Mod For Wider Frequency Span

Some kit builders want a wider span of frequencies such as 7.020 to 7.120 or so. This is possible but the power level on both ends suffer a little if the T2 and T3 are peaked in the center of the span so keep that in mind when doing this mod and if you favor the lower end of the band, peak the transformers for that section and know that the upper will suffer a little power loss which is for the most part negligible but acceptable.

The only thing you need to do is replace (or jumper on bottom of board) a capacitor, C8. Of course you will need to replace C7 to compensate for the high and low end of the band. You will need to juggle the caps to get just the area of the band you desire and the frequency span table on page 13 of the assembly manual won't be usable.

Make sure you use good quality NPO or C0G temperature stable capacitors or the unit will run all over the place in frequency with temperature changes.

Of course the tuning will be touchy so it will be a good idea to replace the tuning pot with a 100k, 10 turn pot. These are available on ebay and other suppliers. We have a limited supply in our inventory too.

Another thing you must do is lower the board so the pot will clear some of the components. Replace the standoffs with nylon hardware. From the bottom, insert a #4 or #6 nylon screw about 3/4 inches long in each hole. On the inside run a nut down to secure screw. Run another nut down almost to the first nut and insert your board followed by the last nut. I have seen some kit builders successfully use #4 stainless steel screws and insulating washers successfully.

I have heard of kit builders slightly move the two interfering components and are able to squeeze in the pot without lowering the board.

Other details about frequency selection can be seen here.

Also read this page for more helps in frequency selection.