[Elecraft] G5RV medium power Balun

[john petters]

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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