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Old 16 May 2011, 14:51   #1
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VHF Antenna and Cable...HELP!

Guy, I am fed of this! honestly....

I curse at myself every time I am on the rib, why I opened the old antenna and cables which were working ok and then decided to install the one which does not work.

In short, the Radio does not transmit/receive through the Antenna.

There is something very weird which I can not explain it, so I need your help. When I lift the coax cable the radio seems to work. It is not a loose connection as I tested the cable, it is all to do with the NOISE affecting the cable I suppose...

How do you guy pass your VHF radio cable in the rib? Is it next to other cables which runs from console to the engine (steering cable, engine cables, battery cables etc.) or not?

Thanks.
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Old 16 May 2011, 14:58   #2
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????
Cant really understand your problem could you give more concise detail
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Old 16 May 2011, 15:02   #3
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The problem is that everything is connected, and some weird noise is affecting the transmission.

One end of the cable is connected to the radio and the other end is connected to the antenna. I have tested it and the connection is OK. So I know that it is def connected!

But I can not transmit anything or even receive anything (sometimes I can hardly receive but it is full of noise) but once when I was cleaning the rib I lifted the cable and suddenly I noticed that the radio started to broadcast and once I put the cable down it stopped, tried again and it started working again, and by moving the cable I could see that the noise level changes on the broadcast...

So I am confused now. Not sure if I should change the cable, change the antenna, change the radio or....!
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Old 16 May 2011, 15:07   #4
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Ok how did you test the cable? did you check continuity of core and screen? and did you check insulation between both?
also to test I guess you moved the cable? can you be sure there is not an intermitant fault / Break in the core that you cant test i.e. ok when tested but not when laid back down?
Have you used a VSWR meter on the installation ?

Mods could you move this to "Electronice" please
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Old 16 May 2011, 19:48   #5
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Ashby is going down the right lines with this. Moving the cable will rectify a loose connection or may reconnect a break in the cable. My money would be on the core where it passes into the pin of the BNC connector. If it's multi strand get a small drill and send it down the end to "bell" out the strands. If it is solid core, remove the connector, put a slight kink in the core and then replace the connector. This would normally ensure that the core contacts with the pin.

HTH
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Old 17 May 2011, 04:22   #6
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It could be the plug/socket connection between radio & cable, the cable might be ok & test ok, but the pin could be a poor fit on the PL59 plug on the back of the radio. Clean the centre pin & make sure it's a good fit into the VHF socket.
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Old 17 May 2011, 13:58   #7
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This is almost certainly a bad connection, either at the antenna or the radio. At the radio end it will be a PL259 connector. You need to check that no part of the centre conductor is bent back and is connecting with the body of the plug. To check this you need to disconnect at the antenna and radio and use a multimeter to ensure that there is no circuit between the outer shell of the plug and the centre pin. (If you don't disconnect at the antenna you'll see a dead short anyway). The centre wire should be soldered into the plug pin and if it isn't it may be only making intermittent contact with the pin, when you jiggle the cable.
I don't know what antenna you have; if it has a PL259 connector in the base, same advice as above. If it is a Vtronix or Glomex proprietary factory crimp connection, I don't know what to advise.
Don't transmit until you find the problem or you could damage your radio.
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Old 17 May 2011, 18:52   #8
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If the cable is sound, then the main culprits are either the inner core is not soldered correctly to the plug pin or the outer conductor could have a bit of wire loose intermittently makeing a short.

As someone has said transmitting with a faulty cable (especially a short) could damage the set.
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