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Re: [CQ-Contest] Which Coax Jumpers Reduce SO2R Interference

To: cq-contest@contesting.com
Subject: Re: [CQ-Contest] Which Coax Jumpers Reduce SO2R Interference
From: "Bob Naumann - N5NJ" <n5nj@gte.net>
Reply-to: Bob Naumann - N5NJ <n5nj@gte.net>
Date: Wed, 2 Feb 2005 07:11:52 -0600
List-post: <mailto:cq-contest@contesting.com>
Ken,

The answer to the mystery may be in your description:

> I would have thought the better shielding of the hardline would have 
> made it better. The only factor that might have affected the hardline's 
> results 
> is that all the hardline came with N connectors, so I used adapters to 
> PL-259s on each end. These were new and the best quality I could buy.

Get rid of the adapters. You can get PL-259 and SO-239 hardline connectors.  
Even so, the hardline is probably overkill, and as some others have hinted, 
RG-8X is probably sufficient for these types of connections in the shack.

Make sure the connectors are tight too.  Yes, use a pair of pliers to "snug" 
them up.  Be careful not to over-tighten them though.  It is possible to 
tighten them too much and break the connector.

You may also have some common mode stuff going on.  What about all of your 
audio switching stuff?  Toroids?  Chokes?  Power supplies?  

Where is your high power switching done?  Can you redesign your system to move 
the high power switching outside - further away from your shack?  At AA5NT we 
have two lengths of RG-213 that go directly from the output of the two 
amplifiers outside the house to two hardlines that run directly to the input of 
an Array Solutions SixPak out on the tower - over 100' from the shack.  This 
means no coax switches or high power switching in the shack.  We have minimal 
RF problems in the shack.

Regardless of where they are, make sure the connectors are tight.  You may need 
to loosen and re-tighten them periodically to assure the quality of those 
connections over time.

73,

Bob N5NJ

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