I purchased a cb radio for $5 at a yard sale that came with mic and power cord. Anyway I went to test it out and I noticed that the transmit is intermittent. I'd transmit and the wattmeter needle on the radio would show "4" however when I talked into the mic I heard dead air on a nearby scanner that I had set for the cb frequency. Then after I keyed up a couple more times the needle didnt move and all and I heard a weird noise that sounded like farting in the nearby radio when I keyed up. The weird thing about it is when I let the radio sit about an hour it would be fine again for a short time then the problem would return, so I am just wondering if maybe something is overheating or if maybe there is a loose connection. Also the battery I had it hooked to was fully charged at 12.9 volts, so its not due to a dead battery. I used a magnetic antenna that I stuck on a car to test and then I used a 50 ohm dummy load and I get the same results with both. It doesnt seem like the final pill is blown either because after letting the cb sit for a while it seems to transmit full power again momentarily. Is there anyway to fix the radio, so far I have taken the cover off, but I do not notice anything that looks broken. Also one thing I did notice however was that that meter needle fluctuated a little when I moved the mic cord back and forth.
Answers & Comments
Verified answer
Try a different mic as the mic you were using might have a loose wire. Could also be a loose wire or solder joint inside the radio.
The Cobra stock mic's are okay mic's. The reason they are less than quality is because if Cobra invested real $$ into their mic's, the whole CB price would go up. You can buy better mic's, but I like the Cobra stock mic myself. I have run the Astatic's, and the RK56's, but you know what, people will be able to understand you no matter what you talking into. The bars on your radio: Possible heavy noise.... Some times AM transmissions will pick up power line or engine noise... some tricks can be done to correct these problems. For a real solution to noise, ground the radio, to your car's chassie. Your noise will be less, and you'll hear more people, than most guys can.
I'm sure there was no real way to test the radio before you made the transaction, but my guess is that you lost five dollars and gained a bookend. Unless you want to spend quite a bit of time trying to sleuth this one, and it may be a better idea to just go to the department store and purchase something that you can return for a full refund if it doesn't work.
There is an intermittent short someplace. Finding it will be difficult.