CB Radio shops

Yes, his audio sounds good in the videos. Unfortunately he likes to replace a lot parts that aren’t necessary, especially the electrolytic caps in new radios. I’m sure the radios receive has a lot to be desired, since he only uses a dB meter and cranks the signal generators modulation to 99% instead of 30%.

 

Nothing wrong with measuring at 99% vs 30%. It's what you do with that measurement that matters. The way my stuff is tuned if someone was to take a measurement at 30% they wouldn't have a clue how well my receiver performs.
I wouldn't knock his measuring method without being able to listen to it in the real world to see how it actually performs.

 

30% is the industries standard of measurement for a cb radio. With just a microamp meter, he’s just tuning for maximum voltage, which means a noiser receiver. Which I know won’t be Rabbi approved.

 

It kinda seems dumb. Why not just inject 100% and reduce voltage as adjustments are made until maximum sensitivity or signal to noise ratio is reached? At that point, a 30% signal at same voltage won't be detected.

 

Well the main idea is to adjust the receiver using the minimum signal to noise and distortion. That’s what a Sinad meter is good for. Granted the sinad meter is best for SSB, but it works fine for AM too. You don’t want too much signal from the signal generator or the AGC circuit will kick in, and you don’t want that to happen.

 

I always thought of test equipment as a way of replicating real-world conditions and none of us run around with our mic gain turned down to 30% modulation. Then again none of us run around with a sinad meter in our trucks, and all we're really concerned about is whether or not we can hear someone and understand them regardless of how weak the signal might be. It seems like minimum detectable signal would be a more accurate way of determining receiver performance since measuring signal level at 12 DB Sinad doesn't tell us where the signal becomes undetectable. It could very well be a sharp drop off after that point or it could gradually taper down which would be ideal.

 

Rabbi said:

“all we're really concerned about is whether or not we can hear someone and understand them regardless of how weak the signal might be. It seems like minimum detectable signal would be a more accurate way of determining receiver performance”




Exactly, that’s why you align the receiver using 30% instead of 99% modulation. Alignment by the book has you adjust the cans for maximum voltage, which also increases the noise in the receiver. I didn’t say anything about carrying a sinad meter in your truck, what would that accomplish?

 

I’m probably not saying this very good. Basically what I’m trying to say is, you tune for maximum audio signal and lease noise and distortion. By using a SINAD meter, that helps you accomplish this. By increase signal level, I don’t mean bumping the signal generator up to 99% modulation. There’s a reason the factory recommends using 30% modulation. To prove my point, maybe you should send a cb radio to SRC, and report back with the results.