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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. W7EET

    W7EET Ham Member

    Hi Folks:
    Yes, I was curious if any Electrical Engineer has a HF amplifier circuit board and parts for the new MRFE6VP61K25h mosfet? If so I would like to have a copy of the circuit board and a list of parts. IF not, I would like to have an electrical engineer design one with two of these mosfets and also with one mosfet. Also, consider, operating frequenices of 160-6meters. With two mosfet's one can turn the power down to max operating power acc/w FCC rules and reg's and loaf along.
    Contact me:
    w7eet@arrl.net
    Thank you,
    Rich:)
     
  2. W9GB

    W9GB Ham Member

    Rich -

    Evaluation baords (with parts lists) are available directly from these RF device manufacturers (Freescale - TX / AZ; NXP - Japan) --
    for the experienced DIY Builder.

    IF you are looking for a "Heathkit style" kit of parts and assembly instructions -- NO, I have not seen such a kit.
    Given the current global economic conditions (prospective buyers) -- I do not expect to see such a kit in the near future.

    Your request analogy is: Ford Motors has a new crate V-8 motor with great horsepower and you desires someone to build a specific car (racing/NASCAR or pleasure).
    You are looking for a Chip Foose ... but are unsure how much that would cost.


    There are qualified RF professionals who could build to a spec, with sufficent $$$ (Tom, W8JI; Paul, WD7S; etc.) -- there are
    also a large number of "want-a-bees" builders -- who will gladly take your money -- but you would likely never receive what you desired.

    There are also some current mfg. (Elecraft, Alpha, etc.) that may entertain your offer -- but that investment (> $75,000) will be more than you likely desire to make.
    ==

    BTW, the BIGGEST issue with an amplifier build of this size (RF wattage output) is proper Thermal handling / dissipation.
    Electrical Engineers are not always well versed in proper Thermodynamics / Heatsink designs. :)
    Commercial products are usually produced by a TEAM of experienced engineers (mechanical, electrical, thermal) from various disciplines for optimal design.

    w9gb
     
    Last edited: Oct 10, 2011
  3. W7EET

    W7EET Ham Member

    Reply to w9gb:
    Freescale has a pc board only for VHF test models and in fact someone has already built one for VHF amplifier with boards and parts. However, this will not perform on HF. I did not ask for a electrical engineer to rebuild Ford company. I am more than wiser than to let some scammer to take my money. There are a numerous of Electrical engineers that are ham radio operators out there that has cad on their computers to design a HF amp for this particular mosfet. Ham radio is for good will not to profit by other ham radio operators. So, what have I got in mind is to have an challange to create something to pass onto other hamradio operators to build from scratch and create one's own heathkit. Also, learn while creating this HF RF Amplifier. I am no newbe to Electronics since my field is Radar and aviation Electronic repair.
    Rich/W7EET
     
  4. W8JI

    W8JI Ham Member

    I wish Freescale would tone down their rhetoric.

    The FET on U-tube is in pulse service. That basically is a 600 watt SSB FET.

    If you look at the actual data sheet, it slides into gain compression at 600-700 watts at 85 degrees C on the case. Their big power ratings come from having the case at -30C.

    If you use one FET and can manage to get the heat out, you have the electrical equal of an ALS-600 in every way, including SWR tolerance.

    Two FET's, if you can get the heat out, will provide about 1200 watts or so with proper cooling.

    The 65:1 VSWR and 1200 watts come from pulse duty service, and probably with a current limited supply.

    That FET is the electrical equal of (4) MRF150 except all the heat is in one place.

    73 Tom
     
  5. W8JI

    W8JI Ham Member

    I wish Freescale would tone down their rhetoric.

    The FET on U-tube is in 20% duty cycle 100uS pulse service. That basically is a 600 watt SSB FET.

    If you look at the actual data sheet, it slides into gain compression at 600-700 watts at 85 degrees C on the case. Their big power ratings come from having the FET case at -30C and using low duty cycle pulse service. I designed a medical device that ran two MRF 150's at 1200 watts pulse serve, and would handle near-infinite SWR (open or shorted load with a very short feedline attached). There is no magic to 1200 watts pulse.

    If you use one FET and can manage to get the heat out, you have the electrical equal of an ALS-600 in every way, including SWR tolerance.

    Two FET's, if you can get the heat out, will provide about 1200 watts or so if you can supply enough cooling.

    The 65:1 VSWR and 1200 watts they show on the video comes from pulse duty service, and probably with a current limited supply.

    That FET is the electrical equal of (4) MRF150 except all the heat is in one place.

    73 Tom
     
    Last edited: Oct 10, 2011
  6. W9GB

    W9GB Ham Member

    Rich -

    Understood. BTW, Elecraft is the company that is trying to fill the void left by Heathkit's departure --
    their designs have been better than many of the kits produced at Benton Harbor.
    The Elecraft KPA-500 is an impressive amplifier design .. in a small package .. and at a price point (and quality level) that should discourage Eastern Asian copies.

    As Tom W8JI noted, the YouTube video has likely created the wrong impression (rhetoric) of Freescale's (and NXP's) newer RF devices.

    Rich -

    You seemed to miss my point.
    Designing a carrier PC board is just ONE STEP of the overall design toward the final product.

    My concern (for any final design) continues to be proper cooling -- now you have the equivalent of 4 MRF 150 RF devices --
    in a concentrated surface area (footprint) -- not dispersed at 4 points of heat generation -- that will produce significant heat (wasted energy of conversion process).
    The next question is DC power requirements and then the overall footprint of the final product design.

    From my perspective, we are still missing the point Steve Jobs (sk) had been making for the past 30 years,
    you have to LOOK at the entire system or device that you are creating and its usability (ease of use, on aspect) for the end user.


    Some amateurs are experimenting (and creating initial DIY builds) with these new devices (Freescale or NXP) -- BUT I have not
    seen any openly available designs/kits from these efforts -- YET.
    ==
    While MFJ has an assembled solid-state unit in this RF output class,
    Elecraft has yet to produce/release a 1.0 - 1.5 kW RF output amplifier ........ kit or assembled.

    A competition is always possible -- what is the end point reward for the build ?

    w9gb
     
    Last edited: Oct 10, 2011
  7. W7EET

    W7EET Ham Member

    I have been a ham for 40 years and have built many ham related equipment. From vaccum tubes to solid state. This newer type devices is a another ball park. The main thing is the board with the mosfet on it that requires the most attention for an engineer design. This I can not do or make. The rest of the circuity I can manage to finish. Like the cooling heat sinks, safety circuits, filters, power supply and so on. I called freescale and ask them about the mosfet and highly questioned them on the power out. They told me this mosfet will cw at 1200 watts. For how long ??? So this will be a experimental circuit and there is someone already has a 1200 watt VHF 2 meter amplifier in use. Using only one mosfet. When I grew up, this is one of the many things as a hobby is to make and build one's own equipment. So, is this old school training,,,yes! and I enjoy it very much.
    Rich/W7EET
     
  8. WB2WIK

    WB2WIK Premium Subscriber

    I'm sure you know the board wouldn't have the MOSFET on it, at all. The FET would mount directly to the heat sink; the board would "surround" the FET with additional circuitry and provide the I-O paths and DC current paths.

    Since the device in question is dissipating 657.4W/square inch (assuming the ~75% efficiency claimed) the HS would need to be extremely good, as well as fan cooled, unless it was in a refrigeration system (maybe possible).

    If I could get a couple of devices for free I might try it; but to risk degrading them to carbon during trials and having to pay for them would be a bit sad.;)
     
  9. AF6LJ

    AF6LJ Ham Member

    That amplifier is a really good candidate for ether water or vapor phase cooling.
    For the few percent lower thermal resistance you would pick up it might be worth it to silver plate the copper heat spreader.
    Regardless one is going to spend as much on the cooling system as they are going to spend on FETs.
     
  10. WB2WIK

    WB2WIK Premium Subscriber

    Yep. Semiconductors can handle a lot of power as long as we keep the material cool and don't melt the internal wire bonds.:eek:

    They're claiming 0.15C/W for Rthj-c and derate MTTF with temperature. Keeping the silicon down to 150C max at full power on CW is going to be quite a trick.
     
  11. AF6LJ

    AF6LJ Ham Member

    Not only that; as Tom pointed out for linear service they are really only good up to about 600W out. per device. Two amplifiers combined would give you a nice legal limit amplifier.

    I wonder how many of those I would have to blow up before I had a stable amplifier. :)

    I have another beef.......
    I really don't 50V is high enough Voltage for devices in that power class.
    I would like to see some 250V FETs in that power class.
     
  12. W7EET

    W7EET Ham Member

    wb2wik:
    Hi, I use to work in a two-way radio shop and radar equipment. I already know about the mounting of solid state devices on heat sinks. I did more than a count on my fingers...and then some. I was considering using 1/2 copper plate to a very large alum heat sink. Of course, I would have to take it to a machine shop to have them resurface (milling machine) to match them both for maxium heat transfer. I was thinking of using apx 6 inches by 12 inch heat sink per mosfet. Having two split modules using baluns. Running a squirrel cage fan for cooling and use a thermal switch to turn on the fan when the temp rises and then turn off when temp drops to a certain. degree of temperature. AND, here I am thinking out loud.
    Rich/W7EET
     
  13. G4COE

    G4COE Ham Member

  14. AF6LJ

    AF6LJ Ham Member

    This device is a little different from the one that was discussed here two months ago.
    That one had in the datasheet IMD figures and was intended for linear operation.
     
  15. W6RZ

    W6RZ Ham Member

  16. WB2WIK

    WB2WIK Premium Subscriber

    A centrifugal blower shouldn't be required, as blowing air across a heat sink creates virtually no back pressure. A high volume axial fan would normally do a much better job of cooling in an application like this.

    Milling a copper heat spreader sounds like a great idea; you'd want very, very good flatness.

    I can believe all sorts of claims about these things in pulse service or even SSB, but "CW" is a whole 'nother story! I think Freescale interpreted "CW" to mean "carrier power, of very short duration" as opposed to the Alpha Power definition, which is "continuous carrier, with a brick on the key, and it can do this forever." Hams have different interpretations.

    Once the matching and decoupling details are worked out (and for HF it's more complex than for VHF, since single-band VHF amps only need to work over a miniscule percentage of the operating frequency; HF amps might have to work over more than a decade) on a prototype, I'd be very tempted to eliminate the aluminum heatsink and just circulate DI water through a copper block using a small pump and heat exchanger. It's simply more efficient. I think that's why we have this system in cars.:eek:
     
  17. AC0OB

    AC0OB Ham Member

    FreeScale hosted a seminar in which they provided some data:

    Example: MRFE6VP6K1K25KH, operating at 1.1kW, with 80% efficiency.
    IDrain = 1100W/(80% x 50V) = 27.5A
    MRFE6VP61K25H have Rth of 0.15W/°C, Case temperature = 80°C
    Dissipated power = PDC – Pout + Pin
    Dissipated power = 50V*27.5A – 1100W +4W = 279W
    Trise = 279W * 0.15W/°C = 42 °C
    TJ = Trise + Tcase = 42 /°C + 80°C = 122°C

    They are currently sampling certain "61K" series of LDMOS MOSFETS

    They also stated they will loan development/application circuit boards to qualified companies and individuals.

    Phil - AC0OB
     
    Last edited: Oct 11, 2011
  18. W7EET

    W7EET Ham Member

    Hey guys:
    Just do not rely on one data sheet for this type of LDMOS MOSFET. There is about 10 variations of this device for power output. Some are lower power out or pulsed for radar applications and there is two types with the full cw power out of 1200 watts out of the 10 under the data sheet. It may have something to do with the wire size to the internal part of the silicon connection to handle the current. The VHF 2 meter amplifier has a poor circuit design on the pc board. The mounting for the balun has two pieces of coax instead of using a pc inductive circuit trace layout. PC circuit inductive balun would be more stable than using coax. The website is above from my listing under W6RZ listing. I will see what I can come up with to prove my point.
    Rich/W7EET
     
  19. W8JI

    W8JI Ham Member

    The data sheet is here:

    DATA sheet

    If you go to page 2 you will see this is primarily a pulsed device with an average power of 250 watts. The 65:1 VSWR is for 250 watts average power, and 1250 watts pulsed power. On page 5 you will see in pulsed duty gain flattens out at about 700 watts peak power, and the device is not particularly linear.

    I'm not sure how this device stacks up in linear service, but I can get similar pulse performance out of two MRF150 FET's. I can get about 1200 watts pulse power from a pair of MRF150's.

    Based on the curves on page 5, this device does not look too linear.

    73 Tom
     
  20. W7EET

    W7EET Ham Member

    Tom:
    There is about 10 different varieties of this device. From pulse, low power out, to full cw of 1200 watts. Here is a link of this new type of continues duty or 100% duty cycle.
    http://www.rell.com/pages/Product-Details.aspx?productId=966540

    Note: the last three letters on the end other part number will give the correct classification to the data of operation.
    so, beware of the part numbers to the data sheet so everyone here will be on the right page for the correct device.
    Rich/W7EET
     
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