Need some help

[Lil'Yeshua]

No O-Scope?
A good modulation meter can work wonders in setting a radio's AMC circuit along with some good cb friends who know the difference between good clean audio and distorted audio.
Of course though have a good tech do a proper alignment and tune. That will go a long ways on having great good audio.

 

[GnG8d]

No O-Scope?
A good modulation meter can work wonders in setting a radio's AMC circuit

A true peak reading watt meter will easily do what a modulation meter will do, and niether will show flat tops or other distorted waveforms.

 

[Lil'Yeshua]

Someone told me that he sets his modulation with his watt meter. I didn't get all he said over the airwaves but I think he sets the modulation to where the needle won't move,don't pick up background noise.

 

[MSGED2007]

Ok, MOGVZ, I didnt want to light into you, but you are begging for it. So let me get this right, you are saying that you know for a fact that my little radio is overmodulating, even though you've never seen/heard/ or tested it, and in spite of 2 cb shops that I've had tested it, yes 2 (I didn't mention the other one in the first post because it was irrelevant) and in spite of multiple contacts from 30' to 15 miles hearing it and reporting that it sounds great? Did I get that right? Man, you really are foolish.

You know, a particular thing about a pots is they are ADJUSTABLE! It's not all the way up or all the way down. And another thing, over modulation that is detectable on an oscope has other side effects too, like clipping and squealing, which my radio is not doing. So are you really going to maintain your losing position of knowing that I am wrong in this particular case or will you just bite the bullet and admit that you've never actually and personally tested my radio and found out for certain that it is overmodulating? The ball is in your court so which will it be: maintain your pride and look stupid or be honest and admit you've never looked at it. You decide.

 

[MSGED2007]

How do you people put up with this guy? Lol

 

[GnG8d]

Someone told me that he sets his modulation with his watt meter. I didn't get all he said over the airwaves but I think he sets the modulation to where the needle won't move,don't pick up background noise.

If your peak reading meter shows 4x the carrier on voice peaks, that will basically tell you the same thing that a modulation meter will. One thing I've noticed about modulation meters built into radios is that they are more of an averaging type of meter so they probably work better with a steady tone. Just don't expect a modulation meter to replace an oscilloscope.

 

[Lil'Yeshua]

Ok. Could you clarify the '4X'? I use a Redman CB modulation meter.
My other meter is a MFJ-971 QRP antenna tuner with the small power/swr meter face on it.

 

[M0GVZ]

You know, a particular thing about a pots is they are ADJUSTABLE! It's not all the way up or all the way down.

Doesn't need to be all the way up to cause issues especially when you're using a power mic as well.

And another thing, over modulation that is detectable on an oscope has other side effects too, like clipping and squealing, which my radio is not doing.

Not always.

So are you really going to maintain your losing position of knowing that I am wrong in this particular case or will you just bite the bullet and admit that you've never actually and personally tested my radio and found out for certain that it is overmodulating? The ball is in your court so which will it be: maintain your pride and look stupid or be honest and admit you've never looked at it. You decide.

Well you've certainly not tested your radio properly to find out that it isn't. Given you've tweaked the factory set level and are driving it with a power mic which it wasn't set up for in the first place and bleated on about it showing 100% which usually means its going over when you've not used an oscilloscope to check, I think I'm on more of a winner than you are.

 

[MSGED2007]

Man, you just don't know when to quit do you. If you honestly think you can tell if a radio is over modulating without having seen, tested, or heard it, you are a fool. You do realize that you are saying that everyone who HAS seen/heard/tested my radio is wrong and that you, who HAS NOT seen/heard/tested my radio is right, don't you? Are you serious dude? Get a freakin clue.

But just so you can have some piece of mind, here: The radio's modulation is adjustable, and the Mic's output is adjustable, and guess what, you don't need an oscope to tell if the audio on the other end is clear or distorted. All you need is someone listening. What do you think the whole purpose is for putting it on an oscope to begin with: to ensure you have clean AUDIO! So there you go, you lose again. I really didn't think you would keep going with this when you have no idea where I set the pots or what tests I have done to make sure my audio is crisp and clean, but man! You have surprised me. Any other things that you haven't the slightest idea about but know everything about you wish to share with the rest of us? Oh and BTW, I really don't like talking with people like you, so if you don't have anything productive to say about the antenna issue I brought up in my first post, then stop talking. I came here looking for information from smart people, not to be criticized by a dumb one that doesn't know what he is talking about.

 

[Captain Kilowatt]

Most of them don't know their ass from their elbow and they're not going to tell you that the mod where it took longer to take the lid off than do which they've just charged you $30 for is going to cause a problem are they? Did you get to see them put it on an oscilloscope and check for flat-topping on the waveform?


Given the crappy audio a CB typically reproduces and the fact that CBers seem to typically favour overdriven booming crud that's not really saying a lot.

As for not knowing what you're doing, yes I think exactly that. You've ramped up the internal audio gain with no proper equipment to monitor the output and then you've shoved a power mike on it which overdrives the mic pre-amp input making a bad situation even worse. So yes, I do think you don't know what you're doing.

Why do you simply assume things? Is it because you are just an arrogant ass or what? seriously man, gets the facts and stop assuming stuff. You do this a lot both since coming here and over on qrz.com where you get your balls busted for it as well.You have NO idea if the shop was doing something right or wrong and you have no idea what the radio sounds like on the air. While I do agree that a lot of CBers do like that echo crap and swinging watt meters I do not make unfounded accusations unless I know the facts. The first line in your qrz.com profile page is "I have been licenced since 2009 and am still learning the hobby". Perhaps you should learn how to show a little respect before making accusations. I realize you are an amateur radio operator and as a result probably hate CBers but that way of thinking doesn't fly here.We all get along for the most part and extend respect and education to those that deserve and need it. I too am a amateur radio operator, licensed back in 1989 and spent 22 years in the engineering dept. of a commercial broadcasting network so I really like good audio on the air. I don't however make comments about someone's audio without proof. I do NOT condone cutting the AMC control but as the OP said he has the pot turned up. If the AMC is still intact the radio still will not exceed 100%. In this case the amplified microphone probably was not needed and likely serves no real purpose other than possibly having a different sound quality to it re freq. response.

 

[Captain Kilowatt]

How do you people put up with this guy? Lol

We have ways of dealing with people that refuse to play nicely.

 

[Robb]

No O-Scope?
A good modulation meter can work wonders in setting a radio's AMC circuit along with some good cb friends who know the difference between good clean audio and distorted audio.
Of course though have a good tech do a proper alignment and tune. That will go a long ways on having great good audio.

Ehhhh . . . I wouldn't bet the farm on that.
Even the best modulation meter is anything but accurate, which is fuel for M0 to make his point further. These meters are really no more than eye candy in function. The human ear cannot really catch all of what is really happening when monitoring and evaluating a station's signal. While you are somewhat correct, it is best to see modulation on a scope, as it can make any irregularity clearly seen.

A.M. TUTORIAL

LY, you may gain something by reading these four pages. It is a bit to read, but it breaks everything down in simplest terms.

100% Modulation.
Notice that the curve is equal as it approaches the center and the top of the peaks are also curved (left diagram).

See the flat line between the modulation peaks? That is the carrier which has gone into negative peak distortion (left diagram).

The human ear or an inaccurate meter cannot always perceive this distortion.

Positive peaks can also 'flat top' distort as well, and on a scope it looks like this:

If either the center line (negative peak) goes flat or the top of the peaks (positive peak) goes flat, then the radio is more than 100% modulating and has gone into distortion. Most radios I've seen usually have negative peak distortion. But if a power mic is used (turned up all of the way) along with the AMC pot wide open, or if the limiter has been clipped, then both positive and negative peak distortion can be seen.

The following is an example that is easy to understand what is happening.

Watch this video by Bells CB Radio and watch it at 2:15:

http://www.youtube.com/watch?v=3FCLZE9zhpU&list=PLE0EC9173F072C0C8&index=24

This is a typical example of what some CB radio operators do to their radios by removing the limiter and run, but not all do it.

 

[MSGED2007]

And just so everyone else who happens to read this thread knows, yes, I agree that it is best to have the right test equipment to check your work when adjusting a radio, but it can and is done without an oscope/spectrum analyzer/ or frequency counter etc... on many occasions if you know what you are doing. Want to know if you are over modulating? Have a friend sit close by and listen while you do it. Want to know if you are not staying on frequency? Have them check above and below for bleed over. I mean come on, if an oscope is the only way to do it right, then how many people who have tuned a radio and did a good job without one "didn't know what they were doing?" Making mistakes has side effects which are detectable in the finished product (your audio on the other end) When you get reports of distorted audio, that's when you go find an oscope if you don't have one to see what's going on, and when you hear that you are bleeding over, that's when you hook up a spectrum analyzer to see what the signal is doing.

What I did was simple. I went online, found out which pot was the modulation pot, bought a powermic because it had echo and talkback built in, and started adjusting them both together while I had a friend sitting close by listening and giving me feedback. When the audio started to distort, I backed it down until it was good, clean, and crisp on the other end, and then I took it to 2 respectable cb shops and had them verify my work for peace of mind, and yes I watched while they tested. After multiple contacts at a multitude of ranges, all I have heard is how good this little compact radio sounds.

If you have oscopes and spectrum analyzers sitting on the shelf, then great, use them, but don't tell someone else that their work is junk because they didn't use one, and especially not before you've had a chance to hear it for yourself.

 

[MSGED2007]

Good info Robb, thank you.

 

[Captain Kilowatt]

Ehhhh . . . I wouldn't bet the farm on that.
Even the best modulation meter is anything but accurate, which is fuel for M0 to make his point further. These meters are really no more than eye candy in function. The human ear cannot really catch all of what is really happening when monitoring and evaluating a station's signal. While you are somewhat correct, it is best to see modulation on a scope, as it can make any irregularity clear..........

Robb, I believe you are talking about the typical CB type modulation meter? In that case I agree however there are indeed mod meters that are very accurate. I have one. It is a Wavetek 4101and measures AM and FM mod to 100% and up to 100 kHz deviation. It is lab quality and admittedly not what most would have in the shack however it is a mod meter that is indeed accurate. They are out there and will read mod levels as good as a scope. Just forget the Dosy test center type meters.