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Re: [IRCA] 9/30/16 DU chase from IL
Merv posted details on the mwoffsets list Steve,
but possibly more detailed than the IRCA list needs!
A quick precis from mwoffsets:
"Using winradio G31DDC as the receiver.
Have a signal generator locked to the 10MHz
output of a GPS disciplined reference oscillator,
Using spectrumlab to display the waterfall from
the receiver with about a 5 10 Hz span"
The signal generator is used to update receiver
calibration for simple offsets, but he calibrates
Spectrumlab as well to get higher accuracy offsets using his own software.
Hope that helps.
best wishes,
Nick
For the quick method I inject a signal at the
dial frequency of the receiver and use the
â??calibrateâ?? facility on the G31DDC to align
it exactly on the spectrumlab â??zeroâ??
display ... then simply read the unknown
carrier from the spectrumlab display ... this
will give one decimal place without any problems
... and once calibrated the G31DDC is generally
good even when you change frequencies ... but can
quickly check â??dial freqâ?? calibration at
anytime by re-injecting a carrier at nominal.
For more accurate frequency readout I have a bit
of software that uses an injected frequency (off
nominal) to calibrate spectrumlab then
interpolate that of the unknown ... it requires
manually setting up the offset reference. Iâ??ve
watched the 4QO/4QB TX pair on 855kHz (which use
to be phase locked but recently it appears only
one remains so) during ground wave propagation at
midday track +/- 50 microhertz of true ... as we
move away from midday you can see the variation
from nominal change as the number of ionospheric
reflections increase resulting in a perceived
â??dopplerâ?? shift on the received signal because of multi-pathing.
I now have a LAN controllable, dual channel
signal generator so I am in the process of
writing the software to automate this process and
use a second reference (one either side of the
unknown) to make the measurement. The software
talks to the receiver, spectrumlab and the signal generator.
At 00:56 07-10-16, you wrote:
Merv has a very professional approach to nailing these offsets down, so
I'd defer to him myself on this topic.
....would love to learn more about this if possible.
Steve
WEB - "The VE7SL Radio Notebook": http://members.shaw.ca/ve7sl
VE7SL BLOG - "Homebrewing and Operating
Adventures From 2200m to Nanowaves": http://ve7sl.blogspot.ca/
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Nick Hall-Patch
Victoria, BC
Canada
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