Topband: Magnetic Loops

[Gary and Kathleen Pearse]

Thanks Tom for the explanation. As always, this is a learning Reflector. Part of my location involves potential BCB, power line, adjacent home electronics, and of course the legal limit transmissions close to the loop/feed/rotator controller. Common mode supression is an absolute requirement on all lines. 

As to it's +- effect on the loop, well, as I mentioned, it was a shotgun process during the installation. Without common mode filtering on all cabling I couldn't operate. Such is the dilemma of the city dweller who has an S4-7 noise floor depending upon season. It's substantially worse in winter as explained below.

I'm told that the effective RF ground in these parts of Alaska is 15+ meters down, and it'll find a way into the shack unless crowbarred at the door. Ground rods surrounded by 4-5' of winter frost and non-conductive soils are useless. 

73, Gary NL7Y

> This doesn't mean loops will never work, or loops with poor feed systems will never make people happy. It just means it is almost impossible to correct a bad feed design by stringing beads or winding conventional chokes, even if you get up to 5,000 ohms. It is always far better to make the antenna with a correct feed system, because a proper feed has far less common mode response without any common mode foolery.
> 
> 73 Tom