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Cobra 25 wx st

Discussion in 'CB Radio Modifications' started by eric brune, Sep 22, 2018.

  1. eric brune

    eric brune New Member

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    Hi,I'm very new to working on my own radios and I have a question about an older Cobra 25 wx. I just finished a putting in a mosfet 520 and now I have a 4 watt deadkey but when I talk the needles on both my Dosy and thae radio both drop a little instead of swinging up. Everyone that I have talked to on it says that it sounds great. Any Ideas?


     
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  2. loosecannon

    loosecannon Sr. Member

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    most likely when you did your alignment of the TX coils after the mod, you tuned them for max deadkey instead of max modulated wattage.

    get your phone, go to youtube and do a search for "1000 hz test tone" you will find a few videos that will play this tone for an extended amount of time.

    hold your phone up to the mic while transmitting and tune the coils for max that way.
    LC
     
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  3. Robb

    Robb Yup

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    Since you said you are new to this; then the first thing I would do is double then triple check all of your work. No offense; but it is easy to make mistakes like this.

    The first thing that comes to mind is that the radio is getting enough current. Make sure you radio's power cable, socket, and power supply doesn't have any resistance.

    Did you peak the TX coils after putting the mosfet in? That is also required.

    There is also a disc cap on the trace side of the board that may need to be added to ensure enough coupling between the driver and mosfet final.

    Doing a job like this does force one to learn faster and gain some knowledge.

    Happy hunting.
     
    Rwb likes this.
  4. eric brune

    eric brune New Member

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    Thanks,I have used the radio with my power supply and in the truck wit a heavy duty cord. This is the second 25 that I have done,the first one came out great. This one has me a little puzzled because it seems to be getting out very well but I'm getting the same thing on two different meters so I know it's in the radio.
     
    Rwb likes this.
  5. eric brune

    eric brune New Member

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    I will try that,thanks
     
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