KV5R: Icom IC-706MkIIG Mods and Tips
NOTE! Various 706 models use different parts to calibrate the Master Oscillator. Refer to your
Instruction Manual. Additionally, the lower diagram on page 63 (11: Internal Views) in my Instruction
Manual is wrong:
1. In the position shown as R602 is a trimmer capacitor (coarse adjustment), and
2. Just above it is R602, the variable resistor (fine adjustment), and
3. Adjustment of L623 is not necessary.
It is possible, if you are very careful, to calibrate the radio to +-1 Hz at 15 or 20 MHz (WWV as
reference). Use the highest WWV frequency you can receive, usually 20 MHz in the middle of the day.
Note: This is not the procedure used by Icon and the Service Manual. I consider this procedure more
accurate because it uses WWV directly, bypassing the possible error of the Service Monitor, which is
supposedly
calibrated to WWV.
This procedure only applies to radios without the optional TXCO (high-stability unit CR-282). Also, this
procedure is only for radios like mine -- having a trimmer cap and a VR nearly under the 60 MHz gray
coax in the lower (front) right-hand (radio inverted) corner. These lie just to the right of the encased
(shielded) master oscillator.
You will need:
1. #1 Phillips screwdriver;
2. Jeweler’s Screwdriver set;
3. 3.5 X headband magnifier and a bright light;
4. Air Conditioner and/or heater, and digital thermometer to control room temperature;
5. And for greatest precision, a computer running MixW in the PSK mode -- read the audio frequency
on the status line with 0.1 Hz resolution.
Not Necessary: Oscilloscope, Service Monitor, or Frequency Counter (thank goodness!).
Procedure:
1. Measure your normal room temperature. The radio (inside) runs about 10 degrees F above
ambient, while closed and receiving.
file:///C|/My%20Downloads/Icom/706.asp.htm (5 of 15)5/4/2009 11:29:12 PM
