CB power

Sorry but you got it wrong... Unless the antenna is one of those "no-ground plane" types The antenna base MUST be grounded. The vehicle body (otherwise known as the ground plane) is part of the antenna. Please show me an example of a "isolated mounting". Where do you buy them?

XS11E wrote:

This guy has no clue what the difference between a ground plane and an electrical ground is. You're beating your head. "No ground plane" type antennas are the absolute last resort on a vehicle and should never be used on a Jeep with a metal body...Fiberglass tubs, a corvette, or a fiberglass boat.

tw

FrankW wrote:

If you use the vehicle chassis as a ground in a new GM vehicle, you will void the warranty for 'all' on board electronics of the vehicle. This includes things like the ABS controller, ignition, etc...

You need to isolate transmitters these days.

Mike

Everywhere Frank.

The mag mounts are totally isolated 'electrically' but require a 3' circle of metal under them for the best 'reflective' ground plane.

The vertical clamp on ones have a nylon insert where the stick meets the metal bracket if you look close. These also need a 'reflective' ground plane.

A 'reflective' ground plane is an area for the signal to bounce off of increasing the range of the antenna. This is 'not' an 'electrical' ground.

I use a trucker's mirror mount on my 'glass bodied CJ7 designed for no or little 'ground plane' and get excellent reception with an old Cobra

1. I have had 2 way conversations from Toronto Canada to Marthas Vineyard on the US east coast and pick up the Mississippi river truckers all the time.

I wheel up on the Canadian Shield south of James Bay and can 'receive only' a gent on British Columbia's Sunshine Coast on the Pacific Ocean regularly from one area.

Mike

A 'ground plane' is a reflective area for amplifying the signal.

An 'electrical' ground is a power path.

The 'only' thing they have in common is the word 'ground', nothing else.

If you use an electrical ground for the transmitter's ground plane, you will void the vehicle's warranty for all things electronic according to all the manufacturers I have dealt with while installing and servicing transmitters for 9 years.

Here is a link to the GM book and others posted links to the Ford and Chrysler books.

OK, so I just did and WOW, the person who wrote the Neon one also has the electrical and reflective grounds mixed up in his head but at least he refers to the TSB which is correct.

Mike

Hi Mike To nit pick, it does not amplify the signal

This site is really good. No garbage

Mike Roma> A 'ground plane' is a reflective area for amplifying the signal. >

No really Mike They are capacitivly coupled to the metal body of the vehicle The negative node of the signal is carried in the vehicle. It can fry the electronics just as easily. In the DC world yes it's isolated But RF = AC.

Mike Roma> Everywhere Frank.

In the Ericsson systems I was using, if you mixed the two, all hell broke loose. We were transmitting data packets and the retries went through the roof if the coax got frayed and touched metal or the edge of the mag mount touched a roof ridge or a beam. (yes some fools insisted on running the antenna stuck to the 'inside' of the van roof or wall despite me showing them page one of the manual that warned, in one inch high bold letters, of burns if you were within 3' of the antenna when it transmitted. These were 6 Watt units)

Mike

FrankW wrote:

Ok, better said, without the proper 'reflective' ground plane, the signal will be weaker than it's potential.

Better? ;-)

Mike

FrankW wrote:

In English?

Just kidding ;-)

My mirror mount antenna on my fiberglass CJ7 works great, the SWR meter says it matches exact when we went to tune it. I use the full length COAX in a loose coil stuffed in the side of the body shell wall.

Mike

FrankW wrote:

Mike Romain wrote:

Well, except for the fact that all mobile antennas other than the "no ground plane" designs use the body as the ground plane and the body also serves as electrical ground. The car body is rather common between the two.

I'm sorry, but when I want to know about radio electronics I read my ARRL handbook and the handbooks of the antenna and radio manufacturers. When I want to know about cars, I read GM and Ford handbooks. What GM and Ford know about CB (11 meter) radios could fit in the palm of my hand.

Correct, which is why I always check these things out with more theoretical handbooks such as the ARRL handbook and with my own measurements. When the ARRL handbook, my own measurements, the antenna manufacturer's websites, the CB radio manufacturer's websites, and the

I have thus far installed my CB in my Jeep three different ways over the years. The first installation was into the cigarette lighter, this was when I didn't have time to do it right because I had just purchased the Jeep and was going on a trip. This worked fine. The next trip, I still hadn't had time to install the radio properly, so I hooked the power wire into a fuse in the fuse box and the ground wire to a screw into the body. This worked, but with significant noise from the electronics hooked to the fuse box. I finally got around to installing the radio properly, and ran a 12 gauge wire directly to the battery and placed an auxilliary fuse block under the driver's dash for my various radios with a very short wire from the radio to the fuse block (the 12 gauge wire has its own 20 amp fuse where it attaches to the battery). A 12 gauge wire with a 5 watt draw basically has no capacitance or resistance in case you're wondering and thus does not serve as an antenna nor pick up RF noise, thus it's okay to run it across the firewall to get to the driver's side. I hooked the ground to the body with the same screw used to attach the antenna junction box to the body (this is the all-in-handset radio). The result is significantly reduced RF noise, I can hear a very little hum in the background that goes up and down with engine RPM but it is inaudible when someone is talking. My SWR settings and tests with a second person holding the handy talky show that my antenna setup (a Firestick) is quite good too and that my radio has no significant distortion on transmit. Indeed, the only significant RF noise that I pick up is from high voltage power lines, which create induced RF noise in pretty much everything in the Jeep, but that's something that a simple filter will not do anything about because most of that noise is getting picked up by the antenna, not by the wiring under my dash.

So, why did I not run the ground wire to the battery? Simple. Adding an additional ground path to the battery risks fire if the body ground comes loose, because the antenna end of the coax is grounded to the body. So that ground path then becomes the ground path that every power-using accessory in the cab of the Jeep will use to send its stuff back to the battery. This is Bad News. With my setup, because the coax ground (both ends - radio and antenna) and the radio ground all go to the same ground (the body) grounding the radio to the body creates no risk of fire. My measurements with the VOM show that the body ground on my Jeep is excellent at all points measured. If your Jeep on the other hand is a rust bucket you may need to do extra work to get a good ground for everything that needs a good ground -- both ends of the coax, the frame of the radio, and the radio itself.

Now, has this affected the electronics of my Jeep in any way? Nope. 5 watts of power simply does not have the juice to do anything to the electronics in a Jeep. You get more induced current just by passing under a high tension power line.

In short, I am both puzzled and baffled by your objections to what every major radio and antenna manufacturer recommends. Perhaps you simply misunderstood what I was posting the first time? Hopefully this clarifies things then.

-Elron

But what GM and Ford know about their warranties is not only correct, it's oftem final and non-negotiable as many have found out. I'd pay attention to them if I were you...

L. Ron Waddle wrote: > I'm sorry, but when I want to know about radio electronics I read my

Yes, you should read and know the ARRL handbook and I believe that you do. It covers the physics of two-way radio installations. Once you understand how the system should work, you _MUST_ address the manufacturer's concerns regarding the vehicle specific installation and make your own decision as to whether their concerns are valid in your case, or you are willing to take a risk. It would be a shame to void a

tw

Ain't that hard in a GM truck these days...nothing but plastic to mount to anyway.

-- Old Crow "Yol Bolson!" '82 FLTC-P "Miss Pearl" '95 YJ Rio Grande BS#133, SENS, TOMKAT, MAMBM

But 'totally' separate!

No ground plane simply means the antenna doesn't need a reflecting surface to set it's SWR, 'not' it doesn't need an electrical hookup....

I have personally seen many ABS systems crap out from a bad install as well as the digital dash and gauges and ignition in one case every time the gent transmitted. This is in the fleet of about 200 delivery vehicles I serviced.

I have personally seen GM void the warranty on 'very' new GM vans and voided on one Ford van that kept 'blowing' trannies.

These arrogant folks that 'knew better than GM' very quickly took the time after that from their 'too busy' of a schedule to have me properly wire the transmitters in rather than use the cigarette lighter socket they were 'insisting' on using.

Their lawsuit against the parent company I worked for, for vehicle damages got dropped before it started because they were shown to be at fault for being lazy and warned in writing of the potential consequences of using the lighter plug.

A bad install in a TJ was reported here on this group as making the tranny go into neutral every time the gent keyed up.

No, you are mistaken. The coax cable is 'physically' isolated from the body at the antenna, it does 'not' act as an electrical route for DC power.

Please go look close at your antenna base. You will see a nylon insert isolating the antenna base from the bracket. If you unscrew the coax at the antenna and use a multimeter on continuity and put one probe on the coax plug's male antenna end threads and on the vehicle body, you will show an open circuit.

That is why the negative wire must be fused so the ground can't run through the CB's 'chassis' ground and back feed into it's power line.

I was transmitting data packets with error correction. It was extremely obvious when anyone's coax got frayed and 'electrically' grounded to the vehicle body by the number of retries in the packets. I would get a service call from the mainframe techs.

No, I 'have' to go by the 'Vehicle' manufacturers booklets to avoid 'me' personally voiding someone's warranty and being liable for the damages or the deaths that can and 'does' occur when the ABS module or tranny module fails. (think van loaded to the roof with newspapers in a panic stop and the 'expected' ABS fails)

I also 'had' to use Ericsson Canada's transmitter wiring specs which are the same as GM's which is two 10 ga. wires both fused at the battery or right at the power tap and main ground cable bolt.

I also worked with RIM (Research In Motion transmitters, think blackberry guts) and their isolated antenna specs and power line specs were the same as Ericsson's.

The long and short of it is whatever works for 'you' is fine, but if you want to be above board and to avoid expensive 'no warranty' fixes on your vehicle, you gotta do it 'their' way.

Mike

I'm not understanding what you're talking about. You seem to be confused. SWR is a rating of how much power is reflected from the end of the antenna back to the transmitter as harmonics instead of radiating to the airwaves. Reflected power ("standing waves") a) causes the transmission to sound garbled (since additional wavelengths are introduced into the amplitude-modulated output), and b) can damage the input capacitor or output amplifier on the transmitter. The secret to avoid standing waves is to carefully tune the length of your transmission chain in order that your power be radiated rather than reflected back. A poor ground plane (reflecting surface) can certainly cause SWR's to be high, since this causes power to be reflected back to the antenna rather than out to the intended destination, but is not by any means the only cause of high SWR's.

The biggest cause of high SWR's is the fact that typically other parts of the transmission chain are radiating or are of a length that is chopping up your waves as they head for the tip of the antenna. Thus if your coax is not shielded with the shielding grounded properly at both ends, your coax length should be a half-wave or quarter-wave in length. For 11 meter band (CB radio), that's 8.25 feet if you want a quarter wave coax. If the shielding on your coax is not grounded to a hard ground at both ends, your coax becomes an antenna, and this makes it harder to adjust your SWR's unless you are quite adept at tuning combined cable-antenna combinations. That is why the "no ground plane" setups require a specially tuned cable-antenna combination to work properly, it isn't necessarily because of lack of a ground plane (I have seen a regular Firestick work just fine on a 4-wheeler with very little reflective surface), but, rather, because due to inability to pull a hard ground on the shielding of the coax on both ends, the coax is now part of the antenna.

With a 5 watt CB radio? I'm going to call BS on you. Not that I'm worried about that, since, like every Jeep TJ I've ever seen, my Jeep TJ doesn't have ABS.

Maybe that's legal in Canada. Here in the U.S., they have to prove that your install caused the problem, or you have a lawsuit against them for breach of the Magnuson-Moss Warranty Act.

The *SHIELDING* of the coax cable is grounded at both ends. (Rolls eyes). Otherwise the coax cable becomes part of the antenna and must be carefully tuned in length. You are correct that the center portion is isolated. Otherwise the antenna wouldn't work, since the whole point of an antenna is to bounce AM-modulated radio waves off the end of the thing, and if it's grounded obviously that's not happening! I realize that American "English" and Canadian "English" are not identical, but we appear to be speaking foreign tongues to each other here, from what little understanding is making it out.

If the coax is not properly grounded at both ends (again, I am talking about the SHIELDING part of the coax, not the CENTER part -- a coax has

On CB radio?! That may be legal in Canuckstan, but CB radio here in the USA is only allowed to be used for voice transmission.

If your coax ground is not the same as your body ground that certainly can happen. (The coax ground is the *SHIELDING* ground, once again). You are then flowing a current through your shielding and inducing distortion in AC flow in the center conductor (doh, it's called

The best way to make sure this does not happen is to make sure that both ends of your coax ground, and your CB radio ground, are grounded to a common ground. Grounding it to the steel body of a Jeep TJ certainly works to insure that all of these are using a common ground. But if you add a second ground path for just two parts of the equation (i.e., for the radio end of the coax and for the radio itself), you do not insure that you have a common ground, thus can have a ground loop through the coax shielding with resulting distortion. In particular, if the body ground wire from the battery to the body goes bad, then everything

In non-metallic vehicles such as fiberglass boats, or on vehicles where the frame cannot be used for grounding such as on aluminum-framed motorcycles with steel components bolted to the frame (electricity flowing through an aluminum-steel junction causes corrosion), generally there is a separate "ground distribution panel" similar to the power distribution panel. The ground from the battery goes to this "ground distribution panel" from whence individual ground wires go to the individual appliances that need power. This is how ground loops are avoided on these kinds of vehicles. To avoid ground loops, you need

This is Electrical 101. This isn't rocket science. We've known this in the electrical field ever since the days of knob-and-tube wiring in the early days of the 20th century where it was discovered the hard way that a common distribution ground panel was the only way to prevent the "earth" from causing a fire (early knob-and-tube installations simply had a ground "bus" that ran to the "earth" on all the plugs). It's pathetic that anybody would even argue different 100 years after the issue was settled conclusively.

Somehow I think catching the vehicle on fire by installing it via a method which violates 100 years of electrical codes might also voide the warranty (grin!).

Please note that these are *NOT* the same as CB radios. You are talking about cellular frequencies, which are very short waves compared to CB waves. CB is in the 11 meter band. 850mhz (the longest-wavelength cellular communication) is in the 0.35 meter band (yep, that's 35 centimeter band). The coax length in a CB installation is shorter than the wavelength of the transmitted radio signal, the coax length in a cellular radio is longer than the wavelength of the transmitted radio signal. The end result is that it is much, much easier to tune the coax length for ultra-shortwave frequencies, and you can dispense with the grounded shielding required for good results with CB radio. In addition,

Please note that a) your "warranty" issues are specific to Canada and do not apply to the United States where we have consumer protection laws to prohibit manufacturers from arbitrarily denying warranty coverage for irrelevant reasons, and b) your installation pointers are applicable to the 35 centimeter band and do not apply to the 11 meter band, which requires shielded coax grounded at both ends to a common ground with the transmitter ground for best results. Please do not confuse the needs of installing an 850mhz transmitter with the needs of installing a 27mhz transmitter. Thank you.

-Elron

If the impedances are matched on the antenna, coax and connectors, the length of the coax is insignificant. Cutting antenna coax to a specific length to match wavelength in an otherwise matched system is an old wives tale. Really old.

tw

L. Ron Waddle wrote: SNIP