Channeling the Radio

This procedure can be used for all four ME series radios but we will show the process for the ME40+ 40 meter band.

The ME series transceivers were designed for a tuning range of about 35 khz. With a standard single turn tuning pot this is a sufficient range for most QRP'ers. You can do a number of things to expand the range but the tuning of the transmitter is not quite as wide going through T2 and T3 transformers but you can stagger tune them for an average range because this will affect the transmitter output power. Also remember that in the ME80+, the VCO tuning is reversed (high side injection) so the higher the VCO frequency, the lower the operating frequency. Just reversing the tuning pot connector will keep wiring and operating normal as pictorial on page 12 in the manual.


Changing the C8 value from a 82pf to a 100 or 120 pf (NPO) capacitor will extend the range from around 45 to 70 khz or so but the capacitors enclosed for selecting the tuning range won't track according to the table shown on the bottom of page 13. Do not try to extend the tuning range any more or you will get diminished results. It would also be a good idea to change the tuning pot to a 10 turn pot. You may have to lower the board for the 10 turn pot to clear the board components so it will involve replacing the nylon standoffs with 6-32 screws and 3 nuts on each corner. Better yet, use nylon screws and nuts because there may be a problem with the nuts shorting out certain components unless you use fiber or nylon insulating washers.

As stated in the manual and places on these webpages, you should make sure, with the highest tuning position, and with C7 NOT installed, you should have a VCO of 3.230 mhz (for 7.230 mhz operating frequency). Make every attempt to change toroid turns or VCO caps to achieve this frequency. Doing so will insure the C7 band changing capacitors enclosed will follow closely to what is stated on Page 13 bottom right table. If you are unable to get it close to 3.230 mhz you will have to fudge different capacitors in order to get the range you desire.

When you have the desired frequency span selected in your unit, don't forget to peak the T1 receive transformer, and the T2 and T3 transmit transformers. The T2, T3 transformers have a distinct peak but they might not pass the full output level for consistent power over the tuning range. You may need to stagger one or both transformers to get an average output across the tuning range.

 


Revised May 19, 2021