Suplying Power to a mobile radio.

[KD0AFK]

Right now I have my radio in the truck being supplied by the Hot wire coming from the battery and it is grounded to the body of the truck which is in turn grounded to the frame. I have been told that when I am driving at speeds of 15MPH and under, I am giving off some engine noise. I don't really have a way to get power cables into the truck and I don't really want to run them around the outside and in through the door.
I have a couple of options;
I can plug my 13.8v Pyramid power supply into my inverter which is already supplied with power directly from the battery
or
Just run off of the power lines that the inverter is using.
Will I get any kind of line noise if I do one of these two things?

[K5LXP]

Why can't you poke a hole in the firewall and run the ground to the battery's frame connection directly?  That would be the first thing I'd try before messing around with all sorts of rube goldberg contraptions which may cause more problems than it cures.

Mark K5LXP
Albuquerque, NM

[AC2RC]

The Ford trucks ,and probably others, have holes with plastic plugs in the fire wall or you can simply drill one .Use grommets to protect the wires ,fuse both sides at the battery .

[K0BG]

The noise they are hearing is most likely alternator whine caused by a ground loop. As Mark told you, you need to run the power directly to the battery. You didn't state what brand of truck you have, but it doesn't make much difference if you drill a hole. This said, GM and Ford trucks have an easy access, unless they're fully loaded (accessorized).

Go to my web site, and look under Wiring.

Alan, KØBG
www.k0bg.com

[KD0AFK]

My firewall is just about as far away from the battery as  it can get. I drive a Century Class Freightliner and they really don't like lease operators punching holes anywhere in the truck except for things like Inverters and APU (auxiliary power unit) installs. I will look and see what I can see. I have both an inverter and an APU. They might just think that the hole I punch for my radio power is just another hole for one of the other things.

[KB1LKR]

Ah, a heavy truck -- I (and I suspect others) assumed a light truck/pickup/SUV). Is there room to run a neg wire back to the battery adjacent to the existing positive wire or thru an existing firewall wiring grommet?

[WT0A]

How did you get power to the inverter?
Glen

[KD0AFK]

I am going to go ahead and drill a small hole right next to the inverter. I don't think they will notice it. I am only going to be running 12 gauge wire so the hole won't be that big. It will also enable me to remount the radio so that it will be out of sight and will let me move my CB back up to the overhead cubbie and give me easier access to the back of the radio so I can mess with the cables and wires easier.

[KE3WD]

>>I have been told that when I am driving at speeds of 15MPH and under, I am giving off some engine noise.<<

If you mean that others are giving you signal reports that there is engine noise on your transmitted audio -- and you are talking about a diesel truck, then it could be alternator whine, injector noise, or possibly fuel pump noise.

One thing to try that would be easy is to place a power inductor as filter right behing the radio on the positive wire in situations like these.

You are in luck these days, due to the proliferation of idiots running super load boombox amplifiers in their cars, we no longer have to search high and low for such a filter that can handle better than 20 Amps, nor do they cost an arm and a leg anymore, due to imports because of that customer demand.

DC Powerline Noise Suppressor, 35A

mcmelectronics.com sells one for $18.83 MCM Part #: 60-1270 -- likely you can find one anywhere those boomboxes for autos are sold out on the road, too.

http://www.mcminone.com/product.asp?catalog%5Fname=MCMProducts&category%5Fname=3829632&product%5Fid=60%2D1270

Attached to the radio, it could even move to another rig or car with you.


KE3WD

[KE3WD]

Tip:  You can place two 10 or 15A noise supressors in parallel, too, in a pinch finding the part.  

The Ampacity is additive.  


.

[KD0AFK]

I think I am going to try hooking it up to the power cable that the inverter runs on first. If that fails I will go with the filters.

[KE3WD]

Sounds like a good frugal plan of action to me.  

Luck,


KE3WD

[KB0USY]

How big is the inverter.Also how big is the cable going to the inverter.
    Also there is a open hole to the outside in your sidebox on the drivers side.Look up under the sleeper corner of you truck.The rubber mat has to be pulled up to see the opening.If your truck has this hole run the cables to the battery or the post that let you jumpstart the truck.Be sure the cables are both fused.Ground and positve.What your company can not see won't hurt them and you can enjoy the hobby you enjoy.I drive for a company in Kansas that lets me use what ever.Our mechanics run my cable to the batteries for me.Not many out there to do that.
Good luck.Steve  caught me on 40 m 7.253.5 or 7.258.20m 14.302.5 (stewil@cox.net)