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RADIO CALIBRATION TESTING AND CORRECTION  

by Kenneth Merring, KM3F

 

Here is how an easy accurate calibration check can be done.  WWV is a good frequency standard transmitting on AM mode.   Best accuracy for checking is to use the highest WWV frequency you can receive.   WWV transmits on 10, 15 and 25 mhz.   Depending on the propagation and time of day for receiving .

 

How  to check calibration of your radio with NO RIT or XIT on!

  1. Tune your VFO to the highest one of the frequencies listed, you can receive.

  2. Make sure your CW tone is set to 800 Hertz offset.     You should/may have to check your menu setting for this offset if your a CW op that likes a different tone to copy from.

  3. On CW listen to the beat tone. To be accurate, it should be the same as WWV tones.

  4. Set CW to CWR or reverse. To be accurate the tone should still be 800 hz.   This indicates you how close the radio's master Oscillator is set at.

  5. If there is a large difference, the calibration can be improved or corrected by adjusting the master Oscillator only so the 800 Hz tone sounds the same when both sides of the CW setting sounds the same (CW and CWR).

SSB could be used for this test by tuning one of the stations at the highest you can receive and noting the beat note.   By switching side bands between upper and lower, the beat note should sound the same or very close. Providing the side band Oscillator shifts have not been changed from factory settings.

 

Note that the VFO reading usually is not quite the same between CW and SSB due to the difference  in offsets used for each mode, You only need to set the VFO to the receiving frequency accurately (on the dial).   If the station is off a noticeable amount, your adjustment of the master Oscillator will bring in onto the dial frequency. This is the calibration part of it.

 

This calibration check and adjust is as close as you need and within the stability of the radio's design for most all normal use and applications.   Be sure you find the master Oscillator only and not some other adjustment, by consulting your Owner or Service Manual for it's location.

 

Note if there is a frequency change when tool is used. If yes, make small change, remove tool to check what you hear.  Make small changes either direction until the tones sound as much the same as possible when switching sides.    Make a verify check be tuning  SSB stations to critical clarity on those supposedly working on even or known frequencies.  Remember, other stations may have poor calibrations so check with averages in mind, to account for this.

Close up the radio and you should feel confident of the accuracy achieved.

Good luck.

 

Ken  KM3F  30301