converting EF Johnson 242-8655 > I'm looking to find out what the Mods are for the EF Johnson 8640 900 > MHz Mobile radios so I can use them on the 900 MHz Ham Radio Band . > Let me know . See: http://www.qsl.net/k0kn/efj.html Pete Dziomba, N2MCI, has a replacement microprocessor for those. Swap the uP, and one chip cap, and reprogram! Included with your purchase of the replacement proc'er and replacement SMD cap of C917, was a CD with the service manual.. Please review the service manual for VCO procedure in the service manual as it best describes where everything is located.. Also changing the C917 will help make the VCO range from Xmit to rec. closer and easier to obtain.. Also as some one, pointed out the VCO range should be about 2v on rec and 6.5v on Rptr. Xmit.. Talk around or simplex on the rptr. output has its own adjustment and you should be able to keep it near the recommended 4v.. --- Pete has mentioned that there is a "known problem" with this radio ... something to do with the +5V regulated supply ... when the car's starter motor drops the battery voltage, the +5V in the radio causes problems with the internal logic. Pete has recommended putting a large capacitor on the +5V line to act as a power supply during the second or so of power input interruption, to keep the logic more stable. I have that radio, I've experienced that problem, and I haven't gone inside the radio to fix it yet. Right now, I just shut the radio off before starting the car...