kopia lustrzana https://github.com/jamescoxon/dl-fldigi
55 wiersze
2.0 KiB
Plaintext
55 wiersze
2.0 KiB
Plaintext
/**
|
|
\page frequency_analyzer_page Frequency Analyzer
|
|
|
|
\tableofcontents
|
|
<br>
|
|
<br>
|
|
|
|
Fldigi can be used to accurately measure the frequency of a remote signal
|
|
that is transmitting a steady carrier.
|
|
<br>
|
|
|
|
\image html FreqAnal.png "Frequency Analyzer"
|
|
\image latex FreqAnal.png "Frequency Analyzer" width=6.5in
|
|
<br>
|
|
|
|
I have set the sound card up using the WWV modem and have it adjusted
|
|
for the proper PPM offset on receive. I followed the frequency calibration
|
|
procedure that ICOM recommends for the IC-746PRO, adjusting WWV at
|
|
10 MHz for a zero beat.
|
|
<br>
|
|
|
|
Then fldigi was used in the "Freq Analysis" mode to track the WWV carrier
|
|
at 10 MHz. In this mode the decoder is merely a very narrow band
|
|
AFC tracking filter. The filter bandwidth is set to 2 Hz and the
|
|
tracking time constants to about 5 seconds. Future releases will
|
|
probably make both of these user adjustable. When the signal is
|
|
being tracked the digiscope (right hand display) will be a horizontal
|
|
line. If the signal is very noisy and tracking difficult the
|
|
digiscope will jump and become wavy. You can see from the above
|
|
image that I am tracking about 0.22 Hz high on WWV. I have
|
|
repeated this measurement at various times during the day and on
|
|
various days with nearly the same result. So I am comfortable
|
|
with knowing that my local oscillator is just a little low (that is why
|
|
the Frequency reads high).
|
|
<br>
|
|
|
|
ARRL frequently announces a frequency measurement test (FMT) which takes
|
|
place on 160, 80 and 40 meters. This is a chance to test your
|
|
skills in frequency measurement. You should be able to make a
|
|
submission to the FMT using this technique. Make corrections to the FMT
|
|
transmission based upon your WWV measurement. You may have to adjust
|
|
for other local oscillator effects as well. If you have some good
|
|
ways to measure and correct for these I would be glad to share them
|
|
with the other fldigi users.
|
|
<br>
|
|
|
|
<br>
|
|
\ref frequency_analyzer_page "Return to Top of Page"
|
|
<br>
|
|
\ref main_page "Return to Main Page"
|
|
|
|
|
|
*/
|
|
|