Checking the Digital Display accuracy in your Receiver or Transceiver and easily aligning the Frequency Time base within 10 Hertz ( cycles ).
Here is a method I have been using since 1990 with my first DDS ( double digit synthesized ) rig, a Icom IC-725 and currently use with my Yaesu FT-1000MP.
Tune in WWV, WWVH, JJY or any world wide frequency and time standard signal using the highest HF frequency that propagates. Such as 10, 15, 20 or 25 MHz ( mega cycles ). I believe WWV puts the 600 Hz tone on between zero and 45 minutes after the hour.
Start with the main dial, purposely off frequency a little such as 150 Hz high. Find the USB , LSB buttons with one hand. Now close your eyes and while flipping between USB and LSB with one hand, slowly move the main dial until the 600 Hz tones are equal in pitch in both sidebands. Now open your eyes and read the main dial. If your main dial readout isn't all zero's after the decimal, and you have a double zero DDS resolution rig ( after the decimal, at least two zeros or 10 hertz resolution ), It's time to learn some more and find and adjust a crystal oscillator time base trimmer, using the same method until tones are similar in both sidebands. Considerable error is expected from all quartz crystals unless the quartz crystal has been pre aged, by running current through it for a full year, In most transceivers this means your dial readout will be off up to 50 to 60 hertz in the first year making you sound like a robot to people with a calibrated time base oscillator at the other end. If you are tone deaf have a friend listen.
Most transceivers try to sell you a higher accuracy time base oscillator as a expensive accessory . Sometimes you can figure out where this would be or is located using the user manual which came with the radio. If it has only one adjustment such as a little flat head slot on a trimmer, you are ready to go. Using a insulated screwdriver tool, with one hand make small changes in the trimmer, while with the other hand, quickly alternating between LSB & USB until the tone has the same pitch on both sidebands.
If you only have a single zero rig, non DDS ( after the decimal, only one zero ) its going to be impossible to operate on frequency using the display, as it doesn't know whether you are plus or minus 49 hertz ( cycles ) of the correct frequency. For SSB, here you are stuck using your ears to detect the harmonic relationship of the frequency components of the vowel sounds. Even if you have trained yourself, you won't be able to use your ears to get on frequency many times, as most people run SSB processing which doesn't even transmit the low human voice frequencies below 300 hertz, which would allow you to minimize the vowel harmonic constants, and you must rely on your inadequate digital display only. Time to buy a DDS, double zero radio.
07/30/2009 09:39 -0700 Back to Ham Index Page Back to Home page