Was this homebrew sig gen made from a kit? - UK Vintage Radio Repair and Restoration Discussion Forum

Julesomega · 20th Feb 2024, 11:58 pm

I found this and took it home, it looks as though it could be useful. It looks quite professional from the outside except it doesn't have any brand or type legend. The impression is that the front panel and PCB may have been supplied as a kit, so I'm wondering if anyone recognises it. Maybe from a magazine article? The frequency range 150kHz – 12MHz looks a bit homebrew.

Terry_VK5TM · 21st Feb 2024, 1:57 am

Last picture, hiding under the bottom of the variable cap - is there a number or some text on the pcb?

Freya · 22nd Feb 2024, 9:38 am

This should answer your question, ignore the panel design.
https://www.vintage-radio.com/projec...generator.html

David G4EBT · 22nd Feb 2024, 9:57 am

And for conclusive proof, here's the PCB:

https://www.vintage-radio.com/images...g-gen-pcb2.gif

Terry_VK5TM · 22nd Feb 2024, 12:14 pm

Good to see it identified.

Personally, I would be leaving out the ground plane - there's too many isolated bits that could act as capacitors between tracks for my liking.

Julesomega · 22nd Feb 2024, 1:04 pm

Thanks so much for finding the original article, which I note is credited to Paul Stenning.
It looks even more useful now I have the schematic and details of a mod to increase the frequency range. When I took the photos I got out the old faithful frequency meter which decided to call it a day and now the sig gen has gone into hiding, but when I find it I shall try it out properly.

Julesomega · 22nd Feb 2024, 6:02 pm

Soon found, sealed in a bag and awaiting attention. It hadn't been tried because the internal mains PSU had been replaced by a DC connector with no clues as to voltage or polarity. Running on a bench supply it is sweet, frequency stability beyond reproach; blowing into the enclosure briefly shifts it a few tens of Hz. The opening comments on the linked page, about harmonic levels, applies to the modulation osc rather than the RF O-P which is probably better than most RF generators in terms of harmonics. The modulation osc certainly needs taming, and switching off when not in use; modulation is 100% square wave when 'on', reducing significantly when 'off'. The top range needs adjusting, otherwise calibration is good.

To bring this to a really useful state will need a pointer dial to give some idea of frequency without needing an external counter.

Philco-Pete · 28th Feb 2024, 12:17 am

Guilty m’Lud

So that’s where it went!
Apologies for the rather poor standard of the internal construction.
Front panel was probably done with that fiddly Photosensitive anodised Ali stuff since I think it was made before we got the laser engraver at work….
Hope you find it useful Jules
Cheers
Pete

20th Feb 2024, 11:58 pm	#1
Julesomega Nonode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 2,122	Was this homebrew sig gen made from a kit? I found this and took it home, it looks as though it could be useful. It looks quite professional from the outside except it doesn't have any brand or type legend. The impression is that the front panel and PCB may have been supplied as a kit, so I'm wondering if anyone recognises it. Maybe from a magazine article? The frequency range 150kHz – 12MHz looks a bit homebrew. Attached Thumbnails __________________ - Julian It's good here

21st Feb 2024, 1:57 am	#2
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,345	Re: Was this homebrew sig gen made from a kit? Last picture, hiding under the bottom of the variable cap - is there a number or some text on the pcb? __________________ Terry VK5TM https://www.vk5tm.com/

22nd Feb 2024, 9:38 am	#3
Freya Octode Join Date: Jan 2009 Location: Falmouth, Cornwall, UK. Posts: 1,992	Re: Was this homebrew sig gen made from a kit? This should answer your question, ignore the panel design. https://www.vintage-radio.com/projec...generator.html __________________ Stephen _________"It`s only an old telly" ___

22nd Feb 2024, 9:57 am	#4
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,770	Re: Was this homebrew sig gen made from a kit? And for conclusive proof, here's the PCB: https://www.vintage-radio.com/images...g-gen-pcb2.gif __________________ David. BVWS Member. G-QRP Club member 1339.

22nd Feb 2024, 12:14 pm	#5
Terry_VK5TM Nonode Join Date: Oct 2010 Location: Tintinara, South Australia, Australia Posts: 2,345	Re: Was this homebrew sig gen made from a kit? Good to see it identified. Personally, I would be leaving out the ground plane - there's too many isolated bits that could act as capacitors between tracks for my liking. __________________ Terry VK5TM https://www.vk5tm.com/

22nd Feb 2024, 1:04 pm	#6
Julesomega Nonode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 2,122	Re: Was this homebrew sig gen made from a kit? Thanks so much for finding the original article, which I note is credited to Paul Stenning. It looks even more useful now I have the schematic and details of a mod to increase the frequency range. When I took the photos I got out the old faithful frequency meter which decided to call it a day and now the sig gen has gone into hiding, but when I find it I shall try it out properly. __________________ - Julian It's good here

22nd Feb 2024, 6:02 pm	#7
Julesomega Nonode Join Date: Dec 2012 Location: Stockport, Greater Manchester, UK. Posts: 2,122	Re: Was this homebrew sig gen made from a kit? Soon found, sealed in a bag and awaiting attention. It hadn't been tried because the internal mains PSU had been replaced by a DC connector with no clues as to voltage or polarity. Running on a bench supply it is sweet, frequency stability beyond reproach; blowing into the enclosure briefly shifts it a few tens of Hz. The opening comments on the linked page, about harmonic levels, applies to the modulation osc rather than the RF O-P which is probably better than most RF generators in terms of harmonics. The modulation osc certainly needs taming, and switching off when not in use; modulation is 100% square wave when 'on', reducing significantly when 'off'. The top range needs adjusting, otherwise calibration is good. To bring this to a really useful state will need a pointer dial to give some idea of frequency without needing an external counter. Attached Thumbnails __________________ - Julian It's good here

28th Feb 2024, 12:17 am	#8
Philco-Pete Tetrode Join Date: Oct 2009 Location: Chesham, Bucks. UK. Posts: 75	Re: Was this homebrew sig gen made from a kit? Guilty m’Lud So that’s where it went! Apologies for the rather poor standard of the internal construction. Front panel was probably done with that fiddly Photosensitive anodised Ali stuff since I think it was made before we got the laser engraver at work…. Hope you find it useful Jules Cheers Pete