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TMSat 38k4 downlink test!
- Subject: [amsat-bb] TMSat 38k4 downlink test!
- From: John Melton - Sun UK - ENS <John.Melton@xxxxxxxxxx>
- Date: Fri, 4 Dec 1998 11:10:59 +0000 (GMT)
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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