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[Towertalk] Really dumb question on coax

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Subject: [Towertalk] Really dumb question on coax
From: W8JI@contesting.com (Tom Rauch)
Date: Wed, 29 May 2002 06:06:15 -0400
> If it were my station the answer would depend a LOT on if this was a
> 10 meter run or a 160 meter run - many people feel the UHF barrel
> connector and two PL259s are visible to the RF - more on 10M than
> 160M.  I know guys who claim to have run tests on this and concluded
> the above.  I have never run the test myself, but I believe it.  Loss
> numbers reported were in the 1-2 db at 28 Mc range.  YMMV.

It's easy to put such claims to a "smell test". 

1-2dB loss and 1500 watts the power loss would be between 150 and 350 
watts in the connector.

A reasonable test would be to run 500-1500 watts for a few minutes 
and see how many connectors melt or glow cherry-red. Even 0.1dB loss 
(2% loss) at several hundred watts TX power would show up as *very* 
obvious connector over-heating!

Impedance of the connector does not come into play until upper VHF or 
lower UHF frequencies are reached. The slight mismatch in the 
connector is much too short in length to make a difference on any 
frequency much below two meters, especially in a long transmission 
line.73, Tom W8JI
W8JI@contesting.com 


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