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Old 06 July 2011, 13:12   #1
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Technical VHF question - poor rx and tx

Just started to have a problem with my fixed Icom m505 vhf set. It's been fine for the last 3 years but has just started with an intermittent fault.

When being first turned on it seems fine for a short while but then suddenly stops receiving and I think doesn't transmit properly either. I have found that it will just about receive when the squelch is turned right down to the point that there is a permanent hiss, but the minute the squelch is turned up to cancel the hiss it will stop receiving. It seems to be ok when tested with a handheld close by. I've yet to try a radio check with a bit more distance.

My question for any radio guru's is..... does this sound like an aerial problem or a set problem. What intrigues me is that the problem is intermittent. Recent testing was with the boat dried out so there is unlikely to be a vibration or movement issue causing this. I've played with the connections and wires and checked everything I can, but can't solve it.
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Old 06 July 2011, 18:01   #2
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Poor connection to the antenna? Try cleaning up all the connectors (stainless wire brush should do if you can get it in to the connectors, or get some contact cleaner from a local electronics store.)

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Old 06 July 2011, 19:21   #3
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Aerial or coax problem. Radio checks are short range are misleading - they almost always work
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Old 07 July 2011, 04:14   #4
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Quote:
Originally Posted by jyasaki View Post
Poor connection to the antenna? Try cleaning up all the connectors
jky
I've remade the connection at the aerial and checked the coax for any damage but nothing obviously wrong. It's just a bit odd that it's ok one minute then not the next, though yesterday it was working for less time than ever.
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Old 07 July 2011, 04:30   #5
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Can you investigate the squelch off operation a bit more? Can you hear distant stuff ok, or is the performace still not right?
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Old 07 July 2011, 06:35   #6
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Can you run a VSWR check on the setup?? if so try this whilst flexing the coax at the extreme's then work along the length
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