[600MRG] MFJ LF Amplifier

[Paul Signorelli]

I was looking at my MFJ  ALS-500M amplifier circuit the other day and was wondering if

the coupling transformers would work on 480 kHz.

I hooked it up to dummy load and it worked !

This ALS-500M is working with out any modifications, just setting the band switch to 1.8 MHz.

(The MFJ ALS-600 and ALS-1300 probably have similar circuits and would work just the same).

I am driving it with John's (KB5NJD) amplifier at 50W.

The output is about 380W.

I built a W1YD  high power Butterworth low pass filter with cutoff around 600 kHz and it works well.

The MFJ ALS-500M requires additional forced air cooling for beacon operation.

I have not tried any QRSS operation because the FET's used (28C2879) in the MFJ amplifiers are hard to find.

I really don't want to smoke it.

Paul   wa2xrm