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Portable VHF - external antenna connection

I have this installed on my panel: my external antenna is connected to a jack, into which I can plug a 4-feet cable which has a BNC plug on the other side; so I can use my external antenna for my portable VHF. Unfortunately the cable’s broken, and ICOM doesn’t sell it separately (not even sure they still do the switch box). I can’t find anything on the web for jack-to-BNC cables, does someone have pointers to where I could source one?

EGTF, LFTF

What looks like a 3.5mm single pole jack to BNC cable is totally nonstandard and probably not good from the impedance matching POV but I will happily make one for you. Just make sure the jack is really single pole

and not say 2+ pole

Administrator
Shoreham EGKA, United Kingdom

I’ll check and revert, actually pretty sure it’s 2 poles

EGTF, LFTF

In that case I would have to open it up. Actually the most likely place for the break is inside that 3.5mm jack plug They have a notoriously crappy cable security arrangement.

Administrator
Shoreham EGKA, United Kingdom

There’s good reasons why you won’t find jack to BNC connectors. Can you not replace the jack on the panel with a BNC? This would be much better.

Andreas IOM

I reckon they are using a switched 3.5mm socket, to detect the plug insertion and switch over the RF. Or using the 2nd pole to power a relay coil which switches the RF.

It is possible to auto detect the insertion of a BNC plug, by putting in a small DC leakage current, but that is more work

I presume that metal box is powered from the aircraft. If not then god knows how they did it… must be using the switch on the socket to switch the RF directly (ghastly).

Administrator
Shoreham EGKA, United Kingdom

It is an ordinary 3,5mm mono jack (a mono jack has 2 poles). Not the best for HF, but pretty common as antenna plug for SW-receivers. You find it in every radio/electronics shop.

(A German Link would be e.g.: https://hamradioshop.net/Koaxialkabel/Koaxialkabel/Adapterkabel-BNC-auf-3-5mm-Klinkenstecker.html )

Germany

Ah that was the trick, look for “3.5mm to BNC” rather than “jack to BNC” :-) Thanks!

EGTF, LFTF

Turns out it’s monopole

EGTF, LFTF

If you can’t get it, I can make one up for you. The connections are obvious, I would say.

Administrator
Shoreham EGKA, United Kingdom
11 Posts
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