20 Meter Transformer Mod

The three transformers designated 42IF123 must be modified for 20, 17, or 15 meter operation. (The 17 and 15 meter kits have not been designed yet but we are thinking about it.) These transformers come from the factory resonant at around 10.7 mhz for typical IF use. In the ME30+, ME40+, and ME80+ series CW transceivers they do not need modification because the resonance can be lowered with external capacitors. Obviously the free resonance is about 10.7 mhz so for transceivers 20 meters and higher in frequency, the small tubular capacitor mounted in the base of the transformer needs to be carefully removed.


The transformer on left has the capacitor broken out.

Carefully take a sharp scribe or small finishing nail and press the center of the tubular capacitor and break it. It is fragile and brittle and should break easily. Carefully remove any broken ceramic pieces. DO NOT attempt to remove the ends of the capacitor or you will break the fine leads going to the coil pins. Just remove enough of the capacitor so it will become open. Verify you have not damaged the windings of the primary and secondary. They should be less than 0.2 ohms or so. Almost a short circuit. Should you damage a transformer its almost impossible to repair so contact Midway and we will send you a replacement. If you would like, request modified ones for US$3.95 each plus postage.