FM alignment - UK Vintage Radio Repair and Restoration Discussion Forum

Ambientnoise · 7th Apr 2020, 9:52 am

During these long days, I would like to have a go at alignment of VHF/FM sets. I have a scope, freq counter, dvm, audio and RF sig gens but nothing with FM capability. What is the simplest way to generate an FM signal at 10.7MHz, for IF and demod setting up ? I don’t want a major build project and don’t mind buying a complete sig gen (within reasonable cost constraints), if necessary.

Ideas welcome.

Ken

Radio Wrangler · 7th Apr 2020, 10:35 am

A DDS kit and a bit of programming to make it sweep might be a good approach. It's been done before.

David

CambridgeWorks · 7th Apr 2020, 10:55 am

Suggestion here:
https://www.qsl.net/va3iul/Wobbulato...cerization.htm and another thread
https://www.vintage-radio.net/forum/...ad.php?p=85309
LOTS of misc. Items here
https://www.qsl.net/va3iul/

Or, Just google forwobbulator
Rob

Nuvistor · 7th Apr 2020, 1:02 pm

Have you checked the alignment instructions for the sets you have, many use a standard AM signal generator for alignment.
Some do require a sweep gen, if that’s required then that’s the way to go but worth checking before spending any money.
You will need a standard AM generator to adjust any AM rejection adjustment.

7th Apr 2020, 9:52 am	#1
Ambientnoise Heptode Join Date: Feb 2006 Location: Marlborough, Wiltshire, UK. Posts: 917	FM alignment During these long days, I would like to have a go at alignment of VHF/FM sets. I have a scope, freq counter, dvm, audio and RF sig gens but nothing with FM capability. What is the simplest way to generate an FM signal at 10.7MHz, for IF and demod setting up ? I don’t want a major build project and don’t mind buying a complete sig gen (within reasonable cost constraints), if necessary. Ideas welcome. Ken

7th Apr 2020, 10:35 am	#2
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,903	Re: FM alignment A DDS kit and a bit of programming to make it sweep might be a good approach. It's been done before. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

7th Apr 2020, 10:55 am	#3
CambridgeWorks Nonode Join Date: Jun 2010 Location: Spalding, Peterborough, Cambridgeshire, UK. Posts: 2,859	Re: FM alignment Suggestion here: https://www.qsl.net/va3iul/Wobbulato...cerization.htm and another thread https://www.vintage-radio.net/forum/...ad.php?p=85309 LOTS of misc. Items here https://www.qsl.net/va3iul/ Or, Just google forwobbulator Rob __________________ Apprehension creeping like a tube train up your spine - Cymbaline. Film More soundtrack - Pink Floyd Last edited by CambridgeWorks; 7th Apr 2020 at 11:01 am.

7th Apr 2020, 1:02 pm	#4
Nuvistor Dekatron Join Date: Aug 2013 Location: Wigan, Greater Manchester, UK. Posts: 9,433	Re: FM alignment Have you checked the alignment instructions for the sets you have, many use a standard AM signal generator for alignment. Some do require a sweep gen, if that’s required then that’s the way to go but worth checking before spending any money. You will need a standard AM generator to adjust any AM rejection adjustment. __________________ Frank