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[aprssig] TM-271A data mod

scott at opentrac.org scott at opentrac.org
Wed Mar 16 06:19:32 UTC 2005

Got the TM-271A today - I broke a personal record and had it for some two
hours before taking a soldering iron to it, but that's mostly because it was
dinner time and then someone called on the phone.  Actually my wife called,
and since that only happens once or twice a year, I figured that should
probably take priority.  Long story.

Anyway, good news... the pads for the data connection not only exist,
they're conspicuous and clearly labeled.  Apparently the European version
ships with a pigtail on it, presumably with a female mini-DIN.  There's only
a small hole under the power lead grommet for the data cable, so it's not a
bulkhead mount.  In the American version the hole just has some foam stuck
in it.

The silkscreen markings on the board are even listed in the manual (PKD =
data in, PKS = standby, PR9 = 9600 out, PR1 = 1200 out, SQC = squelch, GND =
ground).  (Standard disclaimer applies - this is all for TNC audio, not
digital signals.)

Close up:  <http://n1vg.net/images/tm271a_mod1.jpg>
Whole board: <http://n1vg.net/images/tm271a_mod2.jpg>

I've got R119 circled for reference - that's the jumper to remove for
extended transmit.

I'll probably stop by the electronics supply store tomorrow and see about
getting an appropriate connector.  I'll let you know how it goes - I don't
anticipate any problems at this point.

So... there IS at least one sub-$200 2-meter radio on the market with a
9600-baud packet connector, if you don't mind 10 minutes of tweaking.

BTW, if anyone knows of a good way to mount one of these in a '99 Honda
Accord, let me know.


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