Has an electrical engineer dev HF AMP with new mosfet MRFE6VP61K25h?

Discussion in 'Amateur Radio Amplifiers' started by W7EET, Oct 10, 2011.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    CW is probably about 50% D/C, higher than SSB but obviously a lot lower than RTTY, AM or FM. To make an amp "sellable" it might have to be marketed as SSB-CW only, or verified to work at 100% D/C, or be derated for full D/C operation as many are.

    Hams are somewhat used to 8877 amps which can run 100% D/C at legal limit power with enough air, and will be operating well within their limits at that power. But SS amps are a bit different.

    TEC cooling is interesting. We use ordinary water cooling of our CPUs in HPCs here, and that works darned well and should be a strong consideration for those who like efficient cooling systems that don't make a lot of noise.

    Freescale says "Tj 150C" (although FETs have no junctions, but we know what they mean) and derates MTTF very quickly above that...down to about zero if you go much above that.
     
  2. W6RZ

    W6RZ Premium Subscriber QRZ Page

    It's a link to the 2005 ARRL product review of the ALS-600S.
     
  3. WB0LSR

    WB0LSR Ham Member QRZ Page

    TECs can deep freeze, in fact some records have been set freezing CPUs with TECs and overclocking them. They are also silent.. Freezing something as hot-running as an RF power transistor isn't really practical, but keeping it WELL below 150C is I'm fairly certain. Never seen one used for this though... They really just move the heat away from the transistor into the heatsink, but using one could eliminate the need for copper or liquid cooling.

    I'll be sharing anything I learn regarding the use of thermoelectrics in this application.. I'm actually pretty excited about the prospect personally.
     
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    But you can run some of those rigs in Class A at reduced power and they clean up well. An FET amp won't require much drive. Even a bipolar exciter that doesn't measure very well at full power will usually measure better at reduced power.
     
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I've never seen them used in that application, either. I always thought of them as ways to keep food cold when travelling, and stuff like that. But seems like a good application...let us know what you find.
     
  6. AF6LJ

    AF6LJ Ham Member QRZ Page

    When I worked at Loral Corp there was a small in house project to use those for cooling transmitters for testing and alignment over temperature. Our existing method was to use liquified CO2. The heat pumps worked marginally wall for that application. The prototype plate that was built used six TC devices attached to an aluminum plate.

    I can attest to how well they work for overclocking CPUs. :)
     
  7. W7EET

    W7EET Ham Member QRZ Page

    Those of the engineers that are on here let me know when you get a print of the pc board and what the matches are for the baluns and the biasing. I have a source for the filters already and for the split balun for the two modules for this mosfet. The power supply will not be a problem either. I am going to use 220 single phase to a 36 vac at 100 amp, into a full wave bridge using 100 amp diodes including filtering. The power supply is going to be separate from the amp. Building this thing is going to be a whole lot of fun. I also have test equipment to test the product for oscillations and distortion.
    Rich/W7EET
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Rich, I suspect "nobody" is going to undertake this unless it's a pure labor of love. Maybe someone retired with a lot of time on his hands. I'd think the best bet is to push Freescale to do this work and publish the circuit, the board layout (preferably complete Gerbers) and parts list. This is probably 40-80 hours of work, full time, and I can't envision anyone doing it unless they were dedicated to some goal.

    Freescale should be most motivated, as such a design could boost sales of the devices. That's why Motorola always did this stuff (and so did Thompson-SGS and many others).
     
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    We never overclock CPUs, but we do water cool them to keep them running. We water cool the Xscale processors on RAID controllers, also, simply to keep then running on sound stages in uncontrolled environments. Without that, they go offline and production stops, since no amount of air can keep them going.
     
  10. W8JI

    W8JI Ham Member QRZ Page

    Actually Motorola and others did the boards because they had to have them anyway to prove the device worked and was stable, and to get IM tests. Without the broads, they could never have really known the devices would be OK in a system. The resonant single-device test setups won't fly for wide band or push pull applications.

    The Motorola boards were never intended for mass production. They were starting points that took over where the factory left off. Some of them are not actually safe for the device. For example the one for 4x MRF150 has a "strip line" resonance at the third harmonic that puts 20-30 extra volts on the drains of the FET's on some frequencies. This can pop FET's.

    If Freescale wants to market the device, they will build a basic starting board for HF.
     
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