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Re: Deviation adjustments etc



Lee Barnett writes:
snip
> I think I saw something a while
> back about transmit deviation adjustments when using the FT-847 with the
> DSP-2232 but, I thought that was for the 1200 baud connection.  My problem
> is with 9600 baud.

I posted the following a while back; a replay may be useful (not just for
deviation setting but general "get the darn thing working" tests too). Lee
should probably start at para 3.


Q: How can I tell if the set-up is working?

1. connect txdata to rxdata on tnc. Prove self-connection. [tnc works]

2. Connect tnc to radio(s); turn tx power down to zero (dummy load too if
   available); set tx frequency (on 145MHz) wherever you like, deviation set
   to minimum, tx ON; tune in third harmonic on 435MHz; prove self-
   connection (increase deviation until it connects). Remember to have mic
   gain on tx rig turned to zero. [connections to radio work]

3. Deviation setting: People with scopes: use a HT (or second rig) to look
   at the audio output of a local 2m repeater, note amplitude on scope (most
   repeaters have their deviation set up properly); now tune in 2m 9600
   txdata and adjust deviation for same scope amplitude; then reduce it
   slightly and follow instructions for folks without scopes. (you are now
   in the right ballpark)
   People without scopes will need to test *live*; start with deviation at
   zero and increase until the following tests work; or get a friend with a
   scope to do the above test on your transmission. You'll find theres a
   bandwidth of deviation that works the satellites, too little *or* too
   much will not. Leave deviation setting in the middle of the range.
   This adjustment is usually quite touchy so be gentle.

4. Use an ordinary terminal program (Procomm etc). When a 9600 satellite
   comes up, see if data appears onscreen (remember to turn MONITOR on).
   What *should* happen is that the screen should rapidly fill with rubbish;
   receive rf side works ! Turn MONITOR off; attempt a connect (this is the
   time to "play" with deviation setting). When you *do* get a connect (or
   even a BUSY) you then know the whole rf side works. After a connect (via
   Procomm) there will be a short piece of nonsensical data and the
   spacecraft will disconnect after a short period; better though to
   disconnect yourself after achieving connection. You can then progress
   into the groundstation software.

5. I'll not discuss groundstation software because theres several different
   programs around and you'll need to find an Elmer for that (and, if all
   else fails, read the help files). Once thats working then find a big
   file (say 50-100K) and upload it, address it to yourself, mark the
   Subject as "upload test" or something similar and set a short expiry
   time. NEVER send test messages addressed to ALL. While the file is 
   flowing upwards you can then play again with the tx deviation and find 
   the middle of the "it works" range.

6. Enjoy

73
Richard W L Limebear G3RWL
g3rwl@amsat.org
FOC # 1188

          So many beautiful girls ..... (sob) so little time
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