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Realistic TRC-427 Mosfet Modification (IRF520N/ ERF2030)

Discussion in 'CB Radio Modifications' started by LeapFrog, Jul 30, 2017.

  1. LeapFrog

    LeapFrog Sr. Member

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    IRF520N mosfet conversion .

    irf520ntrc427mos .
    EKL_EN-1230 .


    I have done two Realistic TRC-427 radios with these steps, I only just came up with the idea to mosfet convert the TRC-427 a few days ago, so the mod could be refined by someone, anyone feel free to comment or suggest a revision!


    Maybe I'll try more voltage at the gate to get a 4 watt carrier, also next time I may try FQP13N10!
    If anybody is interested in seeing the RF Peak to Peak Voltage, let me know..

    I can re-visit the scope and look at the volts/per div. then measure for max with audio before I see distortion in the positive peaks... That'd be more accurate than most all consumer level P.E.P. meters, "true peak reading" or not.

    I had about 1 volt on the gate of the mosfet after these steps, if someone did more and added voltage the carrier and total output would increase (assuming)

    I'm not worried about the "Max Watts", i'm just glad I have a cheap alternative to traditional transistors, and they have "headroom" over the factory part, maybe!?.
    One radio I keyed up a few times w/ no antenna to see if the part would "instantly fail", nope it still works fine, as far as I can see.

    Cheers!
    Me and this duck pluckin' Realistic, are back out. :sneaky:

    -LeapFrog


     
    #1 LeapFrog, Jul 30, 2017
    Last edited: Jul 30, 2017
    tecnicoloco and Tallman like this.

  2. Tallman

    Tallman W9WDX Amateur Radio Member, KW4YJ EXTRA class

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    Have you checked the output with an spectrum analyzer?
     
  3. LeapFrog

    LeapFrog Sr. Member

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    I will check it for in-band splatter on my RTL-SDR, tis all I can do w/ my budget at the moment.

    I'll check at 54 MHz w/ RTL-SDR also, hopefuly the stock TVI trap is still "doin' the business", even though the mosfet is not an RF device. :)

    I don't have any screen capture software, but I can snap a pic or film a quick vid.
     
    #3 LeapFrog, Jul 30, 2017
    Last edited: Jul 30, 2017
    tecnicoloco and Tallman like this.
  4. LeapFrog

    LeapFrog Sr. Member

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    Alright gentlemen, here it is..
    Please forgive my presentation, the video screen rotated 90 degrees unexpectedly.
    Also I did not prepare a tone to inject, so once again please forgive my hooting and hollering! I know it's not very scientific or professional; but it shows the IRF520N can be used as a suitable replacement for an RF final @ 27 MHz, after component changes & fine-tuning.

    Also, I apologize, for the SCREECH and SQUEALING from feedback in the beginning of the video.
    I can do better for the presentation, and next time I will try a little harder.

    ~Cheers!~
    73
    -LeapFrog
     
    #4 LeapFrog, Aug 5, 2017
    Last edited: Aug 5, 2017
    tecnicoloco and Robb like this.
  5. LeapFrog

    LeapFrog Sr. Member

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    I recommend the ERF2030+, they are tough cookies!
    I had set a (constant) bias voltage too high and saw one of these mosfets "take-off" into thermal run-away while I was testing, something wild, the heatsink was VERY HOT, and I saw a few smoke trails rise, immediately I unplugged the unit.

    I thought for sure the little mosfet was cooked, nope! After it cooled back down I lowered the bias voltage from about 4.2 V to a more reasonable 3.6-3.8 V :p it didn't fail, I tested it after everything cooled down and it is still alive! :cool:

    ERF2030+ get a thumbs up from me, I have tried FQP13N10, IRF520n, and so far I prefer the 2030+; a plain-Jane SiHF520 mosfet will be used for the next test.

    While the TRC-427 is very similar to the 21 LTD, PC66 /Cobra 25 GTL radios it has a different audio chain, the pre-amp is not the same, you get an antenna warning indicator and mod indicator on the 427, something the others don't have.
     
    #5 LeapFrog, Jan 22, 2018
    Last edited: Jan 23, 2018
  6. Robb

    Robb Yup

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    The 2030+ took a lickin' and kept on tickin'? Woah! I'd seen regular mosfets blow up just like fireworks! Me like.

    BTW - what software are you using in that video if you don't mind my asking?
     
  7. LeapFrog

    LeapFrog Sr. Member

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    Yes, I honestly thought it was done but these new generation of mosfets are tougher!

    That software is called SDR#, it is freeware that I use with an RTL-SDR dongle.
    https://airspy.com/download/
     
    #7 LeapFrog, Jan 22, 2018
    Last edited: Jan 22, 2018
  8. LeapFrog

    LeapFrog Sr. Member

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    Updated!
    Realistic TRC-427 Mods


    Schottky Receive Mod Location:
    Little Power/Audio Boost:
    The Mosfet Mod:
    Optional:
    Correction! in my first post of this thread I mislabeled R42 as R44, when I discuss L14, will need mod to edit the post.

    Optional Bias Voltage
    I don't mind if you copy this somewhere else as long as you give credit to WWDX's Moleculo post on the high-power MosFet mod for a Cobra 25/PC68, & a thanks to CBtricks, & EKL, for the mod install sheet for Cobra 25 LTD,
    they also inspired this TRC-427 Realistic Mod Sheet.

    All the best regards!
    -LeapFrog Tampa Bay
     
    #8 LeapFrog, Jan 23, 2018
    Last edited: Jan 23, 2018
    Shadetree Mechanic likes this.
  9. Redbeard U812

    Redbeard U812 Member

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    I have one of these radios. Never knew it was a stable radio. It works like it should. Not a real fancy radio but same chassis as Uniden I'm told. Moth balled it on a shelf, maybe I'll get it out. Now what did I do with the dammed mic for it?
     
  10. LeapFrog

    LeapFrog Sr. Member

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    I like to do a "Cobra/Uniden/Galaxy 4 pin" conversion, the 5 pin DIN connector is shoddy and leaves much to be desired.
     
    #10 LeapFrog, Aug 20, 2018
    Last edited: Aug 20, 2018
  11. Redbeard U812

    Redbeard U812 Member

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    Pulled mine off the shelf and thought about the same thing. That 5 DIN is the same as what's on this old Commtron CXX, which needs a 4 pin, also. Now.....wher's that damned mic at. Shouldn't be hard to find, it's the only one with that wimpy DIN. I did copy your text about the Mosfet and mods. Good info.
     

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