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  1. #1
    Bobtail Member
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    Big, Loud, Cobra 29 LTD Radios

    Hello to all my fellow brother_truckers...This will be somewhat of a long post, but worth reading...WHY?...The info contained herein will save you some money. Ohhhh Yesss it Will...

    BTW...They call me Texas Trash on the road...I know some of you may know me...so here we go...about Cobra 29 LTD CB Radios...

    If you want your Cobra 29 LTD to be a loud booming talker you don't have to pay some cb hacker to "fix ya up". Swing Mods are snake oil...Don't pay to have this done...Any kind of mod...like cutting your limiter...ie..D11 etc, etc..only junks your radio and makes it distorted. If you really want your radios audio loud and proud you can do it yourself. It is real easy. Just open that badboy up on the speaker side and find VR4...(VR4 is the AMC pot...commonly known as the audio potentiometer)...It controls your audio output...

    Once you find VR4...Take a plastic screwdriver (get a cheap set at Radio Shack...or borrow one) and turn VR4 counter-clockwise all the way. That's it...you just turned your audio up as high as it will go. Put the cover back on and go ask a buddy on another cb how loud your audio is. Make sure your dynamike is all the way up too. It's that simple guys and gals...

    Now for the microphone...Do not pay big bucks for an RK56 noise cancelling mic. You know the Turner Telex Road King 56...You are paying for name only...Guess what? The Workman SS56 noise cancelling mic is the exact same mic...Ohhh Yesss it Issss!!!...

    The insides of the Workman have the exact same mic element...the exact same transformer, the exact same capacitor, and the exact same Push to Talk Switch....Ohhh Yesss They Are...Guess What? You can buy one for $15.00 most anyplace that sells 'em...cept maybe the truck stops...And they work, look, and sound just like the RK56 mic...Now if you want to fool yourself and everybody else into thinking your radio is even louder...go out and buy an RF Extreme TRB-X2 echo board and install it. If you can solder...you can do this too...If you want you can pay a "cb hacker" $15.00 to $20.00 and no more to install it for you. Just make sure they have installed many of them before...

    Now with your radios VR4 turned up...dynamike all the way up...a Workman SS56 mic...and an echo board....you will sound loud and proud like any other mother truckers son...only you will be understood and not distorted...BTW...keep that talkback turned down or off and you won't squeel like a stuck pig...

    So there ya go...Save yourself some money...Maybe spend it on your favorite LL and the Pilot...LOL

    Pete...AKA Texas Trash...Third in line from the original Texas Trash...namely my old Grandad...See ya out there on the big road...I'm down and off the key...


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  3. #2
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    Hhhmm I wonder how much distortion just cranking VR4 all the way to the right, introduces?

    I don't suppose this same quick mod also works on Cobra 25's?

  4. #3
    Bobtail Member
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    Turning VR4 all the way to the right will turn off the audio...It must be turned counter-clockwise...This is on a Cobra 29 LTD and no it won't distort your audio if your limiter D11 is left alone and none of those other snake oil mods are done and you don't use a power mic.

    On a Cobra 25 LTD the audio pot is VR5...I can tell you...this one thing will make that radio loud and proud. Everybody will think you had it peaked and tuned and other mods done. As far as getting out further this will not help...it will only make your audio very loud...If you cut out D11 the limiter diode you will get very loud also, but will be distorted cuz the limit is no longer there...

    Remember...Cobra 25 LTD...the audio pot is VR5...

    Texas Trash...

  5. #4
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    Thanks...just for gee whiz time I opened the radio...found VR5. Has "MOD" next to it. Also found VR3 it says "PWR"....wonder what this one does?

    I could also use a receive boost too. I see there's another pot that is VR2 with a "RX" next to it. Perhaps this will bring in some far off stations?

    Nope, no swing kits here or any other crap. Bone stock radio. And I don't see a D11 in there but I see a D10, next to VR3.

  6. #5
    "Instigator of the Legend"
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    My Truckers Blog
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    Quote Originally Posted by Turbo-T View Post
    Thanks...just for gee whiz time I opened the radio...found VR5. Has "MOD" next to it. Also found VR3 it says "PWR"....wonder what this one does?

    I could also use a receive boost too. I see there's another pot that is VR2 with a "RX" next to it. Perhaps this will bring in some far off stations?

    Nope, no swing kits here or any other crap. Bone stock radio. And I don't see a D11 in there but I see a D10, next to VR3.
    If you want the guy next to you to blow your eardrums out when he talks go ahead and turn that VR2 up otherwise leave it alone. Trust me I know this the hard way.

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  8. #6
    Bobtail Member
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    Audio Limiter Diode in Cobra 25 LTD

    Quote Originally Posted by Turbo-T View Post
    Thanks...just for gee whiz time I opened the radio...found VR5. Has "MOD" next to it. Also found VR3 it says "PWR"....wonder what this one does?

    I could also use a receive boost too. I see there's another pot that is VR2 with a "RX" next to it. Perhaps this will bring in some far off stations?

    Nope, no swing kits here or any other crap. Bone stock radio. And I don't see a D11 in there but I see a D10, next to VR3.
    You don't want to turn VR2...The audio limiter diode in a cobra 25 LTD is D9...The audio pot is VR5...If you are having a recieve problem...here is where I would recommend a radio alignment done according to Cobra alignment procedures. A good electronics man can do it...Shouldn't cost more than $20.00...but for good and loud audio VR5 is it...The rest of the VR pots you see are used for meter, receive, etc...alignments...

    BTW...Those so called "receive mods" done by cb hackers will work, but they may also and will probably peg your s meter and you don't want that...A good alignment is all that is needed...Don't get ripped by all these roadside truck stop cb hackers...man all they want is your money...and 99.99% of the time...your radio will end up out of whack and distorted...If you want more power...I don't know why one would...cuz even if you can get way out there with more power...it is unlikely you could hear anyone that far off anyway...even if they are running power...Want to talk far off...get a sideband radio....my 2 cents...

    Texas Trash

  9. #7
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    For mercys sake I tried the VR5 adjustment...on my radio if you turn it CCW it turns it down, CW turns it up. Had it as far CW as it would go. Had a guy I chat with regularly on sideband 2 miles out from me. He said it sounded a little louder as opposed to stock, but sort of rattly. He also reported I was bleeding on both of the adjacent channels. Oops.

    Also was told I sounded better on this radio using the stock coffin mic as opposed to the ST65DX mic I typically use.

    I agree with you no the more power thing....however anymore it seems the only way to get heard is to run more power than the next guy...because most truck drivers I'm sure don't run around with 4 watt radios these days.

  10. #8
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    VR5 Pot On Cobra 25

    Quote Originally Posted by Turbo-T View Post
    For mercys sake I tried the VR5 adjustment...on my radio if you turn it CCW it turns it down, CW turns it up. Had it as far CW as it would go. Had a guy I chat with regularly on sideband 2 miles out from me. He said it sounded a little louder as opposed to stock, but sort of rattly. He also reported I was bleeding on both of the adjacent channels. Oops.

    Also was told I sounded better on this radio using the stock coffin mic as opposed to the ST65DX mic I typically use.

    I agree with you no the more power thing....however anymore it seems the only way to get heard is to run more power than the next guy...because most truck drivers I'm sure don't run around with 4 watt radios these days.
    Yeah...I forgot to mention...some 25's have that backwards pot...As far as sounding rattly..I suspect it is the ST65DX mic. Although it is a good mic...and although it is a noise cancelling mic...it is quite a bit more "lively" than an RK56 type or it's clone...That mic almost acts like a power mic...but without the battery...It uses a transformer and a capacitor that allows more highs to pass through...the bass parts of your voice "fall off" way to soon...or are filtered out at the mic making it sound thin...so what you might try is backing down on VR5 just a smidge to get rid of the rattle...but I would see what others think first...could be he had a rattly speaker too...

    Texas Trash

  11. #9
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    Quote Originally Posted by garmich1000 View Post
    BTW...Those so called "receive mods" done by cb hackers will work, but they may also and will probably peg your s meter and you don't want that...A good alignment is all that is needed...Don't get ripped by all these roadside truck stop cb hackers...man all they want is your money...and 99.99% of the time...your radio will end up out of whack and distorted...If you want more power...I don't know why one would...cuz even if you can get way out there with more power...it is unlikely you could hear anyone that far off anyway...even if they are running power...Want to talk far off...get a sideband radio....my 2 cents...

    Texas Trash
    No receiver mod will pin your meter the most used the 2sc1674 to 2sc2999 mod will add ONE s unit. Unless someone is doing something strange otherwise I have never seen this.

    As for SSB this is why it is used ( other than code or some digital modes )
    for most long distance work. SSB can be recovered long after AM signals are gone.
    FM is very good for Mobile work and is the choice for repeater and land mobile.
    There was a time when AM was the mode of choice above 10 meters but is only used by a few legecy hams and CB and aircraft today.

  12. #10
    Rat
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    Don't need to turn it more then 3/4. Any more then that usually causes it to sound choppy etc.


    Do a quick google search on cobra 29 mods or cobra 25 mods. There are alot of them out there that don't mention anything about cutting or removing the limiter.

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