[CQ-Contest] bandwidth measurements

[Chuck]

If you want to measure your bandwidth you need a
couple things.

1 - A GOOD SOLID strong signal so you can FIND
the suppressed carrier. (This provides a
reference point for the other measurements of the
supppressed sideband as well as other parameters)

2 - A way of measuring the signal levels of the
station in question so as to determine where the
points are that are identified in the FCC rules
for determining bandwidth.

3 - An ACCURATE means of determining EXACT
frequency being measured so you can state, with
some integrity, that the signal being measured is
from xx kHz to yy kHz and therefore is either
above or below the band limits (depending on
where you are looking).

4 - The patience to take the TIME necessary to
get a good, average, reading on where the -26 dB
points are on the signal to determine the
bandwidth for enforcement purposes.

I used to work for the FCC (at Laurel Mon. Stn)
and was charged with doing measurements of
signals. One of those was bandwidth of SSBSC (SSB
Suppressed Carrier) signals for compliance to
bandwidth limitations, staying 'in-band', and
other such measurements.  

Trust me.. EVEN with the equipment we had, the
skills of the highly competent technical types,
the constant training, checks, and retraining we
had, PLUS good, strong signals, measuring actual
bandwidth for determination of 'in-band' or
'out-of-band' compliance was, at best, a
challenge at times.

That is why the rule-of-thumb '3 kHz for SSB
measured from the appropriate sideband being
used' and '.25 to .5 kHz for CW from the band
edge' was promulgated. 

It allowed for almost ALL of the hardware to be
compliant without having to be a hardware guru.
Plus it meant that if someone was heard OUT OF
BAND even with those specs it meant that they had
an OVERT problem.

So, unless an OO can prove that they measured the
apppropriate parameters and determined your
bandwidth that way.. they don't have much of a
leg to stand on.

I think if it were me, I'd send a polite note
back thanking them for their efforts and
inquiring as to their methodology used to
determine that I was 'in fact' out of band.

73

Chuck K3FT


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