[HomeBrew] Re: RE: Homebrew Equiv. of Ameritron ALS-500M?

[DavidE Benedict]

aaron.hsu at nbcuni.com writes:
>Just so there's no confusion...
>
>The ALS-500M and ALS-600 are not "equivalent" amplifiers.  Yes, they are
>both 500W amps, but they have completely diferent designs.  The ALS-500M
>uses 12-volt Toshiba 2SC2879 bi-polar transistors and the ALS-600 uses
>48-volt Motorola MRF150 MOSFETs (hence the voltage differences).
>
>I missed the original question, but DIY designs are out there...search
>Google.  Many power transistor spec sheets include a "reference" design
>that can be used - in fact, many commercial products (not just amps) use
>"reference" designs.
>
>73,
>
>  - Aaron Hsu, NN6O

Hi,... Thank you Aaron,... Happy 4th!!

I did know that.

I was actually looking around for two things:

1) Good homebrew designs for 500-700watt mobile linears, and,
2) For scarce possibilities for some way to use the recent QST 50 volt
linear in mobile....because to me those higher voltage MOSFETS are better
all around than the Bipolars for 13.6 volt use. But, efficiency is the
hold up! Check this out....

A person could take a 1000-1500 "auto to 120VAC" inverter, rewire the
output transformer (toroid) in it to a centertapped 50-0-50 volt winding,
bridge rectify & filter it, and have a cool power supply to run that QST
amplifier... Kludgy, I know, but it would work. BUT, it would take about
twice as many watts from the battery(s) to get the 500 SSB this way (maybe
1500 watts because both the amp xistors and the inverter conversion are
cascaded in this application, and both have poor efficiency...the amp
about 50% and the inverter about 80%). The amp needs about 1000 watts for
500 out, and the inverter about 1300-1400 to provide that 1000.

Another possible solution, which is more efficient, is to have a high
capacity alternator rewound for 60 volts, and use huge capacitors and some
inductor/filters to smooth the AC ripple & whine...maybe even use 4 small
motorcycle batteries as part of the smoothing needed for the ssb voice
demands on the supply, ...and they would probably greatly decrease the
amount of capacitors needed too, I think. The 2 big hang-ups with this
scheme are the probable expense of the alternator rewind and finding a
place on the engine to hang another alternator.

All this considered, hanging an Ameritron (or equivalent) mobile amp on
the car's battery is looking pretty attractive.


David B.
W7DBH
Mobile-Only ...in NW Oregon