The AM Forum

  Good morning Group. I am starting to change My BC transmitter to  160 and maybe 75 meter and I just got to wondering do most of you use the Large tank coils for 160 or do you wind up your own and go from ??? ??? there?? Thanks  Tim..WD4TC..

With most BC xmtrs it shouldn't be a problem to move them to 160 by readjusting the coils and maybe changing out some fixed capacitors.  After all, 160 is just a hair above the top of the AM broadcast band.

But moving them to 75m and  higher frequencies can be more of a challenge, especially since many BC transmitters have extremely sloppy physical layouts, due to the fact that at MW frequencies you can get away with long leads and high residiual capacitance.

You could probably push the issue with most transmitters and get them to work on 75 using the original layout, but 40m and higher in frequency may present insurmountable challenges.  I would prefer to gut the rf section of the transmitter and build a new circuit and layout from scratch, using as many of the original components as possible.

Tim...as Don said, most of us with the Gates rigs just reduce the capacitor values in the tank and loading circuit and retune the inductors. It depends on where in the BC band that your transmitter was tuned. The manufacturer supplied different value capacitors depending on the frequency it was ordered for.

I don't know what TX you have, but as for my Gates BC-1G. I halved the capacitance for 160 and then halved it again for 75. It works FB on both bands. Again, depending on the freq and component values you start with you can play around with it to achiever resonance with a satisfactory Q.