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Modulation radio seems to have very small amount of forward swing when speak into the mike . i have hade radio tuned and tried 3 or 4 mikes. set at 5 watts and maybe swing to 6 or 7 watts on radios meter and a good external meter. radio is 1 year old . finals are ok also. swr good. ant 2 k40 5k

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Have you happened to check the cable to your antennas? maybe you got a cut in the insulation. thats the only idea i can come up with being that you have had all the work done to it and still havin problems.

Posted on Oct 21, 2008


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FT-890AT yaesu transceiver has distorted transmit audio

Hi Ronald,

Could the problem be related by having the mike to close to your mouth? This is the most common cause of over-modulation/ distortion from the transmission end.

If you have the mike 3-6 inches from the mouth and speak in an even non loud tone, that would help sort that out. If this is not the source of the over modulation/distortion, then you may have a transmitter issue, which would require the unit to be serviced by a qualified radio technician or ham radio operator, if you know one willing to look at it for you.

I hope that this has helped you.


Dec 01, 2012 | Radio Communications

1 Answer

Have a sequel when keyed up

If this is a powered mike the modulation is set to high. If you have a standard mike check your settings on the radio, if that does not help sub another mike.

Apr 03, 2012 | Cobra 29 LTD CB Radio

1 Answer

How do i find and turn up modulation

If your asking for an internal adjustment,you need to be a qualified technician to do this and the radio's schematics..which I don't know either answer to,so external adjustments would be mic gain knob,you can also gain modulation by lowering the output power knob,both can be adjusted to get the most forward swing by watching your meter swing when am or sideband transmitting.If you are using the stock mike,you could also upgrade to power mic properly wired for your radio.If you are a qualified to do so,there are online sites that have info on upgrading the modulation to this 10 meter radio by adjustments,modifications and add on parts,which does require an amateur license to operate unless modified for cb bands and only transmits on these bands..according to fcc rules.

Aug 14, 2011 | Magnum DeltaForce CB Radio

1 Answer

Reception is fine, cannot transmit. checked swr's and all below 2. how to check out transmission modulation?

To see if your radio is "modulating" you need to do one, or both of these things. The first and easiest is to look at the RF/Signal meter in your radio. If you see forward movement of the needle then you know the radio is modulating the carrier. NOW, the second and best way to see if the radio is modulating is to go out to your local Truck Stop and purcase a Power/SWR meter. They generally run about $30 bucks. You will also need a short coax jumper (at least 3 feet, no more than 6 feet) to link the radio/meter/antenna. By the way, they should go in that order. The meter will be clearly marked as to how to hook it up and it will come with instructions.
To check forward modulation, the meter should be in Power mode (not SWR mode) with the power scale switch set to 10 watts. You then key the microphone. You should see a carrier (dead key) of about 4 watts. To check for proper modulation, you should then speak into the mic at a normal level. You might try saying AAAAUUUDDDIIIOOO (audio). If the radio is working properly the needle should rise off of 4 watts and swing forward to around 8-10 watts....give or take a few, depending on weather or not the radio has been modified (peaked and tuned). If you see forward movement on the meter, you know it is working properly.
If you do see that the radio is modulating properly but you cant seem to contact anyone on the air waves, then you need to start looking at your antenna setup. I will not go to deep into this subject because it is so extensive. The antenna system is VERY important. you said you checked SWR and it is below 2. This is a little high...but acceptable. You should really try to get your SWR as close to 1.0 : 1 as you possibly can. Hope this helped. Lost Jeep, Athens GA, 10-7 !!!

Feb 18, 2011 | Cobra 29 NW CB Radio

1 Answer

I have a Fender Passport 150 and my microphone is won't work but everything else does......????? Thanx Mike

Mike try the microphone if possible on another set If the mike makes a noise check for frayed and bad cables. As far as I know the mike is a dynamic mike and connect it to the speaker of a small transistor radio and it should a small speaker for dynamic mikes and ordinary speakers work just the one as a generating device(Speaker) and the other as a sound pick up Look at small to way radio's the send is the speaker a mike and on receive it is a speaker, Hope this help

Nov 14, 2010 | Lectrosonics FENDER PASSPORT PD-150 + 1...

1 Answer

Will not get good recepiton.

Hi stormnorm157,

Much of the time this is caused by problems in the antenna system. Make sure there are no shorted or open connections in the coax or PL-259 connectors. Use your radio's meter or better still, a Power/SWR meter to check the SWR of the antenna. Try to get that as close as possible to a 1:1 ratio on the meter. A shorted or open antenna can keep the audio receive on your radio at very low levels. Plus, this will harm your transmitter if you continue keying the mike.

Another problem can be in the radio itself. This will be noticed if you can transmit, but have no "Modulation". Modulation can be described as the voice heard above the "Carrier" (your transmitted signal). Every CBer knows about the term, Modulation. The Truckers will definitely inform you about your modulation This problem can be due to a defective AMC (Automatic Modulation Control) stage in the receiver circuit. And, there will be no modulation upon transmit.

One other thing could be causing this lack of receive. Defective wiring or switching in the microphone can result in no audio. Or, in many radios, a missing mike will not allow receive, because the mike connection completes the RX (Receive) circuit.

1. Check the antenna system, and rule that out or fix.
2. Check mike, or substitute another one.
3. Using meter, and or another radio for listening on same channel, check power and receive.
4. You can probably fix 1 and 2 yourself, or with a friend.
5. AMC problem in radio (as described above) will require professional service.

Let me know how this turns out, and inform me if I can offer any more help. Thanks.

Regards, Bill

Sep 18, 2010 | Midland 1001Z 40-Channels Base CB Radio

2 Answers

I have a general lee and I am running a 2 by 8 box. What should I turn my radio down too to run this box I was told 3 watts wgat do I turn to accomplish this I doesn't seem to have much modulation either

The radio needs to be tuned for the box. 3 watts sounds too high for a 2x8.

I would say it would be more like 1-1/5 to 2 watts. That may be why your not getting that much swing.

You should set the radio so the box dead keys around 300 to 400 watts.

Aug 24, 2010 | Cobra 148 GTL 120-Channels Base CB Radio

1 Answer


That's usually a defective amc stage that produces RX audio and TX modulation. It's an integrated circuit that will require a tech fixing it. You will have a transmitted carrier with no modulation, and no sound in your speaker. However, make sure you have a good mike plugged in first, and substitute a known good mike to verify it's not the mike.

Jul 30, 2010 | Radio Communications

1 Answer

Cobra ltd classic no modulation

Assuming that you've tried another mike, the problem may lie in the speech amplifier circuit within the radio, something that will require someone with technical knowledge to repair.

Sep 22, 2008 | Cobra 25 LTD 40-Channels Base CB Radio

3 Answers


You never want to clip modulation limiters All youll get is a overmodulated splatterbox and it will sound like crap!! Try and youll find the tuning info for that radio...Chia

Dec 24, 2007 | Cobra 150 GTL DX Base CB Radio

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