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TMSat 38k4 downlink test!



Hi,

did anyone else try to copy the 38K4 downlink on the 10:55 UTC (ish) pass over 
the UK yesterday.

If you did, I (and Chris) would be interested in knowing how you got on.

Chris tells me that there was a problem when it was first switched over,  but 
for most of the last half of the pass it was working.

I did not do too well.  I was at work and had left the station setup so that it 
would accept packets from two interfaces one at 9k6 and the other at 38k4.

I really need to be at home next time so I can see what is actually going on ;-)

For those of you that are interested in the setup that I am trying to use, it  
looks like this:

Note:  you need to view this with a fixed font - didn't wanty to be flamed for 
sending an image ;-)


  
                         38K4 Hardware configuration

                      ^                               |
                      |                               |
                      | uplink                        | downlink
                      |                               v
              +---------------+               +---------------+
              |               |               |               |
              |   Icom-821H   |               | Icom PCR-1000 |
         +--->|               |               |  50KHz Filter |<---+
         |    |               |               |               |    |
         |    +---------------+               +---------------+    |
         |         ^                                  |            |
         |         |                                  |            |
         |         |                                  |            |
         |         |                                  |            |
         |    Out  |     +----------------------------+            |
         |    9k6  |     |                            |            |
         |         |     |  In                        | In         |
         |         |     |  9k6                       | 38k4       |
         |         |     v                            v            |
         |    +---------------+               +---------------+    |
         |    |               |               |               |    |
         |    |   Motorola    |               |     FX589     |    |
         |    |   EVM56002    |               |     based     |    |
         |    |               |               |     Modem     |    |
         |    +---------------+               +---------------+    |
         |            ^                               |            |
         |            |                               |            |
         |            | 9k6                      38k4 |            |
 Uplink  |            | Kiss                     HDLC |            | Downlink
  Freq   |            | Interface          Bit Stream |            | Frequency
 Control |            |                               |            | Control
         v            v                               v            v
      +---------------------------------------------------------------+
      | 9k6          9k6                             38k4         9k6 |
      |async        async                            HDLC        async|
      | port         port  Sun SparcStation 20       port         port|
      |                    -------------------      (8530)            |
      |                                                               |
      +---------------------------------------------------------------+



I am running a modified version of the JStation AX.25 protocol code that 
initializes 2 receive packet sources,  and have written a small amount of native 
C code to drive one of the built in ports, that is a Zilog 8530 chip, in its 
synchronous HDLC mode to decode the packets from the FX589 based modem.

All trans mit packets are sent on the 9k6 interface.

In this mode,  I should be able to work both the 9k6 satellites and TMSat when 
it is in the 38K4 mode without having to change any hardware/software. If it is 
transmitting at 9k6,  the EVM56002 board will decode the packets,  and if it is 
transmitting at 38k4,  the FX589 will decode the packets.


-- John Melton  n6lyt/g0orx


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