Question about Radio Communications

1 Answer

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 tune and there numbers... The works... I have a 102 whip grounded really good and have low SWR readings now but the radio is crackley.... Id like to tune it up and be able to reach out... AM modulation pots.... coils and which ones to adjust and there numbers on the board internally... schematics on motherboard of cb... I cant find anything online and im having to pay to find out.... because i dont know...

Posted by Randy Smith on

Ad

1 Answer

Mr BrokRench

  • Level 3:

    An expert who has achieved level 3 by getting 1000 points

    Superstar:

    An expert that got 20 achievements.

    All-Star:

    An expert that got 10 achievements.

    MVP:

    An expert that got 5 achievements.

  • Master
  • 1,623 Answers

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.

A 1:1 SWR implies a perfect match between all elements of the antenna system...this is what you want. If an antenna system is not working well, the power reflected by the antenna will travel back through the transmission line and arrive at the output of the transceiver. From a practical point of view, SWR numbers in the range from 1:1 to 1.5:1 are considered to be very good, meaning that the antenna is radiating most of the power sent to it...

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.

Here is a link for your radio, in case you don't have one.

http://support.radioshack.com/support_electronics/36554.htm

Posted on Nov 16, 2011

  • 2 more comments 
  • Randy Smith Nov 16, 2011

    I have got my readings to a 1.2 swr close to perfect.. like i said i have a 102 wire whip.. my whole think is I want to know how to get full modulation, and adjust the internal pots on this radio.. what i need to do internally... It was a free radio. So if it blows it goes... I Have a General Lee that will eat it alive...

  • Randy Smith Nov 16, 2011

    I have got my readings to a 1.2 swr close to perfect.. like i said i have a 102 wire whip.. my whole think is I want to know how to get full modulation, and adjust the internal pots on this radio.. what i need to do internally... It was a free radio. So if it blows it goes... I Have a General Lee that will eat it alive...

  • Randy Smith Nov 16, 2011

    basically i want to let the radio swing... get more watts... without paying anymore money to someone... what do i need to adjust internally... every other cb has something on it... I cant get **** on here.... couldnt catch a skip on a good day with good numbers on swr....

  • Mr BrokRench
    Mr BrokRench Nov 16, 2011

    Ok...on the board the little white and blue pot by the transformer is your modulations. To super swing that radio, you'll have to pull the inductor that feeds the RF driver. The inductor there looks like a resistor and is green. On top of that you have to leave the inductor in and just pull the voltage side. Install a cap and you have to play with the resistor value...youll probally need about a 220 uf capacitor,and somewhere between a 50-100 ohm resistor.the idea is to locate the 13.8 volt dc feed,to the driver section,disconnect it by either cutting the land pattern on the solder side of the pcb.or either disconnecting the proper resistor,choke,or capacitor,whatever the case maybe.what i gently do is locate the pcb land pattern feeding the driver stage,using a exacto knife,gently cut the land pattern,completely isolating it.then install my 220 uf capacitor,on the componet side of the board,then install my 50-100 ohm resistor across the capacitor,on the solder side of the board.remember the negative side of the capacitor,needs to be towards,the driver....usually a 50 ohm resistor,gives you about 2 watt dead key...

    In order to increase your power by 1 S-Unit, you're talking the production of 6 dB gain. That power is generated by doubling the power twice over, so on AM you're talking 12- 16 watts. The adjustment of any "parts" inside your CB is pointless, you can't tweak them that much.... Get an amplifier if you want to produce serious power with preamp for DB gain...Many of the most popular are the Texas Star, Palomar, Xforce, Davemade, Ameritron, and Fatboy, amplifiers...
    This is what i use & i have it tuned down! http://cbworldinformer.com/200112/cobra_...

    I hope this information is helpful.

×

Ad

Add Your Answer

×

Uploading: 0%

my-video-file.mp4

Complete. Click "Add" to insert your video. Add

×

Loading...
Loading...

Related Questions:

1 Answer

Trc 446


with this radio,I would probably go and buy another . It will be cheaper than having someone fix it.give more information about what its doing or not doing and maybe some one will give you the help you need but I would buy a better radio.

Sep 03, 2014 | Radio Shack 40 Channel Cb Radio Model...

1 Answer

How to clip and tune


why do you want to clip and tune a radio? Clipping the diode will make the radio modulate higher and unrestricted but if you take that radio and turn the power down to 2 watts give variable 4 a full turn to the right and open the modulation pot it will sound a whole lot better then if you clipped it. when you clip a radio you create a splash box that wipes out all channels lose by and the others will also be effected. the diode you want to clip is D-11. but I advise you not to.

Nov 24, 2013 | Uniden Bearcat Pro PC68Elite 40-Channels...

3 Answers

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


  • 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.

Nov 16, 2011 | Radio Communications

1 Answer

Radioshack trc-487


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.
Hope this was of help

Nov 16, 2011 | Radio Communications

1 Answer

CB receive volume is low to out on the output. Weatherband output and reception is fine. Any suggestions?


The problem could be with the mic. If there is a problem with the mic it will make either the receive not work, or the volume seem real low. The weather will work fine if the mic is bad.

Sep 29, 2010 | Radio Shack TRC-447 CB Radio

1 Answer

I have no problems just would like to tune and peak my trc-447


RV2 is modulation. turn that up to get full modulation. L9 and L12 is AM power.

Dec 16, 2009 | Radio Shack TRC-447 CB Radio

1 Answer

I was wondering what was the range for the radioshack TRC-447 cb radio with a good cb antenna


Antenna :
-should be tuned, have good coax with no pinches, whip is centered over highest flat metal surface, no metal beside adjacent to whip, power is wired to battery direct, not to ignition or cigg lighter. whip is wiped clean of corrosion, whip is up, longer is better.
Praire City car-to-car: 15-20 km's
Praire Rural car-to-car: four-thirds over the horizon. Probably 60 km's.
Alot further over water.
Less within trees and mountains/valleys.
Google "Ham radio" & "ducting" "inversion" "skip" "sun-spots"
these refer to a condition where a radio signal getting stuck between the upper and lower atmospheres and travel intact for 1000's of km's (canada to mexico for example)

Sep 06, 2009 | Radio Shack TRC-447 CB Radio

4 Answers

Radio shack trc-447


According to the service manual for the TRC-447, the only adjustment is for "power" which is #L205. The only other step in the transmitter alignment is for the "S" meter.
On the Cobra, VR4 is AMC, L14,L13,L12 is AM power.

Jan 31, 2009 | Radio Shack TRC-447 CB Radio

Not finding what you are looking for?
Radio Communications Logo

Related Topics:

220 people viewed this question

Ask a Question

Usually answered in minutes!

Top Radio Communications Experts

eradiostore
eradiostore

Level 3 Expert

1664 Answers

Brad Brown

Level 3 Expert

18564 Answers

Marvin
Marvin

Level 3 Expert

85239 Answers

Are you a Radio Communication Expert? Answer questions, earn points and help others

Answer questions

Manuals & User Guides

Loading...