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 2013 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 have 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 too easy to be true. Go ahead, burst my bubble. :-)
73, Bill W6WRT
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