6M VSWR FIX

For HR-50's S/N 1200-1400 (above 1400 this fix is already on the PCB)

Hardrock-50 amplifiers have traditionally had high input VSRW on 6M. 3:1 is typical with ampls equipped with the T/R relay even higher for amps with the QSK option. I had assumed that the cause of this was the gate capacitance of the MOSFETs which becomes more of a problem as the frequency increases. But I was wrong, Phil AD5X, told me that the high SWR was most likely due to the inductance of T1 and recommended placing a 33pF 50V NPO cap across the AMP_IN terminal block like this:

If you have the T/R relay installed a a 2nd 33pF 50V NPO cap on the RF_IN terminal block like this:

If you have the QSK board installed add the 2nd 33pF 50V NPO cap across the RLY_OUT jumper on the QSK PCB like this:

On both types of amplifiers the SWR on 6M after the modifications described here, is less than 2:1.

For HR-50's S/N 1000-1200

For earlier amps you will need to put one cap on the back side of the amplifier PCB at the AMP_IN 2 pin header the other cap across the RLY_OUT jumper also on the back side of the amplifier PCB. Use a 33pF 50V NPO cap at both locations. This will be the same with or without the QSK board.