That's the paper I was referring to earlier. Really useful for 160m folks! Charlie, K4OTV
-----Original Message----- From: Topband [mailto:[email protected]] On Behalf Of DAVID CUTHBERT Sent: Wednesday, December 12, 2012 6:14 PM To: Guy Olinger K2AV Cc: [email protected]; [email protected]; Ashton Lee Subject: Re: Topband: Fw: GAP VERTICAL QUESTION Guy, you make it sound like magic. See the IEEE paper RADIATION EFFICIENCY AND INPUT IMPEDANCE OF MONOPOLE ELEMENTS WITH RADIAL-WIRE GROUND PLANES IN PROXIMITY TO EARTH Dave WX7G On Dec 12, 2012 3:13 PM, "Guy Olinger K2AV" <[email protected]> wrote: > Not all loss is visible as series resistance in the counterpoise > system, which is the tack you are taking. Note that a dummy load is > 50 ohms, and does not radiate worth a hoot. > > It takes modeling to identify some situations. One of my favorites in > NEC4 results in a max gain of -18 dBi or so. This is compared to a > commercial BC 1/4 wave of plus 1.2 dBi in the same ground. The reason > for the extreme loss is completely counter-intuitive. > > We have a lot of mental simplification devices for thinking about > antennas. In the end you need something to add up all the induced > currents, all the losses > > > > On Wed, Dec 12, 2012 at 3:13 PM, DAVID CUTHBERT <[email protected]>wrote: > >> 20 dB implies that the ground system loss is 10X the inverted-L >> radiation resistance. >> >> This would result in an input resistance of 250 ohms and a minimum >> VSWR if 5:1. >> >> I don't think that is what the real deal will deliver, do you? >> >> Dave WX7G >> On Dec 12, 2012 12:54 PM, "Guy Olinger K2AV" <[email protected]> >> wrote: >> >> > With the following caveat: The very sparse and short buried radial >> systems >> > he is showing are FAR more lossy in practice than shown in his gain >> tables. >> > Four twenty foot buried radials beneath a 1/4 wave L on 160, could >> place >> > you down 20 dB. You really can't do that as your 160 meter counter >> poise >> > and expect decent results. You can end feed the same wire on >> > 80/40/30 meters (full wave worth of wire in the L on 80m) with four >> > buried 20 >> foot >> > radials and it will be an excellent antenna. This is due to the >> > high Z feed at the ground with current max AWAY from the feed point. >> > >> > A quarter wave L on 160 MUST deal with the counterpoise loss >> > issues, one way or another. >> > >> > 73, Guy >> > >> > On Wed, Dec 12, 2012 at 2:07 PM, Ashton Lee >> > <[email protected] >> > >wrote: >> > >> > > This wonderful article written by L.B.Cebic W4RNL sure can make >> > > you a believer in a simple wire inverted L. It is the last >> > > antenna >> discussed. >> > > http://www.users.on.net/~bcr/files/backyard%20wire%20antennaes.pd >> > > f >> > > >> > > A $3 wire pulled up into a tree will beat just about any >> > > commercial antenna. because it is longer. So on low bands it has >> > > increased band >> > width >> > > and efficiency, and on higher bands it has gain. Yes, I know , >> > > some of >> > that >> > > high band gain is horizontally polarized, but that's not all bad. >> > > Just >> > get >> > > the vertical portion 33 feet or so and you'll be happy as Larry. >> > > The article shows that an extensive radial field may not be necessary. >> > > >> > > And a wire is a lot less visible than a big hunk of aluminum. >> > > Without trees, just top load a 43 foot (or possibly even shorter) vertical. >> The >> > top >> > > loading could be a T just as easily as an L. People can argue >> > > that one >> > all >> > > day. >> > > >> > > >> > > >> > > >> > > On Dec 12, 2012, at 11:30 AM, k6xt <[email protected]> wrote: >> > > >> > > > My first antenna, still in use, on moving to CO is a GAP Titan, >> > > advertised to load up 80 thru 10 including WARC bands. The Titan >> > > is a >> bit >> > > shorter than Voyager, 28 feet or something like it. The >> > > advertising is correct, it loads up 180 thru 10. >> > > > >> > > > But wait. Is it effective on all those bands? No. >> > > > >> > > > On 80 its a dummy load. On 40 it works extremely well after I >> > > > added >> a >> > > one foot extension to the bottom wire that encircles the antenna. >> > > In >> some >> > > cases it is the equal of my shorty HyGain 40 at 70 ft - which >> > > probably >> > says >> > > more about the HyGain than the GAP. For the rest its better on >> > > the traditional bands than the WARC bands. It worked a lot of DX >> > > for me >> for >> > the >> > > couple years it was my only antenna. >> > > > >> > > > Carrying my experience to the few feet taller Voyager, and from >> > > > what >> > > I've been told by Voyager users, the ant will meet its spec which >> > > is >> to >> > > load up on the low bands. Expectation wise I'd expect it to be >> > > like >> the >> > > Titan. It loads up but is otherwise a dummy load. Maybe with a >> > > batch >> of >> > > radials it could be made to work as well as any other extremely >> > > short vertical or GP. >> > > > >> > > > Not to say there's anything wrong with GAP. My brother had up >> > > > an R7 >> > > which he rated about like the GAP on bands both cover. Those >> > > multiband halfwave short verticals work but you get what you pay for. >> > > > >> > > > 73 Art K6XT~~ >> > > > Success is going from failure to failure without a loss of >> enthusiasm. >> > > > ARRL, GMCC, CW OPS, NAQCC >> > > > ARRL TA >> > > > >> > > > On 12/12/2012 10:00 AM, [email protected] wrote: >> > > >> With the prospect of downsizing and moving into senior housing >> > > >> in >> the >> > > future >> > > >> I am starting to look at vertical antennas that will allow me >> > > >> to >> > > continue >> > > >> this wonderful hobby.? I have heard "some" good things about >> > > >> the >> GAP >> > > series >> > > >> of antennas but the company says they do not need radials on >> > > >> most >> of >> > > them >> > > >> and that worries me.? Over the years I have become very >> > > >> skeptical >> > about >> > > >> claims and the other BS put out by most companies ( maybe it >> > > >> is a >> > > function >> > > >> of age I dunno) so I wonder if these antennas really work.? >> > > >> The two >> > > antennas >> > > >> that I am interested are the Voyager DX for 160/80/40? and the >> Eagle >> > DX >> > > for >> > > >> the rest of the bands. >> > > >> >> > > >> So my question is.... does anyone have actual experience with >> > > >> these >> > > antennas >> > > >> (especially the voyager) as compared to other antennas for a >> specific >> > > >> frequency.? Now guys .. I know you cant really compare a 6 >> > > >> element >> > beam >> > > to a >> > > >> vertical of this kind but I am talking about a comparison that >> > > >> is realistic.. like how does it hear, tune, match & get out >> > > >> compared >> to >> > > >> something like another vertical or a dipole up some reasonable >> > distance. >> > > >> >> > > >> I sure hope this has not opend another can of worms.. some how >> > > >> I >> seem >> > > to do >> > > >> that .. private emails are ok..especially it the topic gets >> > > >> out of >> > hand >> > > and >> > > >> we get a large volume of comments (Tree please dont shoot me >> > > >> before Christmas my wife will miss me.) >> > > > >> > > > _______________________________________________ >> > > > Topband reflector - [email protected] >> > > > >> > > >> > > _______________________________________________ >> > > Topband reflector - [email protected] >> > > >> > _______________________________________________ >> > Topband reflector - [email protected] >> > >> _______________________________________________ >> Topband reflector - [email protected] >> > > _______________________________________________ Topband reflector - [email protected] _______________________________________________ Topband reflector - [email protected]
