soomre@mred.DEC (02/18/85)
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. 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 ? Keep up the good info, questions and answers, as I look forward to reading news on this net daily. ....... 73's Ed Soomre (N1BFF) Digital Equipment Corp 1 Iron Way Marlboro, MA 01752
karn@petrus.UUCP (02/19/85)
> 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
mjg@ecsvax.UUCP (Michael Gingell) (02/21/85)
ACSB sounds a lot like LINCOMPEX - a modulation scheme used in radio equipment made and sold for years by Standard Telephone and Cables in Britain. I understand it is sold mainly for diplomatic (embassy) communications equipment all over the world. Mike Gingell (..decvax!mcnc!ecsvax!mjg)
jhs%Mitre-Bedford@d3unix.UUCP (02/21/85)
ACSB is Amplitude Companded Single sideBand or something like that. As near as I can tell, it is very much like the SSB widely used on the ham bands these days by speech processor afficionadi, except that the receiver has a provision for expanding the dynamic range again, so it shouldn't sound quite so awful on receivers so equipped. If you listen with your Kenwood, it should be perfectly intelligible, but probably would sound like someone running a lot of compression (which they are). According to some of my old cohorts at Motorola, ACSB is nice in theory, but loses out to FM (which they conveniently happen to be able to supply from their standard product line) in urban environments where the real limiting factors are adjacent-channel interference, intermod, multipath, and all those things that don't show up in the academic investigations of SNR in FM versus ACSB systems. Clearly, Motorola has an axe to grind, but they also have a whole lot of RF systems expertise and actual experience with urban environments, so their opinion should be considered very seriously before everybody converts madly to ACSB! 73, John Sangster, W3IKG jhs at mitre-bedford
dave@rocksvax.UUCP (02/25/85)
In ACSB a few percent of the channel power is dedicated to sending a pilot
carrier that is related to the actual carrier in some fashion out of the normal
"audio" band. The receiver phase locks to this pilot tone and adjusts the
BFO of the receiver to the exact frequency, eliminating the normal
"Donald Duck" effect of SSB mis-tuning.
From what my roommate who owns a two-way shop says, the stuff is great in
strong signal areas, but when you get into the fringes the signal deteriorates
very rapidly, especially in fluttery conditions prevail.
My partner in my new company was the marketing VP for Sideband Technology
who perfected the technology told me of the gawking that the Motorola
folks did at the trade show they demonstrated their radio at, seems that
they where playing Barbara Striesdan(sp?) through their box and it
didn't sound half bad.
Motorola is like the IBM of the radio industry, whatever they invent is
"real". No one belieese anything can be done 'til they commercialize it.
Kinda like the recent IBM development of 'full-duplex' terminals.
Dave N2GH
arpa: Sewhuk.HENR@Xerox.ARPA
uucp: {allegra,rochester,amd,sunybcs}!rocksvax!dave