Re: Topband: K2AV FCP with 43' vertical
Tom W8JI w...@w8ji.com wrote: Completely agree, but you didn't say how to get past the garden committee. :) 73, Guy. Thin wire or move. When I was in a townhome in Tampa I was able to use what is called paddle wire. This is 22 ga. steel wire painted in green enamel. It is used in crafts work for tying up plant stems for floral decorative work and is sold e.g. in the crafts dept in Walmart or Michaels etc. For antenna work it can't be easily soldered, is subject to kinking and may develop rust spots and probably can't well handle QRO. But, when run through trees is really hard to see. I used it as an end fed random wire for a good while on HF and it was the difference between being on-air or not. Being steel it is pretty strong. It is sold in bobbins that have to be unwound and straightened. ..just a suggestion. 73 Bob k2euh ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: K2AV FCP with 43' vertical
It's that thing about at the top that probably doesn't get past the garden committee. Folks don't really understand reactionary until you've crossed swords with the garden committee. Maybe something that slides INSIDE a fiberglass flag pole. I've heard some fairly suffocating stories from folks in HOA or garden committee situations asking FCP questions. 73, Guy On Tue, Jul 31, 2012 at 5:35 PM, Clive GM3POI gm3p...@btinternet.com wrote: Fair point Guy, I'd then suggest adding a relay at the top of the vertical to add in loading wires when on 160. Easily done and could be unseen. 73 Clive GM3POI -Original Message- From: guyk...@gmail.com [mailto:guyk...@gmail.com] On Behalf Of Guy Olinger K2AV Sent: 31 July 2012 21:26 To: Clive GM3POI Cc: Charles Damico; TopBand List Subject: Re: Topband: K2AV FCP with 43' vertical Well, If I'm getting it right, the 43' feet is being used on all bands, and there are approved by the garden committee kinds of issues. I don't argue with your general take in the least, but we are working in severely restrained circumstances in this thread, not laying out universal rules for the masses. For sure, some of the proper issues you list will not be within reach in this case, at least not without family or HOA repercussions. It IS possible to put up black wire in trees and construct a system that can't be seen from the street. One fellow (call him Danny Boy to protect anonymity) put up poles supporting an FCP, and tortuous threading of black insulated #12, and a matching box, all with camoflauge painting. Invisible from the street even if you know where it is. Wifey came home expecting to be upset, Danny Boy had been pushy about it all, and she could not see it from the street even when told where to look. Neighborhood folks have been over since, Dinner out on the patio, barely 50 feet from the thing in full view, and noone noticed. (Ah, there is a REASON why camouflage works.) I don't think everybody has Danny Boy's chutzpaz. So I take these 43 foot inquiries seriously, rather than suggesting a divorce and moving away. Have to raise all the issues and possibilities to enable the fellow that's living on the scene. In the end, only he knows what can be gotten away with. Scaring about high currents and losses gives him reasons to involve in his choice. 73, Guy. On Tue, Jul 31, 2012 at 5:02 PM, Clive GM3POI gm3p...@btinternet.com wrote: Why would anyone use just 43ft of vertical without at least top loading the vertical section.? Without considering maximizing the antenna efficiency, I don't think considering losses in matching coils is valid. Not many people know this but my 160m vertical is but 51ft tall, top loaded but has sufficient ground radials to bring the overall losses down to a low figure. My overall point is the equation for efficiency relies on minimising ground losses irrespective of antenna height as per Brown Lewis and Epstein. This should be the object of anyone seeking to improve their 160m antenna. 73 Clive GM3POI -Original Message- From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] On Behalf Of Guy Olinger K2AV Sent: 31 July 2012 19:44 To: Charles Damico Cc: TopBand List Subject: Re: Topband: K2AV FCP with 43' vertical Hi, Charles, The short, short twitter answer: 43 feet is too d*mn short for 160. Do something else. Merely short answer: Yes, you can use an FCP. But... Hate to say it's the wrong question, sounds too much like a put down which I don't intend. The real question is why use a 43 foot vertical with that antenna's hypersensitivity to loss issues on 160. 43' on 160 is a very short antenna, electrically. A model of it with four full size radials and all sources of loss removed shows a radiation resistance of 2.6 ohms (two point six), and a feed current in the neighborhood of 25 amps. Over dirt it's possible you are down TWO S units, depending on exactly what you meant by four radials, plus other loss factors. Do you have to use the 43' on 160? If you really do, that's one direction. If you can substitute an L, that's another direction. Long answer: To answer your first question, you would be the first that I know of considering this combination. Rare I think, because there are such better alternatives for a small lot without all the downsides. The downsides are fairly extreme, and why so is worth a few paragraphs. Very short solutions have certain characteristics, a natural very low radiation resistance, very high current levels, and a very narrow SWR bandwidth. The way to assess these is to model an lossless environment. We'll use 43' over four 125' raised radials at 8 feet, made of zero resistance conductors and over salt water to eliminate ground losses. Magically in the model we have a transmitter right at the feed point, which has a very large matching range to deal
Re: Topband: K2AV FCP with 43' vertical
It's that thing about at the top that probably doesn't get past the garden committee. Folks don't really understand reactionary until you've crossed swords with the garden committee. Maybe something that slides INSIDE a fiberglass flag pole. The major problem with ANY 43 ft vertical is it is nearly like a mobile antenna on 160. Unless the system has huge losses, RF voltages are off the map. With low-loss ground systems and loading coils, even the voltage across a base loading coil is far too high for any reasonable relay. (I know there have been articles that say otherwise, but I modeled systems and I actually tested several on 160 meters.) With a modest ground system, high-Q loading coil, and very good base insulator, and with only 500 watts applied, arcing distance for connections across the coil or from base to ground, was nearly one inch through moderately dry air at sharp points. If I wanted to run higher power with a 43ft vertical on 160, I'd just add two or three wires from the top that could fold in and be tied to the antenna at the bottom. Then, on 160 and 80, they could be fanned out away from the base and a modest amount of base load used on 160. Top loading with a hat not only gives *up to* four times the radiation resistance (reducing ground losses), it increases bandwidth and makes base voltages tolerable. Or you can just do like the original design plan called for. Have so much distributed loss voltages never get high. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: K2AV FCP with 43' vertical
Completely agree, but you didn't say how to get past the garden committee. :) 73, Guy. On Wed, Aug 1, 2012 at 8:31 AM, Tom W8JI w...@w8ji.com wrote: It's that thing about at the top that probably doesn't get past the garden committee. Folks don't really understand reactionary until you've crossed swords with the garden committee. Maybe something that slides INSIDE a fiberglass flag pole. The major problem with ANY 43 ft vertical is it is nearly like a mobile antenna on 160. Unless the system has huge losses, RF voltages are off the map. With low-loss ground systems and loading coils, even the voltage across a base loading coil is far too high for any reasonable relay. (I know there have been articles that say otherwise, but I modeled systems and I actually tested several on 160 meters.) With a modest ground system, high-Q loading coil, and very good base insulator, and with only 500 watts applied, arcing distance for connections across the coil or from base to ground, was nearly one inch through moderately dry air at sharp points. If I wanted to run higher power with a 43ft vertical on 160, I'd just add two or three wires from the top that could fold in and be tied to the antenna at the bottom. Then, on 160 and 80, they could be fanned out away from the base and a modest amount of base load used on 160. Top loading with a hat not only gives *up to* four times the radiation resistance (reducing ground losses), it increases bandwidth and makes base voltages tolerable. Or you can just do like the original design plan called for. Have so much distributed loss voltages never get high. 73 Tom ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: K2AV FCP with 43' vertical
Completely agree, but you didn't say how to get past the garden committee. :) 73, Guy. Thin wire or move. ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: K2AV FCP with 43' vertical
Hi, Charles, The short, short twitter answer: 43 feet is too d*mn short for 160. Do something else. Merely short answer: Yes, you can use an FCP. But... Hate to say it's the wrong question, sounds too much like a put down which I don't intend. The real question is why use a 43 foot vertical with that antenna's hypersensitivity to loss issues on 160. 43' on 160 is a very short antenna, electrically. A model of it with four full size radials and all sources of loss removed shows a radiation resistance of 2.6 ohms (two point six), and a feed current in the neighborhood of 25 amps. Over dirt it's possible you are down TWO S units, depending on exactly what you meant by four radials, plus other loss factors. Do you have to use the 43' on 160? If you really do, that's one direction. If you can substitute an L, that's another direction. Long answer: To answer your first question, you would be the first that I know of considering this combination. Rare I think, because there are such better alternatives for a small lot without all the downsides. The downsides are fairly extreme, and why so is worth a few paragraphs. Very short solutions have certain characteristics, a natural very low radiation resistance, very high current levels, and a very narrow SWR bandwidth. The way to assess these is to model an lossless environment. We'll use 43' over four 125' raised radials at 8 feet, made of zero resistance conductors and over salt water to eliminate ground losses. Magically in the model we have a transmitter right at the feed point, which has a very large matching range to deal with complex impedances with low single digit resistance and up to 1000 ohms capacitive reactance. Also have other magic in models, wires that support themselves above ground, etc, but I digress... We'll be using NEC4 engine in W7EL's EZNEC Pro, and the Sommerfeld ground approximation method aka high accuracy. There is controversy about accuracy of currently available modeling programs for sparse radials like yours, a really good case that ground loss is UNDER-estimated, but again I digress... Going to try and do this in a manner that skirts those issues. At 1500 watts on the lossless antenna, the peak current on the vertical is 24 amperes, and the feed impedance is 2.6 ohms -j986 reactance. Not a typo, that's two point six ohms. The peak gain is 4.68 dBi. Eliminating the capacitive reactance of the short radiator takes 86 uH to get 2.6 +j0. 86 uH is quite the large coil, but in this example it's made of super-conducting wire. The 2:1 SWR bandwidth is 3 kHz (yes, that's THREE kHz). Now let's start to inject reality, dirt, etc. Any increase in resistance above 2.6 ohms is ALL due to loss. Any broadening of the 2:1 SWR bandwidth of 3 kHz is due to loss. Let's change the ground medium in the model from over salt water to EZNEC's average dirt, and change the conductors to copper. The feed R goes to 4 ohms. The max gain drops to -0.72 dBi. The 2: 1 SWR bandwidth goes to 5 kHz. The peak current drops to 19.2 amps. If we add a conservative 5 ohms for the effective series resistance (ESR) of the huge loading coil necessary to provide 86 uH inductance to tune the antenna, the current drops to 12.8 amps, the gain to -4.2 dBi (), the feed R is up to 9 ohms, and the 2:1 SWR bandwidth is a semi-usable 10 kHz. In the coil, the current squared times 5 ohms is around 800 watts dissipated in the coil. The heat loss in the coil at QRO, particularly inside a protective enclosure that can trap heat, will be hot enough to soften the plastic bars used to support coil stock and cause them to get gravity droops, or be destroyed, perhaps set the whole thing on fire. I have destroyed similar components myself in years past, unaware of the level of current. We are the kings of burning things up, Jack and I, but I digress... At 100 watts, the dB loss is the same but the power dissipation is not large enough to signal the degree of loss by deforming or destroying things. If we add in Guy's personal pessimistic adjustment for NEC's underestimation of ground losses at MF in these kinds of sparse radial situations (only 4 elevated radials) , the gain drops toward -6 dbi. Ten dB below perfect, and more than an S-unit less than easily obtainable with an L over an FCP. The killer is the coil. You could do something with silver plated 1/4 inch copper tubing to get the ESR of the coil down, to where the losses in the dirt were controlling. Yes, the FCP will improve things, and raise the feed Z some, but you are now running the isolation transformer at current levels we haven't had running for two years watching results. 43 feet and 160m takes you into the land of compromises. You expect these kinds of losses in low band mobile installations, you don't expect fixed stations to be constrained in this manner. 73, Guy On Sat, Jul 28, 2012 at 11:22 AM, Charles Damico frontsigh...@yahoo.comwrote: I would like to hear from
Re: Topband: K2AV FCP with 43' vertical
Why would anyone use just 43ft of vertical without at least top loading the vertical section.? Without considering maximizing the antenna efficiency, I don't think considering losses in matching coils is valid. Not many people know this but my 160m vertical is but 51ft tall, top loaded but has sufficient ground radials to bring the overall losses down to a low figure. My overall point is the equation for efficiency relies on minimising ground losses irrespective of antenna height as per Brown Lewis and Epstein. This should be the object of anyone seeking to improve their 160m antenna. 73 Clive GM3POI -Original Message- From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] On Behalf Of Guy Olinger K2AV Sent: 31 July 2012 19:44 To: Charles Damico Cc: TopBand List Subject: Re: Topband: K2AV FCP with 43' vertical Hi, Charles, The short, short twitter answer: 43 feet is too d*mn short for 160. Do something else. Merely short answer: Yes, you can use an FCP. But... Hate to say it's the wrong question, sounds too much like a put down which I don't intend. The real question is why use a 43 foot vertical with that antenna's hypersensitivity to loss issues on 160. 43' on 160 is a very short antenna, electrically. A model of it with four full size radials and all sources of loss removed shows a radiation resistance of 2.6 ohms (two point six), and a feed current in the neighborhood of 25 amps. Over dirt it's possible you are down TWO S units, depending on exactly what you meant by four radials, plus other loss factors. Do you have to use the 43' on 160? If you really do, that's one direction. If you can substitute an L, that's another direction. Long answer: To answer your first question, you would be the first that I know of considering this combination. Rare I think, because there are such better alternatives for a small lot without all the downsides. The downsides are fairly extreme, and why so is worth a few paragraphs. Very short solutions have certain characteristics, a natural very low radiation resistance, very high current levels, and a very narrow SWR bandwidth. The way to assess these is to model an lossless environment. We'll use 43' over four 125' raised radials at 8 feet, made of zero resistance conductors and over salt water to eliminate ground losses. Magically in the model we have a transmitter right at the feed point, which has a very large matching range to deal with complex impedances with low single digit resistance and up to 1000 ohms capacitive reactance. Also have other magic in models, wires that support themselves above ground, etc, but I digress... We'll be using NEC4 engine in W7EL's EZNEC Pro, and the Sommerfeld ground approximation method aka high accuracy. There is controversy about accuracy of currently available modeling programs for sparse radials like yours, a really good case that ground loss is UNDER-estimated, but again I digress... Going to try and do this in a manner that skirts those issues. At 1500 watts on the lossless antenna, the peak current on the vertical is 24 amperes, and the feed impedance is 2.6 ohms -j986 reactance. Not a typo, that's two point six ohms. The peak gain is 4.68 dBi. Eliminating the capacitive reactance of the short radiator takes 86 uH to get 2.6 +j0. 86 uH is quite the large coil, but in this example it's made of super-conducting wire. The 2:1 SWR bandwidth is 3 kHz (yes, that's THREE kHz). Now let's start to inject reality, dirt, etc. Any increase in resistance above 2.6 ohms is ALL due to loss. Any broadening of the 2:1 SWR bandwidth of 3 kHz is due to loss. Let's change the ground medium in the model from over salt water to EZNEC's average dirt, and change the conductors to copper. The feed R goes to 4 ohms. The max gain drops to -0.72 dBi. The 2: 1 SWR bandwidth goes to 5 kHz. The peak current drops to 19.2 amps. If we add a conservative 5 ohms for the effective series resistance (ESR) of the huge loading coil necessary to provide 86 uH inductance to tune the antenna, the current drops to 12.8 amps, the gain to -4.2 dBi (), the feed R is up to 9 ohms, and the 2:1 SWR bandwidth is a semi-usable 10 kHz. In the coil, the current squared times 5 ohms is around 800 watts dissipated in the coil. The heat loss in the coil at QRO, particularly inside a protective enclosure that can trap heat, will be hot enough to soften the plastic bars used to support coil stock and cause them to get gravity droops, or be destroyed, perhaps set the whole thing on fire. I have destroyed similar components myself in years past, unaware of the level of current. We are the kings of burning things up, Jack and I, but I digress... At 100 watts, the dB loss is the same but the power dissipation is not large enough to signal the degree of loss by deforming or destroying things. If we add in Guy's personal pessimistic adjustment for NEC's underestimation of ground losses
Re: Topband: K2AV FCP with 43' vertical
Well, If I'm getting it right, the 43' feet is being used on all bands, and there are approved by the garden committee kinds of issues. I don't argue with your general take in the least, but we are working in severely restrained circumstances in this thread, not laying out universal rules for the masses. For sure, some of the proper issues you list will not be within reach in this case, at least not without family or HOA repercussions. It IS possible to put up black wire in trees and construct a system that can't be seen from the street. One fellow (call him Danny Boy to protect anonymity) put up poles supporting an FCP, and tortuous threading of black insulated #12, and a matching box, all with camoflauge painting. Invisible from the street even if you know where it is. Wifey came home expecting to be upset, Danny Boy had been pushy about it all, and she could not see it from the street even when told where to look. Neighborhood folks have been over since, Dinner out on the patio, barely 50 feet from the thing in full view, and noone noticed. (Ah, there is a REASON why camouflage works.) I don't think everybody has Danny Boy's chutzpaz. So I take these 43 foot inquiries seriously, rather than suggesting a divorce and moving away. Have to raise all the issues and possibilities to enable the fellow that's living on the scene. In the end, only he knows what can be gotten away with. Scaring about high currents and losses gives him reasons to involve in his choice. 73, Guy. On Tue, Jul 31, 2012 at 5:02 PM, Clive GM3POI gm3p...@btinternet.com wrote: Why would anyone use just 43ft of vertical without at least top loading the vertical section.? Without considering maximizing the antenna efficiency, I don't think considering losses in matching coils is valid. Not many people know this but my 160m vertical is but 51ft tall, top loaded but has sufficient ground radials to bring the overall losses down to a low figure. My overall point is the equation for efficiency relies on minimising ground losses irrespective of antenna height as per Brown Lewis and Epstein. This should be the object of anyone seeking to improve their 160m antenna. 73 Clive GM3POI -Original Message- From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] On Behalf Of Guy Olinger K2AV Sent: 31 July 2012 19:44 To: Charles Damico Cc: TopBand List Subject: Re: Topband: K2AV FCP with 43' vertical Hi, Charles, The short, short twitter answer: 43 feet is too d*mn short for 160. Do something else. Merely short answer: Yes, you can use an FCP. But... Hate to say it's the wrong question, sounds too much like a put down which I don't intend. The real question is why use a 43 foot vertical with that antenna's hypersensitivity to loss issues on 160. 43' on 160 is a very short antenna, electrically. A model of it with four full size radials and all sources of loss removed shows a radiation resistance of 2.6 ohms (two point six), and a feed current in the neighborhood of 25 amps. Over dirt it's possible you are down TWO S units, depending on exactly what you meant by four radials, plus other loss factors. Do you have to use the 43' on 160? If you really do, that's one direction. If you can substitute an L, that's another direction. Long answer: To answer your first question, you would be the first that I know of considering this combination. Rare I think, because there are such better alternatives for a small lot without all the downsides. The downsides are fairly extreme, and why so is worth a few paragraphs. Very short solutions have certain characteristics, a natural very low radiation resistance, very high current levels, and a very narrow SWR bandwidth. The way to assess these is to model an lossless environment. We'll use 43' over four 125' raised radials at 8 feet, made of zero resistance conductors and over salt water to eliminate ground losses. Magically in the model we have a transmitter right at the feed point, which has a very large matching range to deal with complex impedances with low single digit resistance and up to 1000 ohms capacitive reactance. Also have other magic in models, wires that support themselves above ground, etc, but I digress... We'll be using NEC4 engine in W7EL's EZNEC Pro, and the Sommerfeld ground approximation method aka high accuracy. There is controversy about accuracy of currently available modeling programs for sparse radials like yours, a really good case that ground loss is UNDER-estimated, but again I digress... Going to try and do this in a manner that skirts those issues. At 1500 watts on the lossless antenna, the peak current on the vertical is 24 amperes, and the feed impedance is 2.6 ohms -j986 reactance. Not a typo, that's two point six ohms. The peak gain is 4.68 dBi. Eliminating the capacitive reactance of the short radiator takes 86 uH to get 2.6 +j0. 86 uH
Re: Topband: K2AV FCP with 43' vertical
Fair point Guy, I'd then suggest adding a relay at the top of the vertical to add in loading wires when on 160. Easily done and could be unseen. 73 Clive GM3POI -Original Message- From: guyk...@gmail.com [mailto:guyk...@gmail.com] On Behalf Of Guy Olinger K2AV Sent: 31 July 2012 21:26 To: Clive GM3POI Cc: Charles Damico; TopBand List Subject: Re: Topband: K2AV FCP with 43' vertical Well, If I'm getting it right, the 43' feet is being used on all bands, and there are approved by the garden committee kinds of issues. I don't argue with your general take in the least, but we are working in severely restrained circumstances in this thread, not laying out universal rules for the masses. For sure, some of the proper issues you list will not be within reach in this case, at least not without family or HOA repercussions. It IS possible to put up black wire in trees and construct a system that can't be seen from the street. One fellow (call him Danny Boy to protect anonymity) put up poles supporting an FCP, and tortuous threading of black insulated #12, and a matching box, all with camoflauge painting. Invisible from the street even if you know where it is. Wifey came home expecting to be upset, Danny Boy had been pushy about it all, and she could not see it from the street even when told where to look. Neighborhood folks have been over since, Dinner out on the patio, barely 50 feet from the thing in full view, and noone noticed. (Ah, there is a REASON why camouflage works.) I don't think everybody has Danny Boy's chutzpaz. So I take these 43 foot inquiries seriously, rather than suggesting a divorce and moving away. Have to raise all the issues and possibilities to enable the fellow that's living on the scene. In the end, only he knows what can be gotten away with. Scaring about high currents and losses gives him reasons to involve in his choice. 73, Guy. On Tue, Jul 31, 2012 at 5:02 PM, Clive GM3POI gm3p...@btinternet.com wrote: Why would anyone use just 43ft of vertical without at least top loading the vertical section.? Without considering maximizing the antenna efficiency, I don't think considering losses in matching coils is valid. Not many people know this but my 160m vertical is but 51ft tall, top loaded but has sufficient ground radials to bring the overall losses down to a low figure. My overall point is the equation for efficiency relies on minimising ground losses irrespective of antenna height as per Brown Lewis and Epstein. This should be the object of anyone seeking to improve their 160m antenna. 73 Clive GM3POI -Original Message- From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] On Behalf Of Guy Olinger K2AV Sent: 31 July 2012 19:44 To: Charles Damico Cc: TopBand List Subject: Re: Topband: K2AV FCP with 43' vertical Hi, Charles, The short, short twitter answer: 43 feet is too d*mn short for 160. Do something else. Merely short answer: Yes, you can use an FCP. But... Hate to say it's the wrong question, sounds too much like a put down which I don't intend. The real question is why use a 43 foot vertical with that antenna's hypersensitivity to loss issues on 160. 43' on 160 is a very short antenna, electrically. A model of it with four full size radials and all sources of loss removed shows a radiation resistance of 2.6 ohms (two point six), and a feed current in the neighborhood of 25 amps. Over dirt it's possible you are down TWO S units, depending on exactly what you meant by four radials, plus other loss factors. Do you have to use the 43' on 160? If you really do, that's one direction. If you can substitute an L, that's another direction. Long answer: To answer your first question, you would be the first that I know of considering this combination. Rare I think, because there are such better alternatives for a small lot without all the downsides. The downsides are fairly extreme, and why so is worth a few paragraphs. Very short solutions have certain characteristics, a natural very low radiation resistance, very high current levels, and a very narrow SWR bandwidth. The way to assess these is to model an lossless environment. We'll use 43' over four 125' raised radials at 8 feet, made of zero resistance conductors and over salt water to eliminate ground losses. Magically in the model we have a transmitter right at the feed point, which has a very large matching range to deal with complex impedances with low single digit resistance and up to 1000 ohms capacitive reactance. Also have other magic in models, wires that support themselves above ground, etc, but I digress... We'll be using NEC4 engine in W7EL's EZNEC Pro, and the Sommerfeld ground approximation method aka high accuracy. There is controversy about accuracy of currently available modeling programs for sparse radials like yours, a really good case that ground loss is UNDER-estimated
Re: Topband: K2AV FCP with 43' vertical
As usual, Guy is once again on target. How do I know? I, was a secret member of the team, that went to the house that Danny Boy owns to put up 80 and 160m FCPs that Guy designed for an Inverted U that Danny Boy's XYL can't see. I also hid my 43 foot Rohn 25 tower from view amongst some pine trees. Why? You may ask... 43' you may ask and the answer is, at 44' (1 Foot Mast) my Hexigonal Beam cannot be seen even by the neighbors next door. I sprayed it with brown, black, blue and gray paint in patterns reminiscent of what I wore on a daily basis during my time in Vietnam during the war. Anyone remember those days. Camouflage works... During my two years in Nam - I did not endure the pain of a VC or NVA AK-47 round penetrating my clothing. And in the past three years, not a single person, even the HOA has had one negative thing to say about my 43' tower - Nope... my 80/160 Inverted L and FCP are not suspended from my Tower? - What Tower? Well, If I'm getting it right, the 43' feet is being used on all bands, and there are approved by the garden committee kinds of issues. I don't argue with your general take in the least, but we are working in severely restrained circumstances in this thread, not laying out universal rules for the masses. For sure, some of the proper issues you list will not be within reach in this case, at least not without family or HOA repercussions. It IS possible to put up black wire in trees and construct a system that can't be seen from the street. One fellow (call him Danny Boy to protect anonymity) put up poles supporting an FCP, and tortuous threading of black insulated #12, and a matching box, all with camoflauge painting. Invisible from the street even if you know where it is. Wifey came home expecting to be upset, Danny Boy had been pushy about it all, and she could not see it from the street even when told where to look. Neighborhood folks have been over since, Dinner out on the patio, barely 50 feet from the thing in full view, and noone noticed. (Ah, there is a REASON why camouflage works.) I don't think everybody has Danny Boy's chutzpaz. So I take these 43 foot inquiries seriously, rather than suggesting a divorce and moving away. Have to raise all the issues and possibilities to enable the fellow that's living on the scene. In the end, only he knows what can be gotten away with. Scaring about high currents and losses gives him reasons to involve in his choice. 73, Guy. On Tue, Jul 31, 2012 at 5:02 PM, Clive GM3POI gm3p...@btinternet.com wrote: Why would anyone use just 43ft of vertical without at least top loading the vertical section.? Without considering maximizing the antenna efficiency, I don't think considering losses in matching coils is valid. Not many people know this but my 160m vertical is but 51ft tall, top loaded but has sufficient ground radials to bring the overall losses down to a low figure. My overall point is the equation for efficiency relies on minimising ground losses irrespective of antenna height as per Brown Lewis and Epstein. This should be the object of anyone seeking to improve their 160m antenna. 73 Clive GM3POI -Original Message- From: topband-boun...@contesting.com [mailto:topband-boun...@contesting.com] On Behalf Of Guy Olinger K2AV Sent: 31 July 2012 19:44 To: Charles Damico Cc: TopBand List Subject: Re: Topband: K2AV FCP with 43' vertical Hi, Charles, The short, short twitter answer: 43 feet is too d*mn short for 160. Do something else. Merely short answer: Yes, you can use an FCP. But... Hate to say it's the wrong question, sounds too much like a put down which I don't intend. The real question is why use a 43 foot vertical with that antenna's hypersensitivity to loss issues on 160. 43' on 160 is a very short antenna, electrically. A model of it with four full size radials and all sources of loss removed shows a radiation resistance of 2.6 ohms (two point six), and a feed current in the neighborhood of 25 amps. Over dirt it's possible you are down TWO S units, depending on exactly what you meant by four radials, plus other loss factors. Do you have to use the 43' on 160? If you really do, that's one direction. If you can substitute an L, that's another direction. Long answer: To answer your first question, you would be the first that I know of considering this combination. Rare I think, because there are such better alternatives for a small lot without all the downsides. The downsides are fairly extreme, and why so is worth a few paragraphs. Very short solutions have certain characteristics, a natural very low radiation resistance, very high current levels, and a very narrow SWR bandwidth. The way to assess these is to model an lossless environment. We'll use 43' over four 125' raised radials at 8 feet, made of zero resistance conductors and over salt water to eliminate ground losses. Magically in the model we have
Re: Topband: K2AV FCP with 43' vertical
Hi Jim, The FCP isolation transformer is not a balun. It does NOT have a common connection between the primary and secondary. It is NOT broadband, which is a specific goal of a balun. On the Balun Designs web page www.balundesigns.com it is listed as FCP transformer. It is an RF transformer, and has residual inductive reactance that has to be tuned out in one way or another. In the simple inverted L plus isolation transformer plus FCP configuration, the left-over capacitive reactance from the FCP is roughly equal to the inductive reactance of the isolation transformer. Neither device is resonant by itself. They are resonant overall when used in tandem. The FCP isolation transformer is specific to a single band. It takes extra switched in/out tuning network circuitry to use a single FCP isolation transformer on more than one band. Its winding ratio is 1:1. It's particular purpose is to not allow ANY direct path between the ANT/FCP and the coax side. One wire in the winding is connected to the FCP and antenna. The other wire is connected between the coax center conductor and coax shield. The 43' radiator has a number of problems on 160 which I am addressing in a separate post. It's feed impedance is but one of them. 73, Guy. On Sat, Jul 28, 2012 at 9:30 PM, Jim WA9YSD wa9...@yahoo.com wrote: Call Balun Designs you can purchase an 1:2 un to un balun. Here you have a true way to feed a vertical. It works well for me. If you can measure your input impedance at the feed point. It should be around 25 to 35 ohms. You may have to re tune the vertical 43 feet is not exactly a quarter wave resonate on any ham band. Resonate freq should be around 5.4mhz you may have to add some aluminum wire. The K2AV FPC balun is a 1:2 unbalanced to balanced balun. The same company sells these as well. Stay on course, fight a good fight, and keep the faith.Jim K9TF/WA9YSD ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
