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Re: Help for AO40 signal verification needed


Thanks for the explanation of where these low level sidebands come from.

I checked this morning at the upper sideband frequency and the signal is 
there as you predicted.



At 14:53 20/12/01 +0000, Michael.Fletcher wrote:
> >Hello all,
>Hi Günter,
>and congratulations on your well working
>system !
> >i am very interested to know if someone
> >else can receive a signal from the beacon
> >at this frequency: qrg= S2 MB - 978 kHZ
> >It is in the S1 band.But you need a big
>I will not confirm the signal level "live"
>(I have a 3 m dish, but will not be
>able to use it for a few days), but
>I CAN confirm that you are quite correct !
>The sidebands are symmetrically on both sides
>of the passband center frequency (MB),
>so you should hear it also above the S2 MB.
>The sidebands you are hearing are leakage
>of the HELAPS modulator switching frequency.
>These spikes are about 40 dB down from the
>Middle Beacon when passband signals are
>9 dB below middle beacon, i.e. the absolute
>level of the spikes will vary with
>transmitter (and receiver) AGC values.
>It is entirely normal operation of a
>HELAPS transmitter to have these spurious
>signals and the -40 dB(MB) levels are
>also normal.
>As a challenge you can try copying the
>carriers at twice this distance from the
>MB but they are even 25 dB lower :-)
> >dish-i think minimum 3m.Here i have at
> >the moment at MA11 Orbit 524 about 5db
> >S+N/N.(6m dish) With various tests i
> >can carefully say its not a local effect
> >(intermod...mixing ...) The best times
> >to listen are between MA235 to MA25.
> >At apogee i also have problems to
> >detect the signal-its very weak then.
>You jolly well should be experiencing
>problems copying these signals - they
>have been suppressed intentionally :-)
> >So please have a look!
> >vy 73 Günter DF4PV
>Kind regards,
>Michael, OH2AUE
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