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QRZ! Ham Radio 21
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QRZ Ham Radio Callsign Database - Volume 21.iso
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MODFILES
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HTX252-2.TXT
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2003-04-12
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I picked up a Radio Shack HTX-252 on sale, I intended it for APRS/
packet use, to free up my HTX-202 HT to go portable again.
No schematics were included in the manual, nor information on how to
hook the little bugger up on packet. And it does not have a lot of
use friendly features!
RS.com and Search Engines turned up little on the rig circuitry... So
doing what any self respecting ham would do, I grabbed my trusty
phillips and reverse engineered it! I opened up the radio and the
MIC, to discover its secrets....
Turns out the mic audio and PTT are on the same line, same type of mic
control as HTX-202 and ICOM hand helds, which I was already using for
packet.
To make a temporary mod, the MIC is unplugged, and front Mic connector
is used, you can attach wires with mini alligators, or the Female Pins
from a DB-9 D sub connector. 276-1428. The MIC Center pin is
ground. The (5 O'clock) Bottom Right pin is PTT/Audio.
o o o
o o o Center pin is ground.
o n o < Ptt/Audio
That drawing probably looks like gibberish on your screen too.
However, You cannot control this rig only from the front panel. This
rig will not allow you to change many of the settings without the
Function Key on the mic.
Drilling a hole in the metal case of the radio to mount a jack seemed
like I was asking for trouble. Metal shavings on a fine pitch surface
mount circuit board, YUK!
So I decided to mod the MIC and install a 3/32" (2.5mm) phone jack
(274-247) in the side of the mic. Remove the 2 bottom screws, and
lift the Back Cover off the mic, being gentle with the wires and
strain relief grommit. Locate a spot on the mic back cover opposite
of the PTT button. There were no parts on the MIC internal circuit
board in that area. I drilled a small mounting hole in the back cover
on the side to mount the jack. I made a pair of stranded twisted pair
wires, about 3" long, and soldered them to the ground and center lugs
of the phone jack. Thin and very flexible Shielded wire would have
been preferred, but I use what I have...
I attached the ground and audio to the pads where the mic cable is
mated to the board. From left to right, 7th pad, audio/ptt, (white
wire) a space and the 8th pad, ground, (yellow spaghetti over twisted
braid)
BE CAREFUL WHEN SOLDERING, THESE WIRES ARE SURFACE MOUNTED, AND DO NOT
GO THROUGH A HOLE, SO WHEN YOU MELT THE SOLDER, THEY MAY MOVE OR COME
OFF!!!
< jack side PTT button side >
O O O O O O O <aud O <GND
Re assemble and feed it packet data like an ICOM HT ! After modding
the mic, you can now plug and unplug your TNC from the side of the mic
and still use the function buttons on the mic!
Enjoy!!!