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Old 30 June 2011, 05:32   #11
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Originally Posted by spartacus View Post
I did check the radio (ICOM M411) with a friend's hand-held and the signal came through loud and clear some weeks earlier. Admittedly it was a matter of some meters away, but I just wanted to check everything was working as it should.
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A VHF set doesn't need an antenna to receive local traffic - the cable will be enough for RX/TX within a marina sized area.

If the antenna is not connected properly, the VHF set may show some kind of alert when you try to transmit - like "ANT" or whatever - no guarantees though.
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Not sure if you are actually saying this but...

A transmitter must never be used without an antenae. (on TX) or you can fry the output stage.
Needs to be taken in context Gary - we're looking for a fault - might be an antenna/cable fault. Bit late for a warning - he's been using it already . Might fry the board - often it doesn't, many's the antenna got disconnected and the discovery made when there was no TX.
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Old 30 June 2011, 06:36   #12
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Originally Posted by Mollers
All was very quiet when I ran a correctly wired Rib Raider aerial. Swapped it for a 1.2m GRP whip, Ch16 burst into life. I reckon you have a twig issue.
Mollers you are always downing the RR!! Each to his own I have always used RR with no problems. On the recent ERR when I whooped up to force 6 st times and there were incidents involving Clyde CG & Oban & Islay lifeboats I never missed s call nor was I myself missed when hailing. So please stop your subjective general rubbishing of a perfectly good operational ariel. Even Willk herd me.

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Old 30 June 2011, 12:06   #13
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Before you do anything else (OP) check that you haven't shorted one of the connectors, which is easily done if you're not familiar with fitting them. Disconnect at antenna and radio. Use a multimeter to check that there is no continuity between the outer shell of the PL259 and the centre pin. Then, if you can, check that there is continuity pin to pin and shell to shell. Sometimes not possible to get the two ends of the cable close enough together for this one, but it is really important you pass the first test, no continuity between centre pin and outer shell. Remember you need to disconnect at antenna and radio ends or you'll just see a dead short on a multi meter.
When you make the connection at the PL259 you have to push the centre stranded core through the centre pin - this when it usually goes wrong - a single strand of that core gets bent back and creates a short. Don't transmit until you've got this bit right.
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Old 01 July 2011, 03:38   #14
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Thanks for all the replys. I tested it last night with a ICOM handheld. Left the boat in the garage and opended the door! Tried it at about 500 yards and the signal was loud and clear. Then drove about a mile and still managed to get a signal. I took off the connectors to make sure the centre-core hadn't strayed and resoldered them. Everything works as it should.
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Old 01 July 2011, 11:31   #15
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Before you do anything else (OP) check that you haven't shorted one of the connectors, which is easily done if you're not familiar with fitting them. Disconnect at antenna and radio. Use a multimeter to check that there is no continuity between the outer shell of the PL259 and the centre pin.
Doesn't always work. Digital Antenna's (the brand, not a description) show a short (or near-short; don't remember) when measuring resistance at the PL-259. I have no idea what's inside the antenna to do that, but I remember reterminating the cable 3 times before I measured the cable and discovered it.

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Old 01 July 2011, 11:45   #16
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That's why you disconnect the cable at radio and antenna. A multimeter tells you nothing about the antenna, most antennas show a dead short across the SO239 socket in their base.
To check that the cable and PL259 connectors are correctly fitted, the procedure is as I've described - it only works with the cable disconnected at antenna and radio.
To check the antenna system performance you need a VSWR meter, but I've never found one that comes with a competent operator attached to it so I don't recommend them to the average boater!
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Old 01 July 2011, 12:52   #17
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[QUOTE=Salty John;408794]To check that the cable and PL259 connectors are correctly fitted, the procedure is as I've described - it only works with the cable disconnected at antenna and radio.[quote]

Both the Digital mentioned earlier and my current Shakespeare have the cable hardwired at the antenna end.


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To check the antenna system performance you need a VSWR meter, but I've never found one that comes with a competent operator attached to it so I don't recommend them to the average boater!
LOL. Good to know.
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Old 01 July 2011, 13:31   #18
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Should also check that the aerial is properly in the base of the Metz and tight. On the Oban trip I could not understand why it was so quiet when so many RIBs were in the vacinity. Then I looked at the aerial and saw that the aerial was leaning back and only held in place by the red plastic boot. Another wave or two and it would have been over the side. Retaining nut nipped up........
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Old 01 July 2011, 14:56   #19
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Originally Posted by jyasaki View Post

Both the Digital mentioned earlier and my current Shakespeare have the cable hardwired at the antenna end.
Yep, that can be a problem. With a factory crimped joint at the antenna end you can't simply remove the antenna and take it home or stow it somewhere safe. Not as big a problem for RIBs as it is for sailboats with 25m of cable to deal with! But then again it's not likely to be knicked from the masthead.
Also, you don't get to choose your cable, you're stuck with the RG58 that comes with the antenna. And you can't eliminate the antenna end connector as a problem.

Losing the whip can be a problem with the aggressive motion of RIBs, you need to be sure the nut is pinched down really tight, or put a non-metallic tether on it - maybe a small cable tie with the end trapped under the base.
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Old 01 July 2011, 16:46   #20
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Quote:
Originally Posted by jyasaki View Post
Doesn't always work. Digital Antenna's (the brand, not a description) show a short (or near-short; don't remember) when measuring resistance at the PL-259. I have no idea what's inside the antenna to do that, but I remember reterminating the cable 3 times before I measured the cable and discovered it.
Yep, been there, done that

I don't know what the antenna internals are either, some sort of tuning coil I guess, but (on vehicle 2-metre band VHF aerials) I always found that the ones that show "open circuit" work better than the ones that show "short circuit" - not necessarily expensive ones either. So I usually take a multimeter when I go to buy a new antenna
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