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[wxsig] T238 update

Ted11 tedlists at hullar.com
Thu Aug 12 04:10:49 UTC 2010

Hey, good to hear from you again!  And your timing is perfect.  I've got
everything built, and have got the weather instruments up and running.  Just
working on implementing the radio portion today.  Having trouble with the
modem, but I'll save that until last.  

Responding to your questions, then posing one of my own:

TAI-603:  For me, at least, it's been working fine.  I've got it on the full
length of the cable provided by AAG (2 x 15' Cat 5).  I'm getting some
errors on temp and wind sensor, but nothing overwhelming.  The red and blue
lights are a bit goofy, but the instrument itself seems accurate and
reliable.  Wiring it was a bit of a pain, but having the RJ-11 duplicated on
a jumper was a brilliant move and saved me from serious headaches.  

Assembly instructions:  I thought they were very good.  Clear, descriptive,
and complete.  I had noted a typo or two to you before, but didn't find
anything else.  One thing I think you may want to add:  suggest users
download and install the latest software version after successful power up
of the device.  I kept getting "no devices found" errors on the T238 after I
connected the TAI-603.  I checked the wiring several times, made sure it
worked on my computer, and so on.  I was just about to post here when a tiny
voice in my head said "check for a software update", and of course that was
it.  It's not really a problem with the instructions, it's just one of those
things some people (me) are going to forget.  

One other possible issue in the instructions:  In the modem assembly
instructions, top of page 5, it says pin 6 of P100 should be +5V.  I'm
getting more like 3.4.  However, I think this is because of the voltage drop
across the diode.  Is that possible?  Or, perhaps something is wrong with my
modem (see below for more details on this).  

DS1904:  I would like to install the DS1904 at some point, not sure if I
will have time to do so before I'm supposed to use the setup at a special
event in a few weeks.  If testing can wait a month or two, I'll be happy to
do it.  

And finally a problem I could use some suggestions with:  I connected the
modem output to a Alinco DR-135 (no internal TNC), using the DB9 in the back
of the radio.  Made a custom cable to do this.  However, I do not get any
packets sent out the radio.  The red XMIT light will light, the modem will
key the radio, as if it's sending something, but I don't get any warbling
sound of the packets when I monitor the transmission.  This may be related
to the voltage being too low at pin 6 of P100 as I noted above, but I'm not
sure of that.  

Diagnosis so far: R109 is fine.  I removed Q100, voltage at pin 4 is still
3.4 V.  I switched D101 and D100, still 3.4 V.  However, I'm not sure if
this 3.4 V indicates a problem or not, perhaps it's something else entirely.
Any suggestions for diagnosis?  One other thing to note - I found only one
100 pf cap when I was assembling the kit (I probably lost it) so I replaced
C100 with a 100 pf ceramic disk cap from radio shack.  Thanks for the help,
I'm running into the end of my knowledge...



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