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Re: [OZAPRS] Re: More ISS Alpha



Someone wrote:
> >boy, i gave up trying to get a packet to the iss. i have come to the 
> >conclusion that any kenwood radio will work just fine as everyone i
> >know with at thd7 or ts2000 gets through just fine. gonna have to junk
> >my [other rig] for an ht.

Of course, the #1 problem is saturation on the uplink.  But that aside,
one thing that SPACE use of 1200 baud AX.25 shows is that just jamming the
plugs from a TNC into a Radio is not a guarantee of success.  Yes, it may
work 10 miles to a nearby BBS with dead full quieting signal and no
doppler, but working over a path of 1500 mi with +/- 3 KHz of Doppler
needs a properly adjusted signal.  

One advantage of the factory integrated internal TNC's in the Kenwoods (or
Alinco's) is that operators don't have to worry about all the interfacing
factors that other users do:

1) Frequency.  Is your many-year-old rig still calibrated in frequency?
It might say 145.990, but is it really on 145.990?

2) Are your TNC tones set below the level of your speech processing and
mic AGC circuits so that they do not compress, distort, or unbalance them?

3) Does your MIC mute when the TNC keys the rig, or does your shack
noise get added to the signal?

4) Is your deviation correct?  (1Khz or so less than that used
terrestrially to allow for the Doppler.  I think 3 Khz or less is the
preferred value, but there are many opinions here.)

5) Are your tones balanced? (Equalized)  Unfortunately there are two
schools here, with and without pre-emphasis.  Your milage may vary.
[The kenwood D7 is without pre-emphasis (tones are balanced at the
discriminator), but the ISS we think is optimized better for mic/speaker
TNC interfaces which include premphasis]   Also note, that unless #2 is
correct, then doing the TNC manual's One-tone-and-then-the-other-tone test
to the same level is meaningless.

One simple test is to transmit at low power to a friend.  Have him go +
and - 5 KHz and see if he still hears you... (this is beyond a worst case
offset seenario which is at least 2 KHz worse than you will actually
experience, but it will tell you something...  I have found several locals
that (after many years of consistent operations with their local BBS)
began to have problems.  Turns out their synthesized radios had aged and
what they thought was 145.010 was actually 5 KHz or more off..

Good luck.  Of course the best solution (for everyone else) is to back
off, and let someone else get in.... and count SUCCESS as how many
other people you RECEIVE... <GRIN>  

de WB4APR, BOb

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