GE MASTR II Highband Preamp Conversion to 220

GE MASTR II High-Band UHS Preamplifier

Conversion to 220 MHz.

By M. Scott Zimmerman

Concept:
Make a 150.8 - 174 MHz. RF Preamp properly tune the 220 ham band.

Description:

The coil in the preamp is physically too long to tune the 220 ham band. To resolve this, turns are removed from the coil to make it tune properly in the 220 band.

Benefit:

The preamp will properly tune the 220 ham band, Circuit Q is as original.

Modification:

Remove the shield that covers the tuning coil.
Carefully remove 1 full turn from the top of the tuning coil.
Replace C2302, a disc capacitor with a 8pf disc capacitor. This capacitor is located beside the tuning coil within the coil shield area.
Replace and solder the shield back in position.
Retune the preamp, as per the GE manual. (Tune for best signal quality) You will enjoy the way the preamp now tunes!

If you can't find an original GE preamp for use with your equipment, I have had good results at very clean sites using the Ramsey PR-10 preamp. The PR-10 is not a better replacement, but it does work well.