VHF plugs

If at all possible, it is always best to run a continuous cable from antenna to radio rather than have connectors. Connectors are the usual source of problems when transmitting.
 
Any connection can cause a loss in signal due to reflection within the line, but you need something to join the cut ends of the cable. I have not used the one that you link to but I dislike BNC connectors at the best of times. I find them hard to fit to the cable and prone to bad connection. To fit the original anteaan, you could try a type F connector (widely used by TV and Satellite engineers) and wrap in well with self-amalgamating tape. Or you could strip baxk come of the cables and solder the inner cores and braids together. You would first slide on several bits of heat-shrink tube to insulate the bits and cover the whole joint. Some epoxy under the last bit of heat-shring would make a waterproof seal.

Or you could invest in a new antenna. Use the existing cable to pull the new one through the mast and fit the supplied PL259 plug to the foot end of the cable. You could fit a PL259 socket to the deck and continue the cable inside to the radio, where the final PL259 plug makes the connection. Many antennae come with a detachable joint at the top. This consists of a bullet that fits into the base and is held in by a plastic nut. This allows the antenna to be easily removed when the mast is taken gown.
 
OceanSprint said:
. . . . . . So I have the choice now of re-connecting it, or installing an inline waterproof connector. . . .

But would this weaken the transmit/receive power? Could I install another at the bottom of the mast?
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When I worked in the government radio research laboratories in Surrey, for a prosecution at Crown Court, I had to conduct tests on various High-band and UHF frequencies and the losses incurred by using various in-line VHF and UHF connectors (PL259/S239, N-type and BNC/TNC).

At best the losses using new cable with correctly connected plugs and sockets will be 0.3dB insertion loss. I suspect under not idea conditions, you should expect a 0.5dB insertion loss possibly 1dB loss per connection.

You would not notice this loss. A 3dB loss would weaken your 25 Watt transmit power down to 12½ Watts and you would probably not even realise this level of loss as the CG antennas are positioned is very favourable locations.

I hope this helps?



.
 
nigelmercier said:
The one in the picture clearly isn't a BNC, even though it says it is. This one is though:
http://www.mailspeedmarine.com/aeri...vtronix/vhf-in-line-connector-kit102601.bhtml

It says "Suitable for 5mm coax cable". If your cable is only 5mm then, depending on the length, much of the loss has already occurred.
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I am sorry that Wight Dawn has given a negative opinion of BNC connectors. They are actually VERY good connectors. I agree that they are not the easiest to fit correctly and accurately, but they are not that difficult and are the professionals choice for small cable sizes in almost all applications alongside the 'N' connector.

BNC connectors come in various grades and the best are silver plated. Mr Google will find several step by step diagrams of how to put them on. BNC connectors are NOT waterproof so plenty of amalgamating tape (and a coat of varnish over the top would be belt and braces).

To the OP: If the cut in the cable is at the top of the mast then a new cable might be your best bet.
 
nigelmercier said:
PL259 connectors are not inherently waterproof either, but the problem with BNCs is that the pin contact area is very small.
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I have never known the pin contact area to be a problem with decent quality BNC's. The great advantage over some cheaper connectors is that the insertion loss of a BNC is minuscule compared to some which correlates partly to the very low impedance mismatch as the transmission line changes from cable to connector to connector to back again. Its this attribute that encourages you to be very careful when fitting them. The soldering of the pin must be very precise and the braid must me fanned out very evenly over the compression collars. I used to have to get a pin vice and a needle file to clean up any excess solder to preserve the cylindrical nature of the pin and make the resultant impedance step uniform. The cable was tested on an RF analyser that would sweep RF from a few Mhz up to several Ghz and check for spurious disfunction's in the impedance of the line.

The point I was making is that I was very surprised to have someone claim that they are poor connectors. They are used on most every bit of RF lab kit alongside 'N' connectors at higher frequencies. (But you have to start getting into the Ghz regions before you will start noticing a difference for our purposes.) Even averagely fitted BNC connectors will almost certainly be superior to most others at 156 Mhz Marine VHF. Just make sure you buy decent quality BNC's; there are some very cheap poor ones about.
 
Wight Dawn said:
you could try a type F connector (widely used by TV and Satellite engineers) and wrap in well with self-amalgamating tape. Or you could strip baxk come of the cables and solder the inner cores and braids together. You would first slide on several bits of heat-shrink tube to insulate the bits and cover the whole joint. Some epoxy under the last bit of heat-shring would make a waterproof seal.
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Impedance mismatch heaven.
 
If I may "hi-jack" the thread. I have the same problem.

Can anybody point me in the direction of how to attach a male connector to the wire - I am going for a male - female - male set up. While not ideal for the moment is my short term fix.
 
Camelia said:
If I may "hi-jack" the thread. I have the same problem.

Can anybody point me in the direction of how to attach a male connector to the wire - I am going for a male - female - male set up. While not ideal for the moment is my short term fix.
Click to expand...

Try page 10-36 and onward of the leaflet available from here:

http://www.datasheetarchive.com/BNC assembly instructions-datasheet.html

for lots of instructions about fitting BNC Male and Female connectors with drawings etc. Click on the top image with '50 pages' annotated against it and download the pdf file.
 
I know this is probably a very crude way of testing the joint, but with a multi-meter across from say the plug at the back of the radio to the deck plug, what resistance would be reasonable?
 
The BNC, being a bayonet connector, is designed for frequent connect and disconnect situations, which is why they are so popular in labs. In an environment where they are subject to vibration they are less good and the threaded version, the TNC, is more appropriate. I favour two PL259s and a barrel connector in situations where mechanical integrity is required - a tough combination although rather bulky.
 
Salty John said:
The BNC, being a bayonet connector, is designed for frequent connect and disconnect situations, which is why they are so popular in labs...
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You would think so, wouldn't you: http://www.tycoelectronics.com/comm..._50-75_OHM&DocType=Data+Sheet&DocLang=English

Page 2: Durability 50 cycles minimum

When I worked at the BBC, we investigated this problem with regard to our oscilloscopes. It turns out that they had an expected life of a few hundred mating cycles. As a result, all the scopes got attached leads with a MUSA socket on them.
 
Salty John said:
The BNC, being a bayonet connector, is designed for frequent connect and disconnect situations, which is why they are so popular in labs. In an environment where they are subject to vibration they are less good and the threaded version, the TNC, is more appropriate. I favour two PL259s and a barrel connector in situations where mechanical integrity is required - a tough combination although rather bulky.
Click to expand...

I won't argue as at the frequencies involved, two PL259's and a back to back will be perfectly adequate. My musings were rather more aimed at the poster who said that BNC's are poor connectors, and that lead to more questions about how to fit them.

I prefer to solder the PL259's (braid and centre conductor - but a lot of them in the cable sizes we are dealing with on Marine VHF's rely on compression of the braid trapped in the screw collar to make the electrical connection. They need to be kept dry and I would still be recommending to the OP that he just renews the whole cable.
 
To clear up my point about problems with BNCs, the only one I have on the boat is for the antenna lead for the sat nav and I am on my third plug. The first developed an intermittant connection fault, so did the second but the fault in it was that the plug fell apart. Ok, I am not the best technician but I found that the soldering involved was seriously tricky. Before fitting a third one, I considered how to solder the lead directly to the internal lead but as I need a disconnection for removal during lay-up, I bought a pre-made lead with plugs at each end. I cut this lead in two and used one piece with one of the hated Belling-Lee connectors to provide the link with the rest of the cable. It works perfectly and even I can fit Belling-Lees.

Prior to those experiences, we had a lot of them in instrumentation equipment in the labs at the college and one of my colleagues (who was a ham radio expert) hated them as well. They were prone to bad contact unless you wiggled them to the right position and they did not tolerate vibration.

As to the F connectors, I actually hate the things and echo he advice to renew the whole cable. I did know of the impedance missmatch, but over the short distance of the connectors, previous experiments (when I was a student) found less signal reflectance than was expected. Mind you, we were trying to measure the reflectance in a supposedly "lossy and imbalanced" transmission line in a physics lab. The imbalance was supposed to be demonstrated by joining a length of 75 ohm cable to a length of 300 ohm stuff. Naturally our results bore no resemblance to the expected values and you know what they say about science experiments. If it involves dead things, it's biology, if it smells it's chemistry and if it doesn't work it's physics.
 
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