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multiband vertical
Hi all, I am just about to get my Foundation licence and am contemplating a
multiband vertical. Many plan talks about "radials" being needed, now I just happen to have a house with a nice tin roof. Can I make use of the whole roof as a ground plain or do I need radials cut to resonance for each band? Thank Andre (vk3 - almost got it!!!) |
multiband vertical
"Andre & Sharon Walker" wrote in
: Hi all, I am just about to get my Foundation licence and am contemplating a multiband vertical. Many plan talks about "radials" being needed, now I just happen to have a house with a nice tin roof. Can I make use of the whole roof as a ground plain or do I need radials cut to resonance for each band? Do you mean a trapped vertical or the like, or are you planning to use an unloaded vertical on multiple bands. If it is a trapped vertical, it probably comes with instructions. For example, http://www.dxengineering.com/pdf/hus...5btv_instl.pdf details the installation instructions for the Huster verticals. You could read the instructions / manual after it doesn't work properly, or you could read them beforehand. Not all verticals require a substantial ground system, it depends on the design. The tin roof might well provide a sufficient counterpoise for some trapped verticals, depending on its size and location of the antenna. Short verticals are invariably quite narrow band on low bands, often as little as 20kHz on 80m. Also, keep in mind that verticals are relatively noisy in city environments. You might be well served with a simple coax fed dipole for one band (40m) initially. Gain some experience, and note how many others are using trapped verticals or the like. Do try to resist the end fed long wire (though it is more correctly described as an end fed random length wire) that seems so popular with FLs. Owen |
multiband vertical
I was hoping to get away from traps, but i dont think its possible :-(. I
only have a smallish yard, with just 30m from the chimmny (brick ) to the back of the yard, so i think a decent wire antenna is out...but i am open to suggestions. I guess the other considerstion is to keep "she inside" happy . Andre "Andre & Sharon Walker" wrote in message ... Hi all, I am just about to get my Foundation licence and am contemplating a multiband vertical. Many plan talks about "radials" being needed, now I just happen to have a house with a nice tin roof. Can I make use of the whole roof as a ground plain or do I need radials cut to resonance for each band? Thank Andre (vk3 - almost got it!!!) |
multiband vertical
Owen Duffy wrote:
You might be well served with a simple coax fed dipole for one band (40m) initially. A similar antenna, but one step closer to multiband operation would be a simple dipole for one band (40m) fed with a multiple of 1/2 wavelengths of ladder-line. At the resonant frequency, it is hard to tell from a coax-fed dipole and an antenna tuner will allow coverage of the entire band. The bonus is that such an antenna can be made to work well on all ham frequencies above the design frequency. If one is willing to vary the length of the ladder-line, one can get by without a conventional antenna tuner. Info at: http://www.w5dxp.com/notuner.htm -- 73, Cecil http://www.w5dxp.com |
multiband vertical
Andre & Sharon Walker wrote:
I was hoping to get away from traps, but i dont think its possible :-(. I only have a smallish yard, with just 30m from the chimmny (brick ) to the back of the yard, so i think a decent wire antenna is out...but i am open to suggestions. I guess the other considerstion is to keep "she inside" happy . A 1/2WL dipole is 20m on 40m and can be made to work on all HF bands 40m-10m. That's probably what I would do and then do something romantic to keep the XYL happy. -- 73, Cecil http://www.w5dxp.com |
multiband vertical
On Wed, 18 Apr 2007 09:45:39 GMT, "Andre & Sharon Walker"
wrote: I was hoping to get away from traps, but i dont think its possible :-(. I only have a smallish yard, with just 30m from the chimmny (brick ) to the back of the yard, so i think a decent wire antenna is out...but i am open to suggestions. I guess the other considerstion is to keep "she inside" happy . Andre You can trust Owen's advice! Here is some recommended reading on the subject from another reliable source: http://www.bencher.com/pdfs/00815ZZV.pdf http://www.bencher.com/pdfs/00816ZZV.pdf I have found Bencher's products to be a bit pricey but they are high quality. They do have some low cost solutions. Cushcraft is my favorite supplier because for a given type of antenna they are the lowest cost solution. You must beware when dealing with them that they are inclined to sell what is popular rather than what is best for a given design. The big problem with a multi band antenna is it is like a Swiss Army knife. You can make it work but never as well as a single purpose device. I find twenty meters to be the most active all-around band. BTW, I spend more time tinkering with antennas than operating. Congratulations on the new ticket! If you don't find what you want in Amateur Radio you are not looking in the right place... John Ferrell W8CCW "Life is easier if you learn to plow around the stumps" |
multiband vertical
My antenna is similar to yours, but slightly longer. I have a 110 feet
dipole running between my chimney and a tree at the back of the lot. The dipole is at a height of 30 feet and is fed with open-wire. I use an antenna tuner and the antenna works fairly well on all bands 80 through 10 meters. John, N9JG "Cecil Moore" wrote in message .. . Andre & Sharon Walker wrote: I was hoping to get away from traps, but i dont think its possible :-(. I only have a smallish yard, with just 30m from the chimmny (brick ) to the back of the yard, so i think a decent wire antenna is out...but i am open to suggestions. I guess the other considerstion is to keep "she inside" happy . A 1/2WL dipole is 20m on 40m and can be made to work on all HF bands 40m-10m. That's probably what I would do and then do something romantic to keep the XYL happy. -- 73, Cecil http://www.w5dxp.com |
multiband vertical
John, N9JG wrote:
My antenna is similar to yours, but slightly longer. I have a 110 feet dipole running between my chimney and a tree at the back of the lot. The dipole is at a height of 30 feet and is fed with open-wire. I use an antenna tuner and the antenna works fairly well on all bands 80 through 10 meters. Your dipole is 8 feet longer than the G5RV length which is a positive for 80m operation. For your favorite bands, there is probably an optimum length of feedline. EZNEC allows one to model different lengths of feedline. I wrote a compiled BASIC DOS program that will estimate the optimum lengths of feedline at: http://www.w5dxp.com/imax.exe -- 73, Cecil http://www.w5dxp.com |
multiband vertical
What do you mean by optimum length since open-wire feedline has minimal
loss? When I moved into this property last July, I just strung the longest wire that would fit into the lot, and reeled out the amount of feedline that would reach between the tuner and my shack on the second floor. I can not make the feedline appreciably shorter, and if I made it longer I would have to figure out how to support the additional feedline. I estimate the feedline has a length of 70 feet. John, N9JG "Cecil Moore" wrote in message et... John, N9JG wrote: My antenna is similar to yours, but slightly longer. I have a 110 feet dipole running between my chimney and a tree at the back of the lot. The dipole is at a height of 30 feet and is fed with open-wire. I use an antenna tuner and the antenna works fairly well on all bands 80 through 10 meters. Your dipole is 8 feet longer than the G5RV length which is a positive for 80m operation. For your favorite bands, there is probably an optimum length of feedline. EZNEC allows one to model different lengths of feedline. I wrote a compiled BASIC DOS program that will estimate the optimum lengths of feedline at: http://www.w5dxp.com/imax.exe -- 73, Cecil http://www.w5dxp.com |
multiband vertical
John, N9JG wrote:
What do you mean by optimum length since open-wire feedline has minimal loss? By "optimum length", I mean the length where you can switch your antenna tuner into bypass mode and obtain a 50 ohm SWR of less than ~1.6:1. For any dipole that is 1/2WL on the lowest frequency of operation, that will be at an SWR current maximum point making the antenna plus tuned feeder system resonant without a tuner. On 20m, for example, if one can vary the ladder-line length by plus or minus 15 feet, one can always locate the SWR current maximum point and usually bypass the antenna tuner. I have a 20m 1/2WL dipole that I use on 20m, 17m, 15m, 12m, 10m, and 6m without a conventional antenna tuner by simply varying the length of the 300 ohm ladder-line. -- 73, Cecil http://www.w5dxp.com |
multiband vertical
Thanks for the explanation. What you have described would be more convenient
from an operating standpoint since I would have one less thing to tune during a QSY. "Cecil Moore" wrote in message t... John, N9JG wrote: What do you mean by optimum length since open-wire feedline has minimal loss? By "optimum length", I mean the length where you can switch your antenna tuner into bypass mode and obtain a 50 ohm SWR of less than ~1.6:1. For any dipole that is 1/2WL on the lowest frequency of operation, that will be at an SWR current maximum point making the antenna plus tuned feeder system resonant without a tuner. On 20m, for example, if one can vary the ladder-line length by plus or minus 15 feet, one can always locate the SWR current maximum point and usually bypass the antenna tuner. I have a 20m 1/2WL dipole that I use on 20m, 17m, 15m, 12m, 10m, and 6m without a conventional antenna tuner by simply varying the length of the 300 ohm ladder-line. -- 73, Cecil http://www.w5dxp.com |
multiband vertical
In article ,
"Andre & Sharon Walker" wrote: now I just happen to have a house with a nice tin roof. Can I make use of the whole roof as a ground plain or do I need radials cut to resonance for each band? Andre, Several years ago I had a tin roof and tried to use it as a ground plain. It did NOT work. I gave up and cut some radials |
multiband vertical
aRKay wrote:
Several years ago I had a tin roof and tried to use it as a ground plain. It did NOT work. I gave up and cut some radials Did you lay the radials on the tin roof? -- 73, Cecil http://www.w5dxp.com |
multiband vertical
Cecil Moore wrote in
: Andre & Sharon Walker wrote: I was hoping to get away from traps, but i dont think its possible :-(. I only have a smallish yard, with just 30m from the chimmny (brick ) to the back of the yard, so i think a decent wire antenna is out...but i am open to suggestions. I guess the other considerstion is to keep "she inside" happy . A 1/2WL dipole is 20m on 40m and can be made to work on all HF bands 40m-10m. That's probably what I would do and then do something romantic to keep the XYL happy. Cecil, Andre will not have access to most HF bands, just 80, 40, 15, and 10m. It takes about 6 hours to train and assess a Foundation Licencee, so your tunerless concept is perhaps more complex than Andre's current knowledge base. For example, I worked a FL chap a couple of days ago on 40m with a 80m half wave dipole fed with a long run of coax, and he was confident that his antenna worked real well, despite my expectation that it was likely that well less than 10% of his permitted 10W PEP was radiated. It was impossible to tell this chap that if he cut the dipole to half the length it would work better on 40m. It is no good telling people that an antenna isn't likely to work real good, they will cite all the contacts that they have had with it, and as we know, anything "works", doesn't it. However, most people listen to the positive suggestion that with change, and antenna will work better (and in the above case, more than 10 times the EIRP). Andre, keep it simple. A coax fed half wave dipole is easy to get going will limited knowledge and experience, and you should have a high confidence that you will be able to deliver a suitable load to your transmitter (ie it will deliver its rated power), and the antenna will be quite efficient (ie that most of your 10W PEP transmitter power is radiated). It will also work well on receive. If you hear strong FL signals around, they have good antennas, and / or are flaunting the power limit. It is easy to do the latter, but if you get the antenna right, you still have the room for improvement when you upgrade to the higher power limit. Owen |
multiband vertical
"Andre & Sharon Walker" wrote in
: I was hoping to get away from traps, but i dont think its possible :-(. I only have a smallish yard, with just 30m from the chimmny (brick ) to the back of the yard, so i think a decent wire antenna is out...but i am open to suggestions. I guess the other considerstion is to keep "she inside" happy . Andre, There are other options than traps, including other multiband designs that depend on other devices to deliver a nominal 50 ohm feedpoint. An unloaded vertical with a tuner at the base is an option. See my earlier comment about noise in urban areas. Your yard is obviously bigger than many suburban yards. A 40m inverted V needs about 8m horizontally each side of the support mast. Owen |
multiband vertical
Wow..looks like I opened a can of worms here!
Thanks to all for the many links and advice..much food for thought. I think ill have to re assess I was considering end fed longwire also, but an inverted V might be a better option. Anyway, should be on the air within 4 weeks...the licence is the easy bit, diverting funds for the radio from the XYL is the tricky part!!! But ive been offered a FT101z , inc Yaseu Desk mix + spare set of finals ( is too early to rember the number of the tubes off hand...just finished night shift), so ill have wind the wick WAY back to start with. I don't care what they say at the club...I like boat anchors!! ( I'd love to replace the Murphy B40 I sold 10 years ago :-( ) Cheers Andre "Owen Duffy" wrote in message ... Cecil Moore wrote in : Andre & Sharon Walker wrote: I was hoping to get away from traps, but i dont think its possible :-(. I only have a smallish yard, with just 30m from the chimmny (brick ) to the back of the yard, so i think a decent wire antenna is out...but i am open to suggestions. I guess the other considerstion is to keep "she inside" happy . A 1/2WL dipole is 20m on 40m and can be made to work on all HF bands 40m-10m. That's probably what I would do and then do something romantic to keep the XYL happy. Cecil, Andre will not have access to most HF bands, just 80, 40, 15, and 10m. It takes about 6 hours to train and assess a Foundation Licencee, so your tunerless concept is perhaps more complex than Andre's current knowledge base. For example, I worked a FL chap a couple of days ago on 40m with a 80m half wave dipole fed with a long run of coax, and he was confident that his antenna worked real well, despite my expectation that it was likely that well less than 10% of his permitted 10W PEP was radiated. It was impossible to tell this chap that if he cut the dipole to half the length it would work better on 40m. It is no good telling people that an antenna isn't likely to work real good, they will cite all the contacts that they have had with it, and as we know, anything "works", doesn't it. However, most people listen to the positive suggestion that with change, and antenna will work better (and in the above case, more than 10 times the EIRP). Andre, keep it simple. A coax fed half wave dipole is easy to get going will limited knowledge and experience, and you should have a high confidence that you will be able to deliver a suitable load to your transmitter (ie it will deliver its rated power), and the antenna will be quite efficient (ie that most of your 10W PEP transmitter power is radiated). It will also work well on receive. If you hear strong FL signals around, they have good antennas, and / or are flaunting the power limit. It is easy to do the latter, but if you get the antenna right, you still have the room for improvement when you upgrade to the higher power limit. Owen |
multiband vertical
"Andre & Sharon Walker" wrote in
: Wow..looks like I opened a can of worms here! Not really Andre. Thanks to all for the many links and advice..much food for thought. I think ill have to re assess I was considering end fed longwire also, but an inverted V might be a better option. Anyway, should be on the air within 4 weeks...the licence is the easy bit, diverting funds for the radio from the XYL is the tricky part!!! But ive been offered a FT101z , inc Yaseu Desk mix + spare set of finals ( is too early to rember the number of the tubes off hand...just finished night shift), so ill have wind the wick WAY back to start with. I don't care what they say at the club...I like boat anchors!! ( I'd love to replace the Murphy B40 I sold 10 years ago :-( ) Ok, now that more detail unfolds, a 7MHz half wave dipole, cut to formula, with a modest length of coax, even RG58 up to 20m in length, will deliver most (80%) of the transmitter power to the antenna to be radiated, and the pi-coupled output in the '101Z will be tolerant of the load presented to the transmitter. This is a pretty good way to start, and you should be heard. You are about to be licenced to learn! Unless you have an inline power meter specifically designed to measure PEP, and that works properly, you can be assured that your PEP is less than the maximum that the '101Z runs, which I think is close to 200W. The tendency for FLs is to "talk it up to 10W" on an inline power meter that doesn't respond to PEP, I call that 10 "Foundation Watts", they are not PEP and they are not average watts, something else, but undefined since most inline power meters don't give valid readings on anything but a steady carrier. If you would like to read some high level stuff about the PEP measurement problem, see http://www.vk1od.net/VSWR/MeasureSSBTxPower.htm . Catch you on air Andre. Owen |
multiband vertical
"John, N9JG" wrote in
et: Thanks for the explanation. What you have described would be more convenient from an operating standpoint since I would have one less thing to tune during a QSY. You might have misunderstood Cecil. I think he is describing a system where the "optimal length" may be different on each band, so whilst you don't tune an ATU, you tune the feeder length. Cecil will confirm or deny... Owen |
multiband vertical
Owen Duffy wrote:
"John, N9JG" wrote in et: Thanks for the explanation. What you have described would be more convenient from an operating standpoint since I would have one less thing to tune during a QSY. You might have misunderstood Cecil. I think he is describing a system where the "optimal length" may be different on each band, so whilst you don't tune an ATU, you tune the feeder length. Throwing a couple of knife switches is certainly an easier and faster QSY than rotating a coil switch and twisting two interacting capacitor knobs. -- 73, Cecil http://www.w5dxp.com |
multiband vertical
"Cecil Moore" wrote in message t... Owen Duffy wrote: "John, N9JG" wrote in et: Thanks for the explanation. What you have described would be more convenient from an operating standpoint since I would have one less thing to tune during a QSY. You might have misunderstood Cecil. I think he is describing a system where the "optimal length" may be different on each band, so whilst you don't tune an ATU, you tune the feeder length. Throwing a couple of knife switches is certainly an easier and faster QSY than rotating a coil switch and twisting two interacting capacitor knobs. -- 73, Cecil http://www.w5dxp.com Cecil, I was thinking of trying your no= tune antenna and the 16 ft piece may not be doable at my QTH, I have to keep it all hidden behind the bushes. Could this piece be replaced with a circuit using lumped LC values. Jimmie |
multiband vertical
On Thu, 19 Apr 2007 12:24:52 -0400, "Jimmie D"
wrote: Cecil, I was thinking of trying your no= tune antenna and the 16 ft piece may not be doable at my QTH, I have to keep it all hidden behind the bushes. Could this piece be replaced with a circuit using lumped LC values. Hi Jimmie, I've been doing it with a binary switched coax matcher for 15 years. It occupies about half a cubic foot and tunes in increments of 1, 2, 4, 8, and 16 feet. 73's Richard Clark, KB7QHC |
multiband vertical
Jimmie D wrote:
Cecil, I was thinking of trying your no= tune antenna and the 16 ft piece may not be doable at my QTH, I have to keep it all hidden behind the bushes. Could this piece be replaced with a circuit using lumped LC values. That would work at one frequency but not others. What I do with the 16 foot length is coil it into a spiral of 4 turns. The diameter of the spiral is about 16 inches and the overall length of the spiral is about 24 inches. That should fit "behind the bushes". I use a piece of fiberglass rod to which to tiewrap the coils. There's nothing magic about the 16 foot length. It is only necessary if you need to vary your length from 0 to 31 feet. In actual practice with my 130 foot dipole, I only needed to vary the length from 0 to 23 feet so I made the "16 ft" section just another 8 foot section. The 16 foot section was required from 3.5-3.6 MHz and I never use those frequencies. That's why I could get away with replacing the 16 ft section with another 8 ft section. -- 73, Cecil, w5dxp.com |
multiband vertical
Richard Clark wrote:
I've been doing it with a binary switched coax matcher for 15 years. It occupies about half a cubic foot and tunes in increments of 1, 2, 4, 8, and 16 feet. Are you using 50 ohm coax to try to match to 50 ohms or just using it to vary the virtual impedance? -- 73, Cecil, w5dxp.com |
multiband vertical
On 18 Apr, 15:11, "Andre & Sharon Walker"
wrote: Wow..looks like I opened a can of worms here! Thanks to all for the many links and advice..much food for thought. I think ill have to re assess I was considering end fed longwire also, but an inverted V might be a better option. Anyway, should be on the air within 4 weeks...the licence is the easy bit, diverting funds for the radio from the XYL is the tricky part!!! But ive been offered a FT101z , inc Yaseu Desk mix + spare set of finals ( is too early to rember the number of the tubes off hand...just finished night shift), so ill have wind the wick WAY back to start with. I don't care what they say at the club...I like boat anchors!! ( I'd love to replace the Murphy B40 I sold 10 years ago :-( ) Cheers Andre"Owen Duffy" wrote in message ... Cecil Moore wrote in t: Andre & Sharon Walker wrote: I was hoping to get away from traps, but i dont think its possible :-(. I only have a smallish yard, with just 30m from the chimmny (brick ) to the back of the yard, so i think a decent wire antenna is out...but i am open to suggestions. I guess the other considerstion is to keep "she inside" happy . A 1/2WL dipole is 20m on 40m and can be made to work on all HF bands 40m-10m. That's probably what I would do and then do something romantic to keep the XYL happy. Cecil, Andre will not have access to most HF bands, just 80, 40, 15, and 10m. It takes about 6 hours to train and assess a Foundation Licencee, so your tunerless concept is perhaps more complex than Andre's current knowledge base. For example, I worked a FL chap a couple of days ago on 40m with a 80m half wave dipole fed with a long run of coax, and he was confident that his antenna worked real well, despite my expectation that it was likely that well less than 10% of his permitted 10W PEP was radiated. It was impossible to tell this chap that if he cut the dipole to half the length it would work better on 40m. It is no good telling people that an antenna isn't likely to work real good, they will cite all the contacts that they have had with it, and as we know, anything "works", doesn't it. However, most people listen to the positive suggestion that with change, and antenna will work better (and in the above case, more than 10 times the EIRP). Andre, keep it simple. A coax fed half wave dipole is easy to get going will limited knowledge and experience, and you should have a high confidence that you will be able to deliver a suitable load to your transmitter (ie it will deliver its rated power), and the antenna will be quite efficient (ie that most of your 10W PEP transmitter power is radiated). It will also work well on receive. If you hear strong FL signals around, they have good antennas, and / or are flaunting the power limit. It is easy to do the latter, but if you get the antenna right, you still have the room for improvement when you upgrade to the higher power limit. Owen- Hide quoted text - - Show quoted text - Andre you did indeed open a can of worms!, A vertical antenna is the most complicated thing in the world that even a newsgroup full of antenna experts are having difficulty in solving. It is quite possible that this thread will top a hundred replies before you arrive at the right question that they can answer. Cheers and beers Art |
multiband vertical
On Apr 19, 12:40 pm, Cecil Moore wrote:
Jimmie D wrote: Cecil, I was thinking of trying your no= tune antenna and the 16 ft piece may not be doable at my QTH, I have to keep it all hidden behind the bushes. Could this piece be replaced with a circuit using lumped LC values. That would work at one frequency but not others. What I do with the 16 foot length is coil it into a spiral of 4 turns. The diameter of the spiral is about 16 inches and the overall length of the spiral is about 24 inches. That should fit "behind the bushes". I use a piece of fiberglass rod to which to tiewrap the coils. There's nothing magic about the 16 foot length. It is only necessary if you need to vary your length from 0 to 31 feet. In actual practice with my 130 foot dipole, I only needed to vary the length from 0 to 23 feet so I made the "16 ft" section just another 8 foot section. The 16 foot section was required from 3.5-3.6 MHz and I never use those frequencies. That's why I could get away with replacing the 16 ft section with another 8 ft section. -- 73, Cecil, w5dxp.com Thanks Cecil, I have been wanting to put up an antenna like yours for quite a while now. Today I was doing a liittle clean up in the attic and found a box of DPDT open frame relays that should work well for remote switches. I should be able to run coax out to my garden shed and and ladder line from there to the antenna locating the switches at the shed. I can hang the dipole at about 40ft and was wondering what the pattern would be. I was thinking this low to the ground it would be almost an omni- directional antenna. If I could ever get all my crap organized I could probably put together one hell of a station. Jimmie |
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