Subject: ICOM IC-281 Mods



I tried to upload the following to oak.oakland:/pub/hamradio/incoming

but got a permission denied.  If you can put it in it might be helpful

to others.



Eric Evans KE6QBU



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ICOM-281 MODS



DISCLAIMER:Some of these mods require knowledge of surface

mount soldering techniques, if you do not know what you are doing

you can easily damage your radio.  These mods may make

your radio illegal to own and/or illegal to use on certain frequencies.

By performing these mods you are taking full responsibility for

any consequences that may arise. Performing these mods may

invalidate your warranty.



Crossband repeat (no internal mod required)



To enable crossband repeat press and hold the BAND

key and the SET key for about a second, a flashing L will

appear in the lower right. To turn off hold the SET key.

Unfortunately code squelch does not seem to work when

crossband repeat is enabled. Don't know about tone squelch.



Extended Receive



To enable extended receive a jumper has to be removed. To

enable extended transmit a diode has to be removed. I have only

tested the extended receive which gives you from 118-174.995

and 320-479.995.



Open the case by removing all the screws on the top, bottom

and left/right sides and separating the top and bottom

covers from the chassis.



Next remove the plastic front panel that covers the logic circuit

board by removing the two top and two bottom screws that attach

it to the chassis.



Next remove the front panel logic board by taking out the four

front screws that attach it to the chassis.



Position the logic board so that the side normally near the chassis

is on top and a round flat battery attached via leads is visible with

the connector near the bottom and the cut out at the bottom right.



Below the battery on the lower right there are a number of

diodes, most likely surfaced mounted. Look just to the left of

the diodes, there will be a very small surface mount jumper at

the bottom (-#WW#- on diagram below). There is no silk screen

on the board to identify it (on mine at least) but the part

itself may have a zero printed on it for zero ohms. Removing

this jumper will give you extended receive capability.



Diagram (very bad but hopefully you get the idea)



        R O U N D

         B A T T E R Y



   !     ! ! ! !

   !     # # # #    -#D#-

         D D D D    -#D#-  -#D#

         # # # #  ! -#D#-  -#D#-

 -#WW#-   ! ! ! !    -#D#-  -***-



Extended Transmit



By removing one of the diodes in the area mentioned above

extended transmit is purported to be possible. I have not verified

this since I don't need this capability but it is supposed to

significantly extend the transmit capability in the VHF band.



To enable extended transmit remove the diode that is most near

the right hand bottom part of the board as indicated

in the diagram above with -***-.



Reassemble and reset CPU per instruction manual.