Dear Gary, LF Group,
At 18:51 18/12/2002 +0000, you wrote:
I tried monitoring but did not receive anything intelligable, may be I
require more tries to get it right ?? as I am not sure of the best method of
setting up the receiver frequency etc for use with JASON. Any advice gents ?
First, use the "options" menu to set Jason up to match your receiver - if
you are using USB, set Jason to USB receive; if you are using LSB, set
Jason to LSB. Set the Jason receive centre frequency to be equal to the RX
BFO offset - it defaults to 800Hz. Set the RX gain and/or PC volume control
to produce about 1/3 full scale on the bar graph at the left of the Jason
screen with the normal signal/noise level at the RX output.
The only other thing is making sure the received frequency is correct. It
needs to be within about +/- 1Hz to guarantee not missing any part of the
signal. Typical amateur-type synthesised receivers will probably be within
a couple of Hz of nominal frequency at LF - the PC sound card may add
several Hz more error. To calibrate out both these errors, set Jason to
receive, and tune to a known carrier signal close to the 136k band - DCF39
on 138.830kHz should do. This should produce a clear line on the waterfall
display (in between the data bursts, anyway). If this is not centered
between the yellow cursor lines, click on the signal trace, and Jason
should adjust it's centre frequency automatically. Then leave all the
software settings as they are, and re-tune the RX to the Jason signal
frequency - it should now work :-)
If the Jason signal is strong enough to be clearly visible on the waterfall
display, you can skip the calibration step and click on the centre of the
visible trace to set the frequency correctly. Not sure what your QTH is,
Gary, but I imagine it should also be easy to hear my signal, which sounds
like a steady carrier with very slight frequency shifts.
Cheers, Jim Moritz
73 de M0BMU
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