Topband: Testing for common mode noise

[Don Kirk]

You won't believe what I found last night in the latest edition (5th edition) of the ON4UN Low-Band DXing book related to my proposed common mode noise test.

Page 7-109 discusses using a battery powered receiver, and connecting the receiver to the antenna using a "very short piece of coax" in order to determine the influence of the feed line on null depth, and this same section also mentions "trash" injection into the antenna via common mode coupling from the feed line (I personally have been using the term "noise" to be what ON4UN calls "trash").

I sure feel the above mentioned information from the ON4UN book supports my general concept of eliminating the feed line in order to understand the magnitude of feed line common mode current problems (be it poor null, or "trash" caused by common mode current on the feed line).  From a scientific standpoint it's the logical approach.

(Note : powering the radio with a battery is an important part of the proposed test)

Just FYI,
Don (wd8dsb)