300% Positive Peaks AM Modulation

[W1AEX]

It's amazing what you can find while browsing YouTube on a rainy day. Tom K1JJ made reference to a post on YouTube by "MotorMouth" who apparently is legendary on 11 meters. I viewed a couple of his related posts and found two that caught my attention. In the last three minutes of the video below, the guy shows some scope patterns that look pretty impressive. He does seem to be able to reach 300% positive peaks without smacking the baseline.

http://www.youtube.com/watch?v=26cB7BeLmbE

Another related video, with fairly poor focus at times, shows more of the same kind of asymmetry in the audio. At about 2 minutes into the video, the camera shows the device they are using, called "The Mauldulator".

http://www.youtube.com/watch?v=C2oe7q59SwQ

Anyone care to guess what is inside "The Mauldulator"? Perhaps a version of the HUZ zener diode limiter? Or a version of the QIX keep alive circuit? At any rate, to their credit, looks like they are having a good time with the toys they play with.

[w3jn]

Whatever they're trying to do, anything much over 80-90% positive is gonna create copious distortion in yer typical diode detector.

[Jim, W5JO]

Yea, but just think of the "SWANG".

[W3RSW]

Check the reflection in the meter windows.
Motormouth's buddy hissself.  Really proud to work the "Maul."
A little photoshopping and we'd get a visual.
http://www.youtube.com/watch?v=AHSSC9eyfRI&NR=1

[ka3zlr]

Whatever they're trying to do, anything much over 80-90% positive is gonna create copious distortion in yer typical diode detector.

I agree 100%.

73

Jack

[W3RSW]

Also;

Anyone care to guess what is inside "The Mauldulator"? Perhaps a version of the HUZ zener diode limiter? Or a version of the QIX keep alive circuit? At any rate, to their credit, looks like they are having a good time with the toys they play with.

Looks like he massages a low level signal by reducing the carrier and keeping the original peaks. (if the pix and description are representative of the real mauldulator.  In one of the tube vids, he makes the statement that oscilloscope vertical gain has to be turned up because the carrier is now less. Then her runs it through an 811.  So much for his SS lecture on ancient tubes. 

http://www.motormouthmaul.com/mmm2_003.htm

[k4kyv]

Looks like he massages a low level signal by reducing the carrier and keeping the original peaks. (if the pix and description are representative of the real mauldulator.  In one of the tube vids, he makes the statement that oscilloscope vertical gain has to be turned up because the carrier is now less. Then her runs it through an 811.

That sounds precisely the same as "ultramodulation" to me.

[ka3zlr]

Check the reflection in the meter windows.
Motormouth's buddy hissself.  Really proud to work the "Maul."
A little photoshopping and we'd get a visual.
http://www.youtube.com/watch?v=AHSSC9eyfRI&NR=1

Hi Rick,

 I think he needs more presence...lol


73

Jack

[K1JJ]

Another possible approach is by using a low level audio circuit that will artificially create more gain in the positive direction than the negative direction, About 10 years ago the Huzman designed one up and I built it. It was actually two op amps with audio split between them. One op amp had a gain adjustment. They were combined at their outputs to produce an asymetrical waveform. I was able to re-make my voice with 300% positive peaks. The waveform looked great. However, in that day of diode detectors, all I heard were complaints of distortion when I ran it up. I concluded that the natural voice asymetricity is all that's needed - 130% positive is all I run these days, maximum.

It was a cool circuit, though.

T

[W1AEX]

Yep,

Very interesting find Rick. His website has very succinct advice regarding how to use a scope and the importance of using one when operating AM or at the very least when setting up an AM transmitter. He seems to have a very good technical background. Apparently, he is also a licensed ham on the west coast AM scene. Looks like he knows what he's doing.

I wonder if he designed and developed the board himself? From the picture on his site it looks like a professional layout.

Tom, I have definitely found that a few of my receivers get very unhappy when tuned to stations with excessive asymmetry in the audio. The worst of all is my portable Grundig (G5) which has difficulty with a few stations on the AM broadcast band that run very heavy audio. They sound a little gritty while other stations that peak right at around 100% sound very clean. I would agree with W1JN that going overboard might look great on the scope, but it can be nasty on the other end depending on what receiver the other guy is using. I think your 130% target is a good one to aim for. It should sound loud, but shouldn't rip through the detectors of most receivers. Be careful with that HUZman technology, you might get strapped and find your life taking a different turn...

Ah well, so much to learn, so little time. Think I'll take a nap!

:O)  

[N3DRB The Derb]

since when do cb'ers care about distortion?

[ka3zlr]

since when do cb'ers care about distortion?

Derb,

 Around my parts there's a couple of CB operators with Behringer Mics and Processors and Yaesus
and Ikems on 11 meters man...they sound like Broadcasters...lol....smooth audio...

And we have a VHF'er FM on 2 that sounds like Tom Brokaw  Audio is out of control brother..LOL

73

Jack.

[Superhet66]

Capt jack
I bet dollars on donuts some of those 11m sharks swim these very waters.. arrghh arrgh.

[ka3zlr]

LOL..

73

Jack.

[N3DRB The Derb]

oh yeah they hang here big time. AM Fone is whirl wide, and there's no doubt , U no it is. 

[ka3zlr]

I think it's Great man...

73

Jack.

[W1GFH]

He seems to have a very good technical background. Apparently, he is also a licensed ham on the west coast AM scene. Looks like he knows what he's doing.

I don't recall running into him in the W. Coast AM scene.

KC6MFX, "Voice of the Central Coast of California"

Ah, that's why. His tech license limits his HF AM stylings to, well, realistically, 11 meters.

[ka3zlr]

What's the General License Limits..

73

Jack

[W1GFH]

Well, a General gets you onto the 75 meter AM Ghetto, which on the W. Coast tends to be very genteel anyhows.   

[flintstone mop]

Yea, but just think of the "SWANG".

The 'Scope patterns are beautiful!!!! I see the trace blanking, would that be from the video syncing? I cannot get a nice trace like that. The display is always moving about, apparently he is using some sort of triggering to get such a nice trace.
Pinching the carrier was impressive WOW!!! Endless modulation.

Don, would that be characteristic of Ultra Mod???

That's it!!!! They like to see the power meter schwang up when they talk and the guy on the receiving end wants to see his meter pegged if possible.
I ALMOST swear this youtube was our Don in there, but listening closer it almost sounds like the DERB!!
http://www.youtube.com/watch?v=hXfod6pgymc&feature=related
Phred

[Steve - WB3HUZ]

MAULDULATOR.  Awesome!

[Opcom]

using a maverick 250 to drive an 811A ? huh.

Wawasee made a classical "modulator" with a 6BQ5 running some 750V on the plate, grounded grid. It worked well giving only a few watts carrier and high peaks.

What is he doing with DB-9 connectors? interesting anyway if it is all analog.

[WQ9E]

The 'Scope patterns are beautiful!!!! I see the trace blanking, would that be from the video syncing? I cannot get a nice trace like that. The display is always moving about, apparently he is using some sort of triggering to get such a nice trace.

Phred

Phred,

What type of scope are you using?  Any of the Tektronix, HP, or similar "lab grade" scopes have no trouble providing this type of display.  You do need a scope with a real triggered timebase, the Heathkit monitor scopes and TV service type scopes with recurrent sweep cannot do this properly. 

You can easily find high quality scopes for little money at hamfests and it will find a lot of use on your repair bench.  I use a couple of Tektronix 7854 mainframes with an assortment of vertical and horizontal plug-ins on the bench and some older Tektronix scopes (Types 545A, 555, and 556) are stationed at various points for monitoring.

[Opcom]

The mauldulator is possibly a differential compander. "It runs on +/- 15 Volts and 24 Volts DC." - and in one page of developmental images there it shows an audio power stage/DC supply breadboard (bread-sink?) hooked to the breadboard of the IC's, and this hooked to the test CB, more of an audio frequency power supply with DC offset to replace the modulator in the CB?

maybe in the CB, which most often today uses an iron-less dc coupled modulator, has a 12V supply and runs the final at 6V for carrier. That is normal Cobra 146GTL stuff.
If this modulated DC voltage is intercepted and the negative half compressed and the positive half expanded (to as much as 24V), then there is 4x carrier voltage possible. The fact that he is going to 3X would account for the added headroom to preserve fidelity, plus avoidance of the real possibility of blowing up the CB final by over-voltage stress.

(The same nonlinearity-type effect to some degree can be had by varying the screen voltage in a voltage amplifier pentode such as a 6GH8 section as I learned designing an APH-1050  tube amp mod some time ago. The sound is quite good, but referenced to the DC plate voltage, the (large signal) negative signals are compressed compared to the positive ones when my "linearity" pot is improperly adjusted. Corrolary: what is good for hi-fi music <> what is good for CB Mauldulation.)

The +/- 15VDC is for the op-amps on the board etc.

It seems like it would compress the negative half of the modulating wave and expand the positive half, or have essentially the same effect. the "symmetry" control varies this action's depth.

This also explains why a DB-9 is a good choice -the several wires necesary. Where does he get the +/-15V and +24V for the production project? a package supply maybe. A mobile version might be of interest but clumsy due to the 24V@6A peak?

Good guess on the secrets of the Mauldulator?

BTW there are 4 diodes on the production PCB along with the several ICs. Not that that's what they are for, but it is funny.

[KM1H]

What are the better boatanchor receivers to receive high positive peaks?

Carl
KM1H