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Motor Mouth Mauldulator. Well done, but not done well.

nomadradio

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Apr 3, 2005
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That's "well done", as in marginally burned.

Here's an example of "Hownot2" if you decide to build your own Motor Mouth Mauldulator. He only sells the "brain", the small circuit board where the magic happens. All that boring stuff like an enclosure, power cord, DC supply, controls, knobs, audio jacks, power transistor and pilot light are your problem. Naturally, those things are all more or less generic in nature, so there's not much money to be made selling you all that stuff. MMM only sells you the heart of his modulation system.

And, yeah. It's a high-level modulator with its own audio input, separate from the radio's mike circuit. Feeds modulated DC straight to the radio's driver and final transistors. AFTER you have severed connections to the factory's AM modulator circuit.

Needless to say, selling just a printed circuit board opens the door for a legion of folks who are willing to buy a cabinet, punch holes, buy knobs, potentiometers, transistors and other stuff to build the complete MMM system around this circuit board.

YmNEHC.jpg


Most common way to do this is buy a chinese switchmode DC-power "brick" to provide the 24 Volts (yes) DC that runs this show. A modulation transistor and heat sink that are big enough are a really good idea.


kwvshb.jpg


Shouldn't take an expert to see this heat sink is probably not big enough. The melted plastic shoulder washer on the transistor is a clue.

I won't reveal whose name is on the cover of this cabinet. Nothing to be gained by that. Besides, I would be accused of bashing. Consider that every one of these that you see built this way represents a market opportunity for me. Bashing that guy is too much like biting the hand that feeds me. Feel free to guess who made it.

This power supply is in theory the right size. I would prefer one a bit larger, but those won't fit inside this cabinet.


I'll cross my fingers and assume the other "kaboom" issues caused this supply to fail. Gotta keep in mind the bigger the power supply, the bigger all the stuff downstream from it has to be, or risk breakdowns. We'll install a new one that says "MeanWell". That's the traditional quality brand, if it's not counterfeit.

U5X9OB.jpg

XG4dfT.jpg



Using double-sided adhesive foam saves assembly time. Has the opposite effect if you ever want to take it back out. We'll be scraping this stuff off and using threaded hardware to secure the power supply.

z6ocEO.jpg


The modulation transistor and heat sink both get upgraded.

FwJ8ZL.jpg


This heat sink just fits on the rear of this cabinet.

20jtUG.jpg


No I haven't plugged it in to see what it does.

Yet. Got it all connected about time to go home for dinner. Murphy's Law says I would never have gotten a quick positive test result when I'm already late for dinner.

Film at 11, or when I get it hooked up.

73
 
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Consider for a moment, a radio that powers the final transistor from 12 Volts DC and also uses a modulation transformer with the secondary winding in series with the DC power. To reach 100 percent positive modulation you need a waveform on the final transistor's collector circuit with a peak amplitude twice that of the carrier voltage.

That's the definition of 100 percent positive modulation, twice the amplitude of the steady carrier. This means that 24 Volt peaks will appear on the final's collector. The MMM simply creates the same scenario for the radio without a modulation transformer. Much like an original Cobra 148, a NPN transistor in series with the DC power to the final also adds the audio waveform to the DC power. The difference is in the power supply voltage. The 148's AM modulator can't put more than 12 Volts or so peak voltage onto the final.

And if you simply crank the carrier knob too high you can poof the radio's final quite efficiently.

Don't know if that's what happened to this one, but I have my suspicions.

The MMM offers you an above-average choice of ways to poof your radio.

Only the operator's skill and attentiveness serve to prevent it.

73
 
Too much low-end and sounds over compressed to my ears then adding echo....lol. typically 11 meter chicken bander
 
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