I recently purchased this item and wondered whether anyone can tell me what it is and where it may have been used. The valves in it are broadcast frequency, a four pin valve is missing. The case looks water resistant and the carrying strap is well used. There are no external jacks.
Thanks.

Does it have a speaker at all.

It looks like it does but it appears to me of a telephone type than a cone speaker. At first I thought it might have been a speaker from a drive-in theatre but I don't think they had valves in them - the power consumed by several hundred of something like that would have bankrupted the operators.

This thing has a shoulder strap so perhaps a piece of audio test gear?

The object stuck inside the grille looks like a cigarette butt.

The only reference I can find to "RBM Long" referred to a senior officer in the Royal Australian Navy during the war years.

Update: I just stumbled into a post elsewhere on this site that indicates that RBM Long of Sydney, NSW made Geiger counters. Maybe this is one of those...

https://vintage-radio.com.au/default.asp?f=1&th=368

Update: A film of a Geiger counter collection, including an example of the one pictured above:-

https://www.youtube.com/watch?v=_U6cbjuCzVk

If there was a aerial jack like for a telescopic whip it possibly could be some sort of short range transmitter. Like in a large factory building.

Otherwise a walkabout receiver for a large factory with a closed loop aerial system so a supervisor could summon people.

Pity there is something missing from the larger socket which would give a clue as to what it does.

Interesting gadget, well made.

That YouTube link returns the message "Not A Server Error But A User Error"

This works:

https://www.youtube.com/watch?v=_U6cbjuCzVk

Indeed a user error - mine. I had the URL in colons instead of inverted commas.

All fixed now.

What is missing by the look of of it is the Geiger Muller tube. How many pins on the socket? Many of those need around 500V for that tube & the rest is Amplifier.

The most interesting one that passed through my hands and working, was one at first purported to be off H.M.A.S Melbourne. Still had its MIL ID. but no ship data. One of the guys in the Radio Club was Ex Regular Army, he delighted in the find and knew who to contact. Its now in the Maritime Museum as it actually turned out to be the real McKoy.

There are two GM tubes here.

Marc

The commentary on the YouTube video shows a glass GM valve inside the RBM Long unit though most of these appear to be metal tubes with a mica window to let the radiation in. How the radiation gets through the cast iron instrument case has me baffled though.

I've blown up the original of the second photo but cannot see the number of pins on the socket. It doesn't appear to be an octal socket.

One I have is a very ancient Glass G10 Probably 1940's. The box of the other one has a variety of hand written numbers on it, one referring to "X-ray Diffraction Apparatus".

The G10 is a 500V type however, The card with the other one says IZK-20/75 and the tube JZK-20/75 and a later serial number. Arbietspannung 1800V: It was tested at 2KV as well. This one is a Wand type. Made by Siemens Halske.

Metal construction screw cap on window.

So the minimum in one of those things is some form of EHT generator and a rectifier that can handle the volts. The one from the "Melbourne" was a wand type from memory.

Bottle numbers just might give a clue to what they do. The electrolytics are by now of the "Cactus" species, but will have voltages on them.

Marc

Thanks for your help with identifying my Geiger counter. RBM Long was the Director of Naval Intelligence during the war and set up a business to produce precision instruments after he retired from the Navy. I haven't been able to find exactly what he produced. The empty socket is four pin. Does that correlate with it holding a GM tube? Thank you all for your interest and help.

As said,if there are numbers on the existing valves (if they are) may help? Most of the scintillation GM tubes I have seen use 2 elements albeit pins 2 & 8 are quoted on G10. I would need to look at it.

Marc

Hello Roy,
Only just found this but can help as I also have one bought back in 2010.
The reason why I am interested is that I am about to restore mine using battery eliminator circuits.
The three Tubes are 1S5 and 2x 3S4 with filaments at 1.4 volt parallel and HT at 90v.
The missing Tube, unfortunately which yours is missing is a KF 2595 Geiger Tube from 20th Century Electronics (Centronics) Type G10 at 1,120 volts.
However, a similar product could be utilised here with only very minor modifications as long as the Tube is about that voltage.

I have two other Geiger Counters here, one coming from Oatley Electronics but is not sensitive enough and another just bought called a 'Smart Geiger' which is a small Geiger head that fits into an Android Phone audio output and all you do is download the App and away you go.
BUT - this is also not as sensitive as I would wish.

What is so good about the RBM Long design is that it covers all of the Alpha Beta and Gamma radiation.
Believe this was produced back in about 1953 when the 'Cold War' was at its peak but have not found any other data as in schematics etc but only your reference here.
That's why I am restoring and should be better than anything solid state in the fact that it is using Tubes.
My research demands that I know just how active certain minerals are and I have Uraninite and Allenite here from Aussie Minerals in Mt Isa as well as a complete array of other radioactive types to test.

I have built Eric Dollard's Cosmic Ray Detector (CRD) and uses a Geiger Tube made by Cintel GM-2 at 1300v and is 21" long and works well.

Hope this answers your questions.

David G

Photos uploaded to Post 13.

The only thing that will stop some radiation is lead. It will likely have caps like a radio, with higher voltage rating and all of the same issues.

I have what I believe is a G10. That is likely using one tube as an oscillator: Reverse engineer.

Marc