[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: AM on existing Satellites? A better idea

Quite a number of years ago there were three voice systems attempting to retain
fidelity and limit bandwidth.  High seas telephone service by AT&T used a SSB
system in which the carrier was about 12 db down.  The shore station was to
lock on to this carrier.  Two problems:  The receiver was rather complex and
the transmitters had a devil of time keeping the carrier amplitude correct.
     Another system used double sideband and no carrier.  The carrier was 
reconstructed by doubling the DSB signal and inserting it back into the original.
It did not work well with atmospheric and other phase changes in the system.
     Amplitude Compounded SideBand transmitted a reference tone at ten percent
amplitude just higher than voice bandwidth.  This worked rather well and even
met with some success in the commercial market.  The hams operated a transponder
in the San Francisco Bay area capable of six simultaneous ACSB conversations
at one time.  It was ready for satellite packaging but never was completed.
Cliff K7RR  AMSAT LM1606  

"G8IFF/KC8NHF Nigel A. Gunn" wrote:
> And if you have a small amount of carrier, perhaps 20dB down on peak
> sideband signal, you can build AFC into your receiver to counteract doppler.
> Howie wrote:
> >".....old fashioned full carrier double sideband AM has no place on
> > existing OSCAR satellites!....."
> >
> >Agreed... however, I belive many HF rigs generate an "AM equivalent" signal
> >by inserting a user adjustable amount of carrier into an SSB transmission.
> >This could be an interesting mode for LEO operation where doppler is a
> >factor.  Since the carrier reference is transmitted with the modulated
> >sideband doppler is tracked, so to speak. Less bandwidth than FM, similar
> >power requirements to digital modes, no capture effect to "eliminate" weaker
> >uplinks.....or I could be wrong !
> >
> >Howie AB2S
> >
> >----
> >Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
> >Not an AMSAT member? Join now to support the amateur satellite program!
> >To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
> >
> >
> >
> >
> --
> <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
> Nigel A. Gunn. 59 Beadlemead, Milton Keynes, MK6 4HF, England.
> Tel +44 (0)1908 604044 or 07774 478270 (mobile)
> e-mail nigel@ngunn.net   http://www.ngunn.net/cyberworld
> Amateur radio stations  G8IFF, KC8NHF
> Member of  AMSAT-NA  LM-1691, AMSAT-UK #182, ARRL, QRPARCI #11644,
>            Flying Pigs #385, Dayton ARA #2128, Milton Keynes ARC, GQRP #11396
> Supporter of MK Lightning and Dayton Bombers Ice Hockey Teams
> <><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><><>
Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
Not an AMSAT member? Join now to support the amateur satellite program!
To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org