vhf antenna connection

[sparkie]

Just bought a new antenna (Banten) cable and plug complete. The (minimal) instructions for connecting the coax to the antenna appear to indicate that the inner core is not stripped but merely shoved up into the antenna base with the sleeve intact. Does anyone know if this is correct? Surely a metal to metal contact is required at this point? Don't want to make a booboo with the mast down between tides!

Also, when testing the antenna connection with a multimeter, there appears to be no electrical separation between the outer metal and the inner core socket. Presumably this is correct, but how does the screen work if it's all connected together?

As you will guess I'm not really a sparky, despite the pen name!

Sparkie



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[Strathglass]

The instructions are correct. You cut the coax as directed and bolt it together.
The DC resistance has no relevance with respect to RF impedance. There may be some form of matching built eithin the aerial which would read an effective short circuit to DC.
I have a SL VHF aerial which uses solderless cable connections. Not happy with it but that is how the aerial is designed to be used.

Iain

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[gjeffery]

I am curious about this. Yes, continuity on the core conductor is required. I have just bought a VHF whip, and the cable plug on the antenna base is the solderless type. The core insulation sleve is stripped back by 6mm and the central conductor is bent back. The core insulation is then pushed into the socket, the bent over core wire making (hopefully) a sound connection. The screen is clamped up in a relatively usual way.

If you test continuity across the cable, while the cable is not connected at either end, then there should be an open circuit.


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[sparkie]

Iain--

Thanks for the response- just one further question- how does the signal get into the core if there is no metal to metal contact?

Sparkie

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[Strathglass]

But there is metal to metal contact (initially) as there will be a small spike which makes contact with the central conductor.
For long term reliability it depends on you preventing any salt laden moisture from entering the coax cable and connectors by the use of sealing mechanisms such as self amalgemating taps.
In order of priority I would prefer
1 crimped connection
2 soldered connection
3 solderless join

But I find that the aerial I have purchased was marketed/manufactured by the now defunct SL.

Such is life.

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[upstream]

Make sure you have a good conection with the centre wire, solder is obviously the best but if your pin is one of the dry push in type, it will break down over a period of years. A poor joint can damage older types of radios as the transmittion engery cannot get up to the arial and therefore bounces back down into the set and pops it.

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[sparkie]

Thanks for the responses all. From what's been said it looks as if I've bought a low spec item, as the mast comes down every year it may be prudent to re-make the antenna connection from time to time. Sea trials this weekend if it stops raining and blowing long enough to get the mast down and up again!

Safe sailing

Sparkie

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