Poll: Over-Mod Myth

[LeapFrog]

EDIT: These graphics came from a google image search, and may be incomplete/incorrect.

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Stays on?
[photo="medium"]4382[/photo] .
Shuts off?
I need a spectrum analyzer, and or more reading / test equipment to figure this out on my own, but thanks for casting a vote & or adding to the thread.

 

[Tallman]

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Stays on?
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Shuts off?
I need a spectrum analyzer, and or more reading / test equipment to figure this out on my own, but thanks for casting a vote & or adding to the thread.

If you have an Oscilloscope you have the proper tool. The S.A. would only show the effects away from the primary frequency. Harmonics/Splatter all caused the same way. Wave form "B" is RIGHT THERE. They do have methods of modulation that exceed 100% and sound good. They use negative peak suppression and enhance the positive peaks well past the dead key level.

 

[LeapFrog]

Negative peak compression comes to mind, or asymmetrical modulation.
But with a standard radio over-modulating the carrier, does the output really "shut off" or does it just look like this happens on the 'scope when the carrier is "pinched"?

 

[Captain Kilowatt]

It doesn't matter so much with the positive peaks but you never want to exceed 100% on the negative peaks. That is when crap develops. Far too many people simply talk about modulation % but don't understand the difference that happens with the positive versus negative peaks.

 

[LeapFrog]

It doesn't matter so much with the positive peaks but you never want to exceed 100% on the negative peaks. That is when crap develops. Far too many people simply talk about modulation % but don't understand the difference that happens with the positive versus negative peaks.

I added a little more to my previous post.
Guess I should have posted a poll asking if the RF output is 0 when the carrier is pinched. This question comes to my mind when I hear people say "clipped limiters get you out farther", if the transmitter is off more than it's on.. The signal integrity is lost and distortion is created (neg peaks exceeding 100%), am I on the right track here?

These (local) guys don't know what the heck they are talking about, it's fiction announced as a fact, more "CB wisdom" lmao "clip this and twist that and you get out good" shaking my head over here like wtf.

I'm starting to realize the "LOUD", "wall-to-wall", "tree-top-tall" code words mean "distorted beyond belief" unless the operator has the transmitter configured with a clipper, or uses compression for (clean) over 100% modulation, any "loudness" gained is going to be pretty useless for fidelity/intelligibility of received audio.

 

[Tallman]

I added a little more to my previous post.
Guess I should have posted a poll asking if the RF output is 0 when the carrier is pinched. This question comes to my mind when I hear people say "clipped limiters get you out farther", if the transmitter is off more than it's on.. The signal integrity is lost and distortion is created (neg peaks exceeding 100%), am I on the right track here?

These (local) guys don't know what the heck they are talking about, it's fiction announced as a fact, more "CB wisdom" lmao "clip this and twist that and you get out good" shaking my head over here like wtf.

I'm starting to realize the "LOUD", "wall-to-wall", "tree-top-tall" code words mean "distorted beyond belief" unless the operator has the transmitter configured with a clipper, or uses compression for (clean) over 100% modulation, any "loudness" gained is going to be pretty useless for fidelity/intelligibility of received audio. .

You are on the right track and do not let any "EXPERT" dissuade from your path.
Captain Kilowatt knows all about high level modulation and has voiced correct information on this topic. The Magnum radio s45hp has a real trick modulator built into it. You can turn down the dead key around two watts and swing all the way to radio maximum output. It is a good sounding radio and punches through the noise and hash and it it is not over modulated. To answer your original question: Yes, in the areas where the carrier is minimal it is off very, very briefly. If you do take modulation too far the sound will be some what like a pop when the carrier is off too long.

 

[sonoma]

Reminds me of a guy a few years ago I kept telling him to turn down his mic gain and he said he would not since his radio sounded good. other guy's on the channel would not tell him he was over modulated . so I recorded a conversation we had then took my tape player over to him and I was on the tape 1st then he started talking and the guy said who is that they sound like crap and can just barely understand them. i told him think about the conversation we just had on the radio and you will know who it is. he set there a minute and said thats me. I did not know I sounded bad like that . I just thought you was messing with me. he turned his mic gain down after that .he was just shocked that all the other guys would tell him he sounded fine. they just did not want to fight with him.
so guys watch how high yor modulation is. you never know when you sound like crap.

 

[Mustang 131]

A little pinch ain't a bad thing (too a point). Most of the splatter associated with over modulation comes high frequency, especially above 10k.

That being said the more positive the the modulation, the louder you are period. You may not be understood. But a 400% peak contains more energy then a 200% peak.

 

[Tallman]

That being said the more positive the the modulation, the louder you are period. You may not be understood. But a 400% peak contains more energy then a 200% peak.

And you can really tell when you are talking to an operator that has the high level modulation going on. Instead of just a solid S-meter it bounces with the modulation.
I sat in my truck in my son's drive way(Texas) and was talking to a guy in Alaska with out running a linear on ten meters.

 

[Robb]

Reminds me of a guy a few years ago I kept telling him to turn down his mic gain and he said he would not since his radio sounded good. other guy's on the channel would not tell him he was over modulated . so I recorded a conversation we had then took my tape player over to him and I was on the tape 1st then he started talking and the guy said who is that they sound like crap and can just barely understand them. i told him think about the conversation we just had on the radio and you will know who it is. he set there a minute and said thats me. I did not know I sounded bad like that . I just thought you was messing with me. he turned his mic gain down after that .he was just shocked that all the other guys would tell him he sounded fine. they just did not want to fight with him.
so guys watch how high yor modulation is. you never know when you sound like crap.

Recently, a local op asked me how his radio sounded. I was on SSB - as usual. Told him it sounded like crap. He said that he just got a good report. I asked 'were you on AM when you got that report?' He said 'yes'. I asked him if he removed the limiter. He didn't respond. Told him I would fix it for him; just bring it by.

Slowly, he is getting the picture . . .

 

[Captain Kilowatt]

And you can really tell when you are talking to an operator that has the high level modulation going on. Instead of just a solid S-meter it bounces with the modulation.
I sat in my truck in my son's drive way(Texas) and was talking to a guy in Alaska with out running a linear on ten meters.

Just be careful about using the term "high level modulation ". I real world tech speak it means the final RF amplifier is modulated as opposed to a preceding dtiver stage which is low level modulation. Calling 200% mod high level is somewhat of a misnomer.

 

[Tallman]

I know what you mean, I was told to turn down the microphone gain on my IC-746 while on SSB because it sounded "Punchy". Now I tune away from the frequency and test my ALC level. If it is good I'll jump in some of those Nets or start a QSO with someone. If not I just turn it down.

 

[Tallman]

Just be careful about using the term "high level modulation ". I real world tech speak it means the final RF amplifier is modulated as opposed to a preceding dtiver stage which is low level modulation. Calling 200% mod high level is somewhat of a misnomer.

Yes sir. I just could not remember to say or how to spell asymmetrical at the time.

 

[LeapFrog]

Yes sir. I just could not remember to say or how to spell asymmetrical at the time.

Yeah dead giveaway (watching the meter) they are using a "swing mod" of some kind lol.

The exports (most) can swing to full output from 2 watts with a diode added In series with a resistor, I think that Magnum has a "Top Gun Compressor" (has an NPC effect) or "Top Gun Modulator" (has "added diode swing mod" effect, I think) I have played with some RCI rigs but not any of the Magnum line-up, nor have I used a "Top Gun" product. I would be interested in looking one over though.

Setting the NPC modification correctly can be done, to produce true asymmetrical modulation on an export/148/2000. Two radios I tried it on had only a modest "swing" (not exceeding the modulation limit as set by AMC/added VR), a Galaxy 66V I tried it on would "swing" from any dead key to full output and still look good on the scope (no diode added ), I think it is doing something the other exports will not do for me (I will look for hidden clips of leads). Positive carrier shift, the average output increases considerably with audio drive (Not just peak).

(As always these are used on a dummy load, not on air. I only use type certified non-modified gear..)

 

[Robb]

True story:
Two local operators - several decades ago - rented a single engine airplane and flew over the Santa Clara Valley in CA ('Silicon Valley'). They brought with them a 5 watt walkie-talkie. Walked the dog on everyone. Everyones - and I do mean everyones - S-meters were all pegged completerly to the right of the meter. Loud and clear and wall to wall. No one else could talk when they keyed up . . .

Did modulation % have anything to do with it?
No.
Did power have anything to do with it?
No.

Soooo; what does that tell you?