[CQ-Contest] Which Coax Jumpers Reduce SO2R Interference

[Bob Naumann - N5NJ]

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