I have observed that a high percentage of Hams are running an error of 40-60 Hz This may be acceptable on older, pre-PLL radios, but modern radios with PLL and a Master Oscillator can be calibrated much closer.
![]() This makes it relatively simple to frequency-align the radio, so that it agrees with the Frequency Display in all modes. Icom 706Mkiig Repair Manual Is WrongAdditionally, the lower diagram on page 63 (11: Internal Views) in my Instruction Manual is wrong. 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. 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. The radio (inside) runs about 10 degrees F above ambient, while closed and receiving. If there is any shift in the CW and CW-R tones, you need to calibrate the Master Oscillator. Simply adjust the VR until the numbers are equalized between CW and CW-R modes. Afterward, you can adjust your soundcard clock (in MixW) to make it alternate 599.9600.0 (in AM mode) and then your computer will also be calibrated. For example, if it is off 1 Hz at 20 MHz, it will be off 0.5 at 10, or 0.25 at 5 or 10 Hz at 200 MHz and 20 at 400. Hence, Icon Service (and the Service Manual) will tell you to calibrate the radio using a lab-grade Service Monitor or Frequency Counter at 60 MHz or higher. However, even the best lab-grade equipment is calibrated to WWV, the National Atomic Time and Frequency Standard, so I recommend just bypassing the Service Monitor and using WWV directly, at its highest frequency, 20 MHz, and getting the Master Oscillator within 1 Hz in a temperature stabilized room. The beep at the top of each minute is exactly 1000 Hz; the continuous tones (when on) alternate between 500 and 600. Thus, you can listen to WWV on AM and get an exact 500 or 600 Hz tone, then switch to LSB and USB and compare them with the true tone heard on AM. You can also beat a 500 or 600 Hz offset tone against the 500 or 600 Hz modulation, when available, but this beat is hard to hear below a few Hz. Youll see it go off a little when the room temperature is not normal, and when the radio is heated up from lots of transmitting, but it shouldnt be more than 2-3 Hz off, at 20 MHz. Divide the differential by two and that will be your error (readable to within - 0.01 Hz using MixW.) If you then QSY down, divide the new frequency by the old (to get the ratio) then divide the error by that. Using this technique, I was able to win the 2004 ARRL FMT award certificate by getting within 0.04 Hz. Have them set to some exact reading and transmit a carrier for 10 seconds or so. Switch your mode to CW and alternate between CW and CW-R, while adjusting your VFO to equalize the tones (set tuning step TS to 1 Hz resolution). Icom 706Mkiig Repair Plus Or MinusThe differential will be their radios display error, plus or minus your own error, which is, hopefully, within 1 Hz, referenced to WWV.
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