re: "Impulse noise is best tracked at the highest frequencies where we can
hear it -- I start around 160 MHz, then go up around 500 MHz when I get
close."
ALL well and good, Jim. What's the most distant impulse 'source' you
ever tracked down? I've had several 'sources' over 4 miles. Want to
see some documentation on that claim, Jim?
See: https://powerlinenoiseallentexas.wordpress.com/
I ALSO describe 'working up the DF in frequency'. THIS can be done
with great success ONCE one has found, say, a power line 'impulse' (arc)
source that NOW needs locating down to a single power pole.
See here: https://powerlinenoiseallentexas.wordpress.com/df-equipment/
So, Jim Brown, been there, done that.
I was describing, in the previous e-mail, techniques to locate the
noise AT the offending frequency, WHICH ASSURES you have
found the *right* source. Switching to a VHF or UHF frequency
will NOT find a source that is four or five miles away (It will,
however, find that noisy pole in your alley behind the house.) DFing
AT the offending frequency *will assure* you arrive very close in the
vicinity of the offending source, where ever that may be. Again,
I refer you to the record of such 'adventures' at the first link above.
Such advice as I offered is rarely given, and has been the result of
years of practicing and perfecting said technique now too. I would
appreciate some consideration of the effort for both the technique
described as well as the time I spent hammering out this text relating
it.
I have also described on this very list the tracking down of 'drifting
carriers' in the 80m and 160m bands. THESE were sinusoidal sources
that DID NOT radiate in the VHF or UHF spectra, leaving techniques
relying on those methods "out in the cold".
I have also relied on the old technique of driving around with a mobile,
and again, that is good for localizing a source that is 4 or more miles
out, but still leaves one with the job of pinning down a source to a
specific pole or residence or business address. One can make use
of ear and S-meter for this task too. No SDR required.
I have also been recently looking at noise sources for their synchronicity
with the power 'grid'; DSL (or some other signal present here) seems to
have an impulse characteristic that comes close to that of the grid, but,
is not locked to the grid. This required new techniques yet again, above
and beyond that commonly present in SDR radio installations.
de AA5CT
.
.
On Tuesday, January 7, 2020, 2:05:08 PM CST, Jim Brown
<jim@audiosystemsgroup.com> wrote:
On 1/7/2020 11:46 AM, AA5CT via RFI wrote:
> DFing at these frequencies is more art than science;
It's important to recognize the difference between electronic sources
and impulse noise sources. Tracking them is VERY different -- the
spectrum of electronic sources consists of harmonics of LF square waves,
so very frequency dependent and rarely goes to VHF, while the spectrum
of impulse noise is infinite, going well into UHF.
Impulse noise is best tracked at the highest frequencies where we can
hear it -- I start around 160 MHz, then go up around 500 MHz when I get
close.
Electronic noise must be tracked on the frequencies where it bothers us,
so a battery operated RX tuned to those frequencies. Even better is DSP
RX with spectrum and waterfall display. See my tutorial about building
contest scores by killing noise and NK7Z's website. k9yc.com/publish.htm
73, Jim K9YC
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|