You might want to take a look at JE1BLI and JA1DJW article from September 2006
QEX
http://www.mods-ham.com/03_Home-brew/Homebrew-Mods/ARF1500-PA/qx9ohsawa.pdf
----- Original Message ----- From: MU 4CX250B <4cx250b@miamioh.edu>
To: Paul Decker <kg7hf@comcast.net> Cc: amps@contesting.com Sent: Thu, 06 Jun
2013 01:42:37 -0000 (UTC) Subject: Re: [Amps] Advice needed for SS amp Seems
to me the 50V limit would be a deal breaker. I love the idea of a
transformerless design. I wonder if the THP problems were really the devices,
as opposed to a design glitch they never figured out. 73, Jim W8ZR Sent
from my iPhone On Jun 5, 2013, at 6:45 PM, Paul Decker wrote: > Hi Bill,
> I had an amp using the MRF1500 parts, based on the commercial Tokyo high
power design. > > I also talked to the THP guys for a while at Dayton and
they are phasing out their ARF1500 design using the Microsemi. The reason I
was told is because of quality issues with the parts themselves. > > IMHO, it
may be better to go with the NXP BLF578XR since it is a 1500W part although it
is only 50V. > > Paul, > kg7hf > > > > Message: 1 Date: Wed, 05 Jun 20
13 09:07:14 -0700 From: Bill Turner To: Amps Subject: [Amps] Advice
needed for SS amp Message-ID: Content-Type: text/plain; charset=us-ascii
I'm thinking of building a solid state 1500 watt amp using some of MicroSemi's
high voltage MOSFETs. This is a new kind of project for me and I would
appreciate any comments you might have which would help me avoid any blunders.
The MicroSemi ARF1500 looks attractive because of its high power capabilities
and relatively low price. Digi-Key carries these for $205 each. A single one
is rated at 750 watts output so I would use two of them. I'm thinking of water
cooling. MicroSemi data sheet is at
http://www.microsemi.com/existing-parts/parts/81770 and there are other
versions with similar ratings. Notice the unusually high power supply
voltage. I'm thinking of running a full wave bridge rectifier directly off the
240 VAC line, thus eliminating the power transformer and giving about 340 VDC
> no-load. The amp would hav
e to be isolated from ground of course, with input and output coupling via
toroid transformers and PTT switching done by a well-insulated relay. A
set of four 10 amp 600 PIV diodes is available on eBay for less than $30 and a
6800 uF 450 VDC capacitor is available for about $50 including shipping.
There's most of your power supply. Pretty cheap, huh? :-) Of course
with that size cap a step-start circuit would be mandatory lest you blow your
main house breaker when you power up. My main use would be RTTY and CW so
linearity is not an issue, but do you have any thoughts on what the IMD might
be for SSB? I can't find any data on MicroSemi's website for that. Maybe it's
no good for SSB. Since the output impedance is about 50 ohms, I'm
wondering if a 1:1 broadband antenna balun might serve for the output toroid?
Just a thought. Might not be a good idea. Like I said, I'm a complete
newbie at solid state amps so all comments are welcome. Th > is almost seems
to be t
oo easy to be true. Go ahead, burst my bubble. :-) 73, Bill W6WRT >
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