[time-nuts] Droitwich
Peter Vince
pvince at theiet.org
Thu Apr 5 11:20:48 UTC 2007
Note specifically that the 198 KHz signal is phase modulated by
low-speed data. John's link below reproduces an old BBC information
sheet with details.
I have just had a quick play with the "Spectran" audio spectrum
analysis and waterfall display program (http://www.weaksignals.com/),
and that clearly shows close-in sidebands at ± 12.5 Hz etc. Compare
that with the French station on 162 KHz, which has "noise" (well, OK,
audio modulation) all the way down to the carrier - the "BBC Radio 4"
signal on 198 KHz clearly has a high-pass filter on the audio
modulator so the audio doesn't interfere with the slow phase-mod data.
I'll try and find out if there is any later information about the
data that is phase modulated.
Peter Vince (Snr.Engr., BBC TV, London)
>Neville Michie wrote:
>> Hello all,
>> I have a HP 5090A fixed frequency receiver which I believe was made
>> to recover
>> precision frequency signals from Droitwich radio station.
>> I can not find any technical information on this receiver, can anyone
>> tell me
>> is Droitwich still active as a stable frequency reference, and where
>> can I find a manual for the receiver?
>> cheers, Neville Michie
>>
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>>
>See http://tx.mb21.co.uk/gallery/droitwich/droitwich-lf-data.asp - half
>a megawatt now on 198kHz
>
>John
>
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