Poll: Over-Mod Myth

[Captain Kilowatt]

Funny.....I thought this posted earlier today when I was on my phone at work. I came home and found it still in the queue so better late than never I guess.


As for exceeding 100% positive peak mod without exceeding 100% negative peak mod........every AM broadcast station in the country is doing it with about 125% positive mod. I once had a Nautel AM transmitter that would POP!! on voice peaks due to a modulator fault. I replaced the mod controller unit and tested it. I used a 20hz tone at up to 300% positive peak mod to really hammer it and make sure all was well. I had the standby tx on the air and the Nautel on the dummy load. B3cause we had a narrow band short antenna I also tried it into the actual antenna. I cannot imagine what some of our listeners thought hearing a REALLY LOUD HUMMMMMMMMMMMMMMMMMM from their beside radios at 3:00am.

 

[LeapFrog]

As for exceeding 100% positive peak mod without exceeding 100% negative peak mod........every AM broadcast station in the country is doing it with about 125% positive mod.

To the best of your knowledge do any HF transceivers exist in the market today (current production or past) that allow for asymmetrical modulation from the factory?

Perhaps there is a regulation that I have not become aware of.

Edit: Meaning amateur transceivers (Icom, Yaesu, Kenwood), not ten meter exports.

 

[Tallman]

The Magnum S45HP has it in there,

 

[StrangeBrew]

I remember back in the day around here the formula for DX was a big ass carrier modulated at a 4:1 peak to dead key ratio, the swing mods were mostly used to achieve a 4:1 ratio on the output of an amp that was less than linear.

My vote is good antenna and big carrier for getting out there, modulation should be set to sound good once there.

 

[Tallman]

I totally agree. A good radio is one half of a system.
Good radio+Crap ant.= .5 crap
Good ant.+ crap radio= .5 crap
Good radio+good ant.= 0 crap!

 

[LeapFrog]

The Magnum S45HP has it in there,

Yes, but do any amateur transceivers have this ability (Kenwood, Icom, Yaesu)?
Maybe there is a regulation that I am not aware of.

 

[Tallman]

Yes, but do any amateur transceivers have this ability (Kenwood, Icom, Yaesu)?
Maybe there is a regulation that I am not aware of.

Ahh, You should have clarified by saying, "A Good quality amateur radio."

 

[LeapFrog]

Ahh, You should have clarified by saying, "A Good quality amateur radio."

laugh out loud, yes I should have clarified (no exports).
I understand the modification likely works with any radio that uses a balance modulator. But, does anybody know of any amateur transceiver that came with a form of negative peak compression or a clipper from the factory? (old or new)

73, & Thank You.

 

[Tallman]

But, does anybody know of any amateur transceiver that came with a form of negative peak compression or a clipper from the factory? (old or new)
73, & Thank You.

I believe most of the Quality radios have a compressor built in, but I think it is an audio compressor and just averages the audio.

 

[LeapFrog]

I believe most of the Quality radios have a compressor built in, but I think it is an audio compressor and just averages the audio.

So in that case they're just trying to increase the average output, it's not truly creating asymmetrical modulation.
(I wonder if any of the expensive radios can produce asymmetrical modulation out of the box? Yes I understand amplitude modulation is becoming a "legacy" form of communication, so demand for this feature would be very small but if there are no regulations preventing this, I'd be surprised to find no manufacturers offer it)

I appreciate everyones input here.

 

[Mustang 131]

The question of THIS thread is a simple YES or NO.

And it's a yes. The more % poditive modulation will let you talk further.

No it will not be clear on some radios after around 120%.

Yes. The more pinch the wider the distortion.

Yes. Asymmetrical audio is good to a point.

Yes I know of people running 1500w carrier and running asymmetrical audio negitives that sound just fine. It reduces the background noise. And is 100% ok.

Yes. The more % modulation, the trickier if gets to sound good.

Try this Mr Radio Expert. Ask someone to go to the fringe of your local operation. Run a 1k test tone at 25,50,75,100,125%. Hmmmm. Do we really have to do this test? Its a math equation...a common sense equation.
I know..stupid question. But that IS the question.

 

[LeapFrog]

The question of THIS thread is a simple YES or NO.

And it's a yes. The more % poditive modulation will let you talk further.

No it will not be clear on some radios after around 120%.

Yes. The more pinch the wider the distortion.

Yes. Asymmetrical audio is good to a point.

Yes I know of people running 1500w carrier and running asymmetrical audio negitives that sound just fine. It reduces the background noise. And is 100% ok.

Yes. The more % modulation, the trickier if gets to sound good.

Try this Mr Radio Expert. Ask someone to go to the fringe of your local operation. Run a 1k test tone at 25,50,75,100,125%. Hmmmm. Do we really have to do this test? Its a math equation...a common sense equation.
I know..stupid question. But that IS the question.

Mustang I have to compliment you on your audio it sounds great, do you by any chance use asymmetrical modulation?

I only ask because very few locals can produce audio that I've heard such as yours.

And yes it is a simple question, no math involved.
If somebody is 10 miles away from me and they had adjusted modulation from 25% up to 100% with a test tone, we all know the higher the modulation percent the tone will sound louder, I am just concerned that much more above 100% will change the frequency of the received tone (distorted audio).

Okay I'm starting to see the fallacy in my request here, yes the transmitted signal will be loud. But how much of that receive signal will contain the original audio information?

It looks like I could post two or three questions from this single thread!

It's one thing to get a signal out further, my concern is to get the most intelligible signal out as far as possible.
(while retaining as much of the original audio as possible)

I'm looking at this as if it was a data transfer protocol, distortion would be unacceptable in a simplex configuration (without "error checking bytes" requesting the lost part of the signal to be re-transmitted)

<131, this thread aside, that "Mustang radio" that I heard was awesome, studio quality audio brother! Blew me out of the chair, crystal clear, please tell me that this is not doable on a Cobra 29 with a clipped limiter and a D104 because if it's that easy everyone would be booming in my receiver not just that "Mustang radio" I remember hearing one day in "DX" land.>

73

 

[Robb]

The question of THIS thread is a simple YES or NO.

And it's a yes. The more % poditive modulation will let you talk further.

No it will not be clear on some radios after around 120%.

Yes. The more pinch the wider the distortion.

Yes. Asymmetrical audio is good to a point.

Yes I know of people running 1500w carrier and running asymmetrical audio negitives that sound just fine. It reduces the background noise. And is 100% ok.

Yes. The more % modulation, the trickier if gets to sound good.

Try this Mr Radio Expert. Ask someone to go to the fringe of your local operation. Run a 1k test tone at 25,50,75,100,125%. Hmmmm. Do we really have to do this test? Its a math equation...a common sense equation.
I know..stupid question. But that IS the question.

Not necessarily; the antenna performs that function - distance.
Hate to say it; but I think you are helping to perpetuate this myth.
Of course, it is just an opinion I realize.
Nothing personal intended, as this misunderstood point still seems to continue.

I'd also like to bring up commercial radio stations that use 125%.
Do you think they distort when using 125% modulation?
No; they do not.
Not an opinion; as they are held by FCC standards of practice.

Thoughts?

 

[LeapFrog]

125% Pos. & 125% Neg. peaks = Loud + Distortion
125% Pos. & 100% Neg. peaks = Loud + Clear

Guys I'm seriously starting to consider that I worded this poll incorrectly, because it's more complex than a simple yes or no question.

But generally I'm speaking of a radio like Cobra 29 LTD, is over-mod going to help you get out further considering the negative peak cut off that will happen unless the radio has been extensively modified.

Again let me jump in and apologize, I now feel as if the poll was worded incorrectly.
Yes this question is too complex due to the fact that not every single a.m. transmitter has the same characteristics, I should have spoken specifically of the high-level modulated a.m. only radios.

In my mind this is a big topic, at first glance we all know the bigger number has more to it (Modulation) but when you bring in the negative peak cut off it complicates things.

Maybe if I had a enough land, I could build a laboratory big enough, yet I know that is not possible.
Is there a theoretical math formula I could use here?
RF really is voodoo!

 

[ExitThirteen]

My Cobra 142GTL I have runs about 220% positive and 90% negative on the scope with my Asymmetric mod done to it. On the spectrum analyzer, 3rd order harmonics checked at -69dB down. Everything else was lower. Acceptable levels is -40 or -45dB down, if memory serves. You CAN make it clean and be loud.

~Cheers~