Circuit needed for simple AM Modulation monitor - UK Vintage Radio Repair and Restoration Discussion Forum

G4_Pete · 15th Feb 2017, 6:27 pm

Hi
During the summer a few of us work our local top band AM net portable home brew. I am looking for a simple stand-alone modulation meter that can be used to get an approximation indication of AM modulation. I have test gear to do this at home but need something simple for field use. Lamp indicators are pretty useless in the sun so will be going for a metered design

There are plenty of circuits on the net but I wondered if anyone had any prefered or proven design. With the addition of some updated components I was leaning towards the one attached Ref AM Phone .
Pete

Biggles · 16th Feb 2017, 9:09 pm

Seems like a workable circuit. I would probably redesign it to run off a PP3 or something a bit more obtainable than the 22.5V battery specified. With a bit of careful thought you should be able to work out the different component values, or simply connect two 9 volt batteries in series to run it of course. You could add a small audio amp or headphone amp after the demod so you can actually hear the modulation quality. A worthwhile addition I think.
Alan.

15th Feb 2017, 6:27 pm	#1
G4_Pete Hexode Join Date: Feb 2014 Location: Southampton, Hampshire, UK. Posts: 419	Circuit needed for simple AM Modulation monitor Hi During the summer a few of us work our local top band AM net portable home brew. I am looking for a simple stand-alone modulation meter that can be used to get an approximation indication of AM modulation. I have test gear to do this at home but need something simple for field use. Lamp indicators are pretty useless in the sun so will be going for a metered design There are plenty of circuits on the net but I wondered if anyone had any prefered or proven design. With the addition of some updated components I was leaning towards the one attached Ref AM Phone . Pete Attached Thumbnails

16th Feb 2017, 9:09 pm	#2
Biggles Rest in Peace Join Date: Feb 2004 Location: Hexham, Northumberland, UK. Posts: 2,234	Re: Circuit needed for simple AM Modulation monitor Seems like a workable circuit. I would probably redesign it to run off a PP3 or something a bit more obtainable than the 22.5V battery specified. With a bit of careful thought you should be able to work out the different component values, or simply connect two 9 volt batteries in series to run it of course. You could add a small audio amp or headphone amp after the demod so you can actually hear the modulation quality. A worthwhile addition I think. Alan.