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Re: PSK modems??



At 12:57 AM 2/11/98 -0500, you wrote:
>Hi all:
>
>I have a question about the Pacomm PSK-1 modem. I'm told that
>this modem is a decode only unit, and must be used in combination
>with a standard TNC.  I understand that LU-19, WO-18 and ao-16 all
>receive standard packet signals and transmit in BPSK. That explains
>the two modem combination.  I have a Baycom tnc, and wondered if
>this modem could work in combination with the PSK-1. 

No it will not work, and that does not explain the two modem combination.
You need manchester encoded AFSK FM 145 Mhz for the uplink and PSK SSB 435
MHz for the downlink.  The PacComm PSK-1 Modem is exactly that, it is a
modem, it does not have a TNC inside it.  It attaches to a TNC via its
modem disconnect port.  


> I was also wondering if one can  receive messages and files
>from these birds with the PSK-1 without uplinking to the satellites??
>In other words, are the files "broadcasted" or does one need
>to send commands in order to receive the files??

You can receive files without transmitting.  In fact, this is a good way to
start if you are short on funds.  It took me several years to put my
station together, but it is complete now.


> Since I cant afford the $500.00+ for a full blown sat modem, 
>I can at least find a used PSK-1 to receive image files from
>WO-18 and other data from the various pacsats. 

Say what!!!!  You can spend $149.00 for the Motorola DSP56002EVM and it
will do all the satellites modes, transmit and receive.  The only question
you have to answer is how industrious are you.  To see the EVM and what it
can do for you see

    http://www.tapr.org

and follow the links to DSP and then EVM.

Also, purchase "The AMSAT-NA Digital Satellite Guide."  It will help answer
many of your questions concerning digital satellites.



 - Steve, N7HPR
 (n7hpr@tapr.org)




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