[AMRadio] new antenna (again).


Brett gazdzinski brett.gazdzinski at verizonbusiness.com
Sat Mar 10 19:57:34 EST 2007


Bill,

The ARRL antenna book as lengths to use, but only on balanced 
antennas and tuners. They say grounding one side 
introduces to many variables, its cut and try with coax.

As it is, with the G5RV, I have only about 30 feet of RG214 coax
in line, so high swr will not cost me much.

If I was to ADD coax to get away from a high voltage point, that
is only going to increase the loss in the coax.

At least that's the way I see it...

Brett
N2DTS

> 
> Brett,
> Heard you thursday loud and clear in northwestern Mass.
> 
>  When I had my station setup down in PA my dipole was a 
> similiar 75/40 double wire from a single coax with half the 
> 75 flattop along the roof peak and then zigged down to a 
> garage roof and zagged back up to a window ledge.
>  The 40 was flat on top at an angle and a single slope to the 
> other corner of the garage roof.
>  Did have some rf in the shack being under the wire but it 
> was no closer than 25 feet at any point.
>  
>  The problem with single feed coax to a dual 40/75 wire is 
> that the coax length does not work out for both bands.
>   Somewhere I found a chart or formula for figuring this out 
> and there is one length that is close.
>   Resonance was checked with the wire as run then I added a 
> piece and checked again but found removing a similiar length 
> got it about in for 75 with 1.5 or so SWR with 40 just a bit worse.
> 
>   Does anyone here know where that coax length table was?
> Might have been an Antenna Hndbk or regular Handbk or online..
>  
> Bill, KB3DKS/1
> 
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