VHF/stereo power/interference problem

C

Cutty Sark

New member
Ok, we were out with the 16's this weekend on the lake, I had a chance to better test everything as far as the electronics go. When we were saying our goodbye's via the VHF I experienced some strange problems. As I pressed the talk button on the mic, my low battery alarm went off on my Garmin, my sonar shut itself off, and I had some interference come through the stereo speakers all at the same time. I had to power off the garmin to reset the sonar, I then noticed I had the VHF on high power, and confirmed it only experience's these symptoms on high power, on low power everything seems normal. Motor was running and charging the batts at the time though we were in idle. I am also having a weird power problem on the stereo iteslf, that I had found previously and now I wonder if it's related. The stereo has two power wires, one for the ignition switch or an on off button, and another that is wired to an always hot for memory functions. When the memory one is hooked up once you turn the power off it will not come back on with out unhooking the power, but if I leave the always hot off it comes on and off at will. I have a new battery that is maybe a month old and in great condition, the boat has a battery charger as well, and I plug it in when its not in use.

So my thoughts so far are:

The cable runs for all the power /radio wires etc need to be seperated and find what is causing the interference and run it seperatly or shield it somehow.

The VHF and stereo are on the same on off switch, should I seperate them?

Also I'm thinking the power consumption might be higher than what the main 12Vcable can carry. I have all the manuals etc so I should be able to figure out what my draw is and if I need a heavier gage cable from the battery to the distribution behind the helm.

Any other thoughts, ideas or similar experiences? I'll dig into the books tonight and do some research but I have never dealt with this type of issue previously.

Sark
 
You'll get a lot of advice here, but to sum it up: you have too much voltage drop from the battery to your electronics. If the battery is good, your wiring is undersized. The answer is to put in larger wires.

There is nothing wrong with wiring two units through the same power switch, if the switch is rated for the current. In fact I put in a power buss to the overhead shelf for Journey On from the upper Accessory switch on the main panel. It operates the radio, depth sounder, stereo and radar. The switch can handle the load and I used 12 ga wire to the shelf. No problem so far.

Boris
 
Agree with Boris--voltage drop. First check all terminals for corrosion (inclluding battery terminals, all bus bars and terminal block and switches at the helm. Also agree, that most of the boats have inadequate size wire from the battery to the console. When you hit transmit, it pulled a lot more power, and dropped the voltage.

I always just connect the memory and power together and switch them "off" when I leave the boat. It does not make sense to draw down the battery with the "memory" of the sterio.
 
Sark,

"Also I'm thinking the power consumption might be higher than what the main 12Vcable can carry. I have all the manuals etc so I should be able to figure out what my draw is and if I need a heavier gage cable from the battery to the distribution behind the helm."
Click to expand...

"I then noticed I had the VHF on high power, and confirmed it only experience's these symptoms on high power, on low power everything seems normal."

I think you might have hit the nail on the head here. The VHF on high power is putting out 25watts, vs 1watt on low power or some do 5 watts on a medium setting. Seems Boris and Dr Bob are agreeing also. Sounds like you might need to run a larger power cable up to the shelf. Also, with the engine at idle, you aren't making much in the way of 12VDC, so may need to bump up the throttle just a notch.

I use a relativley cheap, Digital volt meter, (Walmart version) that plugs into a cigarette lighter/power plug. It stays there all the time so I can watch where the power level is. Amazing the difference between idle (600 RPM) and say 1000 RPM. (There are several threads here about voltage monitoring and this type of voltmeter.)

Oh, If/when you get ready to pull those wires --- Use them to do the work by taping the ends of the larger diameter, heavier gauge wires to the end of the lighter ones before you pull them. Saves fishing for wire ends in places that are hard to reach.

Enjoy,

Harvey
SleepyC :moon
 
Voltage drop ahh yes the technical term that was eluding me. After looking around, I think it's a combination of voltage drop being too severe for all the equipment the previous owner added, my guess is the wiring is original and wasn't desinged to handle that large of a load, 2nd there is definitly some resistance problems, as I noticed some minor corrosion at the main distrubutiuon posts and fuses all under the splashwell(terrible spot). Also noted very few if any terminals are heat shrink, in the cuddy maybe... but under the splashwell? 3rd all the cables are bundled tightly together stereo, sounder, power, everything, I think I will try to seperate a bit and group them as Calder suggests.

Thanks for the tips.

Sark
 
Excellent suggestions all across the board.

For the more crazy look and see---- :idea:

If you still have a problem with noise or stange happenings when you transmit in the HI power position with the radio you may want to check the antenna coax connections and the radio ground.

If all has been working fine to this point, I would think the antenna location is not an issue, but corrosion -as noted earlier- could be. If you get weird problems that require more in depth research you may want to fine a local ham radio operator who could help isolate the problem. He may some choke filters to place on the radio's power leads, for instance.

A portable marine VHF,with the antenna removed with a dummy load replacing it could be used to "sniff" around the cockpit with your marine radio transmitting in the LO power position.

Art
 
Back
Top