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Sangean ATS-909 external antenna impedance??
Does anyone know what the Sangean ATS-909's external antenna input impedance
is? I searched for days for documentation on that radio and found plenty, mods, schematics, service manuals, reviews, but no straight word on the impedance of that input! (Not even in the service manual specs). The only reference I found was a from a guy on a 7-page set of ham reviews, and all he said was that it was a mystery! Maybe the only way to know is to start from the schematic but I don't know how, but here's the best schematic I could find: http://eric.horsemensociety.info/TEC...chematic_A.gif (Antenna input is near top right). (Link appears to be dead, 403, forbidden. I'm sure it worked last week..) What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. |
Sangean ATS-909 external antenna impedance??
On Dec 19, 3:14*pm, Lostgallifreyan wrote:
Does anyone know what the Sangean ATS-909's external antenna input impedance is? I searched for days for documentation on that radio and found plenty, mods, schematics, service manuals, reviews, but no straight word on the impedance of that input! (Not even in the service manual specs). The only reference I found was a from a guy on a 7-page set of ham reviews, and all he said was that it was a mystery! Maybe the only way to know is to start from the schematic but I don't know how, but here's the best schematic I could find:http://eric.horsemensociety.info/TEC...chematic_A.gif (Antenna input is near top right). (Link appears to be dead, 403, forbidden. I'm sure it worked last week..) What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. just hook it up with the coax even without the transformer and it should be fine. |
Sangean ATS-909 external antenna impedance??
Lostgallifreyan wrote:
Does anyone know what the Sangean ATS-909's external antenna input impedance is? SNIP What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. There's a 1K0 pot across the input which is used as a cheap and cheerful RF gain control. So i'd assume about 1K. You wouldn't have a problem with the wire attached direct, but you'll get lots of front end intermod, as it's wide open - just a low pass filter (presumably 30MHz cut off)before the RF amp. A bit of preselection is pretty necessary for an external wire of any size. |
Sangean ATS-909 external antenna impedance??
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Sangean ATS-909 external antenna impedance??
"Lostgallifreyan" wrote in message . .. Does anyone know what the Sangean ATS-909's external antenna input impedance is? I searched for days for documentation on that radio and found plenty, mods, schematics, service manuals, reviews, but no straight word on the impedance of that input! (Not even in the service manual specs). The only reference I found was a from a guy on a 7-page set of ham reviews, and all he said was that it was a mystery! Maybe the only way to know is to start from the schematic but I don't know how, but here's the best schematic I could find: http://eric.horsemensociety.info/TEC...chematic_A.gif (Antenna input is near top right). (Link appears to be dead, 403, forbidden. I'm sure it worked last week..) What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. Who cares what the impedance is for that radio. Unless you plan on putting up an antenna for one very narrow band of frequencies, the impedance of the system will be all over the place. YOu can probably run coax to the antenna and never have any problems. |
Sangean ATS-909 external antenna impedance??
Gaius wrote in
: Lostgallifreyan wrote: Does anyone know what the Sangean ATS-909's external antenna input impedance is? SNIP What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. There's a 1K0 pot across the input which is used as a cheap and cheerful RF gain control. So i'd assume about 1K. You wouldn't have a problem with the wire attached direct, but you'll get lots of front end intermod, as it's wide open - just a low pass filter (presumably 30MHz cut off)before the RF amp. A bit of preselection is pretty necessary for an external wire of any size. Front end intermod? Do you mean pickup from local active gain stages or other RF subcircuits in the receiver being picked back up by the wire antenna and makign sum/difference signals or similar effects? Also, I see that pot now, (and noticed that it also affects the telescopic inbuilt antenna's pickup on SW (not FM as far as I know)), but I also see a lot of other parts associated with that part of the circuit. I don't know enough to be sure but it seems they might complicate the picture. If not, I don't know why the impedance seems to be a mystery. If it were well established I know my searches would found it so in triplicate by now... |
Sangean ATS-909 external antenna impedance??
"Ralph Mowery" wrote in
m: "Lostgallifreyan" wrote in message . .. Does anyone know what the Sangean ATS-909's external antenna input impedance is? I searched for days for documentation on that radio and found plenty, mods, schematics, service manuals, reviews, but no straight word on the impedance of that input! (Not even in the service manual specs). The only reference I found was a from a guy on a 7-page set of ham reviews, and all he said was that it was a mystery! Maybe the only way to know is to start from the schematic but I don't know how, but here's the best schematic I could find: http://eric.horsemensociety.info/TEC...chematic_A.gif (Antenna input is near top right). (Link appears to be dead, 403, forbidden. I'm sure it worked last week..) What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. Who cares what the impedance is for that radio. Unless you plan on putting up an antenna for one very narrow band of frequencies, the impedance of the system will be all over the place. YOu can probably run coax to the antenna and never have any problems. Ok, so that's two people saying that could work, and sure, I won't be relying on a single narrow range, I want to see what's out there and detectable. I might want to limit peaks and troughs in sensitivity by using a 9:1 transformer though, as I read several times that it is a useful way to do that for general SW listening via a long wire. That alone means I probably DO need to care about impedance matching. |
Sangean ATS-909 external antenna impedance??
Lostgallifreyan wrote:
Gaius wrote in : Lostgallifreyan wrote: Also, I see that pot now, (and noticed that it also affects the telescopic inbuilt antenna's pickup on SW (not FM as far as I know)), but I also see a lot of other parts associated with that part of the circuit. I don't know enough to be sure but it seems they might complicate the picture. If not, I don't know why the impedance seems to be a mystery. If it were well established I know my searches would found it so in triplicate by now... I've just found a schematic JPG - 475Kb. It claims to be a "RK777", but I think that's one of the 909's aliases. I can send it - mail me at john at aultmore dot net. |
Sangean ATS-909 external antenna impedance??
"Lostgallifreyan" wrote in message . .. "Ralph Mowery" wrote in m: "Lostgallifreyan" wrote in message . .. Does anyone know what the Sangean ATS-909's external antenna input impedance is? I searched for days for documentation on that radio and found plenty, mods, schematics, service manuals, reviews, but no straight word on the impedance of that input! (Not even in the service manual specs). The only reference I found was a from a guy on a 7-page set of ham reviews, and all he said was that it was a mystery! Maybe the only way to know is to start from the schematic but I don't know how, but here's the best schematic I could find: http://eric.horsemensociety.info/TEC...chematic_A.gif (Antenna input is near top right). (Link appears to be dead, 403, forbidden. I'm sure it worked last week..) What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. Who cares what the impedance is for that radio. Unless you plan on putting up an antenna for one very narrow band of frequencies, the impedance of the system will be all over the place. YOu can probably run coax to the antenna and never have any problems. Ok, so that's two people saying that could work, and sure, I won't be relying on a single narrow range, I want to see what's out there and detectable. I might want to limit peaks and troughs in sensitivity by using a 9:1 transformer though, as I read several times that it is a useful way to do that for general SW listening via a long wire. That alone means I probably DO need to care about impedance matching. You need an impedance matching device otherwise incorrectly called "antenna tuning unit". It doesn't tune the antenna, it only matches the impedance for a given frequency. The main loss will be with the aerial NOT being resonant at your chosen frequency. The only way you are going to find out is try what people have suggested, then compare the results for yourself. |
Sangean ATS-909 external antenna impedance??
On Sat, 19 Dec 2009 09:14:46 -0600, Lostgallifreyan
wrote: Does anyone know what the Sangean ATS-909's external antenna input impedance is? The Sangean external antenna input is a 2.1mm jack which would acommodate a high impedance long wire, as per the instructions: "ANT-60 PORTABLE SW ANTENNA Included with the ATS-909 is the Sangean ANT-60 Portable SW Antenna. The antenna is plugged into jack (26) labeled EXT AM ANT. When fully extended this antenna should improve SW reception. For maximum performance this antenna should be placed as high as possible above the ground and in an unobstructed area if possible." Your idea of attaching the antenna via 50 ohm coax would probably be below the impedance range of the jack, tho' I'm not sure you would really hear much difference. If the Sangean external antenna input were designed for 50 ohm coax, it would probably have a coax jack, not the 2.1 mm jack. bob k5qwg I searched for days for documentation on that radio and found plenty, mods, schematics, service manuals, reviews, but no straight word on the impedance of that input! (Not even in the service manual specs). The only reference I found was a from a guy on a 7-page set of ham reviews, and all he said was that it was a mystery! Maybe the only way to know is to start from the schematic but I don't know how, but here's the best schematic I could find: http://eric.horsemensociety.info/TEC...chematic_A.gif (Antenna input is near top right). (Link appears to be dead, 403, forbidden. I'm sure it worked last week..) What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. |
Sangean ATS-909 external antenna impedance??
In message , Bob
writes If the Sangean external antenna input were designed for 50 ohm coax, it would probably have a coax jack, not the 2.1 mm jack. The 'type' of connector - especially on something like a small portable radio - is absolutely NO guide to the input impedance (which, actually could be almost anything). It's often determined by the need to keep it small. I have a small VHF/UHF TV set which use a 3.5mm audio jack. -- Ian |
Sangean ATS-909 external antenna impedance??
Bob wrote in
: The Sangean external antenna input is a 2.1mm jack which would acommodate a high impedance long wire, as per the instructions: 3.5mm, not 2.1mm "ANT-60 PORTABLE SW ANTENNA Included with the ATS-909 is the Sangean ANT-60 Portable SW Antenna. The antenna is plugged into jack (26) labeled EXT AM ANT. When fully extended this antenna should improve SW reception. For maximum performance this antenna should be placed as high as possible above the ground and in an unobstructed area if possible." I know that, it was the first thing I found, but it doesn't answer any questions about impedance, especially if the radio you buy is second hand and doesn't have the antenna wire with it. Your idea of attaching the antenna via 50 ohm coax would probably be below the impedance range of the jack, tho' I'm not sure you would really hear much difference. If the Sangean external antenna input were designed for 50 ohm coax, it would probably have a coax jack, not the 2.1 mm jack. Agreed, which is why I don't assume it's 50 ohms, and I start looking for answers. I think you're likely right that it might not make enough difference to worry about though. If using coax can get the SNR higher I'm in business so long as the signal is strong enough for the input's gain to use. |
Sangean ATS-909 external antenna impedance??
Gaius wrote in
: Lostgallifreyan wrote: Gaius wrote in : Lostgallifreyan wrote: Also, I see that pot now, (and noticed that it also affects the telescopic inbuilt antenna's pickup on SW (not FM as far as I know)), but I also see a lot of other parts associated with that part of the circuit. I don't know enough to be sure but it seems they might complicate the picture. If not, I don't know why the impedance seems to be a mystery. If it were well established I know my searches would found it so in triplicate by now... I've just found a schematic JPG - 475Kb. It claims to be a "RK777", but I think that's one of the 909's aliases. I can send it - mail me at john at aultmore dot net. Thanks, but I'm ok, I got a schematic.. It just appears that those links became forbidden access in the week or so since I found them. Might even be a local error, thogh as I no longer do HTML or User-Agent filtering or similar things I can't see what the cause might be. |
Sangean ATS-909 external antenna impedance??
"IanT" wrote in
: Ok, so that's two people saying that could work, and sure, I won't be relying on a single narrow range, I want to see what's out there and detectable. I might want to limit peaks and troughs in sensitivity by using a 9:1 transformer though, as I read several times that it is a useful way to do that for general SW listening via a long wire. That alone means I probably DO need to care about impedance matching. You need an impedance matching device otherwise incorrectly called "antenna tuning unit". It doesn't tune the antenna, it only matches the impedance for a given frequency. The main loss will be with the aerial NOT being resonant at your chosen frequency. The only way you are going to find out is try what people have suggested, then compare the results for yourself. Thanks, that could be useful. I've heard of them, wasn't sure if I'd need something beyond a means to reduce peaks and troughs in resonance or sensitivity across bands while trying to match impedance though. I read some old posts by John Doty (archived on web sites) that suggested that a single device could be set and placed at the end of the antenna wire and grounded there too, and then weatherproofed and ignored. :) It's an attractive idea. |
Sangean ATS-909 external antenna impedance??
"Lostgallifreyan" wrote in message . .. Bob wrote in : The Sangean external antenna input is a 2.1mm jack which would acommodate a high impedance long wire, as per the instructions: 3.5mm, not 2.1mm "ANT-60 PORTABLE SW ANTENNA Included with the ATS-909 is the Sangean ANT-60 Portable SW Antenna. The antenna is plugged into jack (26) labeled EXT AM ANT. When fully extended this antenna should improve SW reception. For maximum performance this antenna should be placed as high as possible above the ground and in an unobstructed area if possible." I know that, it was the first thing I found, but it doesn't answer any questions about impedance, especially if the radio you buy is second hand and doesn't have the antenna wire with it. Your idea of attaching the antenna via 50 ohm coax would probably be below the impedance range of the jack, tho' I'm not sure you would really hear much difference. If the Sangean external antenna input were designed for 50 ohm coax, it would probably have a coax jack, not the 2.1 mm jack. Agreed, which is why I don't assume it's 50 ohms, and I start looking for answers. I think you're likely right that it might not make enough difference to worry about though. If using coax can get the SNR higher I'm in business so long as the signal is strong enough for the input's gain to use. Hey Lost, This page has lots of good info, http://www.hard-core-dx.com/nordicdx.../magbalun.html Sounds like the N8KDV Transformer would work for you, but you still don't know the input impedance of your radio. You could try getting that info from Sangean. The problem you have is whatever antenna you have the impedance changes with frequency. If you find a band that interests you, build an antenna for that band. Here's another that shows how impedance changes with frequency, it's put in mismatch loss rather than resistance and reactance, but it gives the general idea. www.iw5edi.com/ham-radio/?swl-longwires,47 Mike |
Sangean ATS-909 external antenna impedance??
3.5mm, not 2.1mm "ANT-60 PORTABLE SW ANTENNA Included with the ATS-909 is the Sangean ANT-60 Portable SW Antenna. The antenna is plugged into jack (26) labeled EXT AM ANT. When fully extended this antenna should improve SW reception. For maximum performance this antenna should be placed as high as possible above the ground and in an unobstructed area if possible." I know that, it was the first thing I found, but it doesn't answer any questions about impedance, especially if the radio you buy is second hand and doesn't have the antenna wire with it. Your idea of attaching the antenna via 50 ohm coax would probably be below the impedance range of the jack, tho' I'm not sure you would really hear much difference. If the Sangean external antenna input were designed for 50 ohm coax, it would probably have a coax jack, not the 2.1 mm jack. Agreed, which is why I don't assume it's 50 ohms, and I start looking for answers. I think you're likely right that it might not make enough difference to worry about though. If using coax can get the SNR higher I'm in business so long as the signal is strong enough for the input's gain to use. Hey Lost, This page has lots of good info, http://www.hard-core-dx.com/nordicdx.../magbalun.html Sounds like the N8KDV Transformer would work for you, but you still don't know the input impedance of your radio. You could try getting that info from Sangean. The problem you have is whatever antenna you have the impedance changes with frequency. If you find a band that interests you, build an antenna for that band. Here's another that shows how impedance changes with frequency, it's put in mismatch loss rather than resistance and reactance, but it gives the general idea. www.iw5edi.com/ham-radio/?swl-longwires,47 Mike You might try posting on rec.radio.shortwave, someone there may know about the Sangean. Mike |
Sangean ATS-909 external antenna impedance??
On Sun, 20 Dec 2009 04:01:16 -0600, Lostgallifreyan
wrote: Bob wrote in : The Sangean external antenna input is a 2.1mm jack which would acommodate a high impedance long wire, as per the instructions: 3.5mm, not 2.1mm "ANT-60 PORTABLE SW ANTENNA Included with the ATS-909 is the Sangean ANT-60 Portable SW Antenna. The antenna is plugged into jack (26) labeled EXT AM ANT. When fully extended this antenna should improve SW reception. For maximum performance this antenna should be placed as high as possible above the ground and in an unobstructed area if possible." I know that, it was the first thing I found, but it doesn't answer any questions about impedance, especially if the radio you buy is second hand and doesn't have the antenna wire with it. Your idea of attaching the antenna via 50 ohm coax would probably be below the impedance range of the jack, tho' I'm not sure you would really hear much difference. If the Sangean external antenna input were designed for 50 ohm coax, it would probably have a coax jack, not the 2.1 mm jack. Agreed, which is why I don't assume it's 50 ohms, and I start looking for answers. I think you're likely right that it might not make enough difference to worry about though. If using coax can get the SNR higher I'm in business so long as the signal is strong enough for the input's gain to use. You might shoot an email to tech at C.Crane Co. -- a lot of their branded radios are actually customized Sangeans...they might be able to tell you the most effective antenna and/or the impedance of the thing. bob k5qwg |
Sangean ATS-909 external antenna impedance??
Bob wrote in
: You might shoot an email to tech at C.Crane Co. -- a lot of their branded radios are actually customized Sangeans...they might be able to tell you the most effective antenna and/or the impedance of the thing. bob k5qwg Nice, I saw their page, didn't check that far though, and it is worth a try. |
Sangean ATS-909 external antenna impedance??
"amdx" wrote in
: www.iw5edi.com/ham-radio/?swl-longwires,47 Oh yeah.. :) Saw that one. That was what I had in mind. It irons the bumps out. That guy mentions John Doty, his page was one of many I found while looking for John Doty's DIY transformer plans. (Still not found those). The way I see it (hopefully this is right) is that those deep level variations really DO need smoothing out as described there, because they represent signal loss greater than is likely to be caused by other errors like basic mismatches, and possible overload at peaks as Europe has many strong SW stations. Again, if I can use coax to increase SNR by reducing noise out of nearby buildings, it reduces the problem to one of loss/gain. As Anthony Alouitius StJohn Hancock pronounced: "Stone me, you've got to have something to start with!". Not that I'd trust his judgement as a radio ham. :) That's my plan for the other end of the wire though, the question is whether I'll have trouble at the ATS-909 radio end if I use it. Though I guess the antenna matcher (misnamed 'tuner' as IanT mentioned in his post) can help, and probably further assist the business. I'll probably try longwire straight to coax first just to see what results, then an earth rod to ground the coax far end, and then the 9:1 transformer, before considering the more complex adjustable impedance matcher though. Got other problems like money and dodgy neighbour problems to solve first too, which is why I'm saying more than doing right now (and gathering info). Once I start doing, I need to minimise the actions so I don't have more than reception issues to worry about. |
Sangean ATS-909 external antenna impedance??
"amdx" wrote in
: Well most tuner/antenna matcher are designed to take the impedance that the antenna cable presents and transformer it to 50 ohms. Your problem is the Sangean is probably not 50 ohms. Ah, but in reverse? :) I don't know if this is good thinking, but if the coax IS 50 ohms, could I not put the 50 ohm connection onto the coax and tweak the other end (on the input instead of the coax) impedance by watching the signal strength meter on the receiver? (Might be undeed according to posts people made earlier that suggest that losses here might matter less than what happens on the longwire end of the coax). |
Sangean ATS-909 external antenna impedance??
Lostgallifreyan wrote in
: undeed Un-needed. Some typos shall not pass. |
Sangean ATS-909 external antenna impedance??
In article ,
Lostgallifreyan wrote: The way I see it (hopefully this is right) is that those deep level variations really DO need smoothing out as described there, because they represent signal loss greater than is likely to be caused by other errors like basic mismatches, and possible overload at peaks as Europe has many strong SW stations. Again, if I can use coax to increase SNR by reducing noise out of nearby buildings, it reduces the problem to one of loss/gain. Looking at it from the opposite angle, though: it's fairly common in the HF bands for the signal level isn't the limiting factor in your reception. Even an inefficiently-matched antenna can deliver enough signal to overcome the self-noise of the front-end circuitry in your receiver. What limits your ability to receive, under these conditions, is band noise and other spurious signals, which "drown out" the desired signal. Improving the antenna matching wil have little or no benefit in dealing with external noise. Neither will a preamp. Now, using coax as a way of excluding some of the close-in interferers isn't a bad idea at all. What you might want to consider doing, is adding an active buffer at the longwire-to-coax feedpoint... basically, a low-gain preamp (a few dB) designed to drive a 50-ohm load efficiently and to overcome the (slight) signal losses in the coax. Some people seem to favor the grounded-base or grounded-gate broadband amplifier, as it has a modest gain, can be quite stable, and has a good resistance to strong-signal overload. You could use a DC inserter/block system to feed 9-12 volts up the same coax which carries the signal down. If you're really concerned about matching the resulting coax-carried signal to your radio's antenna input, you could wind a fixed-ratio broadband transformer with the correct impedance ratio. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Sangean ATS-909 external antenna impedance??
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Sangean ATS-909 external antenna impedance??
"Lostgallifreyan" wrote in message . .. "amdx" wrote in : Well most tuner/antenna matcher are designed to take the impedance that the antenna cable presents and transformer it to 50 ohms. Your problem is the Sangean is probably not 50 ohms. Ah, but in reverse? :) I don't know if this is good thinking, but if the coax IS 50 ohms, could I not put the 50 ohm connection onto the coax and tweak the other end (on the input instead of the coax) impedance by watching the signal strength meter on the receiver? Ideally you would adjust the impedance of the antenna to match 50 ohms then attach your 50 ohm coax, then connect to a 50 ohm receiver. (you don't have) But trying to adjust an antenna that is way out there (say 4000 ohms with 200 Reactance) from the shack is not an easy task. (Might be undeed according to posts people made earlier that suggest that losses here might matter less than what happens on the longwire end of the coax). I'm in agreement with those that say just put up a wire and listen. Then pick your favorite band and put up a resonant antenna and compare the two. Then your learning something. Mike |
Sangean ATS-909 external antenna impedance??
"amdx" wrote in
: (Might be undeed according to posts people made earlier that suggest that losses here might matter less than what happens on the longwire end of the coax). I'm in agreement with those that say just put up a wire and listen. Then pick your favorite band and put up a resonant antenna and compare the two. Then your learning something. Mike Right now I have no idea what my favourite band might be. :) I'll try the basic wire, I used to try that many years ago as a kid, in places where it was easy, on private land with space for it. But that was the seventies, in the country. Now I'm in an inner city full of mobile phones and computers, things have changed so much that I know it won't be the same. I like that 18' whip scheme you linked to though, I really like that one and want to try it. |
Sangean ATS-909 external antenna impedance??
In article ,
Lostgallifreyan wrote: Right now I have no idea what my favourite band might be. :) I'll try the basic wire, I used to try that many years ago as a kid, in places where it was easy, on private land with space for it. But that was the seventies, in the country. Now I'm in an inner city full of mobile phones and computers, things have changed so much that I know it won't be the same. I like that 18' whip scheme you linked to though, I really like that one and want to try it. Lost- I agree that the "basic wire" antenna approach will almost certainly work. At least you will get your feet wet. That is the kind of external antenna most often used with that type of radio. If you want to continue the search for input impedance, consider trying something like an MFJ Antenna Analyzer (MFJ-259 or 269?), which uses a sufficiently low signal level that it shouldn't hurt the radio. Instead of analyzing the antenna, use it to analyze the input of the radio. You can use the information to design a matching circuit, but you may find that the improvement is disappointing for reasons already discussed. Fred K4DII |
Sangean ATS-909 external antenna impedance??
Bob wrote in
: You might shoot an email to tech at C.Crane Co. -- a lot of their branded radios are actually customized Sangeans...they might be able to tell you the most effective antenna and/or the impedance of the thing. bob k5qwg I got a reply, but Sangean didn't tell them that either. :) But he says what many here do, that it doesn't matter that much, and that 50 ohm line should be ok. One thing that keeps coming up is the need to make my own transformer for the far end, whatever scheme I use, and in that context I often see mention of a ferrite co Amidon FT-114-75 (AL about 3000, permeability u=5000, about 1.14 inch outside diameter as described on one page). Cheap but apparently not easy to find in Britain. Does anyone know a current source of something equivalent to it? It's beginning to look like I should get a small handful of them. Another thing that might be better fetched locally is something like the broadband preamp for LW to 30 MHz sold by Kiwa Electronics. If anyone knows of one, please point me to it.. It's a Norton balanced input amp with gain of around 10 dB. Even if I don't need it I'd like to know where to find such things locally. I can likely build something based on the Dallas design in a PDF I found but a good picture of the construction would help, as I can't easily visualise the coil and former arrangements from the schematic. |
Sangean ATS-909 external antenna impedance??
Fred McKenzie wrote in
: In article , Lostgallifreyan wrote: Right now I have no idea what my favourite band might be. :) I'll try the basic wire, I used to try that many years ago as a kid, in places where it was easy, on private land with space for it. But that was the seventies, in the country. Now I'm in an inner city full of mobile phones and computers, things have changed so much that I know it won't be the same. I like that 18' whip scheme you linked to though, I really like that one and want to try it. Lost- I agree that the "basic wire" antenna approach will almost certainly work. At least you will get your feet wet. That is the kind of external antenna most often used with that type of radio. If you want to continue the search for input impedance, consider trying something like an MFJ Antenna Analyzer (MFJ-259 or 269?), which uses a sufficiently low signal level that it shouldn't hurt the radio. Instead of analyzing the antenna, use it to analyze the input of the radio. You can use the information to design a matching circuit, but you may find that the improvement is disappointing for reasons already discussed. Fred K4DII I'll pass. :) I think the reason no-one knows is that as you (and others) say, it's not important enough. What does seem important is to try to reduce localised noise, and to break the current link to protect the radio input from static discharges. Whether I use coax or a balanced loop made from speaker wire, it loooks like my next step is to get Amidon FT-114-75 ferrite cores to play with, and in Britain I can't easily do that, but if anyone knows a local direct equivalent to them I can try that. I'll Google for things that fit the description (AL about 3000, permeability u=5000, about 1.14 inch outside diameter) but I think it's wise to ask here to try to save time. |
Sangean ATS-909 external antenna impedance??
In article ,
Lostgallifreyan wrote: I'll pass. :) I think the reason no-one knows is that as you (and others) say, it's not important enough. What does seem important is to try to reduce localised noise, and to break the current link to protect the radio input from static discharges. Whether I use coax or a balanced loop made from speaker wire, it loooks like my next step is to get Amidon FT-114-75 ferrite cores to play with, and in Britain I can't easily do that, but if anyone knows a local direct equivalent to them I can try that. I'll Google for things that fit the description (AL about 3000, permeability u=5000, about 1.14 inch outside diameter) but I think it's wise to ask here to try to save time. You can probably at least start your experimentation using the common sort of interference-suppression ferrites that are found in many computer accessories - e.g. molded onto DC cords, VGA cables, USB cables, and so forth. Here in the U.S. these are easily available at electronics surplus stores, ham-fest flea markets, and other such sources. In my experience, these tend to be a ferrite mix such as type 43, which is optimized for use at somewhat higher frequencies than HF/SWL... so they will probably not be optimal for your purposes. However, they can be made to work. A few years ago I constructed a common-mode feedline choke for our local ARES/RACES ham station, to try to keep 40- and 80-meter signals from being carried back down the outside of the coax and into the building (our signal was audible on phones in the city's "911" emergency dispatch center... *not* good). I took several tubular computer-interference-suppression ferrite cores (large inner diameter), glued them end-to-end with cyanoacrylate, let them dry, and then ran some RG-8X coax through the center and back around the outside and through the center again. The coax looped through the tube of ferrites three times. This resulted in an extremely effective common-mode choke. According to my MFJ antenna analyzer, the impedance looking up through the coax in the usual way (standard hookup, into a 50-ohm dummy load) was 50 ohms... the ferrites had no effect at all on the differential-mode signal in the coax. But, when I measured the impedance along the braid (i.e. from the ground shell at one end of the coax, to the ground shell at the other... a DC short circuit), I couldn't get a reading at any frequency... the meter just said " 1500 ohms". Even at the lowest frequency of interest, these non-optimal ferrites added so much inductance to the common-mode signal path that they were blocking the feedline current flow very effectively. [Unfortunately, we determined that the phone interference was caused by direct RF pickup by the phone wiring, which was in the "near field" of the antenna above the roof. It occurred even if we completely disconnected the building feedline, and fed the antenna directly from a radio located up on the roof. The feedline choke couldn't help us.] In your situation, I'd guess that you could probably make an efficient feedline choke by using almost any surplus ferrite toroid which is sufficiently large to wind your feedline (coax or speaker wire) through it a few times. Or, use several surplus ferrite cores, end-to-end, and if they're large enough in diameter, loop the feedline down through the center more than once. It won't be perfect (nor as good as if you used a ferrite optimized for use at lower frequencies) but it will probably help matters, and will give you some sense as to whether it makes sense to go to the trouble and expense of buying ferrites that are better for your purpose. -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
Sangean ATS-909 external antenna impedance??
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Sangean ATS-909 external antenna impedance??
On Dec 19, 10:14*am, Lostgallifreyan wrote:
Does anyone know what the Sangean ATS-909's external antenna input impedance is? I searched for days for documentation on that radio and found plenty, mods, schematics, service manuals, reviews, but no straight word on the impedance of that input! (Not even in the service manual specs). The only reference I found was a from a guy on a 7-page set of ham reviews, and all he said was that it was a mystery! Maybe the only way to know is to start from the schematic but I don't know how, but here's the best schematic I could find:http://eric.horsemensociety.info/TEC...chematic_A.gif (Antenna input is near top right). (Link appears to be dead, 403, forbidden. I'm sure it worked last week..) What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. Ive measured the input impedance of a few SW receivers and found them to be in the 1Kohm ballpark for the most part. I did this by applying a voltage through a series resistor to the frontend of the radio and adjusting the value of the resistor until the voltage dropped by 50%. If you have a schematic an analysis of the front end circuit might give you and idea. Jimmie |
Sangean ATS-909 external antenna impedance??
|
Sangean ATS-909 external antenna impedance??
On Dec 19, 3:14*pm, Lostgallifreyan wrote:
What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. lets go back to the beginning... this is what i would do. 1. hook up whatever coax you have to the radio and run it as far outside away from the house as it will go. 2. hook up a wire directly to it as long as you can go in whatever random direction you may be able to go 3. enjoy. if in the future there are signals that just aren't strong enough, but still above the local noise, then start playing around with either a matching network or a preamp. but until you know how well the receiver by itself works with the plain wire/coax you are wasting time over designing something you probably won't need. |
Sangean ATS-909 external antenna impedance??
On Dec 24, 5:15*pm, Dave wrote:
On Dec 19, 3:14*pm, Lostgallifreyan wrote: What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. lets go back to the beginning... this is what i would do. 1. hook up whatever coax you have to the radio and run it as far outside away from the house as it will go. 2. hook up a wire directly to it as long as you can go in whatever random direction you may be able to go 3. enjoy. if in the future there are signals that just aren't strong enough, but still above the local noise, then start playing around with either a matching network or a preamp. *but until you know how well the receiver by itself works with the plain wire/coax you are wasting time over designing something you probably won't need. You may find that a good RF ground more benificial than any particular antenna. I discovered this while in the military and had a chance to hook my little cheap portable Setico rx to an antenna made of 20ft of emt conduit and the ground system on an abandoned comm unit. Lots of good info arounf on RF grounds on the web and this group. Jimmie Jimmie |
Sangean ATS-909 external antenna impedance??
On Sat, 19 Dec 2009 09:14:46 -0600, Lostgallifreyan
wrote: What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. Hello Dr, Well, I've been on the East Coast for several weeks and am just catching up with your particular problem (which is not too uncommon for SWL'ers who post here). Many suggestions have been useful, but some contra-indicate others, while some merely rely on lore and superstition. One of the last suggestions, from JIMMIE, is probably the single greatest boon for signal strength: Ground. Ground is always the least appreciated component, and is always the single most important one. Ground for RF is not always the same as the ground for safety. Worse yet is that mixing them can sometimes introduce grief (AKA ground loops). ALL grounds should eventually find their way to the service ground. This advice serves both safety and engineering. More can be said - but we move on. One antenna does not always work for all bands (not without a lot of work and the ability to change its polarization). As such, two or more antennas are necessary for SWL'ing. They don't need to be isolated to one band, but if any antenna is resonant for one, it will probably be difficult on another band that is twice or half that frequency. Thus you add another antenna that is half or twice the first's dimension. The benefit here is that they can be wired to the same feed point with little interaction between them. More can be said here too. Matching with a one-size-fits-all doohickey is pabulum for the masses. When it is tossed into the mix, it usually forces the user to add the components already described above that are responsible for most of the benefit attributed to the doohickey. Hosanna's are misplaced. More can be said here, to not good outcome. Matching with an antenna tuner (yes, I am aware of the irony in its name) satisfies all issues (except for the transmission line loss - if it matters) of matching. The tuner's responsibility is to see to it that an unknown source is matched to an unknown load (that is why it has so many adjustments). You can use any Ham grade tuner, get one without a meter to save the big bucks. Whatever product that is designed for the ham bands is satisfactory for the SWL bands. Of course, you could build your own (what a concept!). Matching with a preselector takes the antenna tuner one step further, and protects your receiver from the scourge of these "modern" designs: intermod. The SWL-monkeys who demand the ability to "quickly" tune up different bands/frequencies usually whine and squeel about the difficulty of tuners and preselectors (and in the same breath praise the doohickey's font of blessings). I let them indulge in their illusions and say no more. INTERMOD is the silent killer (as they used to say about high blood pressure). A strong station (a nearby AM transmitter in town) can easily close down your 31M listening experience by simply driving the AGC into overload without you being aware of it. Preselectors and Tuners will drive down that off-band signal, peak the selected frequency, and give you what you tuned for in that band. Beware of imitations that suggest they do the same without tuning (what a crock). As for that antenna impedance. Others have suggested a myriad of possibilities. The first active component's shunt reactance (often the base-emitter capacitance) is the limiting factor even when humongous resistance bridges those same points. Resistance is for bias folks. More can be said, but enough has been said here. Feel free to ask for more to be said. 73's Richard Clark, KB7QHC |
Sangean ATS-909 external antenna impedance??
Richard Clark wrote in
: On Sat, 19 Dec 2009 09:14:46 -0600, Lostgallifreyan wrote: What I really want to know is whether the ATS-909 will work ok with a long(ish) wire outside feeding a 50 ohm coax via a 9:1 transformer, or if that would cause more bother than connecting a wire directly to it and putting up with local noise picked up from nearby buildings. Hello Dr, Well, I've been on the East Coast for several weeks and am just catching up with your particular problem (which is not too uncommon for SWL'ers who post here). Many suggestions have been useful, but some contra-indicate others, while some merely rely on lore and superstition. One of the last suggestions, from JIMMIE, is probably the single greatest boon for signal strength: Ground. Ground is always the least appreciated component, and is always the single most important one. Ground for RF is not always the same as the ground for safety. Worse yet is that mixing them can sometimes introduce grief (AKA ground loops). ALL grounds should eventually find their way to the service ground. This advice serves both safety and engineering. More can be said - but we move on. One antenna does not always work for all bands (not without a lot of work and the ability to change its polarization). As such, two or more antennas are necessary for SWL'ing. They don't need to be isolated to one band, but if any antenna is resonant for one, it will probably be difficult on another band that is twice or half that frequency. Thus you add another antenna that is half or twice the first's dimension. The benefit here is that they can be wired to the same feed point with little interaction between them. More can be said here too. Matching with a one-size-fits-all doohickey is pabulum for the masses. When it is tossed into the mix, it usually forces the user to add the components already described above that are responsible for most of the benefit attributed to the doohickey. Hosanna's are misplaced. More can be said here, to not good outcome. Matching with an antenna tuner (yes, I am aware of the irony in its name) satisfies all issues (except for the transmission line loss - if it matters) of matching. The tuner's responsibility is to see to it that an unknown source is matched to an unknown load (that is why it has so many adjustments). You can use any Ham grade tuner, get one without a meter to save the big bucks. Whatever product that is designed for the ham bands is satisfactory for the SWL bands. Of course, you could build your own (what a concept!). Matching with a preselector takes the antenna tuner one step further, and protects your receiver from the scourge of these "modern" designs: intermod. The SWL-monkeys who demand the ability to "quickly" tune up different bands/frequencies usually whine and squeel about the difficulty of tuners and preselectors (and in the same breath praise the doohickey's font of blessings). I let them indulge in their illusions and say no more. INTERMOD is the silent killer (as they used to say about high blood pressure). A strong station (a nearby AM transmitter in town) can easily close down your 31M listening experience by simply driving the AGC into overload without you being aware of it. Preselectors and Tuners will drive down that off-band signal, peak the selected frequency, and give you what you tuned for in that band. Beware of imitations that suggest they do the same without tuning (what a crock). As for that antenna impedance. Others have suggested a myriad of possibilities. The first active component's shunt reactance (often the base-emitter capacitance) is the limiting factor even when humongous resistance bridges those same points. Resistance is for bias folks. More can be said, but enough has been said here. Feel free to ask for more to be said. 73's Richard Clark, KB7QHC Thanks. :) Well, my plan is to use a ground at the antenna end, right underneath it. My neighbourhood problems recently were solved when a guy on the first floor ****ed off someone enough that said someone blew their flat door in with a shotgun! So the whole problem ended with a neat flameout a few days ago. I couldn't go out there rigging antennae while paranoid criminals were still active, it's seriously asking for BAD trouble. Right now I have the lesser problems of dental and other bills imminent, but I'll get a good 4' ground rod and rig up an 18' vertical whip as I learned of in details I posted about earlier. I understand that good reception depends on a good compromise between selectivity and sensitivity, and no doubt the antenna 'tuner' helps with that, though I'll mainly be concerned with good ground and local common mode noise rejection. My first attempt at the line between antenna and receiver will be a balanced line with a toroid at each end for current isolation and possibly the suggested Norton preamp on the receiver input, but I'll try without it first as I suspect I'll get enough signal strength to satisfy me for a while. If I have to use coax I will but I'll try the easier options first. This basic plan does involve a 10:1 ratio in windings on the far end toroid which should help smooth out peaks of resonance as described by John Doty and others as mentioned before, and if nothing else, drives a stronger current in the balanced line part of the system. I'm no longer much concerned about matching impedances, but I will be watching for results of changing antenna length if resonance seems to be an issue. My interest in the 'doohickey' or any other widget was mainly in what appeared to be a means of reducing the difference in signal strength extremes due to resonance. I understand that if I subsequently have to select the weaker of two close stations I'll either have to add some 'trap' for a specific offender, such as a trimmed lengh of unterminated coax (though as far as I know, that trick is usually reserved for much higher frequencies), or use a manually tuned system which I'll explore if it becomes a dominant concern. |
Sangean ATS-909 external antenna impedance??
On Sat, 02 Jan 2010 13:21:03 -0600, Lostgallifreyan
wrote: Well, my plan is to use a ground at the antenna end, right underneath it. This bodes ill if you do not tie that ground directly to the service ground. Further, a "ground" as you describe it (incompletely) sounds suspiciously like a ground rod. This is NOT the same thing as RF ground - not even close unless you live within several meters of low tide along a major ocean shore. I'll get a good 4' ground rod and rig up an 18' vertical whip as I learned of in details I posted about earlier. Suspicions confirmed.... I understand that good reception depends on a good compromise between selectivity and sensitivity, and no doubt the antenna 'tuner' helps with that, though I'll mainly be concerned with good ground and local common mode noise rejection. This does not acknowledge the significance of INTERMOD problems. Experience may have to teach that (when you make all these improvements and have poor results for your effort). My first attempt at the line between antenna and receiver will be a balanced line with a toroid at each end for current isolation This is a very, very curious novelty. You do not describe a "balanced" system with a ground rod and vertical, so any effort at "balanced" lines is window dressing only. The reason for placing "balanced" within quotes is due to the inordinate care and skill required in obtaining a balanced design. It is more often achieved with coax. Too often, "balanced line" is approached with the mysticism of universal relief for whatever ails a listener. and possibly the suggested Norton preamp on the receiver input, I must have missed that posting. Sounds like another elaboration. but I'll try without it first as I suspect I'll get enough signal strength to satisfy me for a while. If I have to use coax I will but I'll try the easier options first. This basic plan does involve a 10:1 ratio in windings on the far end toroid which should help smooth out peaks of resonance as described by John Doty and others as mentioned before, and if nothing else, drives a stronger current in the balanced line part of the system. This is the doohickey I spoke of. It is basically the refuge accessory of the lowfers where the span of frequencies is, maybe, three to one and not like the ten to one of HF SWLing. I'm no longer much concerned about matching impedances, but I will be watching for results of changing antenna length if resonance seems to be an issue. This is at cross purposes. You don't have many realistic options of changing antenna length (height) as you do with a simple tuner when it comes to matching. My interest in the 'doohickey' or any other widget was mainly in what appeared to be a means of reducing the difference in signal strength extremes due to resonance. I understand that if I subsequently have to select the weaker of two close stations I'll either have to add some 'trap' for a specific offender, such as a trimmed lengh of unterminated coax (though as far as I know, that trick is usually reserved for much higher frequencies), or use a manually tuned system which I'll explore if it becomes a dominant concern. Traps don't work very well for adjacent AM/SSB stations, you need cascade XTAL ladders to do that. Tuners, also, can only operate within the combination of number of reactive elements and Q. Please respond to your perception of the problem of INTERMOD as it is, as I said, the silent killer of reception. 73's Richard Clark, KB7QHC |
Sangean ATS-909 external antenna impedance??
Richard Clark wrote in
: On Sat, 02 Jan 2010 13:21:03 -0600, Lostgallifreyan wrote: Well, my plan is to use a ground at the antenna end, right underneath it. This bodes ill if you do not tie that ground directly to the service ground. Further, a "ground" as you describe it (incompletely) sounds suspiciously like a ground rod. This is NOT the same thing as RF ground - not even close unless you live within several meters of low tide along a major ocean shore. I'll get a good 4' ground rod and rig up an 18' vertical whip as I learned of in details I posted about earlier. Suspicions confirmed.... I understand that good reception depends on a good compromise between selectivity and sensitivity, and no doubt the antenna 'tuner' helps with that, though I'll mainly be concerned with good ground and local common mode noise rejection. This does not acknowledge the significance of INTERMOD problems. Experience may have to teach that (when you make all these improvements and have poor results for your effort). My first attempt at the line between antenna and receiver will be a balanced line with a toroid at each end for current isolation This is a very, very curious novelty. You do not describe a "balanced" system with a ground rod and vertical, so any effort at "balanced" lines is window dressing only. The reason for placing "balanced" within quotes is due to the inordinate care and skill required in obtaining a balanced design. It is more often achieved with coax. Too often, "balanced line" is approached with the mysticism of universal relief for whatever ails a listener. and possibly the suggested Norton preamp on the receiver input, I must have missed that posting. Sounds like another elaboration. but I'll try without it first as I suspect I'll get enough signal strength to satisfy me for a while. If I have to use coax I will but I'll try the easier options first. This basic plan does involve a 10:1 ratio in windings on the far end toroid which should help smooth out peaks of resonance as described by John Doty and others as mentioned before, and if nothing else, drives a stronger current in the balanced line part of the system. This is the doohickey I spoke of. It is basically the refuge accessory of the lowfers where the span of frequencies is, maybe, three to one and not like the ten to one of HF SWLing. I'm no longer much concerned about matching impedances, but I will be watching for results of changing antenna length if resonance seems to be an issue. This is at cross purposes. You don't have many realistic options of changing antenna length (height) as you do with a simple tuner when it comes to matching. My interest in the 'doohickey' or any other widget was mainly in what appeared to be a means of reducing the difference in signal strength extremes due to resonance. I understand that if I subsequently have to select the weaker of two close stations I'll either have to add some 'trap' for a specific offender, such as a trimmed lengh of unterminated coax (though as far as I know, that trick is usually reserved for much higher frequencies), or use a manually tuned system which I'll explore if it becomes a dominant concern. Traps don't work very well for adjacent AM/SSB stations, you need cascade XTAL ladders to do that. Tuners, also, can only operate within the combination of number of reactive elements and Q. Please respond to your perception of the problem of INTERMOD as it is, as I said, the silent killer of reception. 73's Richard Clark, KB7QHC I haven't a clue about intermod, yet. One thing at a time. Right now I see at least three contradictions (re ground rods, transformers, and feedlines) with advice from several people, one of which (the guy who wrote the description of the antenna and balanced line I mentioned) is part of a group of hams who is turned to for advice by the others. No guarantee of correctness, perhaps, but if I keep on being told I'm wrong when my stuff is coming as directly as I can get it from others with experience, then as far as I'm concerned I'll do what I think best and get out of the crossfire. Specifically, many times I've seen advice that service grounds are not adequate because of common mode noise and local currents, hence the ground rod you vehemently negate. I can ground to service ground at near end but if the receiver is on batteries, not connected to anything except a transformer coupling RF from the antenna, then the ground only needs to be at the antenna end, according to advice I've seen in several places. Even if I do ground to a water pipe or other local ground, all advice I see until now insists on having a ground rod as close to the antenna as possible, no matter what else I do, yet now you urge against this. I will stop asking for advice if all I see is vigorous contradiction between people who claim knowledge I do not have. Diverting that disagreement to one with me doesn't alter this, I did not originate the info behind the choices I am considering. Even if all the various contributors come here and duke it out between them it appears I'll be none the wiser. |
Sangean ATS-909 external antenna impedance??
Lostgallifreyan wrote in
: ...several people, one of which (the guy who wrote the description of the antenna and balanced line I mentioned) is part of a group of hams who is turned to for advice by the others. To save time: "http://www.kongsfjord.no/dl/Antennas/The%20Best%20Small%20Antennas%20For%20M W,%20LW,%20And%20SW%20rev%202.pdf The start page for that link is here; http://www.kongsfjord.no/dl/dl.htm" (Copied from a post by 'amdx' earlier in this thread). The line IS balanced, as it carries only its own internal current, driven by an isolated coupling with the antenna circuit. Anyway, if he's wrong, there's not much point in taking it up with me, for obvious reasons. He wrote that. I didn't. |
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