Pre-war TV aerial connectors

[Panrock]

Belling-Lee style TV aerial connectors became commonplace on sets in the UK post-war. There were also the direct clamp-and-screw connections, as found on Bush sets (and maybe others?) But what came before?

As far as I can tell, the first-generation (1936-7) EMI sets used a thick pre-connected coaxial lead, terminated in a bulky (GPO?) brass coaxial plug.

Second-generation (1938-9) EMI sets used the 'twin-slat' socket. There's one (on an HMV 904) shown here. This looks similar to the one shown by Jac in another thread, on an Ekco TA201 from the same period (pic repeated here on the left).

These later twin-slat sockets look like they should be for a balanced feeder, but as far as I can recall, in the sets I've encountered, have actually been wired for unbalanced. I know of no original matching plugs in existence, though it's possible to do a passable job using a vintage 'American' mains connector, with some bending and filing of the pins.

As ever, I welcome corrections to the information above. Were any other aerial connectors used pre-war?

Steve

[Restoration73]

The connector design must match the type of feeder in use, so it would be interesting
to see what was available here then.
A useful text on the development of 300 ribbon feeder in the US can be found on p.329
of this RCA 1940's book;
https://worldradiohistory.com/BOOKSH...-Goldsmith.pdf

[stevehertz]

Steve, that subject and question was very much in my mind when I restored my Ekco TA201 back in the early 80s. Not having the correct plug, my get around was to simply insert the 'bend double' centre core of the coax into the top slat, and apply solder to the flattened end of the inch or so of braiding and insert it into the lower slat. But I'd love to know what the proper plug was like. I bet there's a few kicking around in drawers and boxes and people don't know what they are!

I recall that there was some data around (BER?) on the Ekco TA201 that didn't have a schematic, but it may have mentioned feeder type? That would be a clue or start point.

[peter_scott]

Baird T5 seems to have a balanced feeder connection.

Peter

[Panrock]

Are those simply two wander sockets?

Steve

[FRANK.C]

Cossor 54 aerial socket and plug pictured below. Which I believe is balanced.
The pins of the plug are 3.2mm in diameter.
The other picture is the cable that connects the aerial socket to the first coil.
It looks to be made of two strands of enamel copper wire embedded in some type of plastic.

Frank

[Jac]

Pye 817:



Jac

[Heatercathodeshort]

This is the aerial connector mentioned by Steve. I think it was first used with the 1938 904 series but was continued for EMIs first post war model the 1803.
I discovered this one in the bottom of my 1803 cabinet.
The 1803 is basically the pre war chassis with minor valve changes and a 15" rather than the 14" CRT as used in the 1802.
Yes Jac! The RCA phono. John.

[Panrock]

A sighting of the rare beast at last! The offset indexing pin indicates it was expecting an unbalanced feed.

Steve

[Restoration73]

Cable in #6 is solid 75 ohm twin. Insulation is polythene with one tinned and one bare copper conductor. It is moulded but is not the familiar figure-8 twin, I saw an old drum of it years back with Radiospares brand.

It is also made in 50 ohm version.

[FRANK.C]

Thanks Restoration73 for identifying the cable. I had not come across it before.

Frank

[beery]

Hi Folks,
I'm sure that the flat pin Ekco and EMI connectors are the same, but it's a surprise that they don't turn up more often, particularly as there are quite a few TA201 sets about.
I've attached some photos of a pre-war Belling Lee TV aerial connector. These were used on RGD and Murphy sets. The chassis connector looks like a giant RCA phono socket.

Cheers
Andy

[Panrock]

Talking of RCA/Phono, the standard size have been used on domestic gear for audio and video. Do they have a recognised characteristic impedance, I wonder?

Steve

[FERNSEH]

My Ekco TS701 has the original aerial connector. A simple co-ax adaptor was made but to do the job properly a balun transformer would be the correct method to connect the set to a co-axial cable.

DFWB.

[Jac]

Hello David,

Maybe a simple coax adapter is not so bad, when you look at the circuitry:



Is there any information available about the impedance of the feeder cable?
The open dipole would suggest 75 ohms?

Jac

[Heatercathodeshort]

The Belling Lee co-ax plug and socket appears to have made it's appearance around 1949.
The Bush TV11, Masteradio T909 and the HMV/EMI 1805 come to mind. There are probably many more. The 1946 PYE B/D16T had a tiny version of the co-ax plug on a fly lead. Did the standard BL plug and socket appear before WW2? John.

[peter_scott]

It looks as if the Einheitsempfänger was not just ahead with rectangular CRT but also using a 75 ohm coax aerial socket. Was it Belling-Lee?

Peter

[marceljack]

Originally Posted by Heatercathodeshort

The Belling Lee co-ax plug and socket appears to have made it's appearance around 1949.
The Bush TV11, Masteradio T909 and the HMV/EMI 1805 come to mind. There are probably many more. The 1946 PYE B/D16T had a tiny version of the co-ax plug on a fly lead. Did the standard BL plug and socket appear before WW2? John.

A very similar connector to the Belling Lee (now known as IEC 652) appeared in France in 1949 with the first 819 lines TVs and was used until the 80s.
It was only slightly different of the Belling Lee by the outside diameter of the male plug which was 9 mm instead of 9,52 mm.
Female sockets compatible with both 9 and 9,52 mm male plugs were introduced in the 70s by Philips on their tuners by adding three small "spring" contacts on the outside of the connector.

[peter_scott]

In the RCA TRK 120 I'm not quite sure what the connector was. Perhaps an RCA phono

I think they were providing for either a 75 ohm coax or 100 ohm balanced feeder.

Peter

[Jac]

Originally Posted by peter_scott

It looks as if the Einheitsempfänger was not just ahead with rectangular CRT but also using a 75 ohm coax aerial socket. Was it Belling-Lee?

Peter

Hi Peter,

It could very well be a connector like the one later used for car radios.
It seems quite deep and it does not look unlike there is a hole for the center connector.



Perhaps it is somewhat similar to the aerial connector of the Ekco TS88/188 etc., but sticking out of the chassis i.s.o. sunken into it as in the TS88.



Jac