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Last season the radio output dropped to very low. I traced the problem to high SWR in the mast wiring/antennae. I have fitted a new antennae and cable but the condition is still there. I have checked the radio output and the lead from the radio to the mast base and these are OK. Any suggestions please??
How are you detecting ‘low output’?
Do you trust your VSWR meter readings?
Have you tried the same tests on a known good antenna/radio combination?
Have you measured the radio on a ‘good’ antenna set up?
Apologies for all the questions but the answers may help us home in on the source of the problem.
Probably a stupid question….. what is your battery situation like?
Low input = low output?Thanks for the input, I used a power/SWR meter and a dummy load to confirm that the radio and the aerial lead to the base of the mast were OK. The radio was showing 25+watts output with minimal SWR. When I connected to the mast lead the SWR went up to over 5 and the radio out put dropped to almost nothing which it apparently does automatically to avoid damage. Replacing the antennae and lead hasn’t improved things.
@reddragon wrote:
Replacing the antennae and lead hasn’t improved things.
That’s disappointing. (I assume you have repeated the tests at the base of the mast using the VSWR meter with exactly the same results?)
Is there anything from the test point at the base of the mast working upwards that has not been changed e.g. a connector?
Is the new antenna and associated cable mounted at the masthead now? If not, maybe you can do some more tests at ground level. Can you substitute another radio and repeat the tests?
Did you test the new antenna/cable at ground level before mounting?
Is the aerial one of the VTronix ones (or equivalent) that has a 10K load across the conductors? If so, try a simple resistance test. If it’s not you will probably get a zero ohms reading.
If you have changed everything from the test point forwards then I am at a loss (no pun intended!) as to what is the cause of the continued high VSWR.
I have a VSWR of 3.5 on my masthead antenna(which is not good) – the cable at the base of the mast is waterlogged. We tried to replace it all a couple of weekends ago. Unfortunately, No 1 son couldn’t shift the nut on the base of the antenna (at the top of the mast) without seriously bending the bracket from the mast so we abandoned the job. A quick call to Solent CG from Northney (not direct LOS) received a “loud and clear” response so I will live with the problem until next winter. I would be much happier with a VSWR of 1.2, though, which is what I get from my AIS (and hence spare VHF) antenna on the pushpit!.
If you are getting 5+ (and the radio is performing auto power reduction) then it really needs fixing.
Good luck.
Roger
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