Dick Rollema wrote:

To All from PA0SE

Not all TV-stations derive their sync-signals from stable frequency sources. Harry, PA0LQ, has investigated this matter some years ago and seemed to remember that BBC1, BBC2 and the German ARD are referenced to an atomic standard and therefore very stable. But Anjo, PA0ZR, recently found out  that this was no longer the case for BBC2. But perhaps this is due to the fact that the BBC2 signal, as distributed over Europe, is picked up near Dover from a station in Kent and perhaps this one does not use the atomic standard.

The digital televison network is not locked in this way. The accuracy there is only that of a good crystal
and will vary as they switch from source to source. So you cannot use any digital cable, satellite or
terrestial transmission as a high accuracy reference.

Also some long distance distribution, ie C4 is distributed arround the UK is done that way and
then converted back to analogue. Only if the analogue broadcaster re-syncs to a high
accuracy reference will that be precise.

Stewart G3YSX
 

 

73, Dick, PA0SE

At 08:13 12-4-02 -0400, you wrote:

Hello Jim, Uwe and group,

Yes of course an LF broadcaster can only be used as reference if he is quite close to your station. Groundwave propagation must be dominant throughout the observation period. But there is a way to find this out:
Use the TV sync as reference to observe the MSF or DCF77 carrier. Requires no hardware (except for a potentiometers to adjust the input signals to the receiver).  Input signals (into the longwave receiver) will be 4*15625 Hz and 60kHz, or 5*15625 Hz and 77.5 kHz. Fortunately, in both cases the signals fit in a standard 3kHz IF bandwidth.

This allows checking if the reference phase is stable enough  -  if you are lucky you'll never have to let the TV turned on overnight ;-). I will try this experiment soon and let you know the results.

Thanks Uwe for the signal gallery. >From your QTH, you can be sure to receive Loran from Sylt via groundwave !

Regards,
 Wolf  DL4YHF.