[TenTec] Antenna Tuners...questions

[Denton]

well sir...I used to run a 2 element tri band Gem quad...and found I had 
best signal to noise and front to back, after resonating the antenna, using 
a pair of mini 8 coaxes tied together..but when I tried to use the mini 8 
pair on the upper WARC bands, the coax would tend to get warm.
My father, K4AK, a real old timer at his old qth fed his 80 meter doublet 
with large sized (about the same size as RG-8) 75 ohm coax in twin lead 
configuration.
He said he did pretty good with the shielded line and also stated that 
signal to noise was a bit improved.
However he never did install common mode chokes at the feedpoint, which is 
something I would consider if I was going to do the same to feed my 
horizontal multiband loop.
I would also consider stripping off the coax for everything but the center 
conductors and the dielectric, taping copper or other conductive tape around 
the center conducter pair and using some kind of pvc pipe or similar to 
protect the copper foil.
Neither Dad or I run afterburners, so can't comment on qro viability.
----- Original Message ----- 
From: "Ken Brown" <ken.d.brown at hawaiiantel.net>
To: "Discussion of Ten-Tec Equipment" <tentec at contesting.com>
Sent: Sunday, May 04, 2008 12:49 PM
Subject: Re: [TenTec] Antenna Tuners...questions


>
>> One thing I have yet to try is running a pair of 75 ohm, with both coaxal
>> shields tied together, with the shields grounded in the shack...in lieu 
>> of
>> the 400 ohm feeders...to the outside 600 ohm feeders.
>>
> I have heard of useing two pieces of coax to make balanced feeders in
> this manner before. I am sure that it can work, however I wonder what
> you lose when you do this. It seems to me that you would now have the
> voltage limitation of the coax, (or perhaps 2X that from hot lead to hot
> lead) and you would also have additional loss due to the dielectric
> being other than air as with open wire feeders. The current handling
> capacity would also be lower due to the center conductor being enclosed.
> At amateur power levels and at HF frequencies I doubt that the reduced
> current handling or the dielectric loss would be noticeable. The voltage
> limitation may be a problem though.
>
> I am interested to hear any first hand experience using dual coaxes
> balanced feed lines, especially at higher power.
>
> N6KB
>
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