BNC connectors and dodgy VHFS

[LeonF]

Radio was fine and dandy week ago and died at weekend.. Seems to be dodgy female BNC connector from aerial end..the wire pulled out easily..tried to reconnect, but only receiving faintly and no transmit. Will try a new connector...any advice on best kind from Maplins ?? I know the PL259 are supposed to be better, but this would involve chopping it off when I drop the mast in November.
Also any idea where I can find a simple diagram showing how to install these connectors ?? I am not sure I did it correctly. I remember one of the sailing mags did a small article a while ago. Just hope I haven't knackered the radio trying to transmit with no aerial connection..its a 1997 Simrad RS8300 and I have been told that it should have enough inbuilt protection.

 

[ShipsWoofy]

If you do not want a deluge of junk mail I would advise against Maplins.

I promised that I would advise everyone I could against them if they did not remove me from the mailing list which I did not ask to be included on. On Tuesday I received a polite mail saying I had been removed from their list. On Sunday I received a Maplins news letter in my inbox.

John Lewis also abuse your email that you trust with them.

Try CPC - http://cpc.farnell.com/jsp/home/homepage.jsp

 

[LeonF]

I shall just head down to my local branch...not mail order...still trying to find some info on how to connect it the the cable in the correct way..Leon F

 

[ShipsWoofy]

In more of a reply to your post.

Without one in front of me I may miss something out or make a mistake, but hopefully I should be able to answer your question. This is a UHF plug, not a BNC, BNC has a half turn and lock bayonet - (Bayonet Neill Concelman)

The plug should break down to pin, body and crimp.

You need to first slide the crimp tube over the coax, so that it will be behind the plug, it is important not to forget this, you will curse later if you do. Also at this time prudent to slide a piece of heatshrink on the cable too.

Strip back the outer plastic sheave and roll back the screen material. You are attempting to make the inner (still insulated) the same length as the plug, i.e. when you have soldered the pin in place if removable, or when the wire shows in the hole at the top of the pin, the rolled back screen is touching the back part of the plug.

Ensure no stray screen wires. You can make the inner too long and snip it down when you slide it in to test for length.

Now strip back about 5mm of the inner insulation if using a fixed pin. Tin this wire with solder. Push the wire back into the plug tight. Now solder the inner wire which you have stripped and tinned to the pin, be liberal with solder, you do not want solder splashes as this will stop you being able to push the connector into the female on the radio. Do not paint the solder either, this will lead to cracked joints over time. If you are not very happy with soldering, best ask a friend who can. This is a big pin and requires a fair amount of skill / practice.

Once soldered, use a DMM and make sure there is no short from the screen to the pin, you will get a reading however through the aerial, but it should not read 0.0ohm. This is worth doing as a check before you crimp the back on, as that is fairly final.

Now, roll the screen over the tube on the rear of the plug. Bring the crimp tube back to the plug and slide it over the screen. Crimp down with the correct tool. Now bring up the heatshrink and seal in the the crimped screen area.

Et voilà, you have a new plug fitted for your radio.

Hope this helps.

 

[petercornish]

Get into a local chandler, Glowmex have just produced a solderless PL259 that you can remove, it also comes with an instruction sheet

 

[Guest]

Why use a BNC ..... a simple coax joiner .... basically a short tube with a joiner inside fitted with terminal screws .... its good enough ... before closing liberally fill with silicon or vaseline to keep out water - or tape it up .... then you have positive joints, dismantleable ... etc.

But Maplins joiners are fine - used them without trouble - I just taped them up to seal ... after smearing vaseline on proverbials !

 

[ShipsWoofy]

Was writing a more helpful reply at the same time, sorry, took a little while.

 

[Guest]

Nice plug .. but

There are various push on BNC's and PL's / UHF's available as well as solderless that have a small screw to catch the inner wire etc.

Solder is a more difinite long-term I agree - but not so necessary nowadays ....

Still like the single coax joiner I use !! Has screws and no soldering !!

 

[ShipsWoofy]

Re: Nice plug .. but

I kind of agree with the ease of installation of certain non solder RF connectors.

But some of the regular questions that appears on PBO are things like, my VHF is noisy, wont transmit, crap range etc. If you use or fit the RF side of radio (connectors, cable, aerial) poorly you are going to have problems at some point.

I believe this is an area you should not scrimp on or use inferior products. If you are unsure or not confident get someone who is to do the work.

Bear in mind, this connector is something you are relying on to save your life possibly.

This is not meant to be patronising, but from experience of working on avionics, RADAR and Comms and military equipment I have seen work that would make a trained monkey look good. RF does not behave like DC, using crimps or screw downs is a very poor substitute IMO. I for one would not dream of it.

It is definitely a personal choice. If I was down on the south coast I would happily wander around the Solent marina's helping people, but unfortunately I am ooop North. Sorry.

 

[Guest]

No prob ... Woofy ...

No sleight or insult intended .....

The proper way is best ... no argument ....

But there are also other ways that I have seen, used, found good / bad etc. etc.

After a life at sea - I am fully aware of life-saving capabilities etc. But still search for easier / sucessful methods ....

Cheers
#

 

[LeonF]

Nigel can you tell me if i can get this from Maplins ?? Ships woofy has been very helpful, but my soldering skills are not up to it and I need to get back to Gravesend for chum to help. Not happening till after the bank holiday, and I have a Thames estaury crossing planned for the weekend that I don't want to do radioless.
I tried re-connecting the female BNC with the help of crew who has a PHD in theoretical physics, but no practical experience of BNCS!
Should the inner have been fed up the pin ? he reckoned that this would be damaged when the male tried to insert itself.

 

[LeonF]

Apologies if I seemed pushy!! Just annoying yesterday when it died and keen to get it sorted. Always appreciate your helpful postings. Leon

 

[Ships_Cat]

The soldered (non crimp type) BNC connectors have just one little soldering job on them, within the capabilities of most anyone. Have a look here - http://www.dse.co.nz/cgi-bin/dse.filereader?42887f5b0614c644273fc0a87f9906f5+EN/catalogs/SUP1000029.

Is a very easy job.

John

 

[ShipsWoofy]

Good link,

I should have found a UHF connector with screw on back, just my preference in this instance is to crimp down the screen, more permanent and less chance of breaking the wires through excessive movement if fitted correctly.

The screw back type have a weak point as the cable leaves the plug, people tend to drag it out a right angles which is an easy way to break down the insulation, the crimped back tends to stiffen up this area considerably IMHO.

Next time I fit a plug I will photograph each stage as I go and post it to the forum, will need a fast camera to get rid of my hands shaking due to stage fright, I hate being watched /forums/images/graemlins/grin.gif

 

[LeonF]

Kim ought to sign you up to work for the mags!!

 

[LeonF]

Thanks for all the info. Just need to know.. is the ferrule the little sleeve that slips over the inner wire? and is this inner wire the dielectric? and whats the equivalent plug avail in this country...Thanks and sorry but I am a complete novice when it comes to co-axial electronics. I just made up an adaptor for my dri-fit plug to use a cigar lighter plug and this was the first soldering I have ever done!! So does tinning mean just coating the wire lightly witn solder before I insert it ?? Presume it has to be very subtle otherwise it would never get in, or do I then heat the ferrule, if this is what I am trying to get into ?? or do i give up and pay someone to do it for me ?? wish there was a simple publication to teach me all this !!

 

[ShipsWoofy]

Tinning wire

Sorry, not stalking you!

When you are soldering wire to a plug, another wire or a circuit board for example (there are many more) it is always sensible to tin the wire. You are right in thinking that it means pre-soldering the wire prior to use.

Practice make perfect! Get some old gash wire and sit at the table and tin away until you are happy.

Basics....

The wire must be clean, you will never ever be able to successfully tin or solder blacked wire from damp, or old wire that has oxidised. Throw it away!

Strip back insulation to correct length. There are two schools of thought as to whether you should twist the bare wire tight. Some say you never should, but if I am fitting it through a small hole on a circuit board I always will, bit like threading a needle, any stray strands can be a problem. I have never seen ill effects from twisting the wire.

The soldering bit.

Make sure the iron is clean, use a damp sponge to clean the hot tip. Not a dry sponge for obvious reasons. A very black unkempt tip should get a light sanding so that it is silver and the solder flows across it easily. A dirty tip will cause the solder to ball up and you will end up painting solder rather than the solder flowing onto the metal you are soldering.

Add a tiny bit of solder to the tip, and bring the tip to the wire, touch the tip on the underneath of the wire. From here on in, the solder should not touch the iron. (see painting on). The iron should be at full temperature, do not be impatient, hobby irons take a while to warm up, give it time. Do not start the moment the solder begins to melt on the tip, it is still only half hot enough. Experience will tell you when the time is right.

The tiny bit of solder on the iron, applied previously is to make a heat conductive seal between the iron and wire, if the wire does not heat up sufficiently for the next part of these instructions, you may need to add some more solder to close the seal.

Heat the wire for a few seconds, and apply solder to the wire, not to the iron. By touching the wire with the tip you have in essence made the wire into an extension of the tip. If the solder does not flow into the strands then a) the iron is not hot enough for the job, b) The wire is not clean enough, c) you may need to add a little more solder to the tip.

Essentially, you should see all the wires, but now they will all be coated with solder. If you have blobs of solder or try to apply the solder by moving the tip over the exposed wire this is what is known as painting. Solder applied like this will easily break off if it takes at all.

Finally, cheaper cable will require quick work or you will see the insulation begin to shrink back. The best cable uses PTFE insulation, but you have to pay for it. The worst IMHO automotive cable bought at car accessory outlets is useless, I have been doing this for years and I still struggle with this crap, you just bring the iron near and the insulation shrivels up!

Practice, the better you get the quicker you will become, the quicker you become the less damage you will do to the insulation.

Hope this helps a bit.....

 

[Ships_Cat]

On a female connector (which is what you are using you say in your original post - BUT LOOK AT my final comment in this post FIRST as is very easy to be confused with BNC connectors) the ferrule fits over the inner conductor's (the wire up the middle of the cable) insulation (which is called the dielectric). It should have a little spigot on one side which pushes under the copper braid - the spigot can be seen on it in the drawing at the top of the instructions I gave the link to, it is the third component from the left under "BNC Type (Female), and in Step 3 you can see how the spigot is pushed under the braid so it cannot be seen.

Tinning the inner conductor is just gently heating the short length off which the inner insulation is trimmed off and melting a little solder over it so as it is shiny with solder (not a glob of solder though - if you get a glob just wipe the tip of the soldering iron clean of solder and then wipe the heated tip of the iron over the wire again). Then the little hollow pin contact is gently heated with the soldering iron and the tinned conductor pushed into it.

Looking at the exploded drawing in the link, working from the left the pieces are Clamp Nut, Pressure Sleeve, Ferrule, Rear Insulator, Contact, Front Insulator (in Step 5 they mistakenly call this the rear insulator again), and Body. It is assembled in that order too. After you have soldered the Contact pin on to the wire, the front insulator slips over it and then the body - the clamp nut then screws into that over all the other bits.

The item you are (probably) looking for is just a female BNC connector, they are called that all over the world. BUT BE VERY CAREFUL, while you refer to your connector as being a female one are you sure it is not a male one. You can see the difference in the drawings in the link - with BNC connectors, unusually, the the body of the female connector pushes inside of the male connector which twist locks over the female one. But if you look at the contact inside you will see that the male connector has a little solid pointed pin but the female connector has a little hollow one (the male solid pin goes into the female hollow one). In which case you need a male BNC connector which again only has one little soldering job but different components.

If it is a male one, then follow the same approach, the pieces go on in the order shown from left to right in the upper exploded drawing in the link.

John

 

[LeonF]

Hi John....many thanks for the private tutorial... hope it helps some other forumites too. I think I might have been missing one of the insulators from the plug I was using yesterday, so shall buy a new plug and try it. Yes the good plug had a litle male protruding pin, the female one is inset inside a white plastic insulator. One final question please. When the male is in contact with the female does the male actually fit inside the female ?? Its so small, and with the conductor and solder I wonder how it fits in... or is the conductor on the female plug not all the way up the silver sleeve, allowing room for the male ?? Thanks, Leon

 

[LeonF]

Re: Tinning wire

Hi Woofy
Don't mind the stalking, glad of the help. been looking at the plug pics you showed me..Looks confusing doesn't it, because I would always have imagined that the braid sleeve , the shiny tube, was somehow under the textured bit at the rear of the plug, but I guess it clamps the braid onto the textured bit ?? I may try another BNC as instructed by Ships Cat, but be useful knowing how to fit the plug you showed me.. it's a PL259 I believe ??..as this is the plug into the radio itself.
One last query please... is the crimpinging tool a special one..it looks too big to use the crimping bit of my wire cutter tool....can I buy one cheaply ??