Question about Radio Shack TRC-503 CB Radio

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Cb radio I have great swr readings and people can hear me just fine sometimes. But when i key the mike my car radio fades out like the vol. is getting turned down and when i let off the sound comes back.

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  • Anonymous Feb 26, 2009

    i have the same problem i can hear my self on my stereo speakers only when my stereo is turned on but if i turnit off it sounds fine and i already tried getting ground from many different spots and it still does the same thing

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You may be overloading the front end of your am/fm receiver, particularly if you am/fm antenna is one of those "in glass" numbers that were/are poplular with a lot of car manufacturers. This problem can be compounded if your CB antenna is in close proximity to the AM/FM antenna.

Disabling the AMC (Automatic Modulation Limiter) in a CB also makes the problem exponentially worse, and that's the first thing a hack technician rips out of there during a tune-up.

Posted on Mar 20, 2009

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You may be generating a harmonic from the cb that is picked up by the radio. Check if different channels and if AM/FM act the same. Also if a cd unit, does playing a cd produce the same effect. If all stations and the cd player do the same thing, interference is most likely coming in on the radio power or ground leads. You can get an inline noise filter from radio shack: http://www.radioshack.com/product/index.jsp?productId=2103979&cp=2032058.2032230.2032273&parentPage=family
or you can make your own if you have an old computer power supply by using the toroids if you can get to the power supply lead. Make sure the radio housing is electrically connected to ground. The interference may also be coming in on the radio antenna. Try moving the cb antenna away from it if possible, or test by rotating the cb antenna to a horizontal position temporarily.

Posted on Nov 30, 2007

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2 Answers

Bought a new cobra Every time mike is keyed it reads antenna warning Radio will transmit short distance and will on receive short distance Very short Cobra 29 L X B T LCD CB radio


The antenna warning is the key, the swr on the antenna/feedline is very high. check antenna connections, coax and connectors for damage

Apr 10, 2014 | Radio Communications

1 Answer

How do I fix SWR spikes?


For CB radio that operates in a relatively narrow bandwidth, you should be able to obtain "perfect" SWR readings for all 40 channels. That would be a reading of 1.1 : 1 or less.
The rule of thumb goes like this: if SWR is HIGHER on HIGHER FREQUENCY (Ch. 40 is higher than Ch. 1) then the antenna whip is too HIGH (too long/tall) therefore it must be shortenned. And vice versa.
Trimming the length requires patience especially when the reading has reached 1.5 : 1 or lower/better. Make a 5mm trim each time and then measure SWR then continue trimming until you are satisfied with the results.
The spike must be contributed by faulty electronic components inside the radio. The radio must be checked by a technician. But before you do that, trim your whip first and see what happens. Ideally, the length of the coax cable must be trimmed as well. But, since we don't live in an ideal world, we can ignore that for the time being. Goodluck. es

Jun 10, 2013 | Radio Communications

1 Answer

Roadpro rpswr


What was the radio that you keyed?

Apr 28, 2013 | RoadPro RPSWR-3C Swr Meter - 10w-100w -...

1 Answer

Antenna warning light


if you see the red light come on before you even set the swr you already have a problem.set the radio on cal and set the needle at the cal arrow.no unkey the mic . set the meter for swr and key it again.write this # down . go to ch 40 and do the same thing, then go to 19 and repeat. now that you have your readings you need to set the antenna. Now check it again for swr on 1-40-19keep doing this until you get an even reading on those channels.

Oct 14, 2012 | Cobra 29lx Cb Radio W/clock 29 Lx Lcd

1 Answer

Swr meter not moving


follow these steps to adjust the
standing wave ratio(SWR).
1. Turn on the CB.
2. Set S/RF/SWR/CAL to CAL.
3. Key the Mic and rotate SWR CAL so the meter points
to CAL.
4. Unkey Mic.
5. Set S/RF/SWR/CAL to SWR.
6. Key Mic again and note the actual measurement on
the SWR scale. Refer to the following table to interpret
the reading.

1:1 - 1.5 Great
1.5 - 2:1 OK
2:1 - 3:1 Not So Good
Higher than 3.1:1 Terrible

Jan 14, 2011 | Cobra 29 LTD CB Radio

1 Answer

Im having a problem with people hearing me on my CB. I can hear people fine and it comes in real clear, but they can't hear me at all, i mean they can but its just that its so low they can hear me. It was...


Tune your antenna. If he took the metal whip out of the base, then he messed the tuning all up.




It is important to tune your CB radio antenna to the proper length. The length must exactly match the wavelength of the frequency you transmit on. Or be really really close.

All Cb antenna's have a way to adjust the length of the antenna. If it's a mag mount, the metal whip can be slid in and out of a metal collar. Usually a set screw. If its a fiberglass whip, the way to tune it is on top. It either has a small metal rod with a set screw to adjust the length, or it threads in and out to adjust length.

Either type you have it will need to be adjusted for proper length. Here is how to tune the antenna to lowest SWR.

Some radios have a built in SWR meter. Some do not. If yours doesn't have an SWR meter, then you have to use an external SWR meter. Radio shack carries one, and you can find them cheap on ebay.

If you have a built in SWR meter or external, the procedure is the same:

1. Turn the radio to CH 20.(This is the center of the band.)
2. Switch the meter switch to CAL. (CAL stand for calibrate.
3. Key the radio. (Important. Do not talk while keying the radio.)
4. turn the CAL knob up until the meter hits the CAL mark.
5. Now while still keying the radio flip the meter switch to SWR.

Where the meter falls after that point is you SWR reading. If its above 3, that is real bad. 2 is not gonna kill your radio but its not the greatest. 1.5 and under is a good place to be, but the lower the better.

If your SWR is high, Here is how to find out if your antenna is too long or too short.

1. Turn to CH 1
2. Repeat SWR procedure. You must calibrate every time you do it.
3. Remember the SWR reading.
4. Turn to CH 40.
5. Again repeat SWR procedure.
6. Compare the reading between CH 1 and CH 40.

Now if the SWR is higher on channel 1 then channel 40 your antenna is too short. You must make it longer.

If the SWR is longer on channel 40 then on channel 1, then the antenna is too long, you need to make it shorter.

Make height adjustments about an eight inch at a time, and take reading each time.

once the SWR is significantly lower and the reading on channel 1 and 40 are about the same, you a about matched. At this point turn the radio to the center of the band, channel 20 and take an SWR reading.

You should now have a low SWR reading, 1.5 or under. If you are 1.5 or under, you are good to go.

If you cannot get the SWR to an appropriate level, there may be an antenna problem.

Nov 12, 2010 | Cobra 29 WX NW ST 40-Channels Base CB...

1 Answer

Cobra 29 nw when you key the radio the swr meter doesnt move and if you move the swicth to cal you can adjust it with out keying the mike but has good recive any help would be good thanks dwayne


To check the SWR, you put the swicth on CAL and key the mike with mike gain turned down all the way,then calabrate it to the meter on the CAL scale,then swicth it to SWR before you unkey the mike, then what ever the needle falls back to, that is your SWR reading.

Apr 26, 2010 | Radio Communications

2 Answers

Tunning the antenna on radio shack cb trc-447


After installing the antenna, follow these steps to adjust the
standing wave ratio(SWR).
1. Turn on the CB.
2. Set S/RF/SWR/CAL to CAL.
3. Key the Mic and rotate SWR CAL so the meter points
to CAL.
4. Unkey Mic.
5. Set S/RF/SWR/CAL to SWR.
6. Key Mic again and note the actual measurement on
the SWR scale. Refer to the following table to interpret
the reading.

1:1 - 1.5 Great
1.5 - 2:1 OK
2:1 - 3:1 Not So Good
Higher than 3.1:1 Terrible

The ideal standing wave ratio (SWR) is 1:1, or a meter
reading of 1 on the SWR meter's top scale. A SWR ratio
of 1.5:1 to 2:1 is excellent for most mobile CB antenna
applications.

Check the SWR on Channel 1 and Channel 40
If the SWR is higher on 1, make the antenna longer
If the SWR is higher on 40, make the antenna shorter
Most antenna's are adjustable. Make small adjustments at a time.

Oct 10, 2009 | Radio Shack TRC-447 CB Radio

2 Answers

When i key up the mike the tx/rx light and the ant


your swr setting are off wack fix your swr

Oct 02, 2009 | Cobra 29 LTD CB Radio

2 Answers

I need the manual/s for a Cobra CB radio, 29LTD Classic,ser#105129711,manufactured 5/01. Thanks for any help you might have, This radio has a built in SWR meter and I need to know how to tune it or do I...


1) push the button marked S/RF / SWR / CAL to CAL

2) Hold in the button on the mic

3) Turn the SWR CAL knob until the needle is over set to the far right of the meter

4) flick the switch (in step 1) to SWR

Your SWR reading will be displayed. The more to the left the better..

Jun 22, 2009 | Radio Communications

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