On Mon, 2 Oct 2006 23:27:02 +0530, Ramakrishnan Muthukrishnan wrote:
>I do not have a HT with AM mode, perhaps I will try to borrow one.
I agree with others that this is a very useful tool in chasing down
RFI.
Consider this basic principle. For low frequencies, the entire
length of a long power line will be the radiator, so direction
finding will simply point to a very broad line source. At much
higher frequencies, the portions of the line more distant from the
source tend to be decoupled from the source, so the segment of the
power line nearest to the source of the noise is what produces the
strongest radiation. Thus, for broadband sources like arcs, that
have content in the VHF or UHF range, a VHF receiver will provide
far more precise information about the source of the noise.
This advice is quite different for noise sources that have little
VHF content, such as oscillators and computer clocks running at low
frequencies, or clocks that are better suppressed at VHF/UHF but not
at HF. Obviously, it's much harder (or impractical) to go looking
for a source that either doesn't exist at VHF or is much weaker at
VHF.
73,
Jim Brown K9YC
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