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S Meter takes a reverse deflection when transmit is OK on receive

12BA6 tube is 2nd IF. I think it controls S Meter

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  • daniel doyle May 11, 2010

    What kind of radio?Have you tried tuning your ant.load and your plate tuning?

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What does rx mean on the cb and it makes alot of nois

Posted on Feb 10, 2009

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How do I adjust my swr on cOnex 3300


SWR is adjusted at the antenna. I am not sure how familiar you are with SWR so forgive me if I repeat something you already know.
The first thing you need is a way to measure SWR, an SWR meter. Theses can be found on ebay or elsewhere. The SWR meter attaches to the radio with a short coax cable of about 2 feet or less. The other connector on the SWR meter goes to the antenna coax. Once hooked up you should see a switch that reads forward and reverse or abbreviations of such. Place it in forward position. Now there should be a knob adjustment that you can turn. You key the radio, meaning press the mic button to transmit. While holding the button and transmitting adjust the knob on the SWR meter until it reads exactly full scale. After you have done that flip the switch to reverse while transmitting and read the value shown. At the low end it should read 1,2,3,4 etc. If you are lucky it should be between 1 and 2. If so say it is 1.5 then you can say your SWR is 1.5:1 which is ok. If you had a 2.0:1 Swr you would be losing only 11% of your power, giving you 89% still going out the antenna. 3.0:1 would be a 25% loss and so on. Really not that big of a deal. But some radios need better than that or they will reduce their power slightly or not at all if its too far off meaning something is terribly wrong with the coax or antenna. If its less than 2.0:1 I would just leave it alone. But if you find in reverse that the meter goes way over to the right, then you need to find the problem. a shorted or open coax or same with antenna. If you are ok with swr but just want to play and dial it in better than all you do is raise and lower the antenna ever so slightly by loosing the set screw at the base of the antenna. Make sure you mark the old spot in case you need to return it back to that position. Now on other antennas there will be an adjustment at the very top of the antenna that can be turned. Like a carbon ferrite type of screw inside the antenna. This is of course for a short antenna. If you are using a 1/4 wave whip which is the best to use in my opinion kit is around 102 inches long. gives you more range and better receive. If you drive a truck then that is out of the question. But somthing that is overlooked is the fact when you take the meter out after you are done checking the SWR. Your SWR will change and wont be what you just had with the meter in line. So leave meter inline or do this: Most meters have a field strength option. What you do is attach a small wire antenna to the SWR box where there is a small screw hole for it to attach. If you dont have an antenna make one out of a bout a 10 inch stiff copper wire. In this test you will not be hooked up to the cb radio with your SWR meter. Hook you cb back up just to the antenna coax to your antenna. Key the mic again to transmit, tape it into place to hold it there. Now put the swr meter on forward or field strength if if has a selection for that. Now walk away from your antenna about 10 feet so with the adjustment turned up all the way for full meter deflection on the swr meter you should see it get stronger as you get closer to the antenna or weaker as you move away from it. You are actually seeing the power coming from the antenna. You can now set you meter on something away from your antenna where you can see the meter but dont have to hold it. Note the reading. Go back to the cb and stop it from transmitting. You can now make adjustments to your antenna then transmit again and look at the meter. Did it go up or down? Ideally you want maximum meter deflection for maximum power. I f you hook up the swr meter again with cables and it shows something other than 1:1 doesn't matter because like I said once you take the meter out or put it in the swr changes. you are changing the length of the coax. What matters is maximum power right? That's what most people try to achieve by adjusting swr. But like I said on that too, really you wont be able to tell the difference on the receiving end of somebody elses CB when you are talking. To be real you would have to 4 times your power in order for the s meter to go up one s unit on your buddys receiver while you are transmitting. So don't get lost in in all the CB hype of other peoples theory of how important swr is. Your radio is looking for about 50 Ohms of value to work as it should. a 2.0:1 swr would say that it is seeing either 25 Ohms or 100 Ohms. The coax cable should be rated at 50 Ohms meaning if there is 50 Ohms t the other end the coax will be 50 Ohms if you were to measure it at any point on the line. But if there is anything different, then these rf waves travel from your radio to the antenna where if not 50 Ohms will not consume or output all the power at the antenna and the result is waves not going out will come back toward your radio, hence the reverse setting where you are seeing this happen. This can be so involved and yes just because there might be 50 Ohms at the antenna doesn't mean the antenna is resonating at the right frequency. This is why the field strength is important too. The value where the coax meets the antenna ideally should be 50 Ohms but it can be anything because of the design and length of the antenna. So you see you can be moving the antenna in and out to make it 50 Ohms but at the same time you are changing the frequency it wants to emit the best too which could be different. So to say the swr can be off a little if you get more power coming out of the antenna. Sorry for such length but hoping it makes more sense for you.

Jul 17, 2016 | Radio Communications

1 Answer

Transmits and receives no modulation out


I am not an expert but I think there can be little or no modulation of the carrier wave unless there is an audio input to the modulator. Like any audio amplifier a transmitter modulator (amplitude modulation) is quiescent without an input.

If the modulation amplifier and audio pre-amp are working and modulating the carrier wave and the antenna is ok then audio modulated radio frequency must be being transmitted.

It would be an extremely good quality CB that had a modulation meter. Mostly all they have is a meter giving an indication of the rf power being sent to the antenna and that rf (radio frequency) power would be the same whether modulated or unmodulated.
The modulation envelope, incidentally, is traditionally viewed or measured with an oscilloscope.

The indicated rf power could be verified using a field strength meter but the only practical way to discover if a standard CB is transmitting modulated rf is to listen to the transmission on a suitable receiver. If the squelch is turned down it will be obvious if the rf carrier wave is being received as the hiss would be silenced. If no audio is received it can be assumed none is being transmitted.

I suggest you try another microphone and lead and if that doesn't work it is clearly a job for a repair shop.

Oct 28, 2015 | Radio Communications

1 Answer

Radio turns on, transmits until there is any modulation power


I like how you think....aged capacitors are very likely but we must go simple first. Check the control pot on front of radio for resistance from open to closed making sure there are no dead spots. These control pots are subject to corrosion. Unlikely the reverse polarity hurt anything because you did not mention the protection diode blowing it must have been brief.

May 22, 2014 | Radio Communications

1 Answer

Realistic TRC-458 Base CB Problem ??HELP??


This uses a uniden board and has a relay for transmitting, check and clean the relay contacts

May 03, 2013 | Radio Communications

1 Answer

On my Cobra 25 LTD CLassic, New my meter drops when transmitting


is this a new out of the box radio?if so you might need a tech to look at it because it could be an internal problem.It would have to be put on an analyzer and a scope to actually be seen doing what you say.don't worry because it can be fixed.the cost of fixing it is the problem.You have to decide whether you want to pay more for the repair than you paid for the radio. Either way,new or used the answer is the same.

Sep 30, 2012 | Cobra 25 LTD 40-Channel CB Radio

1 Answer

Sparking And Crackles On CRT Neck


tried to clean the anode cap and the crt tubes holes but make it sure before you do this, must have proper discharge of voltage from the tube.if still the same problem it could be the flyback transformer has problem.

Aug 29, 2012 | Televison & Video

1 Answer

I can,t transmit or receive signal antena is ok


Does radio show receive or transmit on display or meter?

Mic has been tested and or eliminated as the problem?

Apr 26, 2012 | Midland 1001Z 40-Channels Base CB Radio

1 Answer

Receive is ok, but when I transmit on SSB the Freq. jumps 10KC. What adjustments can I do to get the transmit back on Freq. without effecting the Receive?


go to you tube and type in your radio make and model and watch the review on that radio there is a freq adjustment pod for ssb adjustment. they might tell you if not take it to a radio tech and he should be able to alighn it. there is more than one pod for ssb transmitt and receive.

Mar 21, 2011 | Galaxy Radios DX-959 40-Channels Base CB...

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