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Author Topic: Honda Element power and VHF antenna cable routing  (Read 1724 times)
KE8YY
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« on: December 12, 2004, 04:16:51 PM »

Here are a few photos detailing how I ran direct battery wiring and a hood-mounted Comet mount in my '03 Element:

http://mind.dreamhost.com/gallery/album12

Wire is 10 gauge stranded THHN, a gas, oil, and abrasion resistant wire. 10 gauge was picked as sufficinet to carry as much current as I'd ever need and then some, whil still being flexible enough to easily pull. The huge 4 gauge and 2 gauge wire used by car stereo enthusiasts is both overkill in terms of amerage, and has a jacket that is inferior to THHN in this application. The +12VDC line is fused at 30 amps right at the battery, for safety, and to make it easy to pull the fuse and safely terminate the wire.

Both (+) and (-) will be individually fused at lower amperage on each rig. Fusing the (-) side isn't as important on a newer vehicle, but on a car with a few mile son it, it's not unheard of for the bond from the (-) end of the battery to become disconnected from the chassis. If this happens and  your radio is bonded to the chassis, it will immediately become the ground path for EVERY electrical device in the car, and will indeed act as a fuse ;-)

As seen in the photos, this part of the job isn't quite done. I still have to terminate the power cables (Anderson Power Poles) and finish dresisng the run by the center console. And cvacuum the car ;-)

Right now the only radio in the car is a 2M rig on a homemade mount. Next step is to add a mount for a whip in the rear, mount an SGC autotuner nearby, and decide where the whip will be mounted. I'm leaning towards a trailer hitch receiver mount.
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K5LXP
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« Reply #1 on: December 12, 2004, 10:03:53 PM »

> If this happens and your radio is bonded to the
> chassis, it will immediately become the ground path
> for EVERY electrical device in the car, and will
> indeed act as a fuse ;-)

You're almost right.

It's when the radio is connected directly to battery negative that the open frame ground scenario turns your radio into a fuse.  Connecting directly to the chassis eliminates this possibility.  Yes, a fuse can protect in cases of catastrophic failure, but in practice the connections become somewhat resistive, not fail open.  Current flows through the radio chassis at a level not high enough to blow the fuse, but enough to cause undesired operation or damage.  I have yet to hear a defendable argument for connecting radio negative directly to the battery.  

Mark K5LXP
Albuquerque, NM
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KB1LKR
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« Reply #2 on: December 13, 2004, 05:12:01 AM »

Suppose the radio is grounded directly to the battery (as many of the recommendations suggest) and the other end of the (fused) ground wire is also grounded to the chassis adjacent to the radio, offering some redundancy while minimising the voltage drop at high power?  
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KE8YY
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« Reply #3 on: December 13, 2004, 05:59:34 AM »

And you're absolutely right.

I was talking to my pal WB8FPQ this morning about that. Bill does RF compatability for Chrysler and wrote a radio installation manual for them that a lot of others have copied. It's on the ARRL site as well.

Bill stressed two things: Never tie directly to the battery (-) and never fuse the (-). He said, as you say, tie to the chassis close to the battery's (-) strap.

He also advised against tying directly to the (+) terminal as corrosion will eventually degrade the connector. I'm going to spray the area with Boeshield to delay the onset of that for now. But eventually I'm going to move the (-) to the chassis and the (+) to a distribution block near the battery.

Bill Also recommended against THHN, saying that the auto industry now uses crosslinked polyethylene, which has better resistence to solvents, heat and abrasion.

But I'm not pulling new wire anytime soon ;-)

mike
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K0BG
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« Reply #4 on: December 13, 2004, 06:47:06 AM »

Funny thing Mike. Ford, GM, and several others recommend attaching directly to the battery and fusing both the + and - leads. And, in Chrysler's own literature, they state is can be done either way. That is to say, directly to the battery with the leads fused, or as you describe.

Adding a ground at the radio may induce a ground loop and they are HARD to find. Further, if the negative lead fuse failed, the radio would still work, but would see a voltage drop due to the extra resistance in the body work, and add a potential noise ingress source.

These recommendations have been covered at length here on eham.net as well as on my web site.

Alan, KØBG
www.k0bg.com
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KE8YY
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« Reply #5 on: December 13, 2004, 07:13:57 AM »

I should clarify something I wrote- Bill suggested tying the (-) wire to the chassis, close to the battery's ground strap. And yes, you do want to avoid ground loops, although that may be difficult with the antenna ground.

I'll check your web site, thanks.
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KE8YY
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« Reply #6 on: December 13, 2004, 07:18:27 AM »

Checked your web pages- great stuff there. But I wonder about using bare braid in an auto environment. I'd want to protect it, or replace it regularly. Or isn't that a problem?
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K0BG
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« Reply #7 on: December 13, 2004, 09:49:08 AM »

The bare braid you see in the pictures does not carry DC power. It is the RF ground path for the tuner. Since I posted that picture, I have added a second one to minimize an RF problem on 17 meters.

In any DC application, you are very correct, braid can and will get you into trouble. As a previous post stated, THHN is the best for automobile applications. Not so much for the basic insulation, but the outer cover as well.

Another application where braid should be used is in ground strapping, better known as bonding. It is flexible, and has more surface area. The latter being a better RF carrier.

Incidentally, one comment made about corrosion is perhaps a little off center. If you're getting corrosion on the battery connections, these should be cleaned properly, and protected by electrical varnish available at just about any hardware store.

Alan, KØBG
www.k0bg.com
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KE8YY
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« Reply #8 on: December 14, 2004, 06:34:29 AM »

I think Bill's opinion regarding corrosion at the battery terminals reflects real-world concerns, rather than ideal conditions. Varnishing the terminals, installing those little neutralizing pads, etc., is something that doesn't often seem to get regular attention.

I was thinking of giving the terminals a regular shot of Boeshield, which I find to be a marvelously tenacious rust preventer on bicycles, lawn mowers and other metal objects that spend a lot of time outdoors. I'm not sure how well it will hold up in an engine compartment in the summer, though.

And yes, good point about RF ground.
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