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A cb radio not working after being sent in for modification

Discussion in 'General Electronics Discussion' started by Paul Grodkowski, Dec 5, 2019.

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  1. Paul Grodkowski

    Paul Grodkowski

    Sep 5, 2013
    Hello everyone !

    This is long and silly but maybe someone out there has an answer to my question if it can be figured out from my long explanation.

    Sometime ago I bought a Uniden pro 520 XL citizen band radio. I connected it in a car and it lit up and started to work. Further, I watched a Youtube video showing that this model of cb radio can be modified to have an output of 30 watts.

    After watching the video, I decided to ship the radio to Uniden and so I did a google search and found an address to ship to and put instructions in the shipping box to have the radio modified to 30 watts output.

    The radio was shipped back to me and I connected it to a 12 volt storage battery that I tested with a DMM and the battery measured 12 volts on the DCV scale. Upon connecting the Uniden pro 520 cb radio to the battery and turning on the power switch, lights on the front panel did not light up and I did not hear any audio from the speaker.

    I am just putting this out there.... what could be the reason that the radio is not working after what I have explained above....?

    Warm regards,

  2. davenn

    davenn Moderator

    Sep 5, 2009
    no way ! ;) you have been deceived
    at best it may get up to around 6 - 10 W. The output transistor and associated circuitry would not be able to do any more than that

    main fuse in it blown, main output transistor blown which then blew the fuse and a few other variations along similar lines
    and finally ….. whoever did the mod totally hacked your radio and they are now in the pub enjoying a few cold beers from the money they scammed from you :(

    bertus likes this.
  3. hevans1944

    hevans1944 Hop - AC8NS

    Jun 21, 2012
    Hmmm. I would never do what you did: blindly return a used item to the manufacturer without asking for permission to do so, and before obtaining a Return Authorization Number or letter or similar document showing proof that the return was authorized and that the item would be accepted by the manufacturer. But, before that, I would have contacted the manufacturer and explained what modifications I wanted them to perform (raise power to RF output stage to 30 watts), ask what that would cost, and provide an estimate of how long the work would take. Only after receiving favorable responses to these there queries would I request an RMA number and ship the item back to the factory.

    But surely you realize (or should realize) that a manufacturer like Uniden is in business to make a profit, which generally does not result from accepting sold equipment already in the field, and then undertaking the engineering labor necessary to make the equipment perform to a different standard than that to which it was originally specified, designed, and approved. That would be a very expensive process, particularly for something as heavily regulated as mobile transceivers which AFAIK must be type-accepted before they can be manufactured and sold to the public.

    If you really wanna break the Law (and it sounds from your original post that you do), you should hang out around a large truck stop with the diesel engine on your rig running, go inside and inquire of some real truck drivers where you might procure a "foot warmer" for your Uniden 4 watt POS rig. I have seen these for sale at interstate truck stops with power outputs touted as high as 200 watts. But caveat emptor on that. Some will just take your money and hand you a box of rocks with some wires hanging out. Dress appropriately lest someone take you for a "Mark" and overcharge you for the rocks.
  4. bertus

    bertus Moderator

    Nov 8, 2019

    You should also check the local regulations for the use of a CB transmitter.
    It can well be that the rules will have a limit on the maximum power.

    In Holland where I live the maximum power allowed is 4 Watts FM or 4 Watt PEP for SSB.

  5. Martaine2005


    May 12, 2015
    Hi Paul. I would be interested to see photos of both sides of the pcb.
    Just curious to see whether it has been altered/modded or hacked!. Either way, as already stated in previous replies, the output stage is not designed as a variable amplifier. Sure, you can spread coils, cut links, pull diodes etc etc. But all you’ll do is over modulate or worse, destroy the radio. Back in the 80s everybody wanted to mod their CB. The above procedures were often done giving another 3 or 4 watts. Nobody really had a clue what they were doing. Nobody checked datasheets for output transistors. Nobody checked ‘if’ things were getting hot. Just a screwdriver in the coils and spread them!.
    CB radios are complex pieces of equipment. After a ‘mod’ they would often require retuning, but nobody knew how to. This led to an inrush of CB repairs at my local shop. He ‘Jay’ would un-mod them and return them to factory spec. Charge them for repair and then sell them ‘boots’ (foot warmers) plus a new antenna to handle the ‘boots’.
    Only winners here are Jay and product suppliers.
    In the UK max output for CB transmission is 4 watts FM.
    I melted a DV27 antenna with a 400 watt burner. Why?, because I didn’t have a clue either!.
    Post some pcb photos.

  6. KMoffett


    Jan 21, 2009
    Legal power limit for CB transmitters is 4 watts in the US and EU.
    shrtrnd and bertus like this.
  7. Externet


    Aug 24, 2009
    What could be the purpose of increasing the power output of a CB radio ?
  8. Alec_t


    Jul 7, 2015
    Out of curiosity, what did Uniden charge you for this CB 'improvement'?
  9. Tha fios agaibh

    Tha fios agaibh

    Aug 11, 2014
    Transmit longer distances
  10. bertus

    bertus Moderator

    Nov 8, 2019

    In stead of higher transmitterpower, a better antenna would also work.
    The ARRL antenna book might have some suggestions:
    The 10 meter antennas are close to the CB band.

    Tha fios agaibh likes this.
  11. davenn

    davenn Moderator

    Sep 5, 2009
    Since the OP is on an illegal quest

    thanks to everyone who responded :)

    the thread is closed
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