Wolf - are you absolutely sure about the TV timebase frequencies ? My
understanding is that ZDF sync pulse form a national standard for time
distribution in D Land and should be exactly 15625.000 This is borne
out by German microwave opertors who use ZDF TV sync for high accuracy
frequency standards and I'm told it is an inheritance from Unification
where the DDR originally used this method of national time and frequency
distribution. Your measurement of 0.19 Hz high suggests a soundcard
sampling error of 12ppm which looks feasible.
I find it hard to believe that any of the TV stations would be out by
more than 30ppm even if a cheap and nasty TTL oscillator module were
used - which WDR and RTL evidently are. Your measurement of ARD looks
to be within tolerance of your quoted accuracy so the betting is those
are the identical frequency
Andy G4JNT
To verify that these differences are not propagation effects,
I also compared
some the TV line frequences (using a soundcard at
44100samp/sec, mixed down,
decimated by 81, 64k FFT size, 0.008Hz resolution). All TV
stations were
received 'old style' via antenna.
The TV line synch frequencies found this way (using the same
"correction
factor as above):
ARD: 15625.18 Hz
ZDF: 15625.19 Hz
WDR: 15626.18 Hz
RTL: 15626.20 Hz
The difference between these signals are still above 1ppm
(!?), but this may
be based on propagation effects (It's not the measurement, I
verified by
switched the stations and watching the effect on the waterfall).
Hope to meet you on the band in regular CW next weekend, even
if it is our
10th QSO !
73's Wolf (DL4YHF, DF0WD)
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