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Television Standards Converters, Modulators etc Standards converters, modulators anything else for providing signals to vintage televisions.

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Old 30th Jun 2005, 5:52 pm   #1
oldeurope
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easy 100% modulation adjustment (sound)

http://www.your-normwandler-page.de.vu/

Good evening,

In my 405 modulator the sound input has a poti to adjust the
modulation depth.

To make the agliment easy I made a 100% modulation detector for the
sound modulation depth adjustment.

It is a red LED that flashes when you have overmodulation.
So adjust the poti that the LED just not flashes to get 100% sound
modulation.

You only need two resistors a transistor and a LED.

I build this very helpfull circuit in the MK III converter/modulator
and in the London Birmingham modulator.

Pics will follow soon, and I will update the converter/modulator thrads
step by step.

Kind regards
Darius
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Old 25th Aug 2006, 8:06 pm   #2
Paul Stenning
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Default Re: easy 100% modulation adjustment (sound)

Moved from archive to main section as requested by Darius
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Old 30th Aug 2006, 4:38 pm   #3
oldeurope
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Re: easy 100% modulation adjustment (sound)

Thanks for making it possible to update it.

An additional resistor from base to ground makes it possible to detect a lower modulation depth.
Here you can see a modulator using this stage:
https://www.vintage-radio.net/forum/...ad.php?t=10790

It is possible to drive an automatic level control ALC with this stage.
I drawed the ALC stage alone for an easier understanding.

Kind regards,
Darius
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