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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. KB9QKR

    KB9QKR Ham Member QRZ Page

  2. W4QBQ

    W4QBQ Ham Member QRZ Page

    Yup, sounds just like him and I had written KC3VL for the call, miss heard the O as L.
    Now you have it. Get him to draw it up and go for it.

  3. KB9QKR

    KB9QKR Ham Member QRZ Page

    I have been following this MOSFET VERY closely and been doing hours of research. (borderline obsessive);)
    This started when I found we had been throwing away 50VDC 120Amp switching power supplies out of telecom and server gear for the price of scrap!

    I am no RF engineer, but probably know just enough to be dangerous so I have been looking for a reference circuit that would steer me in the right direction.

    My brainstorming (as it stands this hour) has lent me to use this test-circuit/board that uses a MRF6VP11KH and install the MRFE6VP61K25H in its place (as they seem to use the same case), and tweak supporting components where needed like using RF transformers from Communication-Concepts.

    This is really just something I have been researching purely for fun. Ham radio has always been trial and error, and I for one love this hobby because of things like this!

    BTW, a month or so back I finished modifying a power supply out of an IBM blade server that now supplies me with 12V DC at 230AMPS! (once again, trial & error)
  4. W8JI

    W8JI Ham Member QRZ Page

    From the data it looks like that FET might be pretty clean up to 600-800 watts, if you can get the heat out of it.
  5. G0HZU

    G0HZU QRZ Member

    Are there any decent non linear models available for the part?

    You should be able to have a play using a decent RF design package like Microwave Office and you could learn a lot from a computer simulation. eg P1dB, Psat, efficiency and IMD/harmonic performance. 1kW power levels are a bit scary (400W limit here in the UK) but I guess if the model for the device is decent then it would be worth a play on a computer. You can also do the thermal modelling on a computer although at these power levels you can't afford to make any errors in your modelling!
  6. G0HZU

    G0HZU QRZ Member

    I just had a quick look to see if there were any non linear models for it but couldn't find any. If you could get these from Freescale you could characterise a design quite well for P1dB and efficiency assuming their models are good.

    For example, companies like CREE release extremely good non linear models of their devices allowing remarkably accurate simulations. But these are for lower powered devices across 10W to 100W for example. I don't know about getting good non linear models of large devices operating at 1kW power levels though...
  7. G0HZU

    G0HZU QRZ Member

    I've skimmed through this whole thread and I think a few of you are prejudging the capabilities of this device based purely on the application circuit in the datasheet (the pulsed amplifier?).

    This is a bit naive if you don't mind me saying and you really need to deal with Freescale directly (i.e. get through to an engineer via a sales rep) and find out what it can deliver with different transformer/balun topologies. Also, some of the spinoff designs linked to in this thread look a bit 'optimistic' based on what I see on their PCB in terms of the choice of output transformer ratio etc.

    It's a very interesting device though :)
  8. G0HZU

    G0HZU QRZ Member

    One thing you can ALL contribute to is towards one of the first essential steps in a design.

    After an initial 'business case' to justify the need for such an amplifier (I assume this has been done already :) ) you can then contribute to and/or peer review a set of requirements for the amplifier.
    A requirements document can typically be as simple as text entries in an excel spreadsheet with lists of design requirements and comments in each column.

    Eg for temperature range you can list columns for max and minimum temperature and include column entries for 'mandatory' and 'desirable' in terms of temperature.
    You will be surprised how quickly the document can grow if several people contribute and it becomes the reference for the design so the more entries the better. Other entries can be the obvious ones for size/power/weight/cost/etc etc

    Adding columns for desirable and mandatory can help the designer strike up a compromise in key areas. Don't overspec it or you can end up with showstopper reports from the designer.

    i.e. without a formal requirements doc you can't really approach a design house and expect them to fill in the blanks (unless they are already on your team)
    Basically it isn't fair on the RF engineer if he/she is expected to keep asking you for this info and if you are paying by the hour then you can waste lots of cash very quickly... :)
  9. G0HZU

    G0HZU QRZ Member

    I contacted Freescale at work today and there are non linear models available for this device :)
    I'm registered with them via my place of work and I've now got hold of their non linear models for this device that have been developed for Microwave Office. They also do models for ADS.

    I've not had a chance to install the libraries or the associated model kit into MWO yet though. It does look a bit fiddly to do.
    But basically anyone with access to MWO should be able to play on a simulator and tinker with RF and thermal modelling of this device. I've designed broadband amplifiers across several GHz with MWO and the simulation results are usually excellent providing the models are good and you know how to model the PCB and components adequately.
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