VHF Radio Install

[PreciousMetals]

I need a little help on a couple of items that I bet you owners know. I am installing a Uniden VHF radio. I have it all mapped out in my head, and I have the routing down but missing two simple pieces.

I am going to place the head unit by my right knee under the steering wheel and will send the wires through the panel into the helm. First question is what do you recommend for getting that fuse holder that is as big as my thumb through the panel? I was hoping to drill a small hole and use a nice grommet or a cable outlet from Shakespeare. Seems like the hole is going to need to be 1/2' to 3/4" now.

The second question is where to tap my power under the helm.

Thanks in advance....

 

[Bruce]

I have the same project on my todo list. I will not be using the fuse. I am installing a new switch with a breaker so no need for the fuse. If I were using it then I would cut the fuse from the wire, run the wire through a smaller opening then solder and shrink tube the fuse back into the circuit.

As for obtaining power, I am installing a new switch panel with a new positive and negative run from the battery since I have installed a lot of new electronics. An easy solution for the VHF would be to tap power from the back of the 12 volt outlet. This would reduce the capacity of the outlet when the VHF is on but the VHF uses little power and can be turned off if you need full capacity for another device.

 

[upperdeck]

I disagree. When simply turned on, it draws very little. But when you transmit it draws significant power.

Last year, just leaving for Bimini, we did a radio test. I transmitted and instantly blew the fuses to both my radio and GPS.

Lessons learned... Test the radio, including transmitting. And give it plenty of juice to run it.

 

[PreciousMetals]

So if it needs plenty of juice, then where would you recommend getting your power from. I am hoping to go after this simply, but want to do it the right way. Is there a hot and ground under the helm that I can tap into to get the power I need to run the radio and transmit, or do I need to run a dedicated set over to the battery?

 

[Bruce]

Looking at the manuals for the Uniden UM380 and UM415 they state that the power requirements are 6 amps for the transmitter and 1 amp for the receiver. The 12 volt outlet should be rated for at least 15 amps.

Certainly testing is very important. Unfortunately with Marine VHF I believe that testing transmission on land would be illegal.

@upperdeck, how did you fix this? Did you upgrade to higher amperage fuses? Were you using the fuses that came with the VHF and GPS?

 

[upperdeck]

I made the mistake of putting the vhf and GPS units on the same switch/breaker. When they both turned on, I figured I was good. But when I transmitted, I blew the breaker.

My solution was to wire the vhf directly to the battery, rely on the inline fuse, and use the switch on the vhf unit itself.

 

[PreciousMetals]

@upperdeck, what guage wire did you use to run from the battery?

 

[Bruce]

For a run of 15 to 20 feet you would need 12 gauge wire to handle the 7 amp draw with less than 3% loss.

This chart http://www.engineeringtoolbox.com/amps-wire-gauge-d_730.html

And this calculator http://www.calculator.net/voltage-drop-calculator.html

Are good references.

 

[upperdeck]

I ran some heavier wire to a terminal under my helm to feed my switch panel. So its not specific to just the radio.