I'm not surprised Bob. The best way is to throw the G5RV away or feed it
with balanced feed - 450 ohm twin or open wire to a balanced atu.
The design of the 5RV is a compromise. The twin section acts as a
transformer and will only present the correct match at certain
frequencies if the antenna is at a certain height above ground, in a
straight line etc.
Feeding a multiband antenna with coax through a balun and relying on the
atu in the shack to tune it up is bad practise and will result in losses
as you have found. The mismatch is occuring between the antenna and the
feeder. The balun is not a matching device unless it is a 4:1 or 9:1 and
then the impedances must be exactly right or a mis maith will occur.
Using balnced line to a balanced atu will elimiate the need for the
balun and will cut out the losses, assuming the balanced atu is
efficient. If you must use coax, try running it to a point where you can
switch to balanced feed and put your atu there - maybe an auto atu - but
with a balanced output or a balun on the atu output terminals to the
twin feeder.
73
John G3YPZ
Nancy and Bob Widmaier wrote:
I recently purchased a "5K watt" PVC balun from a very well known supplier of wire antenna and baluns. This supplier has a G5RV antenna that they are marketing with this balun.
I believed the vendor that it would work on my G5RV; particularly because I am running
medium (not high power) of 600 watts from an AL 811-H. The balun saturated in 1 hour of
operation and failed. The "expert ham and marketer" at the vendor did not call
me or e-mail me when I asked what the balun power specification is at the G5RV ladder
line SWRs which vary from 1.9 to 8.2. I operated in the 1.9 to 6.0 range.
I also emailed 2 other well know more expensive balun vendors asking them what
the specifications were for their baluns at the above SWRs. Not one of them
would e-mail be back in spite or their recommending that I buy their balun.
It appears that none of these baluns would work and that the only solution is
to use a coax choke (one balun vendor did tell me this). G5RV indicated this
in his write up of the G5RV many years ago. Is this correct? What are your
experiences?
73,
Bob Widmaier
K3JOP
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