Bob,
You're right that it would no longer be a G5RV. As you know, the G5RV was
originally designed to present a reasonably low impedance on the 80, 40 and 20
meter bands. That's all. It worked satisfactorily enough for the
vacuum-tube transmitters of that era..
By moving to a fully balanced-fed antenna with a tuner, we enable it to
provide a 50-ohm load to match today's fussy solid-state rigs, and add bands
such
as 30, 17, 15, etc., for which the G5RV was never designed.
Yes, a resonant dipole would produce a more predictable radiation pattern,
but if the tuner is a low-loss design, the radiation efficiency of the
102-foot wire would be so close to it as to be indistinguishable in practice.
When
I replaced my New Jersey G5RV with a full-size. balanced-fed 80-meter dipole,
I could see the improvement on 80 but the performance on the higher bands
was virtually the same.
73,
Ray W2RS
In a message dated 2/1/2009 4:09:51 A.M. GMT Standard Time,
RMcGraw@Blomand.net writes:
Then it's no longer a G5RV. It is then a chunk of wire with a balanced feed
attached to a tuner which matches the transmitter to the load. Those work
quite well but not as well as a 1/2 wave at the lowest intended frequency
and those other higher frequencies harmonically related.
73
Bob, K4TAX
----- Original Message -----
From: <Rsoifer@aol.com>
To: <tentec@contesting.com>
Sent: Saturday, January 31, 2009 5:31 PM
Subject: Re: [TenTec] G5RV
>I don't consider myself an expert, but in my considerable experience with
> G5RVs and similar antennas, any G5RV can be improved by putting an antenna
> tuner
> between the coax and the balanced feedline. If that is done, the balanced
> feeder can be virtually any length at any frequency above 3.5 MHz.
>
> 73 Ray W2RS
>
>
> In a message dated 1/31/2009 8:47:18 P.M. GMT Standard Time,
> mathenyr@marietta.edu writes:
>
> The G5RV has been well reviewed by several experts. The best review I
> know of is by VE2CV and VE3KLO, in the ARRL Antenna Compendium Vol. 4.
>
> The long and the short of it is this: A G5RV is a 100 foot long piece of
> wire. The best way to feed that on multiple amateur bands would be with a
> multi-band matching network a selected point on the wire. Then the
> feedline (whatever type) would be in a matched condition and losses would
> be least. An automatic antenna tuner would be ideal for such purpose,
> mounted at wherever the feedpoint is to be located. If you can't put the
> tuner up there, well-made openwire line will come close in performance,
> with a proper tuner in the shack. You may have to trim the open-wire
> length to get an easy tune on all bands. But the antenna is a 100 foot
> piece of wire--with all the traits of any 100 foot piece of wire!
>
> Adding baluns, stubs, coax, etc. as is often shown will only add loss
> to the system. That loss is what improves the match on some bands!
>
> Pattern wise, that feedpoint mentioned above should be at the center if
> you want best results at 20 meters and below. If the higher bands are
> your favorite, then there may well be a better spot...perhaps at an end.
> But that will create other problems, and probably losses.
>
> The marvelious thing, however, is this: Despite all that one can
> find wrong with this "100 feet of wire" there are a gizilion and a half
> of
> these things out there making QSO's at this very second. It doesn't take
> a great antenna to make a lot of contacts.
>
> Ralph Matheny
> K8RYU
> 207 Gibbons Place
> Marietta Ohio 45750
> mathenyr@marietta.edu
>
>
>
>
>
>
>
>
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