[Amps] Advice needed for SS amp
MU 4CX250B
4cx250b at miamioh.edu
Wed Jun 5 21:42:37 EDT 2013
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 at 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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