I recently purchases a new MFJ 1786 loop which covers 10 to 30 MHz. I think I would have been better served getting the 1788 model which 7 to 21 MHz. As I paid a lot of money for what I have, and MFJ does not provide schematics, I thought I would investigate what changes are necessary in this forum. My gut tells me it is a matter of more capacitance, which should be obtainable by paralleling a fixed capacitor across the variable motor-driven capacitor. If this is the solution, I recognize it will need to be a high voltage capacitor. Any one have a 1788 they could measure the maximum and minimum capacitance of the variable? I can do that with mine and we could swap data.