Stefan:
I wouldn't change the phase reversal time - if
you announce to the world you're transmitting
WOLF-10 that means phase transitions can occur
only at exact multiples of 100 milliseconds -
everyone's receiver will make that
assumption. Don't worry about sync-ing phase
shifts to the zero crossings of the audio
waveform, let's see if your computer-to-computer
test works first. You can specify a relaxed
tolerance for the receiver: e.g. +/- 2 Hz away
from the nominal carrier frequency to allow for
slightly different sample rates at Tx,
Rx. Ultimately for long term coherent
integration both Tx and Rx must agree on the
timing but for a first test with a strong signal
(just to see if everything is working), you won't
need that. For longer integration times it is
probably better to use a GPS-stabilized DDS to
directly generate the WOLF signal at the Tx
end. I find sound card sampling rates are stable
enough for WOLF once everything has warmed up a
bit. It's not the small instabilities that will
hurt, it's that the absolute sample rate must be
known accurately and entered to allow the Rx
clock to keep same time as the Tx clock. Did you
download that .wav file I made last night? I
intended that only for testing your Tx to see
what the sidebands look like with no waveform
envelope shaping. Don't expect anyone else to
copy that message unless your sample rate is very
close to 24000 s/s and the signal strength at the
Rx is high enough to enable decoding within seconds, not minutes or hours.
Good luck!
73,
Bill VE2IQ
At 01:57 PM 1/30/2012, Stefan DK7FC wrote:
Bill,
Thought about the zero-crosings. Does it
actually make sense to change the phase reversal
time? Since the samplerate is drifting anyway,
there will be a small time difference between a
phase shift and there zero-crossing. Also -if
the samplerate would be exactly 24 kS/s-, the
time when the phase shift occurrs can be
somewhere, i.e. wouldn't be sync'ed to the zero-crossing. Right?
So it may be easier (also for the receiving
side) to let it remain at 0.1 seconds.
Comments welcome.
73, Stefan/DK7FC
Am 30.01.2012 19:24, schrieb Stefan Schäfer:
Changed the phase reversal time from 0.1 s to
0.111482720178372 s (=1000/8970Hz) Seems to work.
Am 30.01.2012 01:37, schrieb Bill de Carle:
Can your Tx handle abrupt phase shifts every
100 msec? We can arrange for the phase shifts
to occur only at zero-crossings of the 8970-Hz sinewave.
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