Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Posting-Version: version B 2.10.2 9/18/84; site petrus.UUCP
Path: utzoo!watmath!clyde!burl!ulysses!allegra!bellcore!petrus!karn
From: karn@petrus.UUCP
Newsgroups: net.ham-radio
Subject: Re: ACSB Transmissions
Message-ID: <291@petrus.UUCP>
Date: Tue, 19-Feb-85 11:31:21 EST
Article-I.D.: petrus.291
Posted: Tue Feb 19 11:31:21 1985
Date-Received: Fri, 22-Feb-85 06:58:54 EST
References: <625@decwrl.UUCP>
Organization: Bell Communications Research, Inc
Lines: 35

> A new experimental mode of transmission on the VHF land mobile
> band (150-174 MHZ) is being used called ACSB. I am not sure what it
> stands for, something like Amplitude Compared Side Band. I think it
> is used like SSB on hf. 

"ACSB" is a trademark of STI (Sideband Technology Inc), the very same
guys who want to take our 220 mhz band. The acronym stands for
Amplitude Compandored [single] SideBand.

> 
> Is a transmission of this type receiveable on a Kenwood R2000 hf
> receiver with the optional 118-174 MHZ converter using either
> LSB or USB modes ?

Yes, ACSB can be received on a standard SSB receiver, although not with
the same fidelity as the intended receiver.  ACSB consists of an ordinary
SSB signal in which the audio has been compressed and a "pilot tone"
indicating the level of compressor gain has been added. The receiver
simply locks to the pilot tone (which has the side effect of providing
a stable frequency reference) and varies the gain of an expander amplifier
so as to keep the pilot tone at a constant level.

ACSB really works, particularly in marginal fading conditions like a
channel on Oscar-10. The extra gain during unvoiced speech segments
and higher average transmitter power makes the difference between being
intelligible and being mostly below the noise floor. Off-axis spin fading
is taken right out. Listening fatigue is considerably reduced because the
background noise almost disappears between syllables.

A couple of stations are beginning to experiment with ACSB on Oscar-10.
For more info, contact Vern Riportella, WA2LQQ, POB 177, Warwick, NY 10990.

Homebrew ACSB circuits are starting to appear in the ham magazines.

Phil