This mod is for installing a International Radio #110 crystal filter into the Icom 706 Mk2G.
Remove the upper cover of transceiver, then unplug two ribbon cables and the rf connectors so circuit board can be removed and turned over to expose trace side.
Unsolder the filter that this radio comes with and solder subminature coax to the pads where
the filter was soldered observing correct orientation of wiring. Leave the coax of sufficient length to go behind board and across top.
The #110 filter is attached to the top side of circuit board at a ninety degree angle from the original. With front of transceiver facing you, orient pins to right with filter on its side all the way left against a crystal on the board. I used a thin double sided tape for attachment and
coupled the coax through .01 mf capacitors. There is room for only one
filter using this arrangement.
 
The curves for the Icom 1.9 Khz and the 2.4 Khz crystal filters. The 1.9 Khz more closely resembles the International radio unit but does suffer some roll off at the pass band on one side. This is probably because these units are mass produced and as long as certain
production standards are met they are sold.
I have to thank George with International radio for the filter sweeps.
The 272 has a 1.7 shape factor and losses the same as the #110. The 110 is shown inside the 272 curve. The 223 has a few dB more loss and some tilt in the pass band, but it's shape factor is 1.5 and it's bandwidth is 2125 Hz similar to the #110.
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