[TenTec] G5RV

Gary Hoffman ghoffman at spacetech.com
Sun Feb 1 14:07:53 EST 2009

I used to be suspicious of the idea of using say, a 135 ft long doublet, fed
with ladder line  (or any low loss line really) as compared to various
"engineered" antennas.

That is, until we changed our field day antennas one year to that design.

What an improvement !

Later, I did some real analysis and replaced my opinion with facts.

I would only add that if you really, really, really hate the idea of using
ladder line, you can get several really low loss types of coax, much better
than the 213 or the 58 that too many people use, and thus get by with pretty
low losses.

I honestly don't think most people realize that in so many cases, most of
their 100 watts is dissipated in the feed line system.

73 de Gary, AA2IZ

P. S.   Love the example given of 250 foot of rg-58 measuring 50 ohms
impedance even with nothing connected to it or with a short circuit.  Its
true - and kinda funny.

----- Original Message ----- 
From: "Bob McGraw - K4TAX" <RMcGraw at Blomand.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Sunday, February 01, 2009 10:05 AM
Subject: Re: [TenTec] G5RV

> Someone mentioned it earlier as I recall, but one of the reasons the G5RV
> appears to have somewhat low SWR is the fact that the coaxial transmission
> line and the associated balun are actually a "lossy line" section.  Now a
> lossy line has loss both ways, going to the load and coming from the load.
> Thus any reflected power from the load is attenuated on its way back to
> transmitter or source.  The net effect is an appearance of a lower
> power or lower SWR as we typically measure SWR at the source.  Case and
> point, a 250 ft. length of RG-58 with show basically a 1:1 SWR at the
> transmitter regardless of what is connected to the other end.  It can be a
> 50 ohm load, a short circuit or an open circuit or anything in between.
> result is that the section of line looks like its characteristic impedance
> of 50 ohms to the source or transmitter.
> I acknowledge the fact that thousands of hams are using the G5RV design
> successfully making many contacts and enjoy the fact that the single
> allows them to work all bands.  The use of a tuner is either required or
> advised and the tuners in the radios of today, having limited matching
> range, do a good job of handling the load presented by the G5RV.
> I have personally conducted tests in a controlled condition, measuring
> patterns and field strength values of several HF antennas with the G5RV
> being one of them.  There is no question about it, the G5RV does not
> as well as the basic 1/2 wave wire that is center fed with a balanced feed
> or low loss coax.  In certain cases the data concluded that the field
> strength was 6 to 9 dB less and in one data set some 12 dB less while
> the G5RV.  From a ERP {Effective Radiated Power} point of view, the 100
> transmitter would then have a ERP of 12.5 to 25 watts.  Still, we all know
> that one can successfully work many stations and DX with only 10 to 20
> watts.
> 73
> Bob, K4TAX
> ----- Original Message ----- 
> From: "Alfred Lorona" <w6wqc at dslextreme.com>
> To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
> Sent: Saturday, January 31, 2009 10:49 PM
> Subject: Re: [TenTec] G5RV
> >A G5RV fed with open wire feedline and a tuner will work just as well as
> > regularly configured G5RV. The flat top wire does the radiating and it
> > the same length in either configuration so the results are the same. The
> > advantage of the G5RV was that no tuner was required for the bands it
> > designed for. That one higher frequency 'problem' band is the cause of
> > the modifications and adjustments already described. The designer of the
> > G5RV did not include that band in his basic design. The advantage of a
> > simple dipole, resonant length or not, fed  open line is a perfect 1:1
> > any frequency on any band and you don't have to use coax anywhere.
> >
> > AL
> >
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