42 What Is SCPC?
Description
This article is from the Satellite TV FAQ, by Gary Bourgois flash@lopez.marquette.mi.us with numerous contributions by others.
42 What Is SCPC?
SCPC (Single Channel Per Carrier) is a method of transmitting audio
over satellite. Primarily this is a service for Radio Stations, and
is not meant for the general public. This alone makes it fascinating
to receive. There are hundreds of SCPC channels in use. Radio
Networks, Sportscasts, Music services, talk shows, all are heard on
SCPC, as well as major market radio stations. SCPC can be received
with a special receiver, and there are a number of "tricks" that
netters have used to pick up these signals, which can not normally
be received on consumer satellite receivers. If one has a satellite
receiver that has a "70 MHZ LOOP", a cheap TV band Radio can be used
to tune SCPC. While it is also possible to use SOME scanners that
tune the 70 mhz loop (such as the RADIO SHACK PRO-2006) the results
are very poor. The TV radio actually sounds MUCH better. The reason
for this is due to the "step" frequencies of the scanner. With SCPC
the main problem encountered is one of BANDWIDTH. SCPC signals can
be found as narrow as 50 KHz bandwidth to as wide as 150 or more.
By comparison, The TV band radio receives approximately 75 KHz bandwidth
and a normal scanner in narrow mode receives 5 KHz. For this reason,
a standard scanner will not give a listenable signal, even if it is
modified to tune the 70 MHZ loop.
Some receivers, with VIDEO FINE TUNE can be used to shift the 70 MHz
IF band UP to the low end of the REGULAR FM band. This can give
fair results, though usually the entire SCPC spectrum can not be tuned
this way.
For satellite receivers that do NOT have a 70 mhz loop, it is necessary
to use a DEDICATED receiver that can tune the 950-1450 mhz band.
The ICOM 7000, 7100, and 9000 have this capability, though they are
quite expensive. The less expensive (~ $600 ) ICOM R-100 is an
extremely wideband receiver which tunes from 100 KHz to 1800 MHz. This
includes the whole 950-1450 block, so it can tune direct signals from
the LNB. To connect the R-100 or a similar receiver, one uses a DC
BLOCK SPLITTER. The isolated side goes to the R-100, and the other
side goes to the Sat Receiver, which is necessary to power the LNB.
The R-100 is very desirable because it also tunes Standard Subcarrier
(available through the RAW VIDEO Jack on your sat receiver) as well
as FM SQUARED audio. It also is a nice public service scanner, and
SHORTWAVE receiver. This one radio does it all AND it doubles on sax.
There are two DEDICATED SCPC receivers. The simpler HEIL SC-ONE, which
features analogue tuning and sells for around $450. The newer UNIVERSAL
SC-100 features 50 memories, digital readout and a built in amplifier.
BOTH these receivers lack MULTIPLE bandwidths, which mean they do not
give perfect reception of all SCPC signals.
Also, SCPC signals are compressed on a 3 to 1 DBX encoding, which
means reception is lacking in dynamic range unless a suitable
decompression scheme is used.
There is no PERFECT consumer SCPC reception system, but the above
methods DO work, and can provide a lot of enjoyment AND the reception
of several hundred new signals.
Author note: A detailed discussion of audio subcarriers is available
in a written transcript of a recent radio show I did regarding the
various methods of tuning satellite audio. Write if interested in a
copy of this transcript. Also, a listing of SCPC audio stations is
available as part of Robert Smathers' SOUTHSCANNER CHART, regularly posted
to the rec.video.satellite.tvro / HOMESAT lists.
I have also written an SCPC FAQ, which contains much of the information you
have just read, with some additional information, it is available by writing
me at the address in the header of this FAQ.
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