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RE: AM on existing Satellites? A better idea



That was amplitude compandored SSB.  I got a piece of hardware from
the primary supporter of this activity at the ARRL at the time. I worked
many many hours getting it to work and then had not one soul to talk to.
I couldn't even get who else got the gear so I could buy it and then
get somebody near me.

Now, amplitude compandored SSB, a FANTASTIC idea, is about 12 lines of
code in the SDR-1000!:  http://www.flex-radio.com

Bob
N4HY


-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of Cliff Buttschardt
Sent: Thursday, February 05, 2004 1:13 AM
To: G8IFF/KC8NHF Nigel A. Gunn
Cc: Howie; Bob Bruninga; amsat-bb@AMSAT.Org
Subject: Re: [amsat-bb] 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.
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----
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