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Cobra 29 "swing kit" or not?

K

KK4JW

Active Member
May 18, 2022
43
39
28
Kentucky
I just bought a new Cobra 29 and will be putting it on the bench tonight. I'm unsure if I wasnt to swing kit (cap/resistor) this radio or not though. I don't plan to ever run an amplifier, ever. I just want the audio to be loud and the signal to be clean.

What is recommended? Adjust L14 to bump the output power up, adjust the AMC pot slightly for a little audio boost, and put the covers back on it? Or would you drop a resistor and capacitor in it and let er' eat?

Thanks!
 
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"loud" and "clean" are two terms that fight each other a lot in the CB hobby.

the "swing mod" for the 29LTD (or pretty much any other transformer modulated AM CB radio of the past) will make the radio sound louder on the other end.

It will not have a clean scope pattern. If you do the mod using a scope and try to clean it up with the AMC control you will notice that right about the time you turn the AMC up too far and start clipping according to the scope, is the exact same point where the audio tone starts to blare out of your bench radio, and the peak reading wattmeter will start to move to the right in a very satisfying manner.

It is specifically the distortion caused by doing this mod and cranking up the AMC that does this.
some people SWEAR BY IT! and will never not do it to their radio.
some people hate when radios sound that way and wish others wouldn't do it.

that's how i see it anyway...
LC
 
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loosecannon said:
"loud" and "clean" are two terms that fight each other a lot in the CB hobby.

the "swing mod" for the 29LTD (or pretty much any other transformer modulated AM CB radio of the past) will make the radio sound louder on the other end.

It will not have a clean scope pattern. If you do the mod using a scope and try to clean it up with the AMC control you will notice that right about the time you turn the AMC up too far and start clipping according to the scope, is the exact same point where the audio tone starts to blare out of your bench radio, and the peak reading wattmeter will start to move to the right in a very satisfying manner.

It is specifically the distortion caused by doing this mod and cranking up the AMC that does this.
some people SWEAR BY IT! and will never not do it to their radio.
some people hate when radios sound that way and wish others wouldn't do it.

that's how i see it anyway...
LC
Click to expand...
I don't mind loud on a channel. Loud on the next three to six adjacent channels is another story.
 
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The only reason on God's green earth to install a carrier control on a CB is for use with a linear. A linear amplifier tends to exaggerate the carrier wattage and underemphasize the modulated power. Tends to reduce the audio quality if a radio is pumping its normal barefoot carrier wattage into an external linear.

The solution is to reduce the radio's carrier, and making sure it still has the same modulated wattage it did with the factory-level carrier. This exaggerates the forward motion of a meter needle, leading to the nickname "swing kit". Besides, people just like seeing the meter kick when they speak. Reducing the radio's carrier so that the audio coming from the linear sounds like the barefoot radio sounds is the main benefit of this trick.

Best case, the radio should sound as good with the linear activated as it does by itself. But any useful tool can be abused, and the carrier control "swing kit" is no exception. Like I said, people just like to see the meter "kick" when they speak.

If you will only use the radio barefoot, a carrier control is wasted effort and money. It won't permit anyone to hear you in the distance that didn't already hear the barefoot radio running stock carrier power.

73
 
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The 29 is thankfully an older through hole parts design, easy to modify and play with. The new radios are all going surface mount with no adjustments on the board, all you can do is talk on it. So if you want to do some mods, here is what I do to for the 29. These mods maximize the radios capabilities while still sounding clean.

Post in thread '29 ltd audio boost,???help' https://www.worldwidedx.com/threads/29-ltd-audio-boost-help.36793/post-727364
 
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Thanks all for your input and advice, and especially YOU, Nomad.

I went with what was recommended and did not install the cap/resistor at JP36. I swapped the resistor off the leg of TR17 for a little microphone audio boost, bumped the AMC control VR4 a little bit, and put the covers back on it.

It isn't going to light the world on fire, and that's okay.
 
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NZ8N said:
I put a 1k to 2.2k in parallel with C71 so it releases faster, then readjust the AMC with an O'scope. Lower is faster release.
Click to expand...

i keep forgetting to try that trick!

somewhere around here i have a schematic for a controlled carrier circuit for this type of radio that im told works very well, but i never got around to building one.
LC
 

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