Re: [amsat-bb] Primestar, Shuttle audio

["Bill Jones" <wejones@xxxxxxxxxxxx>]

> Monitoring Times indicates that Shuttle audio is available via GE-2 transponder 13v C-band in SCPC (single channel per carrier) 81.3mhz subcarrier format. 
> 
> Has anyone received this feed?

I've never checked this specific signal, but I have monitored other SCPC feeds. I'll try 
it next shuttle mission.

> Is it the same feed as NASATV?

No.  NASA TV is on channel 9, and is not in SCPC format. NASA TV generally has most of 
the shuttle audio during missions also, but recently they tend to break off occasionally 
for news conferences, etc., so I assume that this is just a more continuous source.

> Is there an easy way to hear the 81.3mhz subcarrier without a special SCPC receiver?
> Is the subcarrier AM or FM?
 
The signal itself is NOT 81.3 MHz.  The signal itself is somewhere around 3950 MHz.  With 
a normal C-band TVRO system, channel 13 is a 40 MHz band between 3940-3980 MHz.  The 
normal TVRO LNBs convert this to a band from 1210-1170  MHz.  Actually the LNB actually 
converts the whole 3700-4200 MHz band to 1450-950 MHz, which is the band the TVRO 
receiver receives.  When you tune a TVRO receiver into channel 13, it further converts 
the 1210-1170 MHz band down to 50-90 MHz. The SCPC signal in question would "probably" be 
found at 1201.3 in the LNB signal.  (although I'd check at 1178.7 if you don't find it 
there)
        The 81.3 MHz you quoted refers to the IF frequency which is available at the "70 
MHz loop" of a typical TVRO receiver (ie 70 MHz is the center freq of the 40 MHz band).  
Not all TVRO receivers have 70 MHz loops... some don't have loops, and some have 140 MHz 
loops, in which case the freq of this SCPC signal would be 151.3 MHz.

To listen to the SCPC signal, which is FM, assuming that you have a sat dish and a 
regular feedhorn/lnb, you can monitor the lnb signal directly (use a "T" and a DC block 
off the lnb coax, both of which you get from radio shack).  I use an ICOM 7000, although 
there are several other receivers/scanners out there that handle the 950-1450MHz band.  
The deviations of these signals can vary quite a bit, anywhere between 15-150 KHz, but 
the ICOM receivers don't have any problems with them. Most tend to be up in the 100-150 
range.   
    You can monitor the 81.3 MHz IF if you have a TVRO receiver with a 70 MHz loop, by 
coupling a "TV-audio radio" (radio shack usually sells these) to the 70 MHz loop, or 
sometimes just by laying the antenna of the TV-audio radio near the appropriate circuitry 
in the TVRO receiver.  
   Be prepared to do quite a bit of tuning, because unless you have a very expensive LNB, 
these signals will drift around by several MHz.  You can listen for a few minutes without 
tuning, but within a few minutes it will require tuning.  I have personally done it both 
ways, and have gotten much better results on the raw  lnb signals, only because there 
seems to be less noise there, and there is less drift in that signal.


************************************
*    Bill Jones   Sweden Maine     *
* wejones@megalink.net             *
* http://www.megalink.net/~wejones *
************************************
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