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MOSFET Question

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

  1. sonoma

    sonoma
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    I have just over 50 radios out with the 13n10 mosfet and never had one blow as of yet. a buddy up in New Jersey has about 100 out and he has not had 1 blow either. what is the gate voltage of the Stryker radios when the mosfets blow? if some one gets ahold of the 13n10L mosfets they only will take 2 volts and blow.


     

  2. wee electronics

    wee electronics
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    There are two versions of that part, one that is set up for logic level drive 2V at the gate and the non L version. There is also the possibility they may have gotten a hold of some counterfeit parts. I don't have near as many out there as you guys do, probably about 30, Ive had at least 6 blow ups on NEW radios. We are seeing more power out of the Vishay IRF520 using a dummy load and LP-100A Digital Vector meter. My point is, its not worth messing with to gain a watt or two.
     
    Captain Kilowatt likes this.
  3. Captain Kilowatt

    Captain Kilowatt
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    [QUOTE="wee electronics, post: 572961, member: 48812" My point is, its not worth messing with to gain a watt or two.[/QUOTE]


    People really need to learn more about dB's and what they mean and less about what a power meter says. My favorite is the single final to dual final conversion for some radios. Lots of work to gain an extra 3 dB at MOST ie half an S-unit.
     
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  4. wee electronics

    wee electronics
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    I agree, I created a chart in excel and then made a graph of it to illustrate your point to my customers. Some of them don't comprehend the meaning of logarithmic. 400 to 500W is the best bang for your buck. Anymore and you are just throwing away money
     
  5. sonoma

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    I like the 13n10 better because the way I do them I do not use the companion part that is out or even build one. the 520 and 13n10 both go in the way I install them and the 13n10 runs cooler using a digital thermometer to check the temp. stated out using the irf520's and a guy talked me into trying the 13n10 mosfets and I just liked them better. I even use them in the Rm kl203 amps when the factory ones are blown. I run the gate voltage at about 3.2 to 3.5 volts. do not try to get a lot out of them like Captain Killowatt mentions that a few watts will never show up on the other end. the only person that ever knows they are running 40 watts or 20 watts is the guy transmitting.
     
  6. wee electronics

    wee electronics
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    Here's a good link for reference when designing with mosfets to operate in the linear region. Bear in in mind a bipolar transistor is a current in, current out device. The MOSFET is Voltage in, current out device given by equation 1 in app note. The manner in which they are used as finals in an HF radio is open loop. The fact they even work in the application in which they are being used blows my mind. Each to his own. Good conversation guys.

    http://www.digikey.com/en/pdf/m/microsemi-power-products-group/microsemi-make-linear-mode-work
     
  7. Vern torney

    Vern torney
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    Mrf255 or mrf 455 work for me( no 477,520 or FQP13N10)
     
  8. strykerman

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    My stryker 655 keeps popping them every time I run it with my texas star sweet 16 amp. I'm changing to 520's.
     
  9. 9C1Driver

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    You might check and see what is causing this or you will just keep smoking 520's too. There might be some kind of a mis match between the radio and Texas Star that needs corrected.
     
    222DBFL, 543_Dallas and psycho like this.
  10. Tim Chambers

    Tim Chambers
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    I would connect the amp output to a 50ohm dummy load, then hook up an antenna analyzer like an MFJ 259B, and see what your input impedance/SWR is. There is often times a trimmer capacitor that can be adjusted inside the amp on the input rail, and trimmed so that the radio see's a good load to transmit into, 50 ohms. Just like transmitting off an antenna with a high SWR, feeding an amp with a high input SWR, you can damage/blow up your finals in the radio.
     
  11. BBB

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    Thinking about doing the FQP13N10 to IRF520 MOSFET conversion on one of my 955s that's down for this all too common issue.

    I would think I should replace all (4) of the 13N10s with the 520s. The Vishay 520 looks to be a drop in replacement... assuming I set the Stryker's pre-drive, drive and final biases at a safe level?
     

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