G
Guest
Guest
This may sound like a dumb ass stupid question but could somebody explain how to fit the standard VHF connector to the aerial coax.
Chris_Stannard
New member
You have to connect the inner core to the pin that goes through the centre and this will almost certainly need soldering, the shield is then connected to the out part of the case. If you are not used to soldering it is best to get someone who is to do it as a bad joint means reception but no outward transmission.
Chris Stannard
Chris Stannard
G
Guest
Guest
Thanks for the advice Chris
pandroid
Active member
You may need a 'reducer'. The normal PL259 is made for UR67 which is about the size of a copper pipe. UR42 needs a smaller hole. If you dont have a reducer, wrap some tape round the cable to make it bigger
wooslehunter
Active member
PL259 are poor connectors. Unfortunately most radios have them fitted at the back. It's far better to use BNC connectors. Fit a PL259 to BNC adaptor to the back of the radio and a BNC to the cable.
You will often find a digram showing how the BNC goes together in the pack it comes in. Be careful though since some are crimp only and to fit those properly you need an expensive tool to crimp both the inner and the outer. Use the solder type where the inner is soldered and the outer is clamped. The cable is normally strain relieved as the plug is screwed together if the cable is the right size.
Don't skimp on the cable or the connectors. Buy good quality and they'll last far longer. Moisture in the cable can cause problems as can badly fitted plugs. Unless you have a VSWR meter then it's not really possible to check how your insallation is really performing. Your radio could be your lifeline.
Dave.
You will often find a digram showing how the BNC goes together in the pack it comes in. Be careful though since some are crimp only and to fit those properly you need an expensive tool to crimp both the inner and the outer. Use the solder type where the inner is soldered and the outer is clamped. The cable is normally strain relieved as the plug is screwed together if the cable is the right size.
Don't skimp on the cable or the connectors. Buy good quality and they'll last far longer. Moisture in the cable can cause problems as can badly fitted plugs. Unless you have a VSWR meter then it's not really possible to check how your insallation is really performing. Your radio could be your lifeline.
Dave.
pandroid
Active member
....and make sure its a 50 ohm one and not 75....
Roberto
Well-known member
Dave, why are pl259 poor connectors? In HF radio for example, supposing you have the whole lot: radio, atu, baluns, antennas etc all fitted with pl259, wouldn't interposing 2 bnc connectors at each junction reduce signal strength too much?
just interested, I have pl259 everywhere with no particular problem (save for an emergency crimped terminal I was forced to use instead of all the other soldered ones, thrown away now) )and wonder if it could be better with bnc, which by the way are much easier to find here..
thanks
<P ID="edit"><FONT SIZE=-1>Edited by Roberto on 28/01/2003 14:59 (server time).</FONT></P>
just interested, I have pl259 everywhere with no particular problem (save for an emergency crimped terminal I was forced to use instead of all the other soldered ones, thrown away now) )and wonder if it could be better with bnc, which by the way are much easier to find here..
thanks
<P ID="edit"><FONT SIZE=-1>Edited by Roberto on 28/01/2003 14:59 (server time).</FONT></P>
DavidTocher
Member
PL259 and SO239 (the matching socket) have a poor impedance match at VHF frequencies. If P259/SO239 is used then there is some reflection at the junction which raises the SWR.
BNC plugs and sockets provide an almost match to the coax cable up to UHF frequencies. Another big advantage is the diamter of the plug is much smaller. I have an unbroken run of coax from the antenna to a BNC plug crimped at the radio end. The BNC plug is small enough to go through a gland in the deck. When I take down the mast I can disconnect the plug from the radio and pass it through the gland without unsoldering/removing it.
BNC plugs and sockets provide an almost match to the coax cable up to UHF frequencies. Another big advantage is the diamter of the plug is much smaller. I have an unbroken run of coax from the antenna to a BNC plug crimped at the radio end. The BNC plug is small enough to go through a gland in the deck. When I take down the mast I can disconnect the plug from the radio and pass it through the gland without unsoldering/removing it.
ccscott49
Active member
I don't doubt you, but it beggars the question, if PL259/SO239 connectors are a mismatch at VH frequencies, why do the manufacturers of VHF equipment all fit them as standard on the sets, they are more expensive than BNC, so why?
DavidTocher
Member
BNCs are designed to be used with thin coax such as RG58 or RG59. The usual coax for HF and VHF fixed radio installations are coaxs like RG8 which much fatter and have lower losses. PL259s can be fitted to either thickness coax. If fat, low loss, coax is required then for a proper RF connection N types are more suitable. They are, of course, expensive.
ccscott49
Active member
Every antenna I've ever seen or bought for VHF radios in marine (leisure) use, are supplied with small cable, obviously the RG58/59 (I'm not sure of the nomenclature) so that doesn't wash for leisure use. On the rig here, where long runs of coax are used, they do use the big stuff mainly for resistance to weather chafe etc. and in fact all my internal wiring for my VHF's is the big stuff, but the cable to the mact head is small, as will be, no doubt 95% of all tyhe VHF's in use on yachts, so why the PL259 connections on the sets? The big N type I have seen, in fact my masthead phone antenna is fed with one and a big cable with solid copper core, bloody expensive stuff that is! Many VHF radios today are aimed directly at the leisure market, is it not time to move over to BNC? The new sets I saw at the show were PL, seems a bit silly to me, being logical about it.
Strathglass
New member
It's just a matter of convienance for the manufacturers of the sets.
As David has said PL259 present a very poor match at VHF frequencies. On VHF sets those losses will not be noticed by the users and PL259 are much more end user friendly than BNC especially when larger cables are used.
There are various connectors both larger and smaller which give a very good match up to UHF frequencies but they require quite a lot of skill and experience to assemble. Even some makes of BNC connectors require specialist tools.
PL259 whilst not the best are generally considered adequate for Marine VHF use.
PL259 plugs are manufactured with rear hole sizes to match various diameters of coax cable, although many marine stockists will only stock one size in a prepacked package.
Even using a PL259 to BNC adaptor in the back of the set then terminating the cable in a BNC plug will not significently enhance the match, although it may make joining the coax to a plug easier for some.
Iain
As David has said PL259 present a very poor match at VHF frequencies. On VHF sets those losses will not be noticed by the users and PL259 are much more end user friendly than BNC especially when larger cables are used.
There are various connectors both larger and smaller which give a very good match up to UHF frequencies but they require quite a lot of skill and experience to assemble. Even some makes of BNC connectors require specialist tools.
PL259 whilst not the best are generally considered adequate for Marine VHF use.
PL259 plugs are manufactured with rear hole sizes to match various diameters of coax cable, although many marine stockists will only stock one size in a prepacked package.
Even using a PL259 to BNC adaptor in the back of the set then terminating the cable in a BNC plug will not significently enhance the match, although it may make joining the coax to a plug easier for some.
Iain
ccscott49
Active member
If the mismatch won't be noticed by the user, what was the point of this discussion in the first place? Would it not have been just as convenient to fit BNC in the first place? BNC are no more difficult to fit than PL259, BNC connectors are available for bigger cable, I still don't see the point, but will just accept that it's the way it's done, thanks for the input.
Strathglass
New member
Like a lot of things on this forum there is no rythm or reason.
Still it's nice to chat. Very often in between ite irrelevances there exists a little gem of information. I have to go out now so I will have to clear the snow away first.
Cheers Iain
Still it's nice to chat. Very often in between ite irrelevances there exists a little gem of information. I have to go out now so I will have to clear the snow away first.
Cheers Iain
ccscott49
Active member
Iain, Yes it is often informative, thats why I'm here, thanks for all your input, I may yet convert to total BNC!!
Colin.
Colin.
john_morris_uk
Well-known member
O what a lot of truths and half truths...
Impedance and mismatch at RF frequencies is a subject much misunderstood.
Can't resist making a couple of points though!
Firstly for manufacturers of radios the SO239 connector is cheaper! Its also relatively easy for many people to fit PL259's. Fitting a BNC connector to provide a correct match is NOT as easy.
Secondly, if your cable is going through the SO239/PL239 route then there is no advantage going to a BNC then an adapter to PL259 - the mismatch will still be there. If you really want to make a better match (and for the average yacht purposes it is dubious whether you will see/hear any difference) then you have to change the SO239 on the radio. Whats the point? Look at the losses involved and look at the S/N ration that we usually work with and you will see what I mean.
Finally, the comment regarding degrading of signals by moisture/water in the coax is true - but you won't detect it with an SWR bridge. In fact one of the ways of measuring loss in cable is to measure the VSWR with the other end open circuit or short circuit (in other words a total mismatch) There are graphs available that tell you from the VSWR what the loss in the cable is. (Don't try it with your yacht VHF or you may damage the transmitter!)
Finally finally, please use a proper adapter when fitting a PL259! Tape round the outer is worrying - both the braid and the inner connections are critical for best results.
Happy sailing!
Impedance and mismatch at RF frequencies is a subject much misunderstood.
Can't resist making a couple of points though!
Firstly for manufacturers of radios the SO239 connector is cheaper! Its also relatively easy for many people to fit PL259's. Fitting a BNC connector to provide a correct match is NOT as easy.
Secondly, if your cable is going through the SO239/PL239 route then there is no advantage going to a BNC then an adapter to PL259 - the mismatch will still be there. If you really want to make a better match (and for the average yacht purposes it is dubious whether you will see/hear any difference) then you have to change the SO239 on the radio. Whats the point? Look at the losses involved and look at the S/N ration that we usually work with and you will see what I mean.
Finally, the comment regarding degrading of signals by moisture/water in the coax is true - but you won't detect it with an SWR bridge. In fact one of the ways of measuring loss in cable is to measure the VSWR with the other end open circuit or short circuit (in other words a total mismatch) There are graphs available that tell you from the VSWR what the loss in the cable is. (Don't try it with your yacht VHF or you may damage the transmitter!)
Finally finally, please use a proper adapter when fitting a PL259! Tape round the outer is worrying - both the braid and the inner connections are critical for best results.
Happy sailing!
ccscott49
Active member
<O what a lot of truths and half truths...
Impedance and mismatch at RF frequencies is a subject much misunderstood.>
My sentiments entirely. I wouldn't use adapters anyway, what's the point?
Impedance and mismatch at RF frequencies is a subject much misunderstood.>
My sentiments entirely. I wouldn't use adapters anyway, what's the point?
john_morris_uk
Well-known member
By 'adapter' I was assuming the previous post was referring to the "reducer" that enables RG58U etc to be fitted to a standard PL259. (although the reducers come in different sizes as well!) Perhaps my comment should read "Please don't use tape when connceting thin coax to a PL259 - use a proper reducer!
Fair winds and may all your impedances make a reasonable match...
Fair winds and may all your impedances make a reasonable match...
G
Guest
Guest
2 questions
1/ are you supposed to feed the braid through the hole in the body of a 259 and then solder it ? or do you rely on the mechanical contact of the screw thread on the braid with insulation removed?
2/ someone suggested to me that it was possible to dry out coax with water in the braid by microwaving at home. not recommended since coax is so cheap, but would it work or would the metal in the coax cause problems in the microwave?
1/ are you supposed to feed the braid through the hole in the body of a 259 and then solder it ? or do you rely on the mechanical contact of the screw thread on the braid with insulation removed?
2/ someone suggested to me that it was possible to dry out coax with water in the braid by microwaving at home. not recommended since coax is so cheap, but would it work or would the metal in the coax cause problems in the microwave?
ccscott49
Active member
1) You can solder it, but an adequate connection will be achieved by the ferrule. If it's small cable and you use the screw in adaptor, bend the braid back over the adapter ferrule, it will then make contact.
2) Never put anything metal inside a microwave, unless you want to see some foreworks. If your co-ax gets wet inside, forget it and renew it.
I always seal my connections, with glue/heatshrink, or self amagamating tape, that should keep the water out.
2) Never put anything metal inside a microwave, unless you want to see some foreworks. If your co-ax gets wet inside, forget it and renew it.
I always seal my connections, with glue/heatshrink, or self amagamating tape, that should keep the water out.
