Advice Needed Oversized Coax Input

Our_Jud

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I was shown a cable/connector today and asked if I knew what it was for. It was at a unit in a long row of arches that run underneath a stretch of railway (the kind of place you find car body shops). Anyway, the aerial looked like a pretty standard TV analogue, but the cable that lead into the building was much thicker than usual and on the end had what appeared to be an oversized coaxial RF. I'd say it was about three times the size of a standard RF input.

Does anybody have any idea what this might be for?

Thanks in advance.
 

Lazarus

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Not easy without a picture!

Could be a PL259, though: Did it look like this?


PL259.jpeg
 

PaulR

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N-plug-400-cable.jpg
Might also be an N-type plug. As one knurled outer ring looks much like another you can see the difference on the open end.

PL259 Plug.jpg
The N plug has an inner sleeve which is the outer shield. The knuled ring is just for connecting purposes. On the PL259 the knurled ring serves double duty as shield and connector.

As to what it's doing there my first thought was that it might from an old taxi service base station but they use simple folded dipoles normally. Another thought is that, especially as it's by a rail line, it was for point-to-point comunication between two stations.

Most of the independant radio communication nowadays has been swallowed up in digital conglomerates such as Airwave which serves the Police and, I think Ambulance services.
 
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Lazarus

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Nobody should have to endure a knurled ring ..................... :-ohmy
 

Our_Jud

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Thanks very much, people.

From memory I'd say the plug Tivu posted (the PL259) was the closest, but without anything to scale it to I don't know if the size is right. The pin (or whatever it's called) sticking out was quite heavty and solid rather than it just having the copper wire exposed. I reckon it was close to an inch in diameter (the plug casing, not the pin)

So tomorrow I can tell him it was probably used for point to point communication between two stations?

Thanks again.

[Edit] A little research on the PL-259 makes me 95% sure this is the one. It's typically 18mm in diameter (very close to the inch I estimated) and seems to be typically used by Ham radio and CB enthusiasts.
 
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Lazarus

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Your edit is on the button: Not just Hams though, but Public Service and Commercial Systems with Transmit and Receive facilities used them quite commonly in the past. No idea if they still do.

Mobile Comms users such as Water Board, the old Electricity Boards, Police (Anybody remember Pye!) etc all had them.

But then I'm getting quite old now ..........................



As an Apprentice with Marconi (Who?) in the 70s, I did a stint with GEC (Who?) Mobile Radio and worked on assembling, testing, installing and commissioning Mobile Comms. base-station racks for an Electricity Board.
 

Topper

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At first I thought it could be a low loss Paknet system for credit card authorisations using the Vodaphone network, on long runs they use the extra thick low loss coax cables, they have a short digital whip antenna at t'other end though and use the N type connector to connect to the Paknet unit
 

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I used to use a connector like the one tivu posted on my cb many years ago, I can't remember the spec of cable I used to use but I remember it was expensive,
 

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This might bring back some memories to some peeps :), I have had this for around 35 years now:eek:
DSCN5454.JPG
 

smoggy07

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If it looks like a TV antenna then it will be a Yagi for point to point comms as mentioned above

Was that location used by the railways in the past as they use (or used to use as it is being phased out in favour of mobile phone tech called GSM-R) band3 VHF comms and also UHF for "Cab Secure" radio and you'd often see Yagi antenna dotted along the trackside to provide coverage (you'd also find one at either end of tunnels pointing into the tunnel to provide cover inside the tunnel)

They point them at each other along the length of the tracks so the drivers can raise the signal men or anyone else they might need and can look similar to the attached pic ANT-YA13-9.png

Next time you are there follow the line of sight and see if you can work out the intended recipient or get a rough idea of where it is pointing, it could be aimed at a hill top repeater site
 
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