close right answer to your question. The answer is that you need to construct a tower, no less than 100', near your house in order to even try to do what you wish to do. Even then, you will need feet of separation vertically in order to get the antenna's to play nice with each other. Would you please name a figure for the required vertical separation? If that figure is less than Thirty Feet then could you explain why one antenna at my home's ridge line and one twenty feet higher wouldn't be enough? I have worked net control for the Marine Corps Marathon in Washington DC for several years now and we have not had problems running two very active Two Meter Nets with only ten feet of vertical separation between the two antennas on a Fifty Foot Tall AB-952/GRC-103 self jacking mast. We also had a receive only APRS receiver set up and had no missed packets when compared with WWW.APRS.FI. The APRS is down at 146.390 MHz and thus Two MHz away from the repeater pairs being used for the two race nets but the race nets were sometimes interlaced with each other with one frequency pair on standard Six Hundred KHz separation straddling one of the frequencies of the other nets repeater. We did not experience the kind of de-sensing or damage that you are warning me of. So what you are saying is at odds with most of the Net Control operations that I have seen at a large number of larger public service events. We have had Twenty Watt continuous output FM ATV repeaters co-located with a voice repeater with both on the Seventy Centimeter Band without the issues that you are reporting with a vertical separation of only ten feet between the two antennas. Your SWR is going to be all messed up, because you have too many of the same antenna's in the same proximity. The antenna handbook says that two Wavelengths of separation from other metallic objects is sufficient to prevent de-tuning at VHF UHF frequencies. Are you saying that because the two antennas are co-resonant that the effect is that much worse. The only good 6 / 2 / 70 cm antenna that I could recommend would be the Diamond v2000. This is the only antenna that I am aware of that has a decent amount of gain - if you want to call it that, along with being semi resonant on all three bands. What you are doing is back-feeding everything that you transmit back into the receive of the front ends of all of the radios in your shack when any one radio transmits. Unless it is in your budget to replace all those radios on a semi annual schedule, you will eventually experience that each of those transceivers will eventually become deaf. Others have said that the DCI-146-444-DX-DB Diplexer and Dual Band Filter will provide sufficient isolation. Since you are saying that is not true would you mind explaining why? I have seen filters promoted in QST that allows two operators on two different bands to share a beam antenna with two transceivers, as long as each transceiver stays on it's band it is ok. But there is a hell of a difference between 20 meters - 14 MHz - CW and 40 meters Phone. We have used such a filter set on our 20, 15, 10 Meter tribander for the last several field days with excellent results and no ill effects. Two of the transceivers used were my Yaesu FT-1000 and FT-857D. I have had no performance changes on either radio. Even though 70 cm is not a harmonic of 2m, and even though there is a heck of a disparity between 440 MHz and 146 MHZ there is always going to be problems when dealing with FM, and Digital modes. What kind of problems? I have to take your wife's side on this one! My Wife's objections are aesthetic. She doesn't want our home to look like a police precinct station when viewed from the street. So what exactly are you agreeing with her on. Tell your club to go out and buy an acre of ground and put up a transmitter and a tower and put their packet and their D-Star crap on their tower, and then you can tune to their tower frequency if you so choose. You are killing not only all of your transceivers by what you are trying to do, but you are diminishing the range at which you yourself can operate... How am I accomplishing that exactly? I have already had several VHF UHF transceivers operating at the same time at my home without harm to any of the equipment. The only change I would be making here is that more than one transceiver would be operating on different bands on a multiband antenna using the DCI-146-444-DX-DB and/or other DCI Four Pole Band Pass Filters for isolation. If you can hear other repeaters / more than 20 miles away though all of that RF noise you have created, you will be lucky.. I've already done this with separate antennas at this location without any loss of range or intelligibility that I could discern. I have run the Baltimore Washington Skywarn net with the Radio Message Server Packet chirping away only twenty feet apart at the same height above ground level (AGL) without either one missing a beat. That includes a net that covered an activation for a tornado watch that actually produced three tornadoes and a very busy net. All of the repeats and fills were caused by over excited operators rather than by de-sensing. It doesn't matter if the radios are all turned on or off, as long as they are connected to the coax / antenna, they are still going to experience front end overload. -- Channel Jumper I realize that I didn't say this previously but I do use grounding coaxial switches on my rigs and they are always in the shorted grounded condition when the radio that they are serving is turned off. I also have both Surge protectors on all my antenna coax entries and EMP protectors on all of the rigs. I don't see how enough energy to damage the rigs could get past the EMP Protectors. -- Tom Horne W3TDH |
Recomend dual band VHF / UHF antenna for two radios
On Saturday, March 14, 2015 at 5:07:37 AM UTC-4, Jeff wrote:
On 14/03/2015 01:48, Channel Jumper wrote: Tom W3TDH;836715 Wrote: I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master antenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Tom, You have too many of the same band antenna's concentrated in one place. No matter how hard you try, they aren't going to play nice with each other. I read 14 posts and no one gave an even close right answer to your question. The answer is that you need to construct a tower, no less than 100', near your house in order to even try to do what you wish to do. Even then, you will need feet of separation vertically in order to get the antenna's to play nice with each other. Your SWR is going to be all messed up, because you have too many of the same antenna's in the same proximity. The only good 6 / 2 / 70 cm antenna that I could recommend would be the Diamond v2000. This is the only antenna that I am aware of that has a decent amount of gain - if you want to call it that, along with being semi resonant on all three bands. What you are doing is back-feeding everything that you transmit back into the receive of the front ends of all of the radios in your shack when any one radio transmits. Unless it is in your budget to replace all those radios on a semi annual schedule, you will eventually experience that each of those transceivers will eventually become deaf. I have seen filters promoted in QST that allows two operators on two different bands to share a beam antenna with two transceivers, as long as each transceiver stays on it's band it is ok. But there is a hell of a difference between 20 meters - 14 MHz - CW and 40 meters Phone. Even though 70 cm is not a harmonic of 2m, and even though there is a heck of a disparity between 440 MHz and 146 MHZ there is always going to be problems when dealing with FM, and Digital modes. I have to take your wife's side on this one! Tell your club to go out and buy an acre of ground and put up a transmitter and a tower and put their packet and their D-Star crap on their tower, and then you can tune to their tower frequency if you so choose. You are killing not only all of your transceivers by what you are trying to do, but you are diminishing the range at which you yourself can operate... If you can hear other repeaters / more than 20 miles away though all of that RF noise you have created, you will be lucky.. It doesn't matter if the radios are all turned on or off, as long as they are connected to the coax / antenna, they are still going to experience front end overload. What a complete load of hog wash!! A dual band antenna and the DCI filter/diplexer will work just fine. The DCI filter provides bandpass characteristics on both 2 & 70 and then provides a single output. The filters provide more than adequate isolation between radios to stop any damage for reasonable power levels. You almost certainly will be able to hear the harmonics from the 2m tx on 70 but the level will not cause any damage. By the way Channel Jumper 70cms IS a harmonic of 2m, perhaps time to brush up on your 3 times table. Jeff On Saturday, March 14, 2015 at 5:07:37 AM UTC-4, Jeff wrote: On 14/03/2015 01:48, Channel Jumper wrote: Tom W3TDH;836715 Wrote: I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master antenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Tom, You have too many of the same band antenna's concentrated in one place. No matter how hard you try, they aren't going to play nice with each other. I read 14 posts and no one gave an even close right answer to your question. The answer is that you need to construct a tower, no less than 100', near your house in order to even try to do what you wish to do. Even then, you will need feet of separation vertically in order to get the antenna's to play nice with each other. Your SWR is going to be all messed up, because you have too many of the same antenna's in the same proximity. The only good 6 / 2 / 70 cm antenna that I could recommend would be the Diamond v2000. This is the only antenna that I am aware of that has a decent amount of gain - if you want to call it that, along with being semi resonant on all three bands. What you are doing is back-feeding everything that you transmit back into the receive of the front ends of all of the radios in your shack when any one radio transmits. Unless it is in your budget to replace all those radios on a semi annual schedule, you will eventually experience that each of those transceivers will eventually become deaf. I have seen filters promoted in QST that allows two operators on two different bands to share a beam antenna with two transceivers, as long as each transceiver stays on it's band it is ok. But there is a hell of a difference between 20 meters - 14 MHz - CW and 40 meters Phone. Even though 70 cm is not a harmonic of 2m, and even though there is a heck of a disparity between 440 MHz and 146 MHZ there is always going to be problems when dealing with FM, and Digital modes. I have to take your wife's side on this one! Tell your club to go out and buy an acre of ground and put up a transmitter and a tower and put their packet and their D-Star crap on their tower, and then you can tune to their tower frequency if you so choose. You are killing not only all of your transceivers by what you are trying to do, but you are diminishing the range at which you yourself can operate... If you can hear other repeaters / more than 20 miles away though all of that RF noise you have created, you will be lucky.. It doesn't matter if the radios are all turned on or off, as long as they are connected to the coax / antenna, they are still going to experience front end overload. What a complete load of hog wash!! A dual band antenna and the DCI filter/diplexer will work just fine. The DCI filter provides bandpass characteristics on both 2 & 70 and then provides a single output. The filters provide more than adequate isolation between radios to stop any damage for reasonable power levels. You almost certainly will be able to hear the harmonics from the 2m tx on 70 but the level will not cause any damage. By the way Channel Jumper 70cms IS a harmonic of 2m, perhaps time to brush up on your 3 times table. Jeff Jeff May I ask that you cool your jets a little. Please turn off the afterburners and stick to the questions that I'm asking. I don't want to be a focus of a flame war. I came here in the hope of getting good information and the task of sorting out conflicting advice is so much easier if I don't need to also filter out gratuitous feuding. Your version of what is possible is attractive because it allows me to do what I want to do to support my clubs D-STAR project and provide a training resource for the ARES Hospital Emergency Net staff to become competent with Winlink. I realize that there are some Hams that despise Winlink and all other automated store and forward systems. I will be doing everything I can to avoid interference to other Amateurs but since we are using this to support hospitals under emergency conditions I think that everyone can just suck it up and bare with the emergency traffic and whatever inconvenience it may generate. b Would you please advise if the third harmonic issue is likely to be serious enough to require the use of a low pass filter between the two meter transceiver and the Diplexer/Band Pass Filter when using separate transmitters? -- Tom Horne W3TDH |
Recomend dual band VHF / UHF antenna for two radios
In article ,
Tom W3TDH wrote: I was under the impression that the persons participating in any given QSO could hear each other over the access point they were using. I had pictured it as somewhat akin to the remote receivers on our club's analog FM repeater in that the other users on the QSO would hear the conversation over the repeaters output. Tom- The more you post, the more complicated it becomes! What you describe sounds like a remote receiver for an existing repeater, not a hot spot. The hot spot I have is a low power DVAP operating on a simplex frequency. Yours might be equivalent, but using a more powerful transmitter. A hot spot does not connect to a repeater via RF. It connects via the internet to another device. That device might be a D-STAR repeater, but often it is a computer hosting a "reflector" that repeaters may also be connected to. If your hot spot is connected to the same reflector as the local repeater, it would be possible for users to talk into the hot spot and listen to the repeater output. But that would be a split frequency setup for the radio. As I said, go ahead and try what you had planned. It will work to some extent, and will help you get your feet wet. 73, Fred K4DII |
Recomend dual band VHF / UHF antenna for two radios
Tom,
Please see inlined... On 3/14/2015 1:17 PM, Tom W3TDH wrote: May I ask that you cool your jets a little. Please turn off the afterburners and stick to the questions that I'm asking. I don't want to be a focus of a flame war. I came here in the hope of getting good information and the task of sorting out conflicting advice is so much easier if I don't need to also filter out gratuitous feuding. If you followed this group before posting (always a good idea), you will see that is pretty normal here. If you're going to post, you can expect both good and bad advice. And some people (like Channel Jumper - who probably isn't even a ham) are so far off with every post you can expect a flame war. But then that is true of almost every place on the Internet. Your version of what is possible is attractive because it allows me to do what I want to do to support my clubs D-STAR project and provide a training resource for the ARES Hospital Emergency Net staff to become competent with Winlink. I realize that there are some Hams that despise Winlink and all other automated store and forward systems. I will be doing everything I can to avoid interference to other Amateurs but since we are using this to support hospitals under emergency conditions I think that everyone can just suck it up and bare with the emergency traffic and whatever inconvenience it may generate. b You are required by law to avoid interference. But you also need to understand what constitutes emergency traffic to the FCC. For that to occur, there must be an IMMEDIATE threat to life and/or property. An example would be reporting an automobile accident, especially one requiring immediate medical attention. It does NOT include 99% of the traffic being passed during an emergency. In the 19 years I've been a member of MoCo ARES/RACES (including the Hospital Net), we have NEVER had emergency traffic passed during a callout. Of course, I could also say that of most of the emergencies I've been involved in in 47 years as a ham. The only times I can think of that I've been involved in true emergency traffic during a callout was when aiding search and rescue after tornadoes. Just because it's a hospital net does not constitute emergency traffic. So, while hams in the area will voluntarily yield the frequency, there is no requirement for them to do so, and any interference would be a violation. Would you please advise if the third harmonic issue is likely to be serious enough to require the use of a low pass filter between the two meter transceiver and the Diplexer/Band Pass Filter when using separate transmitters? Your diplexer should handle that well enough. What would be more of a concern to me would be just the spurious radiation around the shack. It's possible that could cause some desense, but I wouldn't expect it to be significant. -- Tom Horne W3TDH Your sig separator is broken. It needs to be exactly hyphen-hyphen-space-newline. You're missing the space. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Recomend dual band VHF / UHF antenna for two radios
On 3/15/2015 5:50 AM, Brian Reay wrote:
Tom W3TDH wrote: Would you please advise if the third harmonic issue is likely to be serious enough to require the use of a low pass filter between the two meter transceiver and the Diplexer/Band Pass Filter when using separate transmitters? It depends on your tx. I've never required filters nor heard of their being required. Remember, you would need to be listening on the 3rd Rx harmonic, or 'close' to it for the rx to suffer and the harmonic should get several 10s of dB down relative to tell 2m carrier. Brian, Yes, it will be several 10s of dB down - but that can still be sufficient to be heard in (and potentially desense) a near-by receiver. It doesn't take a lot of signal if it's within the receiver's passband. But Tom's diplexer should handle this easily. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Recomend dual band VHF / UHF antenna for two radios
On Saturday, March 14, 2015 at 1:24:03 PM UTC-4, Fred McKenzie wrote:
In article , Tom W3TDH wrote: I was under the impression that the persons participating in any given QSO could hear each other over the access point they were using. I had pictured it as somewhat akin to the remote receivers on our club's analog FM repeater in that the other users on the QSO would hear the conversation over the repeaters output. Tom- The more you post, the more complicated it becomes! What you describe sounds like a remote receiver for an existing repeater, not a hot spot. The hot spot I have is a low power DVAP operating on a simplex frequency. Yours might be equivalent, but using a more powerful transmitter. A hot spot does not connect to a repeater via RF. It connects via the internet to another device. That device might be a D-STAR repeater, but often it is a computer hosting a "reflector" that repeaters may also be connected to. If your hot spot is connected to the same reflector as the local repeater, it would be possible for users to talk into the hot spot and listen to the repeater output. But that would be a split frequency setup for the radio. As I said, go ahead and try what you had planned. It will work to some extent, and will help you get your feet wet. 73, Fred K4DII I'm not confused about how the hotspot connects to the repeater's reflector.. I would think that the words "somewhat akin" would have made it clear that I was talking about a functional similarity rather than physical one. Part of the reason that I have never developed any enthusiasm for D-STAR is the reliance the system puts in Internet connections between various portions of that system. I see any radio system that depends on non radio pathways to function as inherently more frangible than one that is entirely RF based. That being said my club has made an investment in the build out of a D-STAR repeater and hot spot system which they are hoping will cover the whole county. All I am doing is trying to support that effort. I didn't devise the approach being used but I know that it is already being used successfully at two other locations in our service area. Does it really matter how the hotspot interacts with the rest of the D-STAR network when what we are talking about here is how to use it on the same antenna as a Two Meter Radio Message Server Packet. -- Tom Horne W3TDH |
Recomend dual band VHF / UHF antenna for two radios
On Saturday, March 14, 2015 at 3:56:38 PM UTC-4, Jerry Stuckle wrote:
Tom, Please see inlined... On 3/14/2015 1:17 PM, Tom W3TDH wrote: May I ask that you cool your jets a little. Please turn off the afterburners and stick to the questions that I'm asking. I don't want to be a focus of a flame war. I came here in the hope of getting good information and the task of sorting out conflicting advice is so much easier if I don't need to also filter out gratuitous feuding. If you followed this group before posting (always a good idea), you will see that is pretty normal here. If you're going to post, you can expect both good and bad advice. And some people (like Channel Jumper - who probably isn't even a ham) are so far off with every post you can expect a flame war. But then that is true of almost every place on the Internet. Your version of what is possible is attractive because it allows me to do what I want to do to support my clubs D-STAR project and provide a training resource for the ARES Hospital Emergency Net staff to become competent with Winlink. I realize that there are some Hams that despise Winlink and all other automated store and forward systems. I will be doing everything I can to avoid interference to other Amateurs but since we are using this to support hospitals under emergency conditions I think that everyone can just suck it up and bare with the emergency traffic and whatever inconvenience it may generate. b You are required by law to avoid interference. But you also need to understand what constitutes emergency traffic to the FCC. For that to occur, there must be an IMMEDIATE threat to life and/or property. An example would be reporting an automobile accident, especially one requiring immediate medical attention. It does NOT include 99% of the traffic being passed during an emergency. In the 19 years I've been a member of MoCo ARES/RACES (including the Hospital Net), we have NEVER had emergency traffic passed during a callout. Of course, I could also say that of most of the emergencies I've been involved in in 47 years as a ham. The only times I can think of that I've been involved in true emergency traffic during a callout was when aiding search and rescue after tornadoes. Just because it's a hospital net does not constitute emergency traffic. So, while hams in the area will voluntarily yield the frequency, there is no requirement for them to do so, and any interference would be a violation. Would you please advise if the third harmonic issue is likely to be serious enough to require the use of a low pass filter between the two meter transceiver and the Diplexer/Band Pass Filter when using separate transmitters? Your diplexer should handle that well enough. What would be more of a concern to me would be just the spurious radiation around the shack. It's possible that could cause some desense, but I wouldn't expect it to be significant. -- Tom Horne W3TDH Your sig separator is broken. It needs to be exactly hyphen-hyphen-space-newline. You're missing the space. -- ================== Remove the "x" from my email address Jerry, AI0K ================== Jerry All I was trying to do by saying that we plan to be careful about interference is to calm and reassure those that are pathologically afraid of Winlink.. I do realize that nothing short of a true SOS like being pinned under a fallen snag with a widfire approaching qualifies as an emergency in the eyes of the Friendly Candy Company (FCC). They have been known to confiscate radios and cancel the license of hams who invaded a public safety channel to ask for help with a person who was bleeding profusely from a scalp wound. As a trained EMT I know that scalp wounds are often scarier than they look but how a ham out mountain biking with friends was supposed to know that I have no idea. The actual reaction of the FCC to any given situation is just as predictable as the reaction of any other organization that is staffed by human beings. Thanks for pointing out the the problem with my signature element. I appreciate the help. -- Tom Horne W3TDH |
Connecting multiple filters to multiband antenna
On Wednesday, March 11, 2015 at 7:11:14 PM UTC-4, Brian Reay wrote:
Tom W3TDH wrote: I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master antenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Diamond do a number of other antennas similar to the x30, essentially longer, with more gain. I would suggest you look at their website and pick one to match you budget, acceptable profile, etc. It may be worth investing in another tribander, you may just want the third band in the future and it will save another negotiation with Senior Management. Or you could take my approach and have an XYL who is licensed ;-) 73 Brian G8OSN/W8OSN Brian Should I follow your suggestion I would need to also provide protection for the radio connected to the third band segment. Do you know of any reason why connecting two separate filters to the same feed line would not work. Can I anticipate any ill affect from placing a coaxial Tee fitting across the output of one filter and connecting a jumper to the output of another filter in order to connect the transceivers to the multiband antenna? Would there be any additional concerns be raised if one of the two filters was the dual band model with separate connections for each of it's two bands on the end being used for input connections? What about if I make up the assembly using Three separate filters with Two of them connected to TEE fittings.. -- Tom Horne W3TDH |
Recomend dual band VHF / UHF antenna for two radios
On 15/03/15 13:33, Jerry Stuckle wrote:
On 3/15/2015 5:50 AM, Brian Reay wrote: Tom W3TDH wrote: Would you please advise if the third harmonic issue is likely to be serious enough to require the use of a low pass filter between the two meter transceiver and the Diplexer/Band Pass Filter when using separate transmitters? It depends on your tx. I've never required filters nor heard of their being required. Remember, you would need to be listening on the 3rd Rx harmonic, or 'close' to it for the rx to suffer and the harmonic should get several 10s of dB down relative to tell 2m carrier. Brian, Yes, it will be several 10s of dB down - but that can still be sufficient to be heard in (and potentially desense) a near-by receiver. It doesn't take a lot of signal if it's within the receiver's passband. But Tom's diplexer should handle this easily. Well, I several of us often run full duplex 2m/70cm or even triplex 4m/2m/70cm nets locally and use a common 2m/70cm antenna without problems- hence my comment that I've never experienced any issues. (Being in the UK, we have access to 4m.) I've even run 2m/70cm crossband duplex while mobile with a common antenna and with dual antennas on the roof of a SUV. True, I've not used the harmonic of the 2m frequency but the desense was never an issue. While mobile and using the single antenna, I relied on the internal duplexer of the radio. When using two antennas, there was no filter or duplexer added. If you think about it from a practical stand point, dual band radio with the ability to operate full duplex cross band would be pretty useless if it was an issue. I'm simply relating my experiences of actually using 2m and 70cm on a common antenna with a duplexer. If your experiences differ, fine. |
Connecting multiple filters to multiband antenna
On 15/03/15 15:42, Tom W3TDH wrote:
On Wednesday, March 11, 2015 at 7:11:14 PM UTC-4, Brian Reay wrote: Tom W3TDH wrote: I am looking for recommendations for a dual band antenna that will serve two separate radios. The reason that I want to use a single antenna is that I have a limited number of mounting points for antennas. At present it will be hard for SWMBO; as in Rumpole's spouse, She Who Must Be Obeyed; to tolerate the use of both our home's gable ends and the chimney being used to support antennas. I am planning to replace my Diamond X-30 with a triband vertical for Six, Two, and .7 Meters. The chimney will then support a rotor aimed Two and .7 Meter beam. The second gable end will support the Two meter / Seventy Centimeter dual band vertical that I am asking for help in selecting. One radio will be a two meter packet node which will be used as a Winlink Radio Message Server. The other radio will be a UHF D-STAR hotspot. I am willing to pay what is needed to to get the best antenna for this application but I don't want to waste money ineffectively. So the two meter radio will be in the 144 MHz portion of the band and I don't yet actually know were the D-STAR hotspot will be run. I have a DCI filter and diplexer to keep the two radios from actually knowing of each others existence. Since a hotspot is not supposed to be a terribly wide area installation I would imagine that I do not want an extremely high gain antenna but I am perfectly open to be reeducated on that. The difficulty is that I would guess that the Radio Message Server / Packet would benefit from as much horizontal gain as can be achieved. I have a home brewed collinear two meter J-Pole that has been a good performer on two meters and presents a low SWR on 440 MHz. I have yet to master antenna modeling but I would imagine; given all the warnings I have read on line; that it has poor radiation pattern on UHF. Is it likely to be too poor a performer for a hot spot on UHF? I really am asking because I want to know. I am not looking for encouragement to do something that will be ineffective. Thank you in advance for any help you may be willing to offer. -- Tom Horne W3TDH Diamond do a number of other antennas similar to the x30, essentially longer, with more gain. I would suggest you look at their website and pick one to match you budget, acceptable profile, etc. It may be worth investing in another tribander, you may just want the third band in the future and it will save another negotiation with Senior Management. Or you could take my approach and have an XYL who is licensed ;-) 73 Brian G8OSN/W8OSN Brian Should I follow your suggestion I would need to also provide protection for the radio connected to the third band segment. Do you know of any reason why connecting two separate filters to the same feed line would not work. Can I anticipate any ill affect from placing a coaxial Tee fitting across the output of one filter and connecting a jumper to the output of another filter in order to connect the transceivers to the multiband antenna? Would there be any additional concerns be raised if one of the two filters was the dual band model with separate connections for each of it's two bands on the end being used for input connections? What about if I make up the assembly using Three separate filters with Two of them connected to TEE fittings. It depends. For example: Some, duplexers are just an LPF and a HPF. Say your 2m filter is LPF and your 70cm filter is HPF and your 3rd band is 220MHz (the one you wish to Tee in). If the Cut Off frequency of the HPF is such that is will allow too much of the 220 MHz to pass to the 70cm radio, you could have an issue with enough 220MHz reaching the 70cm radio to be an issue. Likewise of for the 2m radio but with the LPF cut off. You really need to know the performance of the filters you are using. I don't know the unit you mentioned, I would suggest you study the data sheet and see what its performance is at the frequency you plan to 'Tee' in. Ideally, build (or buy) a unit designed to work with three signals, which you may be able to do using the unit you have when you know the characteristics. |
Recomend dual band VHF / UHF antenna for two radios
On 3/15/2015 11:54 AM, Brian Reay wrote:
Well, I several of us often run full duplex 2m/70cm or even triplex 4m/2m/70cm nets locally and use a common 2m/70cm antenna without problems- hence my comment that I've never experienced any issues. (Being in the UK, we have access to 4m.) I've even run 2m/70cm crossband duplex while mobile with a common antenna and with dual antennas on the roof of a SUV. True, I've not used the harmonic of the 2m frequency but the desense was never an issue. While mobile and using the single antenna, I relied on the internal duplexer of the radio. When using two antennas, there was no filter or duplexer added. If you think about it from a practical stand point, dual band radio with the ability to operate full duplex cross band would be pretty useless if it was an issue. I'm simply relating my experiences of actually using 2m and 70cm on a common antenna with a duplexer. If your experiences differ, fine. Brian, Have you actually measured desense with good test equipment? If not, you really don't know, do you? I've run 2m/70cm crossband mobile also. However, I also haven't measured the desense when trying to receive on the third harmonic. Have you? Additionally, when running crossband mobile, I've always gone from a nearby handheld on 70cm to a 2m repeater. Never tried it the other way around, and since the handheld is always (relatively) nearby, it always has a strong signal into the mobile. So even if there were desense I wouldn't see it. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Recomend dual band VHF / UHF antenna for two radios
On 3/15/2015 11:25 AM, Tom W3TDH wrote:
On Saturday, March 14, 2015 at 3:56:38 PM UTC-4, Jerry Stuckle wrote: Tom, Please see inlined... On 3/14/2015 1:17 PM, Tom W3TDH wrote: May I ask that you cool your jets a little. Please turn off the afterburners and stick to the questions that I'm asking. I don't want to be a focus of a flame war. I came here in the hope of getting good information and the task of sorting out conflicting advice is so much easier if I don't need to also filter out gratuitous feuding. If you followed this group before posting (always a good idea), you will see that is pretty normal here. If you're going to post, you can expect both good and bad advice. And some people (like Channel Jumper - who probably isn't even a ham) are so far off with every post you can expect a flame war. But then that is true of almost every place on the Internet. Your version of what is possible is attractive because it allows me to do what I want to do to support my clubs D-STAR project and provide a training resource for the ARES Hospital Emergency Net staff to become competent with Winlink. I realize that there are some Hams that despise Winlink and all other automated store and forward systems. I will be doing everything I can to avoid interference to other Amateurs but since we are using this to support hospitals under emergency conditions I think that everyone can just suck it up and bare with the emergency traffic and whatever inconvenience it may generate. b You are required by law to avoid interference. But you also need to understand what constitutes emergency traffic to the FCC. For that to occur, there must be an IMMEDIATE threat to life and/or property. An example would be reporting an automobile accident, especially one requiring immediate medical attention. It does NOT include 99% of the traffic being passed during an emergency. In the 19 years I've been a member of MoCo ARES/RACES (including the Hospital Net), we have NEVER had emergency traffic passed during a callout. Of course, I could also say that of most of the emergencies I've been involved in in 47 years as a ham. The only times I can think of that I've been involved in true emergency traffic during a callout was when aiding search and rescue after tornadoes. Just because it's a hospital net does not constitute emergency traffic. So, while hams in the area will voluntarily yield the frequency, there is no requirement for them to do so, and any interference would be a violation. Would you please advise if the third harmonic issue is likely to be serious enough to require the use of a low pass filter between the two meter transceiver and the Diplexer/Band Pass Filter when using separate transmitters? Your diplexer should handle that well enough. What would be more of a concern to me would be just the spurious radiation around the shack. It's possible that could cause some desense, but I wouldn't expect it to be significant. -- Tom Horne W3TDH Your sig separator is broken. It needs to be exactly hyphen-hyphen-space-newline. You're missing the space. Jerry All I was trying to do by saying that we plan to be careful about interference is to calm and reassure those that are pathologically afraid of Winlink. I do realize that nothing short of a true SOS like being pinned under a fallen snag with a widfire approaching qualifies as an emergency in the eyes of the Friendly Candy Company (FCC). They have been known to confiscate radios and cancel the license of hams who invaded a public safety channel to ask for help with a person who was bleeding profusely from a scalp wound. As a trained EMT I know that scalp wounds are often scarier than they look but how a ham out mountain biking with friends was supposed to know that I have no idea. The actual reaction of the FCC to any given situation is just as predictable as the reaction of any other organization that is staffed by human beings. Thanks for pointing out the the problem with my signature element. I appreciate the help. Tom, From your previous statement: "I will be doing everything I can to avoid interference to other Amateurs but since we are using this to support hospitals under emergency conditions I think that everyone can just suck it up and bare with the emergency traffic and whatever inconvenience it may generate." I'm just pointing out that by law you are REQUIRED to avoid interference. Also, your traffic is almost NEVER emergency traffic, and any interference you cause will be illegal. Other hams do NOT have to "suck it up" just because you're calling it a "hospital net". If you cause interference, you are liable - unless it is a true emergency. And yes, I was part of the local hospital net before you ever got your license. I manned Suburban Hospital. Of course, we had an 800MHz channel at the time, not ham. But the hams were the operators of the system. BTW - I also was an EMT - and probably have worked more runs than you've ever dreamed. I know how bloody a scalp wound can be. But I also know it can be a symptom of a much more serious injury such as a skull fracture (BTDT). To a non-trained person, this would be emergency traffic. As an EMT, I would never consider such a wound to NOT be emergency traffic when reported by a non-trained person. Neither would any of the other EMS people I have known over the years. And I'd like to see the details of the "hams who invaded a public safety channel to ask for help with a person who was bleeding profusely from a scalp wound". I suspect there is much more to it than you are reporting. References? -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Recomend dual band VHF / UHF antenna for two radios
On 15/03/15 16:40, Jerry Stuckle wrote:
On 3/15/2015 11:54 AM, Brian Reay wrote: Well, I several of us often run full duplex 2m/70cm or even triplex 4m/2m/70cm nets locally and use a common 2m/70cm antenna without problems- hence my comment that I've never experienced any issues. (Being in the UK, we have access to 4m.) I've even run 2m/70cm crossband duplex while mobile with a common antenna and with dual antennas on the roof of a SUV. True, I've not used the harmonic of the 2m frequency but the desense was never an issue. While mobile and using the single antenna, I relied on the internal duplexer of the radio. When using two antennas, there was no filter or duplexer added. If you think about it from a practical stand point, dual band radio with the ability to operate full duplex cross band would be pretty useless if it was an issue. I'm simply relating my experiences of actually using 2m and 70cm on a common antenna with a duplexer. If your experiences differ, fine. Brian, Have you actually measured desense with good test equipment? If not, you really don't know, do you? I've run 2m/70cm crossband mobile also. However, I also haven't measured the desense when trying to receive on the third harmonic. Have you? Additionally, when running crossband mobile, I've always gone from a nearby handheld on 70cm to a 2m repeater. Never tried it the other way around, and since the handheld is always (relatively) nearby, it always has a strong signal into the mobile. So even if there were desense I wouldn't see it. I haven't measured the desense, I was relating practical experience as I said. In the circumstances, they are probably more relevant in my opinion*. Tom is free to take which ever advice he decides is relevant. * The desense would have a number of variables, including the tx power (which may vary), tx and rx frequency (also variable). Plus the impact of the dense on the receive performance is almost impossible to predict in terms of who/what you could receive- by which I mean you could generate a raft of numbers for loss of system sensitivity but how do you translate that into practical link budgets, other than for known stations? It would be virtually useless for a random contact. 73 Brian |
Recomend dual band VHF / UHF antenna for two radios
On 3/15/2015 4:47 PM, Brian Reay wrote:
On 15/03/15 16:40, Jerry Stuckle wrote: On 3/15/2015 11:54 AM, Brian Reay wrote: Well, I several of us often run full duplex 2m/70cm or even triplex 4m/2m/70cm nets locally and use a common 2m/70cm antenna without problems- hence my comment that I've never experienced any issues. (Being in the UK, we have access to 4m.) I've even run 2m/70cm crossband duplex while mobile with a common antenna and with dual antennas on the roof of a SUV. True, I've not used the harmonic of the 2m frequency but the desense was never an issue. While mobile and using the single antenna, I relied on the internal duplexer of the radio. When using two antennas, there was no filter or duplexer added. If you think about it from a practical stand point, dual band radio with the ability to operate full duplex cross band would be pretty useless if it was an issue. I'm simply relating my experiences of actually using 2m and 70cm on a common antenna with a duplexer. If your experiences differ, fine. Brian, Have you actually measured desense with good test equipment? If not, you really don't know, do you? I've run 2m/70cm crossband mobile also. However, I also haven't measured the desense when trying to receive on the third harmonic. Have you? Additionally, when running crossband mobile, I've always gone from a nearby handheld on 70cm to a 2m repeater. Never tried it the other way around, and since the handheld is always (relatively) nearby, it always has a strong signal into the mobile. So even if there were desense I wouldn't see it. I haven't measured the desense, I was relating practical experience as I said. In the circumstances, they are probably more relevant in my opinion*. Tom is free to take which ever advice he decides is relevant. So you really don't know if you have any desense or not. You just haven't noticed any. That does not mean it's not there. * The desense would have a number of variables, including the tx power (which may vary), tx and rx frequency (also variable). Plus the impact of the dense on the receive performance is almost impossible to predict in terms of who/what you could receive- by which I mean you could generate a raft of numbers for loss of system sensitivity but how do you translate that into practical link budgets, other than for known stations? It would be virtually useless for a random contact. 73 Brian Actually, knowing the characteristics of the transmitter and receiver, as well as the characteristics of whatever filters are used, it's possible to quite accurately determine desense. That allows you to predict with pretty good accuracy how much signal it would take to attain a certain signal level (i.e. 12db SINAD) in the receiver. But that's the important part of ANY system. And it's impossible to predict the results of ANY random contact without knowing the details of the other station. But then that's true on any frequency with any mode. Something I did a fair amount of back in the mid 70's when I worked for a worked for a 2-way shop and planned UHF repeater systems. I doubt it's changed any today. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Connecting multiple filters to multiband antenna
On Sunday, March 15, 2015 at 12:36:28 PM UTC-4, Brian Reay wrote:
It depends. For example: Some, duplexers are just an LPF and a HPF. Say your 2m filter is LPF and your 70cm filter is HPF and your 3rd band is 220MHz (the one you wish to Tee in). If the Cut Off frequency of the HPF is such that is will allow too much of the 220 MHz to pass to the 70cm radio, you could have an issue with enough 220MHz reaching the 70cm radio to be an issue. Likewise of for the 2m radio but with the LPF cut off. You really need to know the performance of the filters you are using. I don't know the unit you mentioned, I would suggest you study the data sheet and see what its performance is at the frequency you plan to 'Tee' in. Ideally, build (or buy) a unit designed to work with three signals, which you may be able to do using the unit you have when you know the characteristics. Brian I was specifically referring to the Digital Communications Incorporated band pass filters that I had identified earlier in the thread. I have in hand a DCI-146-444-DX-DB I was thinking of adding a DCI-223.5-3H for 125 Centimeter band for the 146/220/446 tri-band antenna. That would give me three separate input ports to attach the three separate transceivers to. On the 6,2,& 0.7 Meter multi-band antenna I would buy a DCI-146-444-DB and a DCI-6M-53 MHz-2-4p. That way I could connect a dual band 146/446 Mhz radio to the dual band filter and the Six Meter Transceiver to the Six Meter band pass filter inlet. The spec sheets for all of these filters can be seen at the manufacturers web site at http://www.dci.ca/?Section=Products&SubSection=Amateur. -- Tom Horne W3TDH |
Connecting multiple filters to multiband antenna
On 3/16/2015 3:55 PM, Tom W3TDH wrote:
On Sunday, March 15, 2015 at 12:36:28 PM UTC-4, Brian Reay wrote: It depends. For example: Some, duplexers are just an LPF and a HPF. Say your 2m filter is LPF and your 70cm filter is HPF and your 3rd band is 220MHz (the one you wish to Tee in). If the Cut Off frequency of the HPF is such that is will allow too much of the 220 MHz to pass to the 70cm radio, you could have an issue with enough 220MHz reaching the 70cm radio to be an issue. Likewise of for the 2m radio but with the LPF cut off. You really need to know the performance of the filters you are using. I don't know the unit you mentioned, I would suggest you study the data sheet and see what its performance is at the frequency you plan to 'Tee' in. Ideally, build (or buy) a unit designed to work with three signals, which you may be able to do using the unit you have when you know the characteristics. Brian I was specifically referring to the Digital Communications Incorporated band pass filters that I had identified earlier in the thread. I have in hand a DCI-146-444-DX-DB I was thinking of adding a DCI-223.5-3H for 125 Centimeter band for the 146/220/446 tri-band antenna. That would give me three separate input ports to attach the three separate transceivers to. On the 6,2,& 0.7 Meter multi-band antenna I would buy a DCI-146-444-DB and a DCI-6M-53 MHz-2-4p. That way I could connect a dual band 146/446 Mhz radio to the dual band filter and the Six Meter Transceiver to the Six Meter band pass filter inlet. The spec sheets for all of these filters can be seen at the manufacturers web site at http://www.dci.ca/?Section=Products&SubSection=Amateur. Tom, It should work nicely. DCI's filters are good quality, and you should easily be able to work all three bands with this setup. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Connecting multiple filters to multiband antenna
On Monday, March 16, 2015 at 3:40:35 AM UTC-4, Jeff wrote:
Should I follow your suggestion I would need to also provide protection for the radio connected to the third band segment. Do you know of any reason why connecting two separate filters to the same feed line would not work. Can I anticipate any ill affect from placing a coaxial Tee fitting across the output of one filter and connecting a jumper to the output of another filter in order to connect the transceivers to the multiband antenna? Would there be any additional concerns be raised if one of the two filters was the dual band model with separate connections for each of it's two bands on the end being used for input connections? What about if I make up the assembly using Three separate filters with Two of them connected to TEE fittings. Hi Using a tee piece is not a good idea as it would effectively be putting a stub on your line, and depending on the length of the coax connections and the frequencies that you are operating on and the out of band impedances of the filters, it may or may not cause you problems. As things have got a bit disjointed as the thread as progressed would it be possible for you to give a short and accurate description of what you are actually relying to achieve, and then perhaps a solution could be suggested. Jeff Jeff It is all here in the rest of the thread but here goes. I have only three antenna mounting points available on my home for antennas to serve: a dedicated two meter transceiver for a digital node, a dedicated Seventy Centimeter transceiver for a D-STAR hot spot. a separate 120 CM transceiver the six meter band of multiband transceiver a dual band 146/446 transceiver That is five radios that need to be able to use Six Separate VHF/UHF frequencies with as many as four transceivers operating at the same time. Two of those transceivers would be operating as automatic stations so as many as three of those transmitters may be transmitting at the same time. Two of the three may even be on the same band given that their will be an automatic station on both Two Meters and Seventy Centimeters and I may be operating as a manual control operator on either of those bands at any given time. I initially asked for advise on which dual band antenna to use to serve a 144 Mhz and a 440 MHz digital stations. Someone then suggested that I use two tri-band antennas in order to provide all band capability for FM operations on 6, 2, 1.25, and 0.7 Meter bands while still operating the two automatic stations on 144 & 440. I would use vertical separation to reduce the de-sensing on the common band stations. I then asked for advise on any foreseeable problems with using the DCI filters to effectively separate the signals at the radios and yet allow the transceivers to share two multi-band antennas to cover the needed bands with only two mounting points. I'm saving the third mounting point for stacked Yagi-Uda beams to provide additional range on 146/440 for the repeaters at the extreme ends of the service area of the Forecast Office that I am serving as Assistant Coordinator for Net Management in their Skywarn Program. I am hoping that between the beams and two amplifiers with receive pre amps I will be able to take reports when appropriate from some of the more distant sub nets. I have done this previously with temporary masts from this location so I am very hopeful that it will work using more permanently mounted beams. All of that is so you will know why the third mounting point is not available for the needed omnidirectional vertical antennas. I hope that makes the expanding questions clear. -- Tom Horne W3TDH |
Connecting multiple filters to multiband antenna
On 17/03/15 08:12, Jeff wrote:
It is all here in the rest of the thread but here goes. I have only three antenna mounting points available on my home for antennas to serve: a dedicated two meter transceiver for a digital node, a dedicated Seventy Centimeter transceiver for a D-STAR hot spot. a separate 120 CM transceiver the six meter band of multiband transceiver a dual band 146/446 transceiver That is five radios that need to be able to use Six Separate VHF/UHF frequencies with as many as four transceivers operating at the same time. Two of those transceivers would be operating as automatic stations so as many as three of those transmitters may be transmitting at the same time. Two of the three may even be on the same band given that their will be an automatic station on both Two Meters and Seventy Centimeters and I may be operating as a manual control operator on either of those bands at any given time. I initially asked for advise on which dual band antenna to use to serve a 144 Mhz and a 440 MHz digital stations. Someone then suggested that I use two tri-band antennas in order to provide all band capability for FM operations on 6, 2, 1.25, and 0.7 Meter bands while still operating the two automatic stations on 144 & 440. I would use vertical separation to reduce the de-sensing on the common band stations. I then asked for advise on any foreseeable problems with using the DCI filters to effectively separate the signals at the radios and yet allow the transceivers to share two multi-band antennas to cover the needed bands with only two mounting points. I'm saving the third mounting point for stacked Yagi-Uda beams to provide additional range on 146/440 for the repeaters at the extreme ends of the service area of the Forecast Office that I am serving as Assistant Coordinator for Net Management in their Skywarn Program. I am hoping that between the beams and two amplifiers with receive pre amps I will be able to take reports when appropriate from some of the more distant sub nets. I have done this previously with temporary masts from this location so I am very hopeful that it will work using more permanently mounted beams. All of that is so you will know why the third mounting point is not available for the needed omnidirectional vertical antennas. I hope that makes the expanding questions clear. Tom The first thing that you have to consider is that none of the DFCI filters will give you any protection when 2 radios are operating in the same band, and paralleling things up with tee pieces is generally not a good idea. The issue with using Tee pieces is inadvertently inserting 'stubs' etc. If care is taken to avoid this, eg by keeping leads very very short, then at the frequencies being used, things should be OK. After all, a duplexer is just a set of filters in one box (ie the connections are very very very short). In fact, as the DCI filters are bandpass (based on Tom's post, I've not looked at the specs), they are probably better in some ways than some duplexers which just use LPFs and HPFs. (Triplexers tend to use at least one BPF but some only use an additional HPF.) |
Connecting multiple filters to multiband antenna
On 3/17/2015 5:19 PM, Brian Reay wrote:
On 17/03/15 08:12, Jeff wrote: It is all here in the rest of the thread but here goes. I have only three antenna mounting points available on my home for antennas to serve: a dedicated two meter transceiver for a digital node, a dedicated Seventy Centimeter transceiver for a D-STAR hot spot. a separate 120 CM transceiver the six meter band of multiband transceiver a dual band 146/446 transceiver That is five radios that need to be able to use Six Separate VHF/UHF frequencies with as many as four transceivers operating at the same time. Two of those transceivers would be operating as automatic stations so as many as three of those transmitters may be transmitting at the same time. Two of the three may even be on the same band given that their will be an automatic station on both Two Meters and Seventy Centimeters and I may be operating as a manual control operator on either of those bands at any given time. I initially asked for advise on which dual band antenna to use to serve a 144 Mhz and a 440 MHz digital stations. Someone then suggested that I use two tri-band antennas in order to provide all band capability for FM operations on 6, 2, 1.25, and 0.7 Meter bands while still operating the two automatic stations on 144 & 440. I would use vertical separation to reduce the de-sensing on the common band stations. I then asked for advise on any foreseeable problems with using the DCI filters to effectively separate the signals at the radios and yet allow the transceivers to share two multi-band antennas to cover the needed bands with only two mounting points. I'm saving the third mounting point for stacked Yagi-Uda beams to provide additional range on 146/440 for the repeaters at the extreme ends of the service area of the Forecast Office that I am serving as Assistant Coordinator for Net Management in their Skywarn Program. I am hoping that between the beams and two amplifiers with receive pre amps I will be able to take reports when appropriate from some of the more distant sub nets. I have done this previously with temporary masts from this location so I am very hopeful that it will work using more permanently mounted beams. All of that is so you will know why the third mounting point is not available for the needed omnidirectional vertical antennas. I hope that makes the expanding questions clear. Tom The first thing that you have to consider is that none of the DFCI filters will give you any protection when 2 radios are operating in the same band, and paralleling things up with tee pieces is generally not a good idea. The issue with using Tee pieces is inadvertently inserting 'stubs' etc. If care is taken to avoid this, eg by keeping leads very very short, then at the frequencies being used, things should be OK. After all, a duplexer is just a set of filters in one box (ie the connections are very very very short). In fact, as the DCI filters are bandpass (based on Tom's post, I've not looked at the specs), they are probably better in some ways than some duplexers which just use LPFs and HPFs. (Triplexers tend to use at least one BPF but some only use an additional HPF.) They do not have to be short - but as long as you have a multiple of 1/2 wavelength between the two diplexer inputs, each input will see the very high impedance of the other input. Rather easy, since you are operating on the third harmonic. This could also be a good application for a hybrid ring duplexer. It's a bit more complicated to build, but should provide better isolation. In either case, the trick is going to be getting the lengths of the coax correct. This is where a grid dip oscillator would be advantageous - actually measure the coax, instead of depending on the listed velocity factor. And BTW - duplexers can also be bandpass. Can duplexers are typically used on VHF and UHF repeaters. They can have very high Q (and therefore very narrow passbands). -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Connecting multiple filters to multiband antenna
On 3/18/2015 3:28 AM, Jeff wrote:
They do not have to be short - but as long as you have a multiple of 1/2 wavelength between the two diplexer inputs, each input will see the very high impedance of the other input. Rather easy, since you are operating on the third harmonic. Don't forget that it is not a simple as being 1/2 wavelength long, you have to take into account the input impedance of the filer which may substantially modify what you are looking at, and may load the other filter affecting its response. The DCI dual band filters are aligned as a unit so those sort of effect can be taken into account. Jeff The input impedance of the filter active filter would be 50 ohms, so no loading. And the impedance of the other filter would be very high. I would not expect matching a 50 ohm antenna to a good quality filter (which these are) would affect their response significantly enough to cause a problem. After all, this is the exact type of operation they are designed for. You *might* be able to measure some effect in a lab, but in the real world it won't make any difference. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Connecting multiple filters to multiband antenna
On Wednesday, March 18, 2015 at 8:13:58 AM UTC-4, Jeff wrote:
On 18/03/2015 10:49, Brian Morrison wrote: On Wed, 18 Mar 2015 06:44:55 -0400 Jerry Stuckle wrote: I would not expect matching a 50 ohm antenna to a good quality filter (which these are) would affect their response significantly enough to cause a problem. After all, this is the exact type of operation they are designed for. The stop band performance is dependent on the antenna and filter impedances out of band, at certain phases this can lead to a re-entering stop band. I've been dealing with the consequences of this in my day job very recently, it is a real and significant effect in some circumstances. It's also not trivial to fix. Indeed Brian, also if you look at the DCI filters there are quite large returns in the stop bands. Jeff What are the effects of this on my proposed operation? -- Tom Horne W3TDH |
Connecting multiple filters to multiband antenna
On 3/18/2015 6:49 AM, Brian Morrison wrote:
On Wed, 18 Mar 2015 06:44:55 -0400 Jerry Stuckle wrote: I would not expect matching a 50 ohm antenna to a good quality filter (which these are) would affect their response significantly enough to cause a problem. After all, this is the exact type of operation they are designed for. The stop band performance is dependent on the antenna and filter impedances out of band, at certain phases this can lead to a re-entering stop band. I've been dealing with the consequences of this in my day job very recently, it is a real and significant effect in some circumstances. It's also not trivial to fix. True. However - this was specifically made for 144/440 mhz with 50 ohm impedance. As long as these are the bands he's using and he stays within a reasonable range of 50 ohms, I don't see what the problem would be. Again - these units are DESIGNED for this operation. What good would it be to design and sell such an item if it doesn't work? DCI has good engineers who know their stuff. Their equipment is top quality. And while I've never tried this particular unit, I know they would not let something with your perceived problems out the door. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Connecting multiple filters to multiband antenna
On 3/18/2015 1:32 PM, Jeff wrote:
On 18/03/2015 13:54, Tom W3TDH wrote: On Wednesday, March 18, 2015 at 8:13:58 AM UTC-4, Jeff wrote: On 18/03/2015 10:49, Brian Morrison wrote: On Wed, 18 Mar 2015 06:44:55 -0400 Jerry Stuckle wrote: I would not expect matching a 50 ohm antenna to a good quality filter (which these are) would affect their response significantly enough to cause a problem. After all, this is the exact type of operation they are designed for. The stop band performance is dependent on the antenna and filter impedances out of band, at certain phases this can lead to a re-entering stop band. I've been dealing with the consequences of this in my day job very recently, it is a real and significant effect in some circumstances. It's also not trivial to fix. Indeed Brian, also if you look at the DCI filters there are quite large returns in the stop bands. Jeff What are the effects of this on my proposed operation? The effects are that it is not a good idea to parallel filters using coax and tee pieces. Jeff Except he is not paralleling filters. The two diplexers feed different radios. And how would YOU suggest he hook them up? -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Connecting multiple filters to multiband antenna
On 3/18/2015 1:52 PM, Brian Morrison wrote:
On Wed, 18 Mar 2015 10:55:18 -0400 Jerry Stuckle wrote: Again - these units are DESIGNED for this operation. What good would it be to design and sell such an item if it doesn't work? Well, not much, sometimes you can get caught out by something unexpected when a change is made to fix a problem and does so but then you discover some unintended consequences. That's exactly what I have been dealing with in a system where it's not easy to measure the frequency response of a combined antenna and filter in a radiated test. But we managed to do it, just took a while to create an appropriate test system. It may not be easy to measure when that isn't your main business. But for a company which is, I'm sure they have the appropriate equipment and procedures. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
Connecting multiple filters to multiband antenna
On 3/19/2015 5:32 AM, Jeff wrote:
Except he is not paralleling filters. The two diplexers feed different radios. If you had been keeping up with the thread that was exactly one the question that the OP was asking: could he parallel filters using coax and tee pieces. I have suggested a solution that only uses diplexers; the addition of filters will probably not make much difference to the resulting performance unless the radios in use have extremely high harmonic or spurious outputs or produce very excessive wide band noise or there is interference from 3rd party out of band transmitters. What will almost certainly be more of a problem is the de-sense caused by the in-band transmissions between the voice and data radios. Filtering that out is not a trivial problem, at least at the spacings available at 2m. Jeff I have been keeping up with the thread, Jeff. And he was asking about using his diplexers. It was others who though adding filters would be helpful. I have never suggested this setup. But what is the suggestion you made? And how is it different than the one I made? And exactly what is wrong with my suggestion? And he was not asking about desense caused by using different radios and antennas on the same band. Tom understands this. But it seems some people keep wanting to to keep going off-topic with extraneous information not related to the original question. -- ================== Remove the "x" from my email address Jerry, AI0K ================== |
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