>On Fri, 10 Jul 2009 12:00:57 -0500
>K4SAV <RadioIR@charter.net> wrote:
> Thomas Damboldt wrote:
>>If I connect my
>>receiver with a very short feedline (say 1m), to the >>antenna, I should not
>>be receiving much common mode >>noise. Is that true?
>> Certainly worth trying.
>>
The RX antenna needs the feedline because we have placed
it away from the shack/house -- all the noise sources. In
a real world environment the length of the line is a
given; we do all the things described in this thread to
ensure that it does not carry and radiate the noise we
moved the antenna away from in the first place.
On a separate note, I have been experimenting with twisted
pair RX transmission lines. I have used a twsited pair
removed from a CAT5 cable. With a well balanced
transformer and a common mode chocke at each end, it seems
to have very high common mode rejection (i.e. I have not
been able to measure it). Loss at 1.8 MHz is about 0.7 dB
/ 100'. Note that for good common mode performance, the
line should be away from other conductors.
George
AA7JV
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