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Hi Peter, Henny,
>> I wonder if it is possible to receive
DHO on 23.4 KHz when you'r transmitting on 8270 Hz ?
Yes, this is not difficult, see pics at
df6nm.bplaced.net/VLF/MSK_sync_during_transmit/
I used a small resonant ferrite loopstick tuned to
23.4 kHz, with the secondary winding connected directly to the soundcard
without a preamp. This worked well even when the little antenna was less than 1
m from the big loading coil. You may have to optimize the antenna
orientation, and set the mixer gain low enough that your TX signal doesn't
saturate the ADC.
With 8.27 kHz one small difficulty is
that the third harmonic will be aliased to near the DHO frequency
(48 - 3 * 8.27 = 23.19 kHz). This was easily fixed by setting up a
23400 Hz Chebyshev bandpass in blackbox one.
One possible pitfall is that after the daily DHO
outage, SpecLab seems to aquire samplerate sync immediately, but
sometimes you are left with a large number (several 1000s) in the
"error integral" tab. This will delay the application of the SR
measurement and may leave the frequency uncorrected for several hours. You
can fix this quickly by switching the SR correction off and on again (tick
measure only - apply - untick measure only - apply).
Best 73,
Markus
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