Joe wrote:
> I'll keep it going then.
Maybe the battery here will hold up for another night.
This signal could be detectable at long distance except that
several dB will be lost unless the rx can correctly guess the
frequency offset. Here I am cheating because the message is
known and I use it to undo the modulation and get a nice clean
carrier to measure.
Reversing the modulation is easy, I just pass the whole band
through a BPSK modulator and then plot the spectrum. You get a
nice clean band - all other signals are smeared out and reduced.
For example
http://abelian.org/vlf/tmp/151205c.gif
VO1NA is at 0Hz and is +/- 0.2Hz wide due to the BPSK. After
the entire band is modulated, VO1NA sharpens to a carrier and
unrelated signals are spread out.
I don't know what's causing those 3.05Hz sidebands of VO1NA.
What could they be?
> There seems to be a jump after local noon.
The strong signal at 13:30 was a surprise, about
6dB or so more than I expected.
VO1NA 2015-12-05 16K21A 5S 5C QRO
start Eb/N0 Freq
13:30 13.0 -222 uHz
15:00 3.1 -256 uHz
16:30 3.9 -482 uHz
18:00 15.1 -558 uHz
19:30 17.3 -228 uHz
21:00 14.2 -330 uHz
The big unknown is how much of this frequency shift is
oscillator and how much is propagation.
--
Paul Nicholson
--
|
