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- From: rvanzant@oreally.sevenex.sol.net (Robert Van Zant)
- Newsgroups: rec.radio.amateur.digital.misc
- Subject: Re: htx-202 9600 mod?
- Date: 24 Jan 1995 15:07:45 -0600
- Organization: Sevenex Public Access Linux
- Lines: 119
- Message-ID: <3g3q71$4lt@oreally.sevenex.sol.net>
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-
- : : Is there a source for a 9600 baud mode for the Radio Shack htx-202 2m
- : : handheld?
-
- : There probably is but I hope you're good at micro-surgery HI.
-
- I wouldn't exactly call it micro-surgery. It's a wee bit tight, but a
- steady hand and a magnifying lense was all I needed (and a soldering iron).
- Actually bringing the leads out of the case is the tough part, as it's
- pretty tight in there. Here's the how-to I've had lying around for some
- time. Obviously, I'm not the author, so credit where credit is due.
-
- ========================================================================
- From: Gene Kennedy <Gene.Kennedy@f470.n3625.z1.fidonet.org>
- Date: Wed, 30 Nov 94 06:04:00 -0600
- Subject: 9600 Baud
- Organization: Di's Online Cafe - Mobile, AL - (205) 661-8945
-
- To Steve and others who may be interested, heres how I connected my 9600
- baud TNC to my HTX-202:
-
- CONNECTIONS TO REALISTIC HTX-202 FOR 9600 BAUD PACKET
-
- NOTE: The following operation requires soldering in very close quarters
- and damage or destruction of your radio is possible if you get too much
- heat on nearby wires or components, or by sloppy soldering.
-
- I performed these operations on my own HTX-202 and it works OK for
- 9600 baud operation with my new Kantronics KPC-9612. I don't take any
- responsibility for invalidation of warranty or improper operation of the
- radio, etc.
-
- I studied the schematics and determined the locations for making
- connections based on general recommendations for 9600 FSK. I didn't
- want to permanently deface my radio by making any holes in the case for
- wire penetrations, so I removed the battery and battery connector which
- is a plastic oval with a spring contact in it held by two screws and ran
- the wires out to the connector that goes to the TNC. I can restore it
- to original condition in just a few minutes. I used the smallest coax I
- had avail, I think it is RG-174. Someone may have a better idea about
- doing that part.
-
- Open up the HTX-202 by removing the five screws, take off back cover,
- and separate front panel and lay it on bench so that flex pc cable won't
- be damaged.
-
- Knobs ______________________________________
- \ __ | |
- | | HF /here ------------ |
- -- | --------'-- -------,---- |
- __ | MIC 0\here |
- |__ | RV1 | <hole in
- __ | ------ | bottom
- |__ | |_vco__| |
- | Top of main PCB |
- |______________________________________|
-
- This is a crude diagram of the inside of HTX-202 after splitting
- case and folding front case aside. There are several sub-PCBs
- standing on edge that I represented by the dashed lines. In my HTX-202
- the sub-board at upper left is labeled HF and the raw output from the
- discriminator IC goes into pin 1, the first solder pad starting from
- the center of the radio. This is where I soldered a small coax and ran
- it out the hole in bottom of case. This is Receive Audio into TNC.
-
- The sub-board labeled MIC is microphone audio to modulator varicap.
- Pin 6 here goes directly into the VCO and this is where I soldered a
- second coax. The solder pad 6th pin from center of radio is right next
- to the RV1 deviation pot. (Dont melt the pot.) This is Transmit Audio
- from TNC.
-
- The third connection, PTT, is harder to describe the actual point.
- What I did was flip the radio over and used a ohm meter to locate the
- solder trace from the center pin contact of external mike socket. It
- runs from just below mike socket to a small SMD resistor. I soldered
- a 2k resistor here and ran a tiny wire from other end of it, along the
- side of radio and out a slot in case where the cover wouldn't pinch
- it, and through the hole in the bottom.
-
- The radio now has to be operated by a power supply, since the
- battery contact is gone and the wires are coming out the hole in the
- bottom. I lengthened the power wire that was removed from the contact
- and connected it to the same power supply as my TNC. The coax and PTT
- wires go to the DB15 connector for the KPC-9612. I used the coax shield
- for RX Audio as the ground connection, but left the TX Audio shield
- un-grounded at the DB15.
-
- I am still in the process of evaluating how well this works on 9600
- baud packet. There are very few VHF 9600 baud stations near me (only
- one, in fact) but hopefully in the future this will change.
- Good luck, and I welcome any feedback about this.....
-
- Gene, WA4WBI
- =============================================================================
-
- ....rvz here again....
-
- I followed these directions, and receive works just lovely. I've only
- managed one connection though, not sure if it's a problem with the hookup,
- or just my measly 30 watts not doing the job. Much like Gene, I'm having a
- hard time finding other 9600 activity close by. Anyone know of activity in
- the Northern 'burbs of Chicago?
-
- Couple of notes... Although it's probably necessary to pull the front
- off the radio just to identify the proper points, I made my connections on
- the rear of the board that's exposed immediately after removing the back
- cover. Be careful with the routing of the rg174, paying attention to what
- will be crimped when replacing the cover. A friend smoked his when he
- screwed the cover back on (what's an ERR 01 mean?), piercing the cable with
- one of the ic pins. I also didn't bother running the PTT cable out as Gene
- describes. I put a plug on the end of PTT lead from the TNC, and use the
- microphone jack on the radio instead.
-
- good luck,
- rvz N9ORG
- --
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- Robert Van Zant Sevenex Public Access Linux
- rvanzant@sevenex.sol.net 414-843-4169 v.fc 24hrs
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