How to extend a coax cable ?

[dogs best friend]

Sounds simple, maybe I'm just trying to make hard work for myself. I need to extend a coax cable by about 20m. The cable is RG-213/U. By what I have gathered from google this is favoured by radio hams although my app is different. To make life easier, the cable that I need to extend has really oddball end fittings which are of the crimped on (non-removable) type with screw-on terminations. Just to make it interesting these fittings are left hand thread and I think they could be Outer Mongolian Gas Thread. I can find the cable required to make the extension but cannot find any suitable hardware to join a middle bit to the 2 ends. The whole has to be weatherproof but I can do this with suitable enclosures if req'd. Any ideas please.

DBF

[Andy Wade]

Is replacement with a single new length out of the question?

And your application is...?

A coax connector with a left-hand thread - that's a new one on me. A photograph of the connector in question posted in a suitable place might be a big help.

[John Rumm]

Two screw on F connectors, and a F coupler. Wrap the lot in self amalgamating tape to make waterproof.

[dogs best friend]

Many thanks Andy

Replacement with a new length is not viable as I cannot find suitable LH thread terminations. The manufacturers will not supply parts or divulge any details of the specs. Unfortunately I can't post any pics as I don't get any webspace. Also a pic would not be of much use. It looks much like a standard but large screw down connector. No pic could show an Outer Mongolian Left Handed Gas Thread. Top LH pic in this page

show something similar but not identical. My application is for an external aerial for a commercial cordless 'phone. This is not to be used in the UK and is based outside the EU where its use is perfectly legal.

DBF

[BigWallop]

Have a web search for "F connector" or "satellite coaxial connectors" which should give you what you need.

[Bill]

In message , dogs best friend writes

N type connectors, try

if you buy two pairs of plugs and sockets and then cut your existing lead at any point you can add in the new length of cable. Henry also sells decent RG-213 too. Weather proofing could be achieved with self amalgamating tape. I'm intrigued, what is your application and do you have a photo of the Mongolian Gas connectors?

[Bill]

He did say it was RG-213/U have you ever seen an F connector for this? They do actually exist but are as scarce as RHS. N types are much more the norm.

>

[Bill]

In message , dogs best friend writes

A LH thread PL259, that could be interesting!

I've already suggested elsewhere that you could use N types for the coupling but how about replacing the sockets on the base unit and aerial to Ns and then it would be a bit more conventional?

Do you have a url for the manufacturers? Could be interesting to see what they have on offer.

[The Natural Philosopher]

Mmm. If you are connecting identical bits of cable, I'd cut, solder the inners, tape up to the same diameter as the inner insulation, then wrap with a bit of fireproof card and solder he braid as well, then coat the whole thing in something like silicone and heat shrink over the top.

It won't be perfect, but it will be very good - probably better than any plug and socket.

[Andy Wade]

What a horrible thought. PL259s are quite bad enough without anyone introducing a left-hand threaded version ...

Might be easier said than done, though, especially for someone with not much RF knowledge.

Seconded.

Cable mount N connectors (by Telegartner, so decent quality) for RG213/U, both male and female, are also available from RS components as stock numbers 112-2094 and 112-2123 respectively. One of each of those plus some self-amalgamating tape would produce a good outdoor cable joint, but it leaves the problem of transferring the weirdo connector from one end of the original length to the end of the extension piece.

And which operates in what frequency band(s), do you know?

[Mark]

really, what would you then calculate the impedance to be ?

[Bill]

In message , Mark writes

Impedance. What's that? ;-)

I've seen many bodges like this and hate to think how many are out there. Just goes to prove that the advice you get on the Internet is worth what you pay for it.

[dogs best friend]

hat took a few seconds to work out! Was wondering how the Royal Horicultural Soc. came into this. Then remembered Nebuchadnezzar, the trusty & most faithful family rocking horse.

Whose whatsname is as rare as any others.

DBF

[dogs best friend]

Yes I can do this but it is a least preferred choice. Good connectors and enclosures would be my preference.

DBF

[John Rumm]

I think CPC have ones that will fit... having said that any fully screened connector such as a N type would be fine/better as well.

[Rob Morley]

I think you'll find the connector in question is reverse-polarity TNC (RP-TNC). Here's a page with pictures of the various connectors. These are supposed to be hard to find, to stop people messing around with antennae, but you can probably track down something suitable if you're patient.

[The Natural Philosopher]

Pretty much what the cable was, if done carefully.

Used to do this a lot when messing around on the RF test bench. Very little different froma BNC plug and socket in there.

[The Natural Philosopher]

If you do it carefully, its often BETTER than a plug and socket. Certainly better than a corroded plug and socket.

I've done it and tested it.

[The Natural Philosopher]

When I were a lad learning my trade in the Marconi Radar company, we were taught that you only use a plug and sockert when you need to take something apart.

Crimps solder and proper insulation are what you use to make permanent connections.

If you ever seen the reflectins that come off a rather tired BNC plug and socket you would avoid connectors too.

[Andy Wade]

Interesting, very. You forgot to post the URL, but a Google search on RP-TNC turns up quite a few hits. The RP bit refers to the plug having the female contact for the centre conductor.

To quote from

"There are two types of TNC connectors: Standard and Reverse Polarity. Reverse polarity is a keying system accomplished with a reverse interface, and ensures that reverse polarity interface connectors do not mate with standard interface connectors. Amphenol accomplishes this by inserting female contacts into plugs and male contacts into jacks. Other manufacturers may use reverse threading to accomplish reverse polarity keying."

This page has "Reverse-Thread TNC-Male Crimp Connectors"

not for RG213 size cable).