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 <kg7hf@comcast.net> 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 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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