Modifications for the ICOM - RogerK

19-07-1998(IC-22) Icom IC22S Packet ModificationThe Icom IC22S is a ten watt diode matrix PLL synthesized 2 meter rig manufactured in the early 1970's. In it's stock condition ittunes 146-148 MHz in 15 KHz steps. Since I am sure there are a few of these sitting on shelves collecting dust due to the limitedtuning range, why not modify them for the perfect packet rig.First replace the 7.68 MHz Oscillator/Divider crystal (X1) with a 5.12 MHz crystal. This will move the band to 145.00- 146.94MHz in 10 KHz increments. The repeater offset will now be 400 KHz which should not pose a problem in simplex packetoperation. I will give the diode matrix settings for the most commonly used packet frequencies. You can formulate others asneeded using the formula N=100*(f-145)+61 and the manual. The diode positions indicated ARE WHERE DIODES ARE PRESENT.The other positions are left empty.145.01= D5,D4,D3,D2,D1145.03= D6145.05= D6,D1145.07= D6,D2145.09= D6,D2,D1This modification is read 719 times.top of page19-07-1998(IC-22) IC-22S mods for 5 KHz stepI have prepared information to modify the IC22S sythesizer to allow it to have 5 KHZ steps in lieu of the original 15 KHZ steps.This will allow the rig to go onto 145.01 MHZ for packet radio operation.In short, the modification requires changing a crystal, making some copper path cuts, adding some jumpers, and installing a newdivide by N counter which consists of three CMOS digital integrated circuits.If you put it on a frequency as low as 145.01 you will also need to re-tune the front end and you may need to re-tune the VCOfree running frequency. I have made the mod to my radio and am using it to up-load this file. I re-tuned the front end toincrease sensitivity back to the normal although it did work without re-tuning. I did not have to adjust the VCO.If you would like to receive the information which consists of a schematic of new counter, old and new block diagrams andinstructions to incorporate and test the modifications, send an SASE (standard business envelope, 22 cents postage) to:Jon Reeves, WB9CNE12125 Trolley Rd.Oaklandon, In 46236-3056NOTE:The information which will be mailed is being prepared for publication.It is requested that the information be used only for modification of your personal radio and not be passed on without this noteor placed on any bulletin board system. I am releasing the information now to assist packet radio operators in their efforts tomove to 145.01 MHz and would appreciate consideration of this request.This modification is read 715 times.top of page19-07-1998(IC-22) Step modification (packet radio operation)Before doing any other modification, pins 13 and 16 of IC1 (programmable divider, TC-5080P, PLL board) should be connectedtogether. This allows the PLL to accept all the binary codes and then cover all the frequency range possible with the 22S. Thismodification is currently done and could be already done on your rig.STEP MODIFICATION (PACKET RADIO OPERATION):The normal STEP between "channels" is 15 KHz. For example, you can tune 146.610, 146.625, 146.640 MHz, but not 146.620,146.630, etc...The step is settled by the crystal X1 (on the PLL board), located near the VCO (big metal box). The normal frequency of thiscrystal is 7.680 MHz. This crystal also sets the offset (normal: 600 KHz) when using duplex mode, since the offset is made by alogic circuit that adds 40 to the binary code applied to the programmable divider (PLL). Think about it: 40 x 15 KHz = 600 KHz!!!