David Albert <albert@ENDOR.HARVARD.EDU> (01/16/90)
My Sony 7600DS has an SSB switch, but I have no idea what I might want to use it for. I'm also not sure what it does (i.e. physically); is it the equivalent of a narrow-band switch? Thanks, ------------------------------------------------------------------------------ David Albert | UUCP: ...!harvard!albert | "My fear, your wish -- both granted." INTERNET: albert@harvard.edu |
hanavin@BBN.COM> (01/16/90)
In article <1265@husc6.harvard.edu> albert@endor.UUCP (David Albert) writes: >My Sony 7600DS has an SSB switch, but I have no idea what I might >want to use it for. I'm also not sure what it does (i.e. physically); >is it the equivalent of a narrow-band switch? > >Thanks, >------------------------------------------------------------------------------ >David Albert | >UUCP: ...!harvard!albert | "My fear, your wish -- both granted." >INTERNET: albert@harvard.edu | The SSB switch is used when you want to tune in a station that is transmitting SSB. SSB stands for Single Side Band, it is a mode of communication used on the shortwave band. You will find lots of SSB being used on the ham bands, so try there first to get the hang of it. It's a little tricky. You can also use the SSB switch to tune in morse code. 73 de Chuck (WB3FJJ)
Ed Schwalenberg <Ed@ALDERAAN.SCRC.SYMBOLICS.COM> (01/16/90)
Date: Tue, 16 Jan 90 15:51:32 GMT
From: David Albert <albert%ENDOR.HARVARD.EDU@CUVMB.COLUMBIA.EDU>
My Sony 7600DS has an SSB switch, but I have no idea what I might
want to use it for. I'm also not sure what it does (i.e. physically);
is it the equivalent of a narrow-band switch?
SSB stands for Single SideBand. Ordinary AM modulation consists of a carrier
(what you hear when nobody's talking) and two mirror-image sidebands, which
carry the information. It's cheap to build transmitters and receivers for AM,
but AM is wasteful of energy and bandwidth, since the carrier and one of the
sidebands can be discarded without losing information. SSB does exactly that:
an SSB transmission is an AM transmission with the carrier and one sideband
eliminated. If you try to listen to one in AM mode, it sounds like Donald
Duck. The SSB switch activates some circuitry which basically tries to
duplicate
the missing carrier, so the signal can be detected like an AM one. (The details
vary with the kind of receiver, so I'm glossing over things here.)
The bandwidth of an SSB signal is exactly half that of an equivalent AM signal;
a narrow bandwidth filter of between 2.5 and 5KHz will give you all of the
desired signal and filter out adjacent interference. (A corresponding AM
filter,
being twice as wide, allows twice as much interference through.) Selecting SSB
mode does not have any direct effect on bandwidth in most receivers; the choices
are orthogonal in theory and usually in practice as well.
Virtually all SW broadcast stations use AM, since that's what common receivers
use. You can hear SSB signals almost anywhere in the shortwave spectrum that
is NOT part of a SW broadcast band. Most non-broadcast stations use SSB because
you can get twice as many stations in a given frequency band and because SSB
provides more readable signals than the equivalent AM (all the transmitter power
goes into one information sideband so you get 2 or 3 times the effective power,
and the receiver can use narrower filters to avoid more interference).
Tuning an SSB signal is harder than tuning an AM signal: if you tune 1KHz off
dead center, the tones in the modulation will be shifted by 1KHz too, so you'll
get squeaks or growls instead of voices. There are two possible sidebands:
lower
and upper, or LSB and USB. If you tune the wrong one, you'll get inverted
speech,
with bass and treble inverted. This also means that successful SSB radios must
be very stable; if your radio drifts by 1KHz on a 30 MHz signal, it's only off
by 1 part in 30,000 but you won't be able to understand anything.
A variant on the SSB idea is used by the VOA for getting programming from the
US to foreign transmitters (so-called "feeders"): ISB or Independent SideBand
sends two different programs via one transmitter on one frequency, using LSB
for one and USB for the other. It sounds like Huey, Dewey and Louie all talking
at once on AM.
Another variant is the ECSS feature in the Sony 2010 receiver discussed
here so often: ECSS amounts to pretending that an AM signal is an SSB one.
You can do that with any SSB receiver by tuning an AM signal in SSB mode until
the zero-beat goes away, but even the slightest drift will cause a 1 or 2 Hz
"motorboating" sound which is extremely annoying. ECSS locks the receiver to
the transmitter frequency, preventing the drift. You can then choose the
sideband
with the least interference, and use a narrow SSB filter to eliminate even more
interference.dalyb@BBN.COM> (01/17/90)
Subject: Re: What does one do with an SSB switch? Newsgroups: rec.radio.shortwave Keywords: novice question Summary: Single Sideband mode of operation References: <1265@husc6.harvard.edu> In article <1265@husc6.harvard.edu>, albert@endor.harvard.edu (David Albert) writes: > My Sony 7600DS has an SSB switch, but I have no idea what I might > want to use it for. I'm also not sure what it does (i.e. physically); > is it the equivalent of a narrow-band switch? SSB stands for "single sideband". SSB is a modulation technique which is used quite extensively by amateur radio operators (HAM's), as well as others. In order to understand what SSB modulation is, let's look at amplitude modulation (AM). The purpose of modulation is to put some information onto a radio frequency carrier signal; when you speak into a microphone of a radio transmitter, the electronics within the transmitter "modulates" the RF signal with the voice information. In amplitude modulation, the amplitude of the RF carrier is changed ("modulated") by the message signal (i.e. the voice). If you were to look at the output of an AM transmitter, say with a spectrum analyzer, what you would find is: a carrier signal and two "sidebands". The carrier is the actual RF signal of the transmitter; this carrier contains no information -- you cannot get the voice message back from the carrier signal. The voice message is carried in each of two "sidebands"; these are upper and lower sidebands. Each sideband contains all the message information. This AM signal looks as folows: ^ ^ | ^ | | | ----------------------------------------- LSB Carrier USB where LSB = lower sideband; USB = upper sideband Note that the sidebands are at a slightly different frequency than the carrier. Now, note that we are wasting transmitter power because in AM the carrier is transmitted -- as well as two sidebands with identical information. What if, then, the transmitter suppresses the carrier and one sideband (either the lower or upper -- it doesn't matter)? This results in single sideband operation -- the transmitter only transmits one sideband. This also has the benefit of conserving precious spectrum, since the SSB signal takes up less room than the wider AM (double sideband) signal. In a radio receiver, to demodulate (recover the voice message) from the RF signal (in this case, a sideband), a product detector is normally used. This detector requires a local oscillator (called a BFO), to recover the voice message from the carrier. There is normally a BFO Frequency tuning control on the receiver to properly adjust the BFO so that the voice is properly received. Standard AM reception does not require this method of demodulation. A single sideband signal received without the receiver set to SSB mode is unintelligible; you can make out that there is something there, but it sounds muffled and unreadable. Tune the receiver to one of these signals, then switch to SSB mode. If the BFO tuning is off, the voice will sound like a "Donald Duck" voice -- use the BFO tuning to adjust to a normal-sounding voice. For more information on modulation or radio in general, refer to some of the American Radio Relay League publications. Brian K. Daly WB7OML UUCP: {...!ames!ncar!noao!asuvax|uunet!zardoz!hrc|att}!gtephx!dalyb AG Communication Systems, PO Box 52179, Phoenix, Arizona 85072-2179 Phone: (602) 582-7644 FAX: (602) 582-7111
postmaster@CUVMB.CC.COLUMBIA.EDU (01/17/90)
SSB is Single Sideband telephony, reduced or suppressed carrier. Thus
to demodulate this form of transmission, the carrier must be re-inserted
and a suitable detector used such as a balanced detector.
SSB sounds like "Donald Ducking when encountered on the air. With the
the SSB switch ON and very slow fine tuning it does indeed become
intelligable. Some receivers have an LSB and USB switch or equivalent, this
stands for Lower Side Band and Upper Sideband as either can be transmitted.
Standard AM Broadcast is "Double Sideband Full Carrier" as a comparison.
SSB results in more power available for transmission and is a favorite of the
Amateur Radio Ops, HAMS.
Some Ham Bands to listen to are 3.5 to 4.0 MHz, 7.00 to 7.3 MHz, 14.00 to
14.35 MHz, 21.00 to 21.45 MHz, 28.00 to 29.7 MHz. SSB is generally on the
upper portion of these bands. With a good antenna you will be able to
receive Amateur Radio Stations World Wide.
Best Regards (73)
Rod Dinkins AC6V