Wiring VHF antenna

[Plymade]

I have just bought a new VHF antenna with a solderless connection at the antenna. when I connect it as per instructions the outer sheath & inner core at the plug end show no ressistance between them. Also the mounting point at the antenna, the threaded bit, shows no resistance when a meter is put between that & the whip. The antenna is not working correctly as I can receive some signals on my handheld that I cannot on my main set. any ideas?

 

[wooslehunter]

Most antennas show a short at the plug but it's not necesarily so. Yours could be desigend to show an open circuit.

The only way to really test an antenna is with a VSWR meter.

With a multi-meter the best you could do is measure continuity between the plug pin & the top of the cable & then the plug outer and the shield at the top. If that's OK then it has to be a problem with the antenna end connection.

What's the antenna? Was the plug pre-attached?

 

[Plymade]

The Antenna is a Banten windex & the plug was not pre-attached. I've sort of tested by plugging it into my AIS & it only seems to find v.close targets slowly while the dedicated AIS antenna, from a RIB detects lots of targets. Also there is continuity between the plug & my mast.

 

[Bilgediver]

I know us fellows think we know best and so avoid reading instructions. In the case of some VHF antennas it is critical to do exactly as the instructions say regarding how you prepare the end of the lead you insert intpo the antenna. Some use a metal washer trapped by the outer braid and the inner core is cut with the wire flush with the insulation as the connection will be made by a pin in the antenna piercing between the cores of the feed. This doesn t work so well with a single core centre feed.

Some antennas the thread is PLASTIC ...

Chech you have followed the instructions as on a few occasions that was the only white mans magic I used to get the radios on friends boats working.

John

 

[jonathankent]

I too had problems with a Banten antenna.... put it together as per instructions, and then nothing.

I took the whole thing apart this year and started again, and this time got it working. I hadn't cut back enough of the core to insert into the base of the antenna and therefore the core and the pin weren't in contact.

I too tested the resistance... nothing before, but once connected there was resistance and I knew it had to be the connection in the base of the antenna as I had already checked the plug itself.

Once fixed I could receive MSI broadcasts from 60nm away (across open sea) with the mast horizontal on the deck - worth a try.

I suggest you cut off the end and start again with a fresh end into the antenna.... and add a little extra to the core distance.

 

[nigelmercier]

[ QUOTE ]
I have just bought a new VHF antenna with a solderless connection at the antenna. when I connect it as per instructions the outer sheath & inner core at the plug end show no ressistance between them...

[/ QUOTE ]

I think we need to establish terms here: when you say "no resistance", do you mean there is a short-circuit? This would be the correct interpretation, but I suspect you actually mean it is open-circuit, i.e. very high resistance.

The latter is what you would expect, there is no DC connection between the core and the sheath.

 

[brianrunyard]

Most VHF antennas show a DC "short" between inner and outer at the plug.
The only way to check is with a VSWR meter.

 

[Salty John]

I think the Banten terminates in an SO239 to accept a PL259 plug, so I assume you are referring to a solderless PL259. If you have one of those "strip the cable and stick it into the antenna things", ignore the following!
On the antenna, detached from the cable, a multimeter will read 0 (dead short) between any metal point and any metal point and 1.0 between any metal and any plastic.
The PL259's attached to the cable, detached from radio and antenna, should show 1.0 (no circuit)between centre pin and outer shell, and 0 (continuity) between the centre pins at each end and between the outer shells at each end.
I hope this helps.

 

[brianrunyard]

[ QUOTE ]
should show 1.0 (no circuit).

[/ QUOTE ]

1.0 what?
An open circuit should read infinity.

 

[Salty John]

Correct. But most multimeters (at least the type I use) read 1. to indicate this.

 

[jonathankent]

Yes... but 1 and then 3 gaps where the other digits shoud be.... i.e. not 1.0 Should try to read 9999 and then go off the scale.

And the Banten antenna that I've got does have a normal soldered PL259, but a 'cut it and stick it in' connection on the base of the antenna.

 

[Honey]

I too have this antenna and have been unable to get it to work. As the mast is now back up I have rigged the old antenna as a temporary job on the backstay and will fit a better antenna at the mast head next year!

 

[Salty John]

OK.
1___.
NOT 1.0
Jeez!

I don't understand your second comment.

 

[brianrunyard]

Ahhhhh, you're using a digital meter, I use an Avo.

 

[jonathankent]

Which bit don't you understand?

The antenna end is the 'cut and stick it in' and then at the other end is a normal PL259 plug for the VHF... i.e. there isn't any different connectors, e.g. SO239.

Hope it now makes sense.

 

[Plymade]

By no resistance I mean a current can flow without resistance, ie '0' on the meter. The same as touching the prongs together

 

[jonathankent]

In that case, if you are getting that and still not getting the proper reception possible on the handheld, I would disconnect the coax from the antenna and check the resistance across the PL259 alone - this should not have any connection. Then you can be sure that the resistance is purely coming from the antenna, which if its the same model as mine you will get a circuit. Be sure to wrap the shield back along the coax properly and make sure you have enough core 'poked' into the antenna - I had to cut slightly longer than the instructions in order for it to work. If a proper connection is made it will out perform the handheld by miles.

Hope that helps.