UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio and TV Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > Specific Vintage Equipment > Vintage Test Gear and Workshop Equipment

Notices

Vintage Test Gear and Workshop Equipment For discussions about vintage test gear and workshop equipment such as coil winders.

Reply
 
Thread Tools
Old 10th May 2021, 8:20 pm   #1
mole42uk
Nonode
 
mole42uk's Avatar
 
Join Date: Aug 2010
Location: Bristol, UK
Posts: 2,211
Default DIY Spectrum Analyser

Here's an oddball - I discovered this in my loft. It's is absolutely something I will have made, but I don't remember what it is for!

The scanner and PSU boards are ones I recognise but I don't remember where from, but the RF bit is one I don't remember at all. It may be for the 35MHz or 459MHz model control bands....there's a 10MHz crystal on the RF board
Attached Thumbnails
Click image for larger version

Name:	scanner inside.jpg
Views:	173
Size:	198.8 KB
ID:	233734   Click image for larger version

Name:	RF board.jpg
Views:	150
Size:	97.1 KB
ID:	233735   Click image for larger version

Name:	panel.jpg
Views:	126
Size:	53.7 KB
ID:	233736  
__________________
Richard

Index:
recursive loop: see recursive loop
mole42uk is offline   Reply With Quote
Old 10th May 2021, 9:26 pm   #2
Skywave
Dekatron
 
Skywave's Avatar
 
Join Date: Jun 2006
Location: Chard, South Somerset, UK.
Posts: 7,151
Arrow Re: DIY Spectrum Analyser

Not wishing to insult you nor state the obvious, but since you seem to design and make a lot of your equipment, do you file the documentation for your finished items - or even those that are 'W-I-P', but never got completed? So perhaps you have that documentation filed away somewhere, but cannot remember where? Perhaps a good search in the attic or W-H-Y might be revealing. I say all that simply based on the way things get done here.
Just a thought.

Al. / May 10th.
__________________
Some people have cats and go on to live normal lives.
Skywave is offline   Reply With Quote
Old 10th May 2021, 9:29 pm   #3
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 17,645
Default Re: DIY Spectrum Analyser

It's not one of the cable TV types.

Is it the G4PMK one (Roger Blackwell) from Radcom?

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 10th May 2021, 10:34 pm   #4
Terry_VK5TM
Octode
 
Terry_VK5TM's Avatar
 
Join Date: Oct 2010
Location: Tintinara, South Australia, Australia
Posts: 1,638
Default Re: DIY Spectrum Analyser

Radcom G4PMK Spectrum Analyser November 1989.

The 10MHz crystal is for the marker generator.
__________________
Terry VK5TM
https://www.vk5tm.com/
Terry_VK5TM is offline   Reply With Quote
Old 11th May 2021, 3:27 am   #5
mole42uk
Nonode
 
mole42uk's Avatar
 
Join Date: Aug 2010
Location: Bristol, UK
Posts: 2,211
Default Re: DIY Spectrum Analyser

Thanks everyone, it is indeed the G4PMK analyser. Now to see if it still works.....
__________________
Richard

Index:
recursive loop: see recursive loop
mole42uk is offline   Reply With Quote
Old 11th May 2021, 6:43 am   #6
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 17,645
Default Re: DIY Spectrum Analyser

If that crystal has three legs, it's likely to be a two-pole monolithic crystal filter used to do one of the resolution bandwidths. It's matched at each end by the two Toko IFTs. The wider IF bandwidth is done by the adjacent ceramic filter. The two blue doodads being relays to switch the filters. Running on old memories, the IF was 10.7MHz with bandwidths like 150kHz and 15kHz. The large silver lump with three screw heads on top is a Toko helical filter. I think it was a commonly used one intended for either the 2m or the 70cm amateur band, and used as the first IF in the dual-conversion up-converting receiver. Old memories 32 years past their sell by date, and the dear old RSGB made world radio heritage remove all old Radcoms....

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 11th May 2021, 7:01 am   #7
Electronpusher0
Octode
 
Join Date: Jun 2016
Location: Bognor Regis, West Sussex, UK.
Posts: 1,501
Default Re: DIY Spectrum Analyser

You mean this one?

Peter
Attached Files
File Type: pdf SimpleSpectrumAnalyser-Radcom-Nov1989.pdf (890.0 KB, 84 views)
Electronpusher0 is online now   Reply With Quote
Old 11th May 2021, 9:25 am   #8
Radio Wrangler
Moderator
 
Radio Wrangler's Avatar
 
Join Date: Mar 2012
Location: Fife, Scotland, UK.
Posts: 17,645
Default Re: DIY Spectrum Analyser

Aye, that one.

Incidentally the earlier DIY spectrum analyser that inspired Roger to get going was by Al Helfrick of Embry-Riddle Aviation University, better known for doing an excellent book on avionics, though it's getting a bit dated nowadays.

David
__________________
Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done
Radio Wrangler is offline   Reply With Quote
Old 11th May 2021, 12:04 pm   #9
mole42uk
Nonode
 
mole42uk's Avatar
 
Join Date: Aug 2010
Location: Bristol, UK
Posts: 2,211
Default Re: DIY Spectrum Analyser

Quote:
Originally Posted by Radio Wrangler View Post
If that crystal has three legs, it's likely to be a two-pole monolithic crystal filter <snip>
David
Yes, it has three legs and yes, it is the 10.7MHz filter, not a crystal. It was late when I took the lid off the box and I was both surprised and excited to find what was inside! Looking at it again this morning, it is exactly the SSA by Roger Blackwell.

I must have made more boards than I remembered, I sold a couple a few years ago. My business used to be involved in frequency scanning at model aircraft displays (health and safety!) so I remember we made a few specialised scanners for 27, 35 and 459MHz. We probably used the Blackwell design as a shortcut....
__________________
Richard

Index:
recursive loop: see recursive loop
mole42uk is offline   Reply With Quote
Old 11th May 2021, 6:47 pm   #10
Jon_G4MDC
Octode
 
Jon_G4MDC's Avatar
 
Join Date: Nov 2015
Location: Welwyn Garden City, Hertfordshire, UK.
Posts: 1,194
Default Re: DIY Spectrum Analyser

Mind what looks like a 75 Ohm BNC on the front panel.
Too easily busted by mating a 50 Ohm one. A silly idea we just have to live with, 2x impedances in same connector type.

Yours looks OK so far!
Jon_G4MDC is online now   Reply With Quote
Old 12th May 2021, 5:55 am   #11
dsergeant
Octode
 
dsergeant's Avatar
 
Join Date: Mar 2006
Location: Bracknell, Berkshire,UK.
Posts: 1,053
Default Re: DIY Spectrum Analyser

75 and 50 ohm BNC are physically compatible unlike N type which are not. The impedance difference in BNC is made by removing dialectric, the diameter of the pin is the same in each type.

I still have my G4PMK analyser, not that it gets much use these days.

Dave G3YMC
dsergeant is offline   Reply With Quote
Reply

Thread Tools



All times are GMT. The time now is 7:34 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2021, vBulletin Solutions, Inc.
Copyright ©2002 - 2021, Paul Stenning.