BNC connectors

[Lady Campanula]

I've had reason to replace a set of deeply-corroded BNC connectors, in the cable runs from VHF/AIS ( ? ) to the mast, with new. Having managed to avoid such techie stuff all my days - until now - I was a little 'confussed' initially to know quite how 'what' fitted into 'which', how, and why.

A visit to Western Electrical in Plymouth solved all problems except for the humungous traffic jam outside their doors - thanks to Gareth, who loaned me a crimping tool, and Mike Cartlidge, 'lecky extraordinaire, who gave me a handful of connectors to practice on. Below is a pic of my first few attempts before the penny dropped. Then I fed the woven wire sheathing onto where it should have gone, 'and Bob's yer.....'

I guessed at the length of the cable's woven sheath, inter-insulator, and core length/thickness for the gold-plated hollow pins. I found I had to cut away half the central core strands before I could get a fit into the pins.

Would experienced time-served RF installation journeymen on 'ere care to tell me how I should have done them? And how I might test them without specialist kit? And anything else I should have known about, but didn't?

 

[Coaster]

It's a bit late for her Ladyship but for others contemplating work on coaxial cable connections may I recommend Salty John's excellent guide. I'm very pleased with the PL259 connectors and other items bought from said expert.

To emphasise the impartiality of my comments I was going to put "no connection.." but realise that might give the wrong impression! There are very strong connections now, at least in my boat.

 

[iangrant]

Wrong BNC??

I guessed at the length of the cable's woven sheath, inter-insulator, and core length/thickness for the gold-plated hollow pins. I found I had to cut away half the central core strands before I could get a fit into the pins.

There are different type of BNC, 50, 75 and 93 Ohm Normally the small hole ones are for computery stuff. (solid single copper core) mind you not a lot of thin ethernet or IBM 3270 or Wang terminals around any more, still a lot of WAN G703 interfaces though so BNC's still in use.



Would experienced time-served RF installation journeymen on 'ere care to tell me how I should have done them? And how I might test them without specialist kit? And anything else I should have known about, but didn't?

Not a time served RF engineer but would suggest the best test would be with a meter to make sure there are no shorts between the center pin and the screens (braid)

Ian

 

[mainmarine]

I've had reason to replace a set of deeply-corroded BNC connectors, in the cable runs from VHF/AIS ( ? ) to the mast, with new. Having managed to avoid such techie stuff all my days - until now - I was a little 'confussed' initially to know quite how 'what' fitted into 'which', how, and why.

A visit to Western Electrical in Plymouth solved all problems except for the humungous traffic jam outside their doors - thanks to Gareth, who loaned me a crimping tool, and Mike Cartlidge, 'lecky extraordinaire, who gave me a handful of connectors to practice on. Below is a pic of my first few attempts before the penny dropped. Then I fed the woven wire sheathing onto where it should have gone, 'and Bob's yer.....'

I guessed at the length of the cable's woven sheath, inter-insulator, and core length/thickness for the gold-plated hollow pins. I found I had to cut away half the central core strands before I could get a fit into the pins.

Would experienced time-served RF installation journeymen on 'ere care to tell me how I should have done them? And how I might test them without specialist kit? And anything else I should have known about, but didn't?

The only way to properly test a VHF aerial and cable is with a SWR meter, similar to this here: http://cgi.ebay.co.uk/SWR-METER-AND...Equipment_SM&hash=item5640bcb380#ht_500wt_922
I always keep one on my boat, the reason you had to pare down the cable to fit the plug was probably that the cable was 75 ohm TV, coax and the plug was for 50 ohm, VHF coax.

 

[Bav32]

My advise would be to avoid the crimped on version.
I've had professional experience of these causing wierd and intermittent faults. ( when you've had to remake over a hundred or so, you don't forget)
Just recently had to replace two of these on NEW GPS antennas with the real thing i.e. the more expensive tighten up with two spanners version.
Yes I know the crimp version is quick and easy but expression good ships and ha'pworth of tar comes to mind.

 

[Lady Campanula]

My advise would be to avoid the crimped on version.
I've had professional experience of these causing wierd and intermittent faults. ( when you've had to remake over a hundred or so, you don't forget)
Just recently had to replace two of these on NEW GPS antennas with the real thing i.e. the more expensive tighten up with two spanners version.
Yes I know the crimp version is quick and easy but expression good ships and ha'pworth of tar comes to mind.

I'm willing to do better. So show me the better type, indicate what they're called and where to get them, and I'll get on with it.

Similarly, how's about some guidance on an appropriate SWR meter....?

Belay that last on 'guidance'. I've just bought one from the given source....
Now tell me how to use it, please!

 

[Salty John]

My Lady,

Your picture is of three BNC female connectors lounging around. I don't want to make this a NSFW thread, but to make any kind of connection there will need to be some intervention by male connectors!
Unless, that is, your corroded connection is at the AIS engine. In this case the male portion is an integral part of the AIS engine and the female connector on your cable slips onto it.
To make a simple join you can use a BNC connector set (M & F) or, for a more secure connection, a TNC set, which is the threaded version of the BNC. B stands for bayonet, T for threaded. Bayonet connectors are, typically, used for quick connections, threaded are for more permanent connections.
My own preferred connection on boats is two PL259 stuffed into each half of a barrel connector, also known (incorrectly) as a PL258, or a double female connector. I like this connection for its mechanical integrity and simplicity, but it is a big connection. A PL259, by the way, is the connector that you use to plug into your marine VHF radio. Icom et al like it, and that's good enough for me.
I wouldn't have bothered with a VSWR meter, myself, because you need some knowledge to interpret the results and a VHF/AIS system is, actually, very simple. Make good clean connections with good cable to a good radio and antenna and you should have no problems. Soldered joints are the best and, although sound daunting, are actually quite easy. Or you can get someone to make the connections for you.

Whew. It's Friday, I have a lovely Cabernet breathing, so I'll leave you to it. PM me if I can be of any help.

 

[Lady Campanula]

'To My Good and Trusty Salty John, Greetings.'

In that the three displayed devices are Female BNC connectors, incorrectly crimped, we have common cause. They are my first ( failed ) attempts at something I know next to nothing about. The helpful 'lecky mentioned above, Mike Cartlidge, gave me a handful of 'em, reasoning that it would take me a while to suss what I was supposed to do. A good judge of character...! The pair of M+F ones I did seemed well enough made, and are in situ and in service.

Now that I've purchased a SWF meter ( see above ) I may as well begin to learn something of how to use it.

In the meantime, I replaced like with like. The previous cockups had been soaked in rain and salt spray dribbling down the cables under some inadequate deck glands, and were so corroded that mushrooms were growing in 'em. It may come as little surprise to practical professionals that the kit had belonged to an academic Fellow of the Institute of Electrical Engineers, and the installation work on this and much else - a blurry nightmare - was done by a pro marine electrical contractor from South East Wales. They deserve each other!

Meanwhile, the Raymarine VHF and AIS are mutually interfering. There is corroded 'domestic' twin-and-earth all over the place, with old black/red connected to newer blue/brown 'harmonised' via chrome-plated choc-box strips, but inverted 'black to brown'.... There's at least one feed where the 'live' comes via a yellow/green coated cable.

Bit by bit, I'll tackle the issues and improve on them, with good guidance from here, for which I'm grateful. The PL259-barrel-PL259 sounds like 'the biz'.

There's one thing I'm certain of. The boat sails and steers, reliably. Usually, that's enough. And I have candles for night time....

 

[john_morris_uk]

The only way to properly test a VHF aerial and cable is with a SWR meter, similar to this here: http://cgi.ebay.co.uk/SWR-METER-AND...Equipment_SM&hash=item5640bcb380#ht_500wt_922
I always keep one on my boat, the reason you had to pare down the cable to fit the plug was probably that the cable was 75 ohm TV, coax and the plug was for 50 ohm, VHF coax.

With respect, a little knowledge is a dangerous thing, and as Salty John says, you need to be able to interpret a VSWR meter. It DOES NOT tell you the whole story - by a long way and it is definitely not the only way to test a bit of coax and its connections.

When testing coax we used to use Hewlett Packard sweep network analysers, but I notice that there are lots other products on the market now, for example:

http://www.lbagroup.com/technology/te1000-impedance-analyzer.php

For those who are still reading, a VSWR meter can give you an apparently 'good' but in reality completely false reading if it is connected to a very lossy bit of transmission line; you can't tell from the meter what is really happening so you have to know what you are doing an be able to do some more checks than simply put the VSWR meter in line and see what it says.

 

[Lady Campanula]

The only way to properly test a VHF aerial and cable is with a SWR meter, similar to this here: http://cgi.ebay.co.uk/SWR-METER-AND-...0#ht_500wt_922
I always keep one on my boat, the reason you had to pare down the cable to fit the plug was probably that the cable was 75 ohm TV, coax and the plug was for 50 ohm, VHF coax.

I appreciate the intention. However, Richard Tyminski, the proprietor of 'Truck-KingRadio' and eBay vendor as above, advised straight away that the product did NOT cover the marine VHF band and was not fit for the intended purpose. I'm well please I asked his advice...

Now back to the drawing board.

 

[Watson47]

Lady Campanula .... In additional to normal voice trafficc, I use this Test Meter;

http://vtronix-antennas.com/accshow.asp?cat=tester&show=art-3

SailGB sell them;

http://www.sailgb.com/p/VTronix_ART...urrency=GBP&country=GBR&SelectedBundle=170441

... and they are also sold under the 'Shakespeare' brand. I purchased mine at 'Capital Stores' for a good bit less, but they are no longer showing them in stock. Salty John mentioned it to me a while back & I find it excellent.

Salty John doesn't make up leads, so I have my leads made up by Martin Lynch & Sons;

http://www.hamradio.co.uk/index.shtml

Great firm - first class service.

 

[LadyInBed]

I put a new VHF aerial on top of my mast about six years ago, the coax was good so just put a new joining connector at the top of the mast.
The secret is to use screw on (as in Salty's illustration) not crimp on connectors and if they are out in the elements, bind the connection with self amalgamating (also known as plumbers) tape.
The connection is still good.

 

[keithandpam]

I use a shakespeare art-1 swr meter and it works real good and i thinks you have used it too in that place were we used to meet befor you had the sex change keith