Re: Topband: Radials on ground v FCP
I took my inspiration for the one turn counterpoise idea from HF Antenna For All Locations page 155, Fig 11.9(m). David G3UNA > On 09 January 2022 at 17:09 CUTTER DAVID via Topband > wrote: > > > Thanks, Rick. > > My particular circumstances limit me to a small triangle of ground in the > corner of a field and the FCP suits that very well. It would be interesting > to know how the FCP compares to something well known, like a broadcast > station ground. > > I like the idea of the spiral counterpoise: I experimented with a one turn > counterpoise in EZNEC > at 3 m above ground level. It looked workable but too big for my space, so, > I could make that into a spiral and perhaps not be too concerned about > symmetry. However, looking to Guy's idea of stacking the wires vertically so > they shade the ground underneath might be worth a try. Compressing things > always seems to limit bandwidth, so, that's something to be wary of. > > David G3UNA > > > > On 09 January 2022 at 16:22 "Richard (Rick) Karlquist" > > wrote: > > > > > > > > On 1/9/2022 4:51 AM, CUTTER DAVID via Topband wrote: > > > Hi Rob > > > > > > I see copper prices have doubled in the last year. > > > > > > My intention is to compare and contrast the cost and performance of short > > > verticals over a large field of ground radials v the very modest amount > > > of wire required for the FCP. In Guy's article > > > > > > > This is a false dichotomy between FCP and a broadcast station ground > > screen. The best use of wire is to have a small number of elevated > > tuned radials with proper RF choking. As shown by N6LF, you can do well > > with just 8 radials, about 100 feet long each. On 160 meters, they > > should be 20 feet high for optimum performance. BTW, cheap aluminum > > electric fence wire works perfectly for elevated radials Also consider > > N6BT's single spiral radial configuration as an alternative to FCP. > > > > Rick N6RK > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Radials on ground v FCP
On 1/9/2022 8:22 AM, Richard (Rick) Karlquist wrote: electric fence wire works perfectly for elevated radials Also consider N6BT's single spiral radial configuration as an alternative to FCP. Rick N6RK _ See: https://nextgenerationantennas.com/presentations-1 Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Radials on ground v FCP
Thanks, Rick. My particular circumstances limit me to a small triangle of ground in the corner of a field and the FCP suits that very well. It would be interesting to know how the FCP compares to something well known, like a broadcast station ground. I like the idea of the spiral counterpoise: I experimented with a one turn counterpoise in EZNEC at 3 m above ground level. It looked workable but too big for my space, so, I could make that into a spiral and perhaps not be too concerned about symmetry. However, looking to Guy's idea of stacking the wires vertically so they shade the ground underneath might be worth a try. Compressing things always seems to limit bandwidth, so, that's something to be wary of. David G3UNA > On 09 January 2022 at 16:22 "Richard (Rick) Karlquist" > wrote: > > > > On 1/9/2022 4:51 AM, CUTTER DAVID via Topband wrote: > > Hi Rob > > > > I see copper prices have doubled in the last year. > > > > My intention is to compare and contrast the cost and performance of short > > verticals over a large field of ground radials v the very modest amount of > > wire required for the FCP. In Guy's article > > > > This is a false dichotomy between FCP and a broadcast station ground > screen. The best use of wire is to have a small number of elevated > tuned radials with proper RF choking. As shown by N6LF, you can do well > with just 8 radials, about 100 feet long each. On 160 meters, they > should be 20 feet high for optimum performance. BTW, cheap aluminum > electric fence wire works perfectly for elevated radials Also consider > N6BT's single spiral radial configuration as an alternative to FCP. > > Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Radials on ground v FCP
On 1/9/2022 4:51 AM, CUTTER DAVID via Topband wrote: Hi Rob I see copper prices have doubled in the last year. My intention is to compare and contrast the cost and performance of short verticals over a large field of ground radials v the very modest amount of wire required for the FCP. In Guy's article This is a false dichotomy between FCP and a broadcast station ground screen. The best use of wire is to have a small number of elevated tuned radials with proper RF choking. As shown by N6LF, you can do well with just 8 radials, about 100 feet long each. On 160 meters, they should be 20 feet high for optimum performance. BTW, cheap aluminum electric fence wire works perfectly for elevated radials Also consider N6BT's single spiral radial configuration as an alternative to FCP. Rick N6RK _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Radials on ground v FCP
Hi Rob I see copper prices have doubled in the last year. My intention is to compare and contrast the cost and performance of short verticals over a large field of ground radials v the very modest amount of wire required for the FCP. In Guy's article https://k2av.com/Olinger_NCJ_article_on_FCP.pdf he says "The reason for the FCP is twofold: minimal space and a low-loss alternative to radials." I would add that it is also lower cost, to your point. I interpret his analysis as saying that the layout of the FCP minimises its own ground loss so well that only the radiator's ground loss is left to compare to the "gold standard" of 120 ground radials. I hope someone will jump in and correct me if I've misinterpreted that. If not, would it be correct to say that the FCP method of loss reduction differs only by 1.7 dB (from Guy's article) compared to the "gold standard" of 120 ground radials? I don't have that Griffith book, so, would you summarise the difference between 120 ground radials and the fewer radials proposed when using <1/4 w vertical? I'd like to get a feel for how it compares to the FCP method. 73 David G3UNA > On 08 January 2022 at 18:14 Rob Atkinson wrote: > > > I can't comment on the folded counterpoise because I am not familiar > with it. The "broadcast model" which I take to mean 120 radials is > used because in the case of a 90 degree tower on medium wave, the > earth current intensity is far enough from the feed point to > necessitate a higher number of radials so that as they diverge, they > are not so far apart from each other that the earth losses are > unacceptable. Few hams have 1/4 w. towers for 160 m., and instead > employ shorter vertical radiators such as inverted Ls* and Ts, (1/8 w. > for example) so the ground current intensity is high much closer to > the feedpoint. This means that fewer radials can be used because they > are shorter and at their ends, are still an acceptable separation from > each other. Of course, ground conductivity plays a part also. This > is good news for hams who want to save money on expensive wire. All > of this is detailed in the Griffith book I referenced previously. > > 73 > Rob > K5UJ > > *Unlike the T, the horizontal portion of the inverted L radiates. > W1BB recommended extending radials that run along underneath it if > possible, and I think that was good advice. > > On Sat, Jan 8, 2022 at 9:27 AM CUTTER DAVID wrote: > > > > Rob > > > > I recall a discussion on here some years ago which proposed that, whilst > > being an amazing antenna for top band, if you could achieve it, the > > broadcast model was not necessarily the best use of resources for amateur > > purposes, on the basis that broadcasters are mainly interested in ground > > wave to cover a defined relatively short range service area, whereas > > amateurs a more interested in dx. > > > > I don't recall how that discussion ended, but for purposes of saving wire, > > at least, the K2AV folded counterpoise (FCP) must be about as good as > > anyone could attain. How it performs against that broadcast model would be > > of interest. > > > > David G3UNA > _ > Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
Re: Topband: Radials on ground
Dear all, Anyone in Europe willing to sell its used 2nd ed. Griffith book? Please send me a private mail. Thanks, Seasons greetings, Michel, ON7EH -Original Message- From: Rob Atkinson Sent: Saturday, January 8, 2022 3:02 PM To: topband@contesting.com Subject: Re: Topband: Radials on ground For medium wave, every ham who transmits with a base excited vertical radiator should get a copy of _Radio-Electronic Transmission Fundamentals_ by B. Whitfield Griffith, Jr. 2nd ed., Noble Pub. Co., Atlanta Ga., c2000, ISBN 1884932134. 638 p. Griffith is a retired principal engineer with Continental. This classic college broadcast engineer textbook explains many fundamentals involving medium wave transmission in an easy to understand way. Getting the most out of your valuable copper wire is more important now than ever because copper has risen to insanely high prices. The book is probably out of print but might be available used from ABE Books https://www.abebooks.com/ 73 Rob K5UJ _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector _ Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
