VHF signal

spartacus · 27 June 2011, 18:56

I should have completed a radio check yesterday with the coastguard - but I had other things on my mind after destroying my wife's digital camera after it ended up in the bilge, and car problems. We were out at Cruden Bay (saw a couple of yachts and usual North Sea traffic in the distance). Switched on the radio - but no conversations on any of the channels. 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. The antenna is Metz, and it's mounted on a handrail (adapter) on the console. The antenna cable plugs were soldered too. I just want to double-check. I assume the outer coaxial mesh (that's revealed when you cut it), simply folds back - as per a TV antenna and makes contact with the plug - and the centre plug is soldered into place. Any suggestions?

Vandad · 27 June 2011, 19:22

How long did you leave the Radio ON for? You should have performed a channel scan to see if there is any conversation other channels.

What I normally carry is a handheld radio. If I get suspicious about my main radio, I switch the handheld ON to make sure there is NOT really any signal!

I had a massive problem last month with my Radio, I could receive but not transmit and I realized nothing is wrong with my radio, or antenna, I was just simply in a bad location.

spartacus · 29 June 2011, 06:06

Thanks for that. Radio was on for around 5 minutes. I did a quick scan. I'm borrowing a handheld from a friend so I can test again.

jyasaki · 29 June 2011, 15:45

Should be able to do a check with any vessel on something other than channel 16 (In the US, channel 9 is the non-emergency hailing freq; though not too many recreational boaters know that.) Local marinas and the like should be able to respond as well, assuming you know their working channel.

If I suspect my VHF is acting up, I try to find something to report to the Coast Guard, contact them, then change my mind, telling them it's not as important as it seemed when I initially made contact. Perhaps not exactly kosher, but it gets the job done without ruffling too many feathers.

jky

Erin · 29 June 2011, 16:02

Quote:

Originally Posted by spartacus

I assume the outer coaxial mesh (that's revealed when you cut it), simply folds back - as per a TV antenna and makes contact with the plug - and the centre plug is soldered into place. Any suggestions?

Sounds about right, though obviously corrosion can creep in and affect the contact after a while. Take care not to transmit if the aerial is not connected properly or at all as you can damage the radio.

spartacus · 29 June 2011, 19:22

Quote:

Originally Posted by Erin

Sounds about right, though obviously corrosion can creep in and affect the contact after a while. Take care not to transmit if the aerial is not connected properly or at all as you can damage the radio.

Everything is new, including the fixed ICOM 411 set, connectors, Metz antenna, cable, etc. Centre core is soldered in place.

spartacus · 29 June 2011, 19:23

Quote:

Originally Posted by jyasaki

Should be able to do a check with any vessel on something other than channel 16 (In the US, channel 9 is the non-emergency hailing freq; though not too many recreational boaters know that.) Local marinas and the like should be able to respond as well, assuming you know their working channel.

I know I'm not meant to do a radio check inland (25 miles from the coast with plenty hills) - but who's likely to hear? I was going to contact my wife on channel 69, while the boat is on the drive. I've borrowed an ICOM handheld for a couple of days for this purpose. Sound like a plan?

willk · 29 June 2011, 19:49

A few random thoughts - not casting any Nastursums...

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.

Was the Volume on and the Squelch set properly during the first trial at sea?

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.

The handheld test 25 miles from the coast is how I caught a broken antenna cable on my old rig. Don't expect to get much range when OK - maybe 3-4 miles at best in lumpy or wooded terrain.

As for the 69...

Mollers · 29 June 2011, 21:16

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.

GaryC · 30 June 2011, 08:48

Quote:

Originally Posted by willk

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.
:

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.

My understanding is that if you are going to test reception then you need the other radio TX to be quite a way off as otherwise you get the bleeding effect onto the amp stage. i.e you are not really receiving but getting interference.

Gary

willk · 30 June 2011, 09:32

Quote:

Originally Posted by spartacus

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.

Quote:

Originally Posted by willk

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.

Quote:

Originally Posted by GaryC

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.

jambo · 30 June 2011, 10:36

Quote:

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.

J

Salty John · 30 June 2011, 16:06

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.

spartacus · 01 July 2011, 07:38

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.

jyasaki · 01 July 2011, 15:31

Quote:

Originally Posted by Salty John

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.

jky

Salty John · 01 July 2011, 15:45

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!

jyasaki · 01 July 2011, 16:52

[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.

Quote:

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.

Richard Selman · 01 July 2011, 17:31

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........

Salty John · 01 July 2011, 18:56

Quote:

Originally Posted by jyasaki

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.

BogMonster · 01 July 2011, 20:46

Quote:

Originally Posted by jyasaki

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