Re: Topband: Bog wire
Ive had a single wire 600' BOG for a bit over a year and I must say Im impressed. Its partially on the ground and rises to 6-8" on ground hugging shrubs. It doesnt require a preamp, likely due to the poor ground here not bleeding off signal. Its quiet and less susceptible to crud from a neighbors house which is about 50-60' from its end as compared to a 2 wire reversible about 6-7' high and about the same horizontally. Im going to try a couple of 2 wire BOG's starting 600-800' away from any noise sources. Just got 2km of Army phone wire for $45. Carl KM1H - Original Message - From: "Bill Wichers" To: "Terry Conboy" Cc: Sent: Thursday, November 17, 2011 6:50 PM Subject: Topband: Bog wire > > I am curious why you specify "#18 Teflon" wire for the BOG wire you list > about 1/2 way down the page. Black polyethylene insulated wire would > hold up a lot better over time and would be far cheaper, so I'm curious > if there is some specific reason you would specify Teflon? The only > thing I can think of here is the velocity factor, which is only differs > from polyethylene about 4-5% and I wouldn't think would make much > difference with an on-ground wire anyway... > > -Bill > >> See http://www.w0uce.net/K2AVantennas.html > [snip] > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1411 / Virus Database: 2092/4022 - Release Date: 11/17/11 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: FS: Antenna related items
The BFS-1's are sold pending funds. Thanks, Julius Julius Fazekas N2WN Tennessee Contest Group http://k4tcg.org/ http://groups.google.com/group/tcg1?hl=en Tennessee QSO Party http://www.tnqp.org/ Elecraft K2 #4455 Elecraft K3/100 #366 Elecraft K3/100 # From: Julius Fazekas To: topband reflector Sent: Thursday, November 17, 2011 8:23 PM Subject: Topband: FS: Antenna related items I have a few items surplus to my needs: Four DXEngineering Beverage Feedpoint Matching System BFS-1 used (metal tabs on on two are a bit rough, but units in good condition, only out one season) $35 each (no resistors) plus shipping. Will sell all four for $100 plus shipping. T-74/CRT-3 RL-48 with AS-207/CRT-3 CNK wire, unused. This is from a "Gibson Girl" Radio Transmitter BC-778-A (SCR-578) or T-74/CRT-3 (for AN/CRT-3). The reel RL-48 inside a front-panel door holds 800 ft. of antenna wire W-148, which was made to be held aloft by either a box kite or balloon. Asking $50 shipped CONUS Drop me a note for pictures. 73, Julius Julius Fazekas N2WN Tennessee Contest Group http://k4tcg.org/ http://groups.google.com/group/tcg1?hl=en Tennessee QSO Party http://www.tnqp.org/ Elecraft K2 #4455 Elecraft K3/100 #366 Elecraft K3/100 # ___ UR RST IS ... ... ..9 QSB QSB - hw? BK ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: FS: Antenna related items
I have a few items surplus to my needs: Four DXEngineering Beverage Feedpoint Matching System BFS-1 used (metal tabs on on two are a bit rough, but units in good condition, only out one season) $35 each (no resistors) plus shipping. Will sell all four for $100 plus shipping. T-74/CRT-3 RL-48 with AS-207/CRT-3 CNK wire, unused. This is from a "Gibson Girl" Radio Transmitter BC-778-A (SCR-578) or T-74/CRT-3 (for AN/CRT-3). The reel RL-48 inside a front-panel door holds 800 ft. of antenna wire W-148, which was made to be held aloft by either a box kite or balloon. Asking $50 shipped CONUS Drop me a note for pictures. 73, Julius Julius Fazekas N2WN Tennessee Contest Group http://k4tcg.org/ http://groups.google.com/group/tcg1?hl=en Tennessee QSO Party http://www.tnqp.org/ Elecraft K2 #4455 Elecraft K3/100 #366 Elecraft K3/100 # ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Bog wire
I am curious why you specify "#18 Teflon" wire for the BOG wire you list about 1/2 way down the page. Black polyethylene insulated wire would hold up a lot better over time and would be far cheaper, so I'm curious if there is some specific reason you would specify Teflon? The only thing I can think of here is the velocity factor, which is only differs from polyethylene about 4-5% and I wouldn't think would make much difference with an on-ground wire anyway... -Bill > See http://www.w0uce.net/K2AVantennas.html [snip] ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Location of beverage close to 60 ft hill
On Thu, Nov 17, 2011 at 1:11 AM, Tom McAlee wrote: > > 1. Why the need to keep it 300' from the inverted L? ... My E/W > Beverage, which runs within 100' of my 160m TX vertical ... It is worth > noting that this antenna merely "passes by" one or more TX verticals within > 100'; the feedpoint is several hundred feet from any TX vertical and > doesn't line up with the base of any TX vertical in a targeted direction. > Nothing wrong at all with doing it like this. The way this Beverage was installed, the fairly deep null off its side was likely pointing at the vertical. However, pointing a Beverage at a TX vertical --and having the Beverage end close to it-- is asking for trouble. 73, Mike www.w0btu.com ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Another non-traditional antenna working.
See http://www.w0uce.net/K2AVantennas.html On 2011-11-16 12:22 PM, Rik van Riel wrote: > On 11/16/2011 12:10 AM, Guy Olinger K2AV wrote: >>> We are testing N3ND's new 160 antenna tonight (Monday local time) 1818 @ >>> 0005Z. This is another antenna based on RBN validated untraditional design. >>> 73, Guy. >> This is an up 70, over 60, down 5 wire fed via a feedline isolation >> transformer against a 5/16 wave single wire folded counterpoise at 8 >> feet. No radials. >> >> There is no way his small lot property could support a dense radial >> field, either buried or elevated. Therefore, presuming that undense >> irregular radials that would fit would be excessively lossy, per RBN >> data previously gathered, the +33, -33 foot linear folded counterpoise >> (FCP) is used instead, elevated at 8 feet. The folds in the >> counterpoise are designed to self-cancel fields as much as possible, >> thereby minimizing ground induction, which is loss to skywave > Is there more info available on this antenna? > > Especially a diagram (or crude drawing) of how things are > done would be appreciated. > > A NEC model would be fantastic, but I'd be more than happy > to prepare that from the crudest drawing anyone could send > me, and then make it available to everybody else :) > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Dimensions of K2AV folded counterpoise
I haven't been following this thread real close, but I folded the two 10' high elevated 1/4λ radials on my own 3/8λ inverted-L --per Guy's suggestion to me a two or three years ago-- as follows: Radial # 1: North about half-way (a little less than 1/8λ), then east 10', then south the rest of the way back, a little past the elevated feedpoint. Radial # 2: South about half-way, then east 10', then north the rest of the way back slightly past the elevated feedpoint. I just used whatever trees in the area were convenient. The radials were not perfectly laid out. Several of of us (including Guy, K2AV) with similar antennas got on 160 CW and compared signal strengths. With that antenna and those folded counterpoises, I then proceeded to work a number of DX stations on 160 CW running 600 watts. (I listened on my Beverages.) It was like shooting fish in a barrel. :-) I may put that antenna back up soon. 73, Mike www.w0btu.com On Thu, Nov 17, 2011 at 12:57 AM, Steve Ireland wrote: > ...I would be very interested - as am sure other users of this reflector > would > be - on what spacing you use between the folded wires on your counterpoise > system. > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Another non-traditional antenna working.
You sort of lost me a day or so Guy as the posts were getting way too long and boring (-; that I deleted after the first page. It appears that the FCP sort of took over the radial discussion somewhere along the way when I was sleeping and the subject line changed.. How about we leave the FCP to those who live in a mobile home or a place where the wife rules. I cant even fathom being stuck with a 10x70 yard! And then concentrate on the average suburban ham with maybe a 100x100 or 200x200 or so back yard to play in as that seems to be more the norm on here. At that prior QTH all I had was 100X200' to work with and the tower was about 30' from the side street (which happened to be due East and yet I had no problem in that direction after the mesh was installed), pure sand and stone for a ground, and no place to tie off an L top wire. Instead of endless discussions on copper wire radials of every length imaginable Im trying to get the point across that an in close and dense layer of plastic dipped fencing blows it all away and for little effort and money along with good longevity. Any radials added to the ends is pure gravy. That is far from a commercial quality installation as it wasnt uniform, length was about .09 wave, and the density was only partial since the fencing was put down as spokes. Lots of trees, brush, shed, and garage in the way. Not even close to ideal by any stretch. Carl KM1H - Original Message - From: "Guy Olinger K2AV" To: "ZR" Cc: ; ; Sent: Thursday, November 17, 2011 2:11 PM Subject: Re: Topband: Another non-traditional antenna working. > Hi, Carl, > > I repeat, a folded counterpoise is NO substitute for a dense and > uniform system, which is what you had in the end. > > My question for you is if you had a 70 x 10 foot strip of that rocky > stuff to construct a counterpoise, and that was all the space you had, > period, and your neighbors hated your guts, what could you have done > in that 70 x10 foot space? The FCP as a device is decidely NOT in > competition with any sturdy conceptual extension of the commercial > grade dense and uniform radial field. To anyone, if you can do dense > and uniform, then do dense and uniform. You will love it. You will > work lots of good stuff like Carl. You need not be concerned with any > of this thread. > > But if you can't do dense and uniform, then get decoupled from the > dirt. Absent dense and uniform, dirt (especially the rocky, sandy and > urban mishmash kind) is your enemy. > > N3ND is in a small lot, it can ONLY go THERE, PERIOD, kind of > situation. The only reason we haven't just totally disinherited him > and stripped him of his Master's degree in plotting and conniving for > backing himself into that kind of a corner (literally), is that it's a > wife's dream house kind of thing. Very pretty, very lovely, gorgeous. > > AND the FUN of it is, we've got him on 160 IN SPITE of that, without a > hint of going ugly :>) > > 73, Guy. > > On Thu, Nov 17, 2011 at 9:16 AM, ZR wrote: >> My 1988 CQ 160 top USA winner was a 90' shunt fed tower with a 10-20M >> stack >> of 4 el on top. It also accounted for over 200 countries in about 3 >> years. >> This was on a 1 acre lot and some of the Beverage feedlines were over >> 1000' >> long going into the woods out behind the development. Also friendly >> neighbors who allowed me to run the feeds. >> >> The ground was all sand and rock and the only thing that really worked >> was a >> mat of galvanized and plastic dipped rabbit fencing extending 50' from >> the >> base with about 60 random length radials out to 130' under it. With just >> the >> radials performance was only fair. >> >> Carl >> KM1H > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1411 / Virus Database: 2092/4022 - Release Date: 11/17/11 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Another non-traditional antenna working.
A diagram would help a lot. Even better if you show the current distribution. 74 Jon LA4RT, Trondheim, Norway ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Another non-traditional antenna working.
Ya... Camouflage works... Hi, Carl, I repeat, a folded counterpoise is NO substitute for a dense and uniform system, which is what you had in the end. My question for you is if you had a 70 x 10 foot strip of that rocky stuff to construct a counterpoise, and that was all the space you had, period, and your neighbors hated your guts, what could you have done in that 70 x10 foot space? The FCP as a device is decidely NOT in competition with any sturdy conceptual extension of the commercial grade dense and uniform radial field. To anyone, if you can do dense and uniform, then do dense and uniform. You will love it. You will work lots of good stuff like Carl. You need not be concerned with any of this thread. But if you can't do dense and uniform, then get decoupled from the dirt. Absent dense and uniform, dirt (especially the rocky, sandy and urban mishmash kind) is your enemy. N3ND is in a small lot, it can ONLY go THERE, PERIOD, kind of situation. The only reason we haven't just totally disinherited him and stripped him of his Master's degree in plotting and conniving for backing himself into that kind of a corner (literally), is that it's a wife's dream house kind of thing. Very pretty, very lovely, gorgeous. AND the FUN of it is, we've got him on 160 IN SPITE of that, without a hint of going ugly :>) 73, Guy. On Thu, Nov 17, 2011 at 9:16 AM, ZR wrote: > My 1988 CQ 160 top USA winner was a 90' shunt fed tower with a 10-20M > stack of 4 el on top. It also accounted for over 200 countries in > about 3 years. This was on a 1 acre lot and some of the Beverage > feedlines were over 1000' long going into the woods out behind the > development. Also friendly neighbors who allowed me to run the feeds. > > The ground was all sand and rock and the only thing that really worked > was a mat of galvanized and plastic dipped rabbit fencing extending > 50' from the base with about 60 random length radials out to 130' > under it. With just the radials performance was only fair. > > Carl > KM1H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Location of beverage close to 60 ft hill
Tom, I only have about 491 ft of window line and thats what I am using for the two direction beverage. Placement is in part dictated by the hill but mostly the rationalle for the 300 or so feet from the inverted L is that it has a lot of noise. It is terrible actually much of which is due to the McMansions they built in the farmers field next to me.. UGH! I didnt realize how good I had it. .. you know the ones.. they have several large screen plasma TVs and loud parties during football, baseball, hockey and basketball season. Geeze thats just about all year of interference. ANyhow over the last 5 years it has gotten progressively worse. I dont want to take a chance on ANY noise being picked up on the beverage and I thought that the hill would be a nice natural barrier and it just happens to be about 300 ft away. Hum I wonder .. leme see can I paint a target on the side of their houses and call in a JDAM strike to get rid of the noise.. OHH NO cant .. sorry thinking out loud again. Seriously.. it is all about mitigating as much noise as possible. Thanks to all of those that responded with encouragement during this effort. Jim WA3MEJ -- Message: 1 Date: Thu, 17 Nov 2011 02:11:52 -0500 From: "Tom McAlee" Subject: Re: Topband: Location of beverage close to 60 ft hill To: Message-ID: <09bf01cca4f8$31e41e60$95ac5b20$@com> Content-Type: text/plain;charset="UTF-8" Go for it. I live in the middle of the Appalachians and my Beverage wires go up and down many hills and valleys and cross many ravines and work great. On their worst day they still hear things my TX vertical couldn't hear on its best day :) > Comments Please 1. Why the need to keep it 300' from the inverted L? You can read a lot about how they should be far apart, but (outside of multiband contest stations where one radio is trying to listen on the Beverage while another is transmitting) it may not be so important in practice. I will explain my experience... A few years ago I put up 580' Beverage antennas for NW, NE, SE, and SW. I read that they should be far from the TX antennas, so the closest point from any of those RX antennas to any TX antenna is about 1000'. To cover the "missing" directions, I put up a 4 square receive antenna from a popular manufacturer. But, I found that the Beverage antennas were (usually, but not ALWAYS) better than the 4 square even in its favored directions. So, I decided to put up Beverages for N, E, S, and W also. N and S were no problem. But, when it came to E and W there was an issue. All of my Beverage antennas are installed on my neighbors property. It is 32 acres (surrounded east through west by 1.6 million acres of national forest!) but very "long". It is about 400' wide by about 3200' long with an odd triangle shape at the far end, all pointed slightly northwest. I am on the west side of that property. A 580' East/West Beverage would just not fit on his property unless I put it in that odd triangle area at the end, which was about 2500' from my house! Alternatively, I could put it in the area where his property and my property lined up. That would give me 800' E/W to work with, but it would mean that the Beverage would come within 100' of my TX vertical (and the miles upon miles of radial wires that lay on/in the ground around them). I consulted my friend and antenna mentor Frank, W3LPL. Frank suggested that I first put up the E/W Beverage where it was close to the TX vertical. If the noise wasn't any louder than it was on the other 6 Beverage directions it was fine. Otherwise, he recommended going the 2500' away route. I did as he suggested and it turned out to be just fine. My E/W Beverage, which runs within 100' of my 160m TX vertical and 80m vertical array, doesn't have any more noise than the other 6 directions whose combined closest point is 1000' away from the TX antennas (the furthest points are much further!) The S/N ratio on the E/W antenna is not discernibly different than the other 6 directions. If I were a multi-band (multi/multi or SO2R) contest station I suspect I would have issues trying to listen on that antenna while transmitting. But, for DXing purposes, it works very well. It is worth noting that this antenna merely "passes by" one or more TX verticals within 100'; the feedpoint is several hundred feet from any TX vertical and doesn't line up with the base of any TX vertical in a targeted direction. 2. You said your target was EU and AF. I have found (from southwestern VA where the bearings aren't much different than they are in MD) that an EU Beverage and an AF Beverage are two different antennas. At least with 580' antennas, 45 degrees is great to EU and northern AF while 90 degrees is great to central/southern AF (and ok to northern AF). A 580' Beverage pointed at E
Re: Topband: Another non-traditional antenna working.
Hi, Carl, I repeat, a folded counterpoise is NO substitute for a dense and uniform system, which is what you had in the end. My question for you is if you had a 70 x 10 foot strip of that rocky stuff to construct a counterpoise, and that was all the space you had, period, and your neighbors hated your guts, what could you have done in that 70 x10 foot space? The FCP as a device is decidely NOT in competition with any sturdy conceptual extension of the commercial grade dense and uniform radial field. To anyone, if you can do dense and uniform, then do dense and uniform. You will love it. You will work lots of good stuff like Carl. You need not be concerned with any of this thread. But if you can't do dense and uniform, then get decoupled from the dirt. Absent dense and uniform, dirt (especially the rocky, sandy and urban mishmash kind) is your enemy. N3ND is in a small lot, it can ONLY go THERE, PERIOD, kind of situation. The only reason we haven't just totally disinherited him and stripped him of his Master's degree in plotting and conniving for backing himself into that kind of a corner (literally), is that it's a wife's dream house kind of thing. Very pretty, very lovely, gorgeous. AND the FUN of it is, we've got him on 160 IN SPITE of that, without a hint of going ugly :>) 73, Guy. On Thu, Nov 17, 2011 at 9:16 AM, ZR wrote: > My 1988 CQ 160 top USA winner was a 90' shunt fed tower with a 10-20M stack > of 4 el on top. It also accounted for over 200 countries in about 3 years. > This was on a 1 acre lot and some of the Beverage feedlines were over 1000' > long going into the woods out behind the development. Also friendly > neighbors who allowed me to run the feeds. > > The ground was all sand and rock and the only thing that really worked was a > mat of galvanized and plastic dipped rabbit fencing extending 50' from the > base with about 60 random length radials out to 130' under it. With just the > radials performance was only fair. > > Carl > KM1H ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Topband: Radials
Moxon, G6XN once proposed using elevated radials that wereless than ¼ wavelength long, tied together and fed through a commoninductor.His idea was it would beeasier to achieve current and phase balance between the radials if they weren’tphysically resonant.I believe this waswritten up in one of the ARRL’s Antenna Compendiums.At the time I had my Butternut HF2V mounted about 20 feet aboveground with one radial for 80 meters that was approximately ¼ wavelengthlong.I replaced that one radial withtwo 1/8 wavelength radials and tied them to the base of the vertical through acommon inductor.I don’t remember muchabout that inductor other than that it was an old piece of B&W made from#14 or #16 wire.As you would expectany change to the values of inductance between the radials and the vertical affectedthe tuning of the whole antenna.Sincethis vertical is heavily loaded anyway, it wasn’t obvioushow I could tune it.I decided to construct a current probe froman old toroid core, some magnet wire, 1N34A diode, a capacitor, apotentiometer, and a milliameter.Thethought was to try a value of “radial inductor”, then tune the antenna toresonance using the vertical’s loading coils, and observe how much current wasflowing on the outside of the feedline below the antenna.I might be all wet but it seemed to me thatproperly balanced elevated radials would effectively “screen” anything underthem. After many iterations and carefully monitoring power into the antenna Iwas able to minimize the current measured on the outside of the feedlinedirectly below the antenna.After usingthis antenna over the course of the winter, I was able to conclude that 1) Icould affect the current on the outside of the feedline, and 2) I couldn’t seeany evidence at all that this antenna configuration was better or worse than anythingelse I had tried at this location. That was probably die to my poor QTH, down in a river valley and surrounded by suburban clyutter and noise. All antennas work poorly in a bad location. 73 Steve K0SR ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Another non-traditional antenna working.
My 1988 CQ 160 top USA winner was a 90' shunt fed tower with a 10-20M stack of 4 el on top. It also accounted for over 200 countries in about 3 years. This was on a 1 acre lot and some of the Beverage feedlines were over 1000' long going into the woods out behind the development. Also friendly neighbors who allowed me to run the feeds. The ground was all sand and rock and the only thing that really worked was a mat of galvanized and plastic dipped rabbit fencing extending 50' from the base with about 60 random length radials out to 130' under it. With just the radials performance was only fair. Carl KM1H - Original Message - From: To: Cc: ; Sent: Wednesday, November 16, 2011 9:33 PM Subject: Re: Topband: Another non-traditional antenna working. > not forgetting my 2010 CQWW 160 award (counter poise + 120 up 130 over) > > mike w7dra > > > On Wed, 16 Nov 2011 17:51:36 -0500 Guy Olinger K2AV > writes: >> This antenna started out as a "U", but in trimming it back to >> resonance (folded counterpoise plus isolation transformer plus >> antenna >> length), the down part of the "U"s up, over and down got nearly >> eliminated. There are four other stations using these who do not >> wish >> to be identified, who have used the counterpoise for significant >> improvements, but to my knowledge have not put up the antenna with >> all >> the recent "refinements for cause". >> >> On Wed, Nov 16, 2011 at 8:40 AM, W0UCE wrote: >> > Top Banders: >> > >> > Further to Guy's report, N3ND's Inverted U Antenna is the third >> operational >> > Top Band Antenna employing K2AV's Folded Counterpoise(FCP)versus >> raised or >> > buried radials. The other two are Inverted Ls with FCPs at K2AV >> and W0UCE. >> > >> > After downsizing to a small QTH with limited space for a Top Band >> antenna I >> > expected my Top Band days were over. Not the case... My inverted >> L vertical >> > section is only 46.5' but results have been good to include >> working JA, ZL >> > and VK. The same antenna is used on 80 meters with ten 25' buried >> copper >> > radials and a matching network designed by Guy. Switching bands >> is >> > accomplished using a vacuum relay at the feed point. >> > >> > Jack W0UCE >> > >> > >> > >> >> We are testing N3ND's new 160 antenna tonight (Monday local time) >> 1818 >> >> @ 0005Z. This is another antenna based on RBN validated >> untraditional >> >> design. 73, Guy. >> > >> > To see the RBN, go to http://reversebeacon.net/srch.php >> > >> > Type in N3ND, hit enter. Look for the 160m spots around 03z 15 >> Nov. The 03z >> > spots are at 400 watts. The 00z spots were at 100 watts, before >> the band >> > was really open to the SE. RBN's from two other stations in the >> area were >> > down by similar measure at 00z and up at 03z. >> > >> > This is an up 70, over 60, down 5 wire fed via a feedline >> isolation >> > transformer against a 5/16 wave single wire folded counterpoise at >> 8 feet. >> > No radials. >> > >> > There is no way his small lot property could support a dense >> radial field, >> > either buried or elevated. Therefore, presuming that undense >> irregular >> > radials that would fit would be excessively lossy, per RBN data >> previously >> > gathered, the +33, -33 foot linear folded counterpoise >> > (FCP) is used instead, elevated at 8 feet. The folds in the >> counterpoise >> > are designed to self-cancel fields as much as possible, thereby >> minimizing >> > ground induction, which is loss to skywave. The 66 foot straight >> line (more >> > or less, not critical) FCP footprint is much easier to place on >> property >> > than some miscellaneous attempt at a broadcast standard radial >> field. >> > >> > 73, Guy. >> > ___ >> > UR RST IS ... ... ..9 QSB QSB - hw? BK >> > >> > >> ___ >> UR RST IS ... ... ..9 QSB QSB - hw? BK >> > > 53 Year Old Mom Looks 33 > The Stunning Results of Her Wrinkle Trick Has Botox Doctors Worried > http://thirdpartyoffers.juno.com/TGL3141/4ec472c21fffd128dfbst02vuc > ___ > UR RST IS ... ... ..9 QSB QSB - hw? BK > > > - > No virus found in this message. > Checked by AVG - www.avg.com > Version: 10.0.1411 / Virus Database: 2092/4020 - Release Date: 11/16/11 > ___ UR RST IS ... ... ..9 QSB QSB - hw? BK
Re: Topband: Another non-traditional antenna working.
Hi, Richard, A bit of errata to correct my previous post: The difference in current will not be as large as I stated in my last post, because for the pair of 1/16 radials I did not divide the source current between the two 1/16 radials, and therefore the difference is not nearly as large. This came clear when I got the time to do a series of models on the loaded 1/16 to quantify sensitivity to coil resistance. The FCP is specified in the NEC 4 model literally as bare #12 copper wires, which they are in reality. My "analysis" is simply retelling the NEC4 calculated current on the wires and field strengths underneath. The specification manner for the wires in the model is very straight-forward and not subject to any of the "gotcha's" that can sometimes bedevil modeling. What one can say it behaves "like" is open to individual elaboration. I would point out that the three parallel wires all all in the same field, and that by itself discourages me from a description other than what NEC4 says the currents would be and field densities at the ground underneath. Further indication that quite different devices are in effect: With all loading out of both models, at the feedpoint, the 1/16 pair under the 125' vertical wire has -j626 ohms to tune out, but the FCP has only -j176 ohms. When the 626 is taken care of with 55 mH of coil, the 1.5:1 SWR bandwidth on the pair is 26 kHz. When the 176 is taken care of by pruning, the 1.5:1 SWR bandwidth is 51 kHz. L's with shorter vertical runs will be proportionately tighter bandwidth for both, making the SWR bandwidth on the loaded 1/16 an issue. Also for the loaded two 1/16 setup, particularly with shorter vertical runs in the radiator with higher feed current, the NEC4 model shows that method is hugely sensitive to the effective series resistance in the coil, and would need to be made of 1/4 inch copper tubing or the like, regardless of the power level, to keep it in the running. Coming up with the proper lumped resistance for the model to represent a given coil in a given situation IS problematic, but it is easy to prove sensitivity or not to coil resistance by gradually varying the resistance up from zero and rerunning the model. Even 5 ohms with a full size 125 foot vertical run costs nearly a dB. In your analysis you said "a" radial, but the FCP clearly has fields underneath proportional to the PAIR of loaded 33 foot radials. So it most looks like a PAIR of opposed 33 foot radials with reduced current. The loss in the FCP in NEC4 is not subject to assumptions about wire losses in coils or a representation of such as a transmission line device because the wires are literally modeled as bare #12 copper in their respective positions. Wire losses, current phases and magnitudes are simply computed by NEC4. Very straightforward. Overall, I think there is a reason why we aren't doing a lot of loaded dual 1/16 wave radials out there. If it worked it would be too much of an advantage, and ON4UN would have published it already. His break-even point would appear to be at the 4 loaded 1/8 wave radials, and I agree with him. 73, Guy On Wed, Nov 16, 2011 at 11:06 PM, Rick Karlquist wrote: > Guy Olinger K2AV wrote: > >> Counting FCP segments 1 through 5. 33 feet per segment. Directions >> used are for illustration only. >> >> 1: center to 33 feet east >> 2: 33 feet east back to center >> 3: center to 33 feet west >> 4: 33 feet west back to center >> 5: center to 33 feet east and end insulator. > > Your analysis IMHO doesn't take into account coupling between > the two conductors in the open wire line. I would characterize > the above as a 33 foot radial in series with two 33 foot > shorted stubs. A 33 foot shorted stub made of 600 ohm line > is equivalent to about 20 microhenries of inductance. > Two of those add up to 40 microhenries. This is close to the > 55 microhenry loading coil you mentioned. Using a shorted > stub of OWL to implement an inductor is an implementation > decision. It seems less lossy because it doesn't get hot; > the heat is spread out over a large area. But you still have > the copper losses of a considerable length of wire which > add up to a similar amount of loss that a big coil would have. > You're probably right that it's cheaper than a coil, at least > if you buy it new. Again, nothing wrong with doing this; > I'm sure it works, but there is nothing magic going on here. > It sounds like a nice ham-proof implementation of short elevated > radials, which can be tricky to install the usual way. > > I don't see how any of this improves bandwidth except > to the extent it adds loss to the system. There is a known > relationship between antenna size, bandwidth and efficiency. > Networks on the ground don't fundamentally affect this. > Replacing an inductor with a shorted stub is always detrimental > to bandwidth because the inductance of the shorted stub is > proportional to frequency, instead of constant like the > inductor. > > R
