Topband: Fw: GAP VERTICAL QUESTION

[Guy Olinger K2AV]

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 <telegrapher9 at gmail.com>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" <olinger at bellsouth.net>
> 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 <Ashton.R.Lee at hotmail.com
> > >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.pdf
> > >
> > > 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 <k6xt at arrl.net> 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, topband-request at contesting.com 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 - topband at contesting.com
> > > >
> > >
> > > _______________________________________________
> > > Topband reflector - topband at contesting.com
> > >
> > _______________________________________________
> > Topband reflector - topband at contesting.com
> >
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