[TenTec] G5RV

Bob McGraw - K4TAX RMcGraw at Blomand.net
Sun Feb 1 10:05:13 EST 2009

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 the 
transmitter or source.  The net effect is an appearance of a lower reflected 
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.  The 
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 and 
successfully making many contacts and enjoy the fact that the single antenna 
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 radiate 
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 using 
the G5RV.  From a ERP {Effective Radiated Power} point of view, the 100 watt 
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 

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 a
> regularly configured G5RV. The flat top wire does the radiating and it is
> 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 was
> designed for. That one higher frequency 'problem' band is the cause of all
> 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 on
> any frequency on any band and you don't have to use coax anywhere.
> AL
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