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Author Topic: Mobile Install Power  (Read 26252 times)

Posts: 4311


« Reply #30 on: November 10, 2012, 12:11:34 PM »

You don't think maybe the #10 wires contributed a lot to fixing the voltage drop problems?

Nope, it didn't fix the problem. Without the capacitor, the IC-706 resets every time the engine is started just as it did running off the aux power outlet (not the regular cigarette lighter). That capacitor also helps me run my SC-500 amp without needing a 12v@80 amp supply.
« Last Edit: November 10, 2012, 12:13:58 PM by W5DXP » Logged

73, Cecil,

Posts: 10248


« Reply #31 on: November 10, 2012, 01:54:59 PM »

I don't want to get into another argument about which system is best (battery or chassis grounding point). It is all most moot now that we have a host of new technologies relating to idle engine shutoff. However, I will dispute one item.

The thought that the voltage drop through the chassis is less than a properly sized ground wire is incorrect. For example, the resistance of a 10 foot long #10 (commonly the size and length for a 100 watt transceiver power cable) is ≈1Ω per 1000 feet (.9989 to be exact). Thus a 10 foot piece is .001 ohms. Due to the accuracy of my DVM, that is what it measures. Connecting that wire and soldered on lug to the battery's chassis ground point, and measuring the resistance at the other end and a lug under one of the front seat bolts in my (unibodied) Ridgeline, measures .018Ω. So, how is it that the chassis is less lossy?


Posts: 7718

« Reply #32 on: November 10, 2012, 03:08:27 PM »

A 10' length of #10 has a resistance of 0.01 ohms, not 0.001 ohms. I don't recall anyone saying anything about the resistance through a vehicle chassis.

I too used a super cap (5 Farads) for an ALS-500 amp and it raised the maximum power to go from 350 to 400 watts. The wiring to the vehicle battery consisted of 4' cables of #8 AWG. 
« Last Edit: November 10, 2012, 03:13:57 PM by WX7G » Logged

Posts: 10248


« Reply #33 on: November 11, 2012, 05:58:43 AM »

You're right David. Yes, Tom alluded to the voltage drop. A few tenths isn't going to make much difference, until you really draw a lot of current.

With about 550 PEP out, the PEP input current is very close to 90 amps, plus the driving transceiver's current. All kinds of funny things happen with the on-board electronics when you do use the chassis for a ground return when drawing that much current.


Posts: 152

« Reply #34 on: November 12, 2012, 06:36:13 PM »

Chris, I agree with you. And I also say that experience counts!

I don't even know for sure how many mobile transceivers I have used over the years. The first all solid state was an Atlas 180. There have been about 20 since that one, including the IC-7600 I've used for the last 60 days. All of them were wired directly to the battery. No chassis ground. No protective diodes, zener or otherwise. No big Farad caps. No isolated batteries. Nada! I have never suffered a failure caused by starting the engine, with or without the radio on. While these facts do not account for every single failure everyone else has had, it is a very good indication that proper wiring is the key.

As for the ASEE or the SAE, the only reference I can find for measured spikes with respect to a 12 volt automotive application is 50+ years old. We have to remember that modern vehicles are literally computer controlled. What about the spikes they experience?

All of this boils down to a simple fact or two. Every single automobile manufacturer on the planet, plus the big four (Alinco, Icom, Kenwood, and Yaesu) all recommend that two way radio equipment be directly connected to the battery or jump points as the case may be. I guess that every amateur in the world knows something they don't know!

Couldn't have said it better, I have run an FT-857 mobile for the last 8 years, I have started the car/truck, literally, thousands of times with the rig on.

Posts: 159

« Reply #35 on: November 13, 2012, 06:48:21 PM »

The idea of connecting the negative lead to the battery is idiotic, and always has been, in a standard negative ground system in a device that has a grounded negative rail. A direct battery connection of negative is just begging for damage.

Then you may want to convey your thoughts to the radio manufacturers. I own a 706mkiig also, and wired the radio directy to the battery as indicated on page 13 of the manual. I figured it was the best way to maintain the warranty. If connecting this way was "begging for damage" then why would they suggest it?

Just sayin' ....


Posts: 2276

« Reply #36 on: December 03, 2012, 06:35:41 AM »

I know that this post is aged,This response is Little late anyway 3.5 yrs ago I followed the manufacturers recommendations for connecting an Icom 718 directly to the battery and used their harness and fuse's fused in the negative lead and positive lead.

But I did not know that the buss rail within the radio is common to everything at ground negative potential...yet more susceptible than their fuse recommendation.

This revelation is troublesome.

My old 1990 Ford Taurus wagon uses an inboard computer for the emissions system, and fuel injection along with ignition system...I did have a problem on 15m once at 300 watts pep but I quickly recognized what was happening and switched off the THP HL-450b amplifier.

Thusly since I have followed the recommendations of both Icom and THP for the powering of the equipment which by default must carry the current under load then how are we supposed to avoid this vulnerability?

I have both negative and positive wire fused with the manufacturers fuses and wire connected directly to the Yellow top which is connected to my automotive system and being used as the single primary battery for the car.Note I have used this system extensively over the past three years starting the car often while hilltopping HF mobile. Never had a fuse open.

I suppose then that to be isolated from the automotive system pitfalls would be to go to and use a separate second battery installed in a good battery box strapped down and use one of those solar re chargers bypassing the automotive system completely.Solar recharge would not keep up to the rigorous demands of my operating habits however I could adjust my practice.

The problems would then be limited to the Icom brand rig ground rail issue Their supplied  fuse and wire harness' ,yellow top battery,rather than hundreds of paths that can go through the rig to ground when using the automotive service battery and system

Not too sure I need this audio market solution of a big capacitor bomb inside the car.


Posts: 6252

« Reply #37 on: December 04, 2012, 04:36:24 AM »

....I have both negative and positive wire fused with the manufacturers fuses and wire connected directly to the Yellow top which is connected to my automotive system and being used as the single primary battery for the car.Note I have used this system extensively over the past three years starting the car often while hilltopping HF mobile. Never had a fuse open....

If the car is properly maintained and serviced, there is almost no chance of that negative fuse opening.  All too many people make the connections as recommended by the manufacturers and had the fuse open--and later found out that the serviceperson who last worked on their car had left a ground strap disconnected, didn't tighten a bolt or a nut properly, or had some other overlooked, disconnected wiring cause the problem.
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