My Marconi style magnetic detector WORKS! - UK Vintage Radio Repair and Restoration Discussion Forum

RadioHist · 22nd May 2016, 2:33 am

I've wanted to play with a Marconi style magnetic detector for decades and 4 years into retirement I have built this contraption that actually does work. The belt is driven by a cheap music box movement that runs about 3 1/2 minutes. That's good enough for demo for right now. I wanted to build using currently available cheap spring motors...

Right now I drive the thing using a series tuned circuit in my trusty Heathkit CR-1 crystal set. The detector simply being in the ground circuit of the Heathkit. My earphone is from a sound powered telephone with a resistance of about 85 Ohms.

I have the reprint of Hawkhead's 1915 Handbook of Technical Instructions for Wireless Telegraphist. In it, it describes how to hook it to a multiple tuner and gives schematics of the tuner but gives no details whatever on the inductances used.

So I solicit ideas as to what might have been done to couple the most magnetizing energy to the magnetic detector. (Best impedance match.)
And what might be a coil design to use for the MW AM band.

Yours, Robert

peter_scott · 22nd May 2016, 9:40 pm

Hi Robert,

I can't help answer your questions but am very interested in the resulting performance of your detector. A YouTube demo would be great.

Thanks for posting,

Peter

ms660 · 23rd May 2016, 10:00 am

This site has a fair bit of info on early Marconi stuff, might be worth a search..magnetic detector..

The site is very comprehensive but navigating it can be a bit of an art...!

http://www.rnmuseumradarandcommunica...his%20site.htm

Good luck.

Lawrence.

Station X · 24th May 2016, 9:07 am

Four posts moved to this thread:-

https://www.vintage-radio.net/forum/...d.php?t=126673

RadioHist · 25th May 2016, 1:31 am

Boy! Navigating that site was a 'whole 'nuther thang' for me

From what I see, the Marconi references don't seem to cover the spark era.

But I do appreciate any possible leads... You never know...

Thanks,
Robert

peter_scott · 27th May 2016, 10:04 am

Quote:

Originally Posted by peter_scott

A YouTube demo would be great.

https://www.youtube.com/watch?v=4CAxWoKD-fw

M0SOE_Bruce · 27th May 2016, 2:30 pm

The 1910 Marconi catalogue says the output should be connected to low resistance telephones. The model of headphone recommended is #128R which the catalogue states "is the standard 150R telephone used by the Marconi company."

Jon_G4MDC · 31st May 2016, 6:23 pm

Magnetic detectors were low impedance at RF. I wouldn't be surprised at only a few ohms

22nd May 2016, 9:40 pm	#2
peter_scott Dekatron Join Date: May 2003 Location: Edinburgh, UK. Posts: 3,274	Re: My Marconi style magnetic detector WORKS! Hi Robert, I can't help answer your questions but am very interested in the resulting performance of your detector. A YouTube demo would be great. Thanks for posting, Peter __________________ http://www.nostalgiatech.co.uk https://www.youtube.com/c/PeterScott/videos

23rd May 2016, 10:00 am	#3
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: My Marconi style magnetic detector WORKS! This site has a fair bit of info on early Marconi stuff, might be worth a search..magnetic detector.. The site is very comprehensive but navigating it can be a bit of an art...! http://www.rnmuseumradarandcommunica...his%20site.htm Good luck. Lawrence.

24th May 2016, 9:07 am	#4
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: My Marconi style magnetic detector WORKS! Four posts moved to this thread:- https://www.vintage-radio.net/forum/...d.php?t=126673 __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

25th May 2016, 1:31 am	#5
RadioHist Pentode Join Date: Aug 2009 Location: Charlotte, NC; USA Posts: 165	Re: My Marconi style magnetic detector WORKS! Boy! Navigating that site was a 'whole 'nuther thang' for me From what I see, the Marconi references don't seem to cover the spark era. But I do appreciate any possible leads... You never know... Thanks, Robert

27th May 2016, 2:30 pm	#7
M0SOE_Bruce Pentode Join Date: May 2013 Location: Deal, Kent, UK. Posts: 139	Re: My Marconi style magnetic detector WORKS! The 1910 Marconi catalogue says the output should be connected to low resistance telephones. The model of headphone recommended is #128R which the catalogue states "is the standard 150R telephone used by the Marconi company."

22nd May 2016, 2:33 am	#1
RadioHist Pentode Join Date: Aug 2009 Location: Charlotte, NC; USA Posts: 165	My Marconi style magnetic detector WORKS! I've wanted to play with a Marconi style magnetic detector for decades and 4 years into retirement I have built this contraption that actually does work. The belt is driven by a cheap music box movement that runs about 3 1/2 minutes. That's good enough for demo for right now. I wanted to build using currently available cheap spring motors... Right now I drive the thing using a series tuned circuit in my trusty Heathkit CR-1 crystal set. The detector simply being in the ground circuit of the Heathkit. My earphone is from a sound powered telephone with a resistance of about 85 Ohms. I have the reprint of Hawkhead's 1915 Handbook of Technical Instructions for Wireless Telegraphist. In it, it describes how to hook it to a multiple tuner and gives schematics of the tuner but gives no details whatever on the inductances used. So I solicit ideas as to what might have been done to couple the most magnetizing energy to the magnetic detector. (Best impedance match.) And what might be a coil design to use for the MW AM band. Yours, Robert Attached Thumbnails

31st May 2016, 6:23 pm	#8
Jon_G4MDC Nonode Join Date: Nov 2015 Location: Welwyn Garden City, Hertfordshire, UK. Posts: 2,015	Re: My Marconi style magnetic detector WORKS! Magnetic detectors were low impedance at RF. I wouldn't be surprised at only a few ohms