That is a PL259 connector, horrible type of plug IMHO.

Strip back 20mm of the outer insulation and tease the braid of your cable back. Strip back 15mm of the insulation from the centre conductor, flux it and tin with solder. Feed the centre cable into the centre pin of the PL259 and screw the cable into the shell of the plug. This provides a grip on the cable and connects the shell to the braid of the cable. Solder the centre tinned cable to the centre pin. Trim the tag end and you are done.

 

Have a look here Dan words AND pictures!

http://www.wescomponents.com/datasheets/PL259.htm

 

Or here;

http://www.lnl.com/howto/termination/uhfc.htm

 

....and...http://www.lnl.com/howto/termination/uhf.htm.

 

What sort of plug would you use instead ChrisP?

 

Unfortunately all VHF radios are fitted with a SO259 socket so you can only use a pl259 to conect up your ariel. They are a messy large plug to connect and being screw fitting tend to vibrate loose on a boat. A much nicer, more secure and more compact plug are the TNC's used for networking.

 

Coax connectors on a boat are similar, or identical, to the connectors on the back of your telly. The difference is marine plugs are supposedly non-corrosive so you can't use domestic ones.

 

Speaking of being non-corrosive only yesterday I went to reconnect my vhf to the antenna and noticed that the cable has corroded inside the connector it had all turned green I assume some sort of oxidation. I stripped back the cable and the braided cable around the core had basically rusted. I has to take it back about a metre before it looked ok. This is in a wheelhouse!!

I dont think the sea pays much attention to whether something is non corrosive or not!!

MarieK

 

thanks for the replies, though I have no idea what tinning is and do not own any soldering equipment

Any alternatives to soldering?

 

Tinning is coating the bare copper wth solder, there is no alternative to solder, if you have a bad connection here it will fry the power output transistors on the VHF so the plug needs to be soldered on.

 

Dan,

Gimme a call for soldering gear.

 

Hi Chris, I am very reluctant to contradict your invariably excellent advice, but I hope you won't mind on this occasion.

The vast majority of modern VHF transcievers have an output level control (ALC) built into the transmitter such that if the transmitter 'sees' an increase in the voltage standing wave ratio, (VSWR) to the antenna, (ie a bad connection to the antenna), the output power of the transmitter is automatically reduced in proportion to the 'badness' of the connection.

I have lost count of the number of marine VHF radios I have been called to service because of 'poor reception' which when I have put an output power meter on have been transmitting milliwatts because the ALC has limited the power output on account of a lousy VSWR.

So a bad antenna connection on a modern radio will not damage the tranmitter side of the transciever, as you suggest, because the transmitter will simply not put out enough power to allow it to be damaged.

Hope you don't mind me chipping into this one.........

Cheers
PB

 

Not at all mate, I try to be as accurate as I can with my answers, to me it is what the site is about. I was not aware of the new bit of tech that had been added to VHF. It used to be that the power transistors were blown, getting old now, sometimers is setting in.

I get a lot of calls to VHF problems and 90% are a fault in the plug or the arial, the set is fine when put on another arial.

Thanks for updating me, I appreciate it

 

Does anyone mind if I add that valuable tip (new to me after 35 years of dabbling) to my web site? As Chris says, learning new stuff is what makes this site so great - and the folk who pass it on, of course.

 

Dan,

Gimme a call for soldering gear.

Cheers gordon I will do, soon as fraser is about and we are actually going to get this boat finally sorted out Ill get in touch cheers

Dan

 

Salar - you may also wish to mention, if you don't already, that in order to keep the VSWR to a minimum, that is a close to 1:1 as possible, the antenna cable must be cut to a whole number of half wavelengths in length. This is important when you consider that a VSWR of 1.5:1, (a mildly bad connection to the antenna), will reduce your actual radiated power from 25 watts to 24 watts, a VSWR of 2:1 will reduce it to 22 watts and a VSWR of 3:1 will reduce it to 18 watts simply because power is being reflected back down the antenna cable instead of out of the antenna. When the VSWR goes beyond 3:1 protection circuits in the radio will start to shut the tranmitter down.

Half a wavelength for the marine VHF band is 0.925 metres. So if you must cut your antenna cable measure it carefully back from the base of the antenna by a whole number of 0.925 metres.

OK, this isn't an amateur radio site, but I thought this might be useful for someone..

PB

 

Thanks, it will turn on my site soon!
Cheers