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Dear Markus, LF Group,
You can see this on some amateur QRSS signals when
they send a CW ID - the ones who are not keying dividers show up as a carrier
with a blur around it, while the ones with keyed dividers are all blur and no
carrier :-)
The same can be seen on the DCF39 "carrier" - with
a high enough resolution spectrogram, this becomes a blur too, with a bandwidth
of the order of 0.05Hz.
Cheers, Jim Moritz
73 de M0BMU
----- Original Message -----
Sent: Sunday, April 24, 2005 9:01
PM
Subject: LF: Re: Divider by 10 or 100 for
136k out
Dear Hans-Albrecht and Jim,
there is one
minor disadvantage in keying a divider: As the phase at each key-down is
arbitrary, the transmitted signal looses its inter-symbol coherence. This does
not affect normal aural or visual decoding in any manner. But on a
high-resolution FFT you will no longer be able to resolve a central spectral
line, which would be useful to detect the presence of a very weak signal or
precisely measure its frequency.
Of course the same holds true for
small keying chirps, as I have recently learned :-(
73 de Markus,
DF6NM
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