VHF pulling 8A while transmitting when it should be 5A

[sebastiannr]

Hi there,

I have a Sailor A1 VHF. When transmitting on high power it pulls 8A instead of 5A as the manual says it should. If the batteries aren't fully charged it turns itself off when I try to transmit, which I believe it's supposed to do if it's not got enough power. With fully charged batteries and prolonged transmitting the circuit breaker for the radio 'breaks'.

My instinct would tell me that it's an antenna problem, but I recently renewed the antenna and cable, and tested for continuity and shorts, so I don't think it's that (at least I hope it's not - embarrassing coaxial soldering fail). I have done a successful radio check (well, 500m away in the dingy, hardly a radio check I admit) so it does transmit and receive, but it's no good if I need the motor running to have enough power to use the VHF!

I've been trying to fix this for some time but can't figure out what the problem might be. If anyone has any ideas I'd love to hear them. Is it likely to be a problem with the radio itself, is it more likely there's a short somewhere, or do I need to triple check the antenna?

Many thanks!

Seb.

 

[nigelmercier]

... do I need to triple check the antenna?...

Yes, with a SWR meter.

 

[srm]

You could also check your power supply for damaged cable, dirty or corroded terminals etc. I assume your batteries were originlly of sufficient capacity but are they still up to the job? When I bought my boat the fridge refused to run due to voltage drop as it started - replaced most of the wiring with heavier guage and it worked for a while, eventually traced the problem to a corroded fuse holder.
Electrics and salt water just do not mix.

 

[William_H]

You could also check your power supply for damaged cable, dirty or corroded terminals etc. I assume your batteries were originlly of sufficient capacity but are they still up to the job? When I bought my boat the fridge refused to run due to voltage drop as it started - replaced most of the wiring with heavier guage and it worked for a while, eventually traced the problem to a corroded fuse holder.
Electrics and salt water just do not mix.

I wonder how OP is checking current drain at 8 amps. Using a multimeter is normally OK on amps scale but beware a digital multimeter will over read if battery is flat.
If VHF is drawing so much current it would get hot after a long transmission. Feel around the back where heat sinks might be.
I can not imagine a bad antenna would cause such high current drain. You could try a dummy load of 50 ohms (25 watts) or at a pinch a 60 watt 240v globe in lieu of the antenna cable. If current reverts to normal into a dummy load then yes it is the antenna.
I presume the radio does not have a low power option which should give much lower current consumption.
My guess is that the radio is faulty and with price of servicing a new one is indicated. good luck olewill

 

[sebastiannr]

Yes, with a SWR meter.

Yeah, will do, I've been trying to get hold of one to make sure that's not the problem.

 

[sebastiannr]

You could also check your power supply for damaged cable, dirty or corroded terminals etc. I assume your batteries were originlly of sufficient capacity but are they still up to the job? When I bought my boat the fridge refused to run due to voltage drop as it started - replaced most of the wiring with heavier guage and it worked for a while, eventually traced the problem to a corroded fuse holder.
Electrics and salt water just do not mix.

That's what I though initially, but the fact that it's drawing so much power led me to believe that the problem isn't related to power supply.

I will check all connections though, your advice is totally sound - electrics + salty environment = head aches! (I've head rumors that dry boats exist, is it true?)