Dave,
All that is theoretical does not translate directly to the physical world.
Take a look at http://www.aa5tb.com/efha.html for more information.
The counterpoise does not need to be very long, but it does need to be
present.
If the coupling between the high impedance side of the matching device
is connected at the "ground side" to the shield of the coax, then the
coax shield can act as the counterpoise (with the attendant risk of
RF-in-the-shack), but does require some minimum length of coax to be
effective - the PAR EndFedZ is one example.
73,
Don W3FPR
On 7/14/2016 5:40 PM, David Gilbert wrote:
I'm confused why an EFHW should need a counterpoise. If it needs a
counterpoise it isn't actually acting like an EFHW. If it needs a
counterpoise that means there isn't enough choking impedance at the
feedpoint, and it means that the feedline is radiating with the
counterpoise acting as ... well, a counterpoise.
Manufacturers state a minimum length feedline simply to have the
feedline losses help swamp out SWR variations along the line, and of
course to marginally lower the SWR.
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