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" <olinger@bellsouth.net> 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 <telegrapher9@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@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@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@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@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@contesting.com
>> > > >
>> > >
>> > > _______________________________________________
>> > > Topband reflector - topband@contesting.com
>> > >
>> > _______________________________________________
>> > Topband reflector - topband@contesting.com
>> >
>> _______________________________________________
>> Topband reflector - topband@contesting.com
>>
>
>
_______________________________________________
Topband reflector - topband@contesting.com
|