Modifications for the ICOM - RogerK

412.37 Mhz. - 498.0 Mhz. 410.5 Mhz. - 470.0 Mhz.792.85 Mhz. - 966.66 Mhz. OFFReceive sensitivity throughout both of the Ham bands was better than .5 of a microvolt. Sensitivity in the 200 Mhz. range was adisappointing 1 millivolt and in the 800 Mhz. band a good .7 of a microvolt. Remember, while the unit will receive on thosefrequencies, it is illegal to monitor cellular telephone communications.This modification is read 1011 times.top of page19-07-1998(IC-24) IC-24AT ext frquencyI received the following mods for 24AT out-of-band from a very reliable source (although they don't specify RX only or RX/TX),for 75-195 MHz, 200-490 MHz, and 740-960 MHz. Rumor has it (unconfirmed) that the unit even switches to AM in the air band!1. Remove diode D8 [see figure below]2. Attach diode D7 [I believe this is already equipped]3. Attach diode D124. Remove diode D135. Simultaneously hold "LIGHT", "B", and "#" keys and turn the power on. Release all keys after the display goes out (checksall LCD segments). [This is supposed to enable the out-of-band frequencies above]6. Simultaneously hold "LIGHT" and "2" keys and turn the power on. This enables the 10 MHz frequency digit entry.7. Simultaneously hold "LIGHT" and "3" keys and turn the power on. This enables the 100 MHz frequency digit entry.__________________| || || || CPU || || || ||________________|o o o D7 lower left pin is[D7] [D8] anode of one diode,o o o lower right is cathodeof the other. Top pino o[D12]ois common__I_ __I_ See text| | | |D13 |__| | | D?|/| | || | | ||__| |__|I ID12 upper pins are cathodesof diodes, loweris common anode.WARNING: I have NOT tried the hardware mods and cannot vouch for them, so proceed at your own risk!I am told that the newer 24AT's (believed not to have made it to the US yet) will have the hardware mods in place, so only steps5-7 will be necessary. So, try this first. Steps 5-7 don't seem to have any effect on a 24AT without the correct hardware mods.BTW, this has been attempted on 2 units with serial numbers around 1000 and mid-1100's, neither of which worked. :-( Like Isaid, the ones with the mods aren't here yet.There are 5 screws to remove the case (5th is on the strap hook). Keep the top panel controls with the front of the radio, and beVERY careful pulling the back off because there are fine ribbon cables connecting the front & back. I don't think they'll take muchflexing.Additionally, diodes D7, D8, and D12 are surface mount components. They contain 2 diodes connected to 3 pins. Diodes D7 andD12 are different configurations. I believe D8 and D12 are different, so I wouldn't put the removed D8 in the spot for D12. Sincethey are surface mount, removal of D8 may not be all that difficult for those with steady hands and a fine low power solderingiron, but adding D12 would be a bear. I know of no reason that small discrete diodes couldn't be used in for D12. D13 is a smallbut standard axial diode, and can be easily cut.It is for this reason I have not attempted the hardware mods. Now, if the referenced posting is correct, and only D13 needs to be