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MOSFET Question

Discussion in 'General CB Services Discussion' started by CTStallion, Jan 6, 2014.

  1. CTStallion

    CTStallion
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    Happy New Year one and all.

    Over the past several years, I've done various conversions from NPN finals to 2030 or IRF520 MOSFETS with mixed results.

    In single final radios, I typically see the MOST gain with the IRF520 versus the 2SC1969. In dual final radios, it's a 50/50 split between a beta matched pair of 1969's, vs. twin IRF520's.

    However, recently it has come to my attention that Fairchild makes a MOSFET called the FQP13N10 (as used in the Stryker SR-955HPC for example) that is a direct drop in replacement for the IRF520, but can dissipate more power (i.e.: the IRF520 being a 60W vs 13N10 being a 65W device.) However, while the wattage dissipation ratings are pretty much inconsequential, the current handling capability of the 13N10 at 12.8A vs. the 520 at 9.2A caught my attention.

    Therefore, my question is:

    Is there any "benefit" to using the FQP13N10 MOSFETS as compared to the IRF520's, or is it pretty much a 'moot' point?

    Thanks and 73.


     

  2. UxCow

    UxCow
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    It's probably more of a moot point, but might be worth trying.

    I have a couple 530N MOSFETs sitting around, and those are rated for a bit more, and I believe a 540N will handle somewhere around 34A @ 100 volts, making it good for quite a few watts. Is it needed? Not even close, but you could run a super high output MOSFET instead of dual finals (perhaps) and still get plenty of drive. This is just an idea of mine; I'm still pretty green.
     
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  3. 9C1Driver

    9C1Driver
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    Unless this new final will double your wattage it's a waste of time, no one will notice.
     
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  4. Robb

    Robb
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    Yup

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    If it offers a bit more output before it becomes unstable; then it is better. Problem is, that heat doesn't help this out. Most new radios on the market don't have the output above ~12 watts, so heat isn't a real issue. Put in a MOSFET and run the output up to 30w and it becomes a factor.

    Since these FQP13N10 MOSFETs sell for less than a buck, it wouldn't hurt to try it out. Most of these MOSFETs were not designed for RF freq - some won't even work. But if it works out if/when you experiment, please post your results!
     
  5. Captain Kilowatt

    Captain Kilowatt
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    Agreed. Here is a link to the IRF520 that seems to be so popular. Look at the applications. Anyone see "RF amplifier" listed?

    http://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&ved=0CD4QFjAA&url=http%3A%2F%2Fwww.futurlec.com%2FTransistors%2FIRF520.shtml&ei=f3bLUoGaMtHlsASIpILoDA&usg=AFQjCNFyRxYdywOyygnekeTTTY0HMx-zSg&sig2=jElfgSZxHNRVd1QsCJkeYg&bvm=bv.58187178,d.cWc&cad=rja

    Pretty much the same thing for the FQP13N10.

    Quote: "These devices are suitable for switched mode
    power supplies, audio amplifier, DC motor control, and variable
    switching power applications"

    http://www.google.ca/url?sa=t&rct=j...K32kQpWAOV7rTVQ&bvm=bv.58187178,d.cWc&cad=rja
     
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  6. jbullard85

    jbullard85
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    What I would like to know is if 13n10 is capable of that high output why does stryker only get about 90 watts out of 4 of them? I have a 655. Great radio! Wish I would have got the 955. Any ideas how I can get 240 Watts out of that setup that's inside the radio now?
     
  7. 543_Dallas

    543_Dallas
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    Because its 1 driving 1 driving 2, not actually 4 finals.Stryker says it's a 60 watt radio. The man with the golden screwdriver says 90.

    240 isn't happening without an amplifier. List look at the tiny heatsink on the back of that radio compared to the one on a radio that was designed to do 100 watts. Too small even if it had adequate sized transistors.
     
  8. jbullard85

    jbullard85
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    That answers my question. thank you
     
  9. ExitThirteen

    ExitThirteen
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    90 watts? Either the tech has a McDonald's Happy Meal meter, or your radio isn't going to last very long, if it's legitimately doing 90 (which I find very hard to believe).

    543_Dallas is right on the money with his last post, the actual final stage is only 2 finals, so 50-60W is as good as it gets. I can't even begin to imagine how much IMD and harmonics are being produced with a configuration like that (1x1x2). Makes me shudder just thinking about it.


    ~Cheers~
     
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  10. jbullard85

    jbullard85
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    It is said you push it to 90 with over modulation. Strykers box and reviews on it says 70plus right out the box. Mine was setup by bells his bird showed 78 for max output. Btw None of the radios I've ever got from him have been over modulated. It was just a round about question as I didn't know it was 1x1x2
     
  11. Robb

    Robb
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    Yup

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    'Shudder' is the right word.
     
  12. BBB

    BBB
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  13. Sonar

    Sonar
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    I'm still a newbie and probably will be forever when gaining knowledge on a level where I'd be helping anyone with a repair or making suggestions but I'm sure it's quadrupling ones output that will show a 1 s-unit gain on the other end.
    Doubling will do nothing as far as s-unit gain. It will make a difference if ones goal is to drive an amplifier in order to get more out of the amp.
    As long as one doesn't exceed the amps rated drive spec's.
    Just a thought.
     
  14. 434 Mouth of the South

    434 Mouth of the South
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    I'm actually tempted to swap my 955's finals out with irf520s. Those 13n10s in that configuration have not lasted while using the radio to test amplifiers. 3 times finals have popped. This was with three different amps, in two different dummy loads (both bird loads). Two straight 4 pills and an 8 pill, all showing minute reflect on a bird meter between radio and amp. The last two times, the 13n10s violently exploded, sounding like a .22 caliber pistol going off. Radio always worked great by itself, but as soon as I'd test an amp, poof.
     
  15. wee electronics

    wee electronics
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    DON'T DO IT! The 13n10's are not suited for operation as finals. I am a Stryker sales and repair center. We have new 655s and 955s that go kaboom after a few days. I finally convinced Stryker to switch to Vishay IRF520's which they did. No issues since then. Any new 955 or 655 that I sell I pull the 13N10s out and replace with 520's. Gregg
     
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