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Got a radioshack trc-487 and I need some information on how to peak and tune it... wheres the modulation pot? which coils do I tune? and whats the numbers on the motherboard

I need help with this cb.... Need to know mods for it...

Posted by Randy Smith on


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  • There is no need to send the radio to some unsanctioned moonlighter.
  • I normally don't recommend clipping parts but for this radio there is not much else to do and it looks OK on an Oscilloscope too. Clip diode 205 to increase modulation. Then take a plastic flat tool and spread L 203 coils apart about a 1/8" each, nice and even and make sure they don't touch any metal.

  • Hope this helps.

Posted on Nov 27, 2011

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  • Nov 27, 2011

    These users asking to tune up radios.. NEED to have Oscilloscopes or watt meters so they can fix it themselves.. otherwise let shop do it for $5-$10 right.. and NEVER CLIP the mod limiter.. keep it in the 5mhz bandwidth.. PLEASE..

  • Iron
    Iron Nov 27, 2011

    Normally never but as I said with this one is OK. I have yet to see this flat top. Your not talking to a rookie here so get of the soapbox now. If one is running it barefoot then my instructions are a nice tune and about the only tune for this rig. If running with an illegal amplifier then leave stock. Your just trying to get people to unnecessarily send their rigs to your shop when it is not necessary. That's why your profile has been reported.

  • Nov 27, 2011

    No Im not! They need to be shown correctly..

  • Iron
    Iron Nov 27, 2011

    Much can be done on here. Not all but a lot can. Almost everyone of your "solutions" is a send it to you response with the occasional how to wire a mic. Talking and instructing someone is not so hard. You just have to know how to slow it down and take the time to explain in detail. If a scope should need to come into play then this can be relayed to them. But you can cut a lot of the cost out of things for them along the way.



Ken A Resendez

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If you cut D205 like the first guy said. The radio will not get any power. D205 is the power diode. I'm working on one now. He maybe talking about D105? Not sure yet. The ALC on this radio is small. But I will update as soon as I'm done.

Posted on Apr 13, 2020


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May need some test equipment to tune that one.
You could send it in to us and we can fix it.
We do not charge to look at any radio -no bench fees-..
Let me know Ill get you any info that you need.

Posted on Nov 27, 2011

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I have a Radioshack trc-487 cb radio with weather band . I would like to turn up the modulation... Peak and tune... get better reception... anything... I would like to know the internal parts I have to...

Hello Randy, do you have a fiberglass or stainless whip? What is your SWR & power meter readings now? --- The stainless whip may be creating a feedback and picking up static from transformers. Do you have a power microphone? If so you need to use a modulation meter to set it for 100% modulation. It could also be causing the crackling, that or your engine alternator.

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I would not recommend tweaking the boards on the realistic radios. You can however tune your whip. Start by making a base coil with some copper wire, 14 gauge will work. Run one end under the whip mount end and then tightly wrap the wire around the base of the whip. Experiment with 20 - 30 wraps for best performance & SWR.

The Astatic 575M6, or the Sadelta MB-4(hard to find) are very good power microphones that will help with modulation and peak power transmissions. Let me know if you need more help with tuning, if the "crackling" is still there.

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Sorry can not suggest even the addition of a aftermarket mic it would be to much hassle to rewire to that 5 pin plug.
Don't spread coils!!!!
Besides it is an older unit that has obviously set unpowered for long periods this makes it a good candidate for dry capacitors.
Don't forget that antenna system when looking for increased radio performance a good antenna(tall) and good shielded coaxial cable can make or break the setup.
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