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World of Ham Radio 1997
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WOHR97_AmSoft_(1997-02-01).iso
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mods
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alinco
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dr1200_2.doc
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1997-02-01
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ALINCO DR-1200 CONSTANT TNC RX AUDIO MOD
Pin 6 on the DR-1200 is connected to the speaker audio lead inside
the rig to allow you to use a single cable to connect your TNC.
The problem with this is that you have to leave the audio level up
a little for the TNC to decode properly. Most people can only
stand so much packet racket! Here's a solution:
CAUTION: THE FOLLOWING PROCEDURE INVOLVES DESOLDERING SMD (SURFACE
MOUNT DEVICES). IF YOU ARE NOT QUALIFIED TO WORK ON SMD DEVICES DO
NOT HAVE THE PROPER EQUIPMENT, DO NOT ATTEMPT THIS MOD! SEEK
PROFESSIONAL TECHNICAL ASSISTANCE. THE ORIGINATOR OF THIS MESSAGE
IS NOT RESPONSIBLE FOR ANY LOSS, INVOLVING THE PERFORMANCE OF THIS
MODIFICATION.
CAUTION: THIS RADIO EMPLOYS STATIC SENSITIVE DEVICES. SUITABLE
MEANS SHOULD BE EMPLOYED TO ASSURE A STATIC-FREE ENVIRONMENT PRIOR
TO BEGINNING WORK ON THIS RADIO.
1. REMOVE POWER AND ANTENNA FROM THE DR-1200
2. REMOVE BOTH TOP AND BOTTOM COVERS
3. REMOVE VOL, SQ, AND VFO KNOBS
4. REMOVE VFO AND MIC PLUG NUTS. USE NEEDLE NOSE AS SPANNER,
BEING CARFULLY NOT TO DAMAGE THE THREADS.
5. CAREFULLY REMOVE THE FRONT PLASTIC COVER. PRY THE FOUR TANGS
GENTLY!
6. REMOVE THE THREE SMALL PHILLIPS SCREWS HOLDING THE CONTROL BOARD
TO THE CHASSIS. GENTLY SWING CONTROL BOARD UP TO EXPOSE THE
BACK OF THE BOARD.
7. LOCATE THE PINK WIRE CONNECTING PIN 6 OF THE MIC JACK ON THE
CONTROL UNIT TO THE UNDERSIDE OF THE MAIN BOARD. DESOLDER THE
PINK WIRE FROM THE >MAIN< BOARD END AND RESOLDER THAT END OF THE
PINK WIRE TO THE "HOT" SIDE OF THE VOLUME CONTROL.
IDENTIFY THE VOLUME CONTROL BY LOOKING AT THE FRONT PANEL
THAT YOU HAVE REMOVED. THE HOT SIDE IS THE TERMINAL ON THE
VOLUME CONTROL (THERE ARE THREE) THAT IS CLOSEST TO THE CPU
CHIP.
8. REASSEMBLE THE RADIO.
NOTES: Some TNCS have a low input impedance on the RX audio line.
The KPC-1 is 10 ohms, the KPC-2 is 600 ohms, but the PK-232 is
10Kohms. The lower impedance TNCS may "kill" the receive audio
when you plug them in. The cure is to remove the offending load
resistor in the TNC!
If you do this, leave one end of the resistor connected for the
next owner to reinstall, if needed. If you run regular 8 ohm audio
into a TNC that has had the load resistor cut out, and don't have
a speaker connected also, you may damage your transceiver's audio
output stage.
Caveats aside, the benefit is that now you can turn the audio all
the way down and still get good copy. And, you can turn it up to
monitor the channel without reaching around and fumbling with a
speaker plug!
73 de BILL, Golden, CO
K0ZL@W0LJF.#NECO.CO.NOAM
---------------------------------------------------------------
MODIFICATION TO HELP WITH INTERMOD PROBLEMS WITH THE ALENCO 1200
DATA RADIO
CAUTION: THIS RADIO EMPLOYS STATIC SENSITIVE DEVICES. SUITABLE
MEANS SHOULD BE EMPLOYED TO ASSURE A STATIC-FREE ENVIRONMENT PRIOR
TO BEGINNING WORK ON THIS RADIO.
1. REMOVE POWER AND ANTENNA FROM RIG
2. REMOVE BOTTOM COVER
3. LOCATE C-19, LEFT SIDE FRONT OF BOARD (LABELED, NEAR Q3).
4. REMOVE C-19: SUCK UP THE SOLDER AND CAREFULLY PRY AWAY
FROM BOARD WHILE STILL WARM.
5. SAVE THE CAPACITOR IN CASE YOU GOT THE WRONG PART!
6. REASSEMBLE THE RADIO, NO RETUNING NECESSARY.
This capacitor connects D1 (back to back diodes) to the first IF
line. D1 is supposed to be a "limiter". Unknown why Alinco chose
to put in such a limiter, as the integrated IF chip IC-1, an
MC3357, has a built-in limiter. Also, the Kenwood TM-231 which
uses nearly the same layout and circuit, doesn't have such a
circuit.
While the intermod hasn't gone away entirely (I'm not done with it
yet!), it has diminished enough to make the rig usable on packet
AND voice now.
73 de Bill, K0ZL@W0LJF.#NECO.CO.NOAM
----------------------------------------------------------------
MODIFICATION TO EXPAND TUNING RANGE OF THE DR-1200T
TO 130-170 MHZ.
CAUTION: IF YOU TRANSMIT OUTSIDE THE DESIGNED LIMITS
OF 144-148 MHZ AND/OR THE MARS FREQS, YOU
MAY BE RISKING YOUR FINAL PA TRANSISTORS!
THE ORIGINATOR OF THIS MESSAGE IS NOT
RESPONSIBLE FOR ANY LOSS OR DAMAGE OR
LOSS OF USE OR SAFETY IF YOU DECIDE TO
ATTEMPT THIS MODIFICATION OF YOUR
EQUIPMENT.
(Horrible that we have to put disclaimers
on something like this, but there's
always one sue-happy jerk who refuses to
be responsible for himself...sigh)
This simple mod will expand the 1200's tuning coverage and
allow you to copy weather radio traffic on 162 MHZ.
Be sure to follow the manual's instructions on tuning,
since you can end up with 350 and 880 MHZ displayed!
1. REMOVE POWER AND ANTENNA FROM THE DR-1200
2. REMOVE THE TOP COVER.
3. WITH THE FRONT OF THE RADIO FACING YOU, YOU WILL
SEE A LOOP OF YELLOW WIRE ON THE LEFT, JUST BEHIND
THE FRONT PANEL. CUT THIS WIRE AND TAPE THE ENDS.
4. REASSEMBLE THE RADIO.
The radio will now tune from 130-170 mhz.
CAUTION: THIS RADIO IS NOT INTENDED FOR COMMERCIAL USE OR
AUTHORIZED FOR USE IN OTHER THEN THE AMATUER,
RACES OR MARS SERVICES! DON'T BE A BOOTLEGGER!