The lineman called me on the phone today to indicate that
the line will be powered on Friday, but it is also scheduled
to be brought down again on Monday. I would like to capture
these moments to provide as evidence. But I need to resolve
and acquire the voltmeter/software this instant to
accomplish this.
Any help you can provide would be appreciated.>>>
Ford,
If I were you I would follow this procedure:
Quickly buy an MFJ attenuator, or another step attenuator.
If you don't trust them, I can loan you one that is tested
IF you pay expenses both directions. I will do a free
calibration chart for the one you buy AFTER you make
measurements if you like, since I have currently certified
test equipment for doing that to within a small faction of a
dB and it will only take a few minutes. Again you have to
cover shipping, since I'm a cheap Ham.
With the attenuator and wide selectivity and the receiver at
FULL gain and medium AGC, set the attenuator for a fixed S
meter reading on a receiver that has a meter with good
resolution. Most S meters are 1-2dB per S unit at the lower
end of the scale, so you should be able to get very good
resolution and repeatability.
Record the attenuation on the pad for each band. Be sure
however you always have at least six dB of pad in, so the
receiver mismatch does not hose up the first level change of
a pad since it may have an input mismatch.
After they make a change, go back and repeat this process
keeping EVERYTHING the same as the first round. Keep a log
of every detail!!!
Now record the change on each band in the pad setting
required to bring the meter to exactly the same point.
What this will tell you is the absolute change in level of
noise.
IMO, this is far more valuable than absolute signal
level....because you won't know the absolute signal level
anyway due to variations in antenna performance and other
things.
You could say with some authority within 1 dB what the
change was.
If you want to convert this to absolute level, you are
probably in for a headache. I can probably help you by
loaning you a calibrated noise source that you can use to
get a baseline of how many dBm sensitivity you had at any
specific attenuator level. I personally think an absolute
measurement of dBuV or dBm in a given BW is a waste of the
extra effort anyway. Even if you know the dBm value, you
would NEVER have an accurate baseline of V/m FS of the noise
anyway.
73 Tom
_______________________________________________
RFI mailing list
RFI@contesting.com
http://lists.contesting.com/mailman/listinfo/rfi
|