IC281

Original from N9QQB to ALL@ALLUS

The mods for the Icom IC-281 mobile rig are not yet widely available. I

got one direct from ICOM that extends the receive covereage of the radio to

118 mHz - 174 mHz and also 320 mHz to 479 mHz.



Not only that, but the radio switches to AM in certain bands automatically!

You can get aircraft and all kinds of neat stuff (aircraft is mostly 119 to

121 mhz).



The mod involves removing a surface mount component labeled W6 on the

logic unit. The logic unit it the board mounted behind the faceplate

and is not the board that is visible with the top (or bottom) covers off.



take the top and bottom covers off and then remove the 4 screws that hold

the faceplate on-- two top and two bottom. Looking into the front of the

radio, you will see several screws recessed into the front panel. Remove

them too.



The entire front panel / faceplate assembly can now be removed. it's

plugged into the rest of the radio at a single connector. Pull it off

care fully.



W6 is a really tiny SMD (surface mount device) along the bottom end of the

logic board. It's right below the lithium backup battery. The next component

to it's right is a chip (SMD) diode, D11. Next to that, in order from l-r

are D12, and then D10. All this is near the lower right of the board.



The chip diode to the right of D10 might be D9, but the print is pretty

smeared.



Look for 4 chip diodes mounted vertically, and one SMD to their immediate

left mounted horizontally. The one mounted horizontally is marked W6 in

unimaginably small print. There is nothing mounted below W6, and there is

one more SMD mounted vecally right above it.



I used a piece of copper wire wrapped around a low-wattage soldering iron,

with the end of the wire sticking out about 1/4 inch. I let it heat up a

good while, and then used the tip of the wire to apply heat the the

soldered ends of W6. I used some solder wick to help remove the solder.

You have to be carefull not to heat the pc board to much, or the traces

will start to lift.



Remov W6 and tape it to the board somewhere. This chip is really small,

about twice the size of the head of a pin.



That;s the whole mod.



73 de N9QQB (Tom Peters)