easy 100% modulation adjustment (sound) - UK Vintage Radio Repair and Restoration Discussion Forum

oldeurope · 30th Jun 2005, 5:52 pm

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

Paul Stenning · 25th Aug 2006, 8:06 pm

Moved from archive to main section as requested by Darius

oldeurope · 30th Aug 2006, 4:38 pm

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

30th Jun 2005, 5:52 pm	#1
oldeurope Retired Dormant Member Join Date: Dec 2003 Location: Solingen, Germany Posts: 727	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 Attached Thumbnails

25th Aug 2006, 8:06 pm	#2
Paul Stenning Administrator Join Date: Dec 2002 Location: Cardiff Posts: 9,071	Re: easy 100% modulation adjustment (sound) Moved from archive to main section as requested by Darius __________________ Paul Stenning Forum Admin/Owner and BVWS Webmaster

30th Aug 2006, 4:38 pm	#3
oldeurope Retired Dormant Member Join Date: Dec 2003 Location: Solingen, Germany Posts: 727	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 Attached Thumbnails Last edited by oldeurope; 30th Aug 2006 at 4:42 pm. Reason: link and text