[Amps] MRF154 amp update

[Dan Sawyer <dansawyer@earthlink.net>]

All,

I have been bringing an MRF 154 based amp on line for HF. The process of 
'configuring' the power supplies is going smoothly. The design is based 
on ganging 5 x 500 watt switching supplies. The voltages are set to 50.0 
volts and connected through a .1 ohm 20 watt resistor. To date only two 
supplies have been configured; however this should scale. This seems to 
work and there have been no problems. They are even powered up 
individually. Have I been lucky or is this supposed to work??

The next part of the project was to build the relay switcher. A DT3P 12V 
relay worked perfectly. The antennas are switched by two pair and the 
amp bias circuit is switched by the 3rd. This is unfortunately close to 
hot switching.

The amp itself seems to bias around 400 watts. The two supply 
configuration is close to 1000 watts. The amp tunes up well and puts out 
close to 400 watts CW on 80 meters. On 40 it drops some, and on 20 and 
above it doesn't do well at all. The input impedance and SWR are good 
across the HF bands; however the grid signal quality matchs the output 
power. From this I speculate that the input network does not support 
above 8MHz or so? There is no visible feedback in this amp. Is there 
anyway a mismatch in the output network can effect the input??

The bottom line is I will probably order the CC AR347 board set and move 
the MRF154 devices. This is based on the assumption that redesigning and 
rewinding transformers is not a feasible task. Is this a valid assumption?

Thanks all again,
Dan

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