Cb disaster!!

It all depends on the vehicle in question. Each vehicle calls for a different antenna. No such thing as one size fits all.

 

Precisely why my homemade antennas have a copper coil hermetically sealed from moisture.

 

The reason is ground loss, no pun intended. A vehicle surface is not an actual ground plane. It act as a capacitor for the surface directly underneath the vehicle, which would be the earth, which is the actual ground plane and is a very lossy one. Some surfaces are better (more conductive) than others, moisture content helps. Ever notice less static on the radio after rain, and the road is still wet? A bridge or overpass is not a good ground plane is all it is, not your mm-9.

I've never heard the claim that aluminum antennas cause more static. Yes, aluminum forms an oxidation layer instantly when exposed to oxygen. If excessive build up of this oxidation caused " extra static," a lot of people would be climbing their 100' towers to sand their 8 element beams. And no one would use aluminum material to home brew any antenna. Static build up is possible on antennas caused by wind, but it it true for all types, not just aluminum.

The op didn't really give enough details to diagnose his problem. I would suspect a hacked "super ears" mod that did nothing but bring more noise into his radio. But the op didn't say he had his rsdio worked on.

 

Bout Z thanks for reminding me why I find scientific information from universities instead of truck drivers. The capacitive ground you are describing has little to do with the ground plane affecting static buildup from charged ions in the air around the vehicle, rather it has more to do with the radio frequency ground which affects the RX-TX performance of the station on the channel being used. Triboelectric charging between the tires and the road surface being affected by the actual composition of both the road and the tires comes into play. This charge buildup will dissipate as rapidly as it can with the greatest discharges occurring at the sharpest points on the best conductors. Obviously that charge bled off by the metal antenna will be heard the most by the radio involved, more so than charge bleeding off other metal surfaces on the vehicle. The greater the voltage at the moment of voltage breakdown the greater the noise heard, copper bleeds the voltages off at lower potentials than sapphire covered Al thus less noise is heard since there is a threshold voltage before the receiver can 'hear' the noise. Moisture on the road as well as the tires reduces this noise by dissipating static faster than it can build up. The reason winter causes more shocks walking on carpet is due to the extremely dry conditions of both the carpet and the air. Likewise the inverse is true for either the carpet or the road. The moisture content eliminates the static buildup between tires and road at the same time it improves the ground-plane effect for the RF signal but these are two different things, which you obviously are confusing.

The road is normally made of asphalt whereas the bridge is typically concrete and this material difference greatly affects the amount of triboelectric charging. This ever building static charge dissipates back into the air at the points which concentrate charge density in decreasing area. The reason good metal whips have a small 'corona ball' on the tip to lower the noise. Edge effects on the ribbon inductor in the MM9 create the greatest area where electrical discharge can occur. I should add people with common sense do not climb towers to sand their antennas. They bring it down to ground level and cleaning the elements is well known to those in the art. However most are smart enough to not sandpaper it for this creates millions of tiny ridges in the metal surface which exponentially increase the number of points corona can occur and at much lower voltages. Charge buildup on the aluminum antenna reaches a point where breakdown occurs through the sapphire layer and this voltage is higher meaning greater noise is produced than if it were to bleed off copper at much lower voltages. The point was the static noise difference between Al and Cu not the difference between Al and every other antenna material ever used on the planet. If you look up charts for the triboelectric series and compare the difference between typical materials used in tires, concrete, and asphalt it is clear why one material will cause a more rapid buildup of electrostatic voltage than another, between the tires and differing road materials. This also adds to the overall noise but is a separate issue from charged ions in the wind impacting the antenna surface. All of which come into play but each thing must be considered on its own for understanding of the physics involved.

http://en.wikipedia.org/wiki/Triboelectric_effect

"And no one would use aluminum material to home brew any antenna"

Pure hyperbole to the extreme. Everything is a compromise. Al is quite simply much stronger while being lighter than Cu. Cu elements would bend in the wind and even from their own weight at the lengths required for typical HF elements. Especially if the tubing is thin enough to reduce the weight. Al is also a good enough conductor that performance is acceptable.

Too busy right now to go into this further and I don't really have the time to argue the point with you. Believe what you wish. It's called freedom.

 

Sorry but this was a simple fix, not complicated as I said it was a ground problem.

as for aluminum, say what you want, it isn't complicated nor improbable that many times there are other issues and not the metal used. There is a problem with what is called dust static where this comes into play, not normally seen unless the driver is going through a very low humidity area. Road static is also a problem but that is easily fixed with a few broken bungee cords hitting the ground on the steps.

Been doing this for a long time, cbs are not complicated nor are they hard to troubleshoot. Most often the circuitry is about the same in the radio (mass produced so it is an easy circuit) and the antenna issues are normally easy to figure out.

start here for grounds

http://www.w8ji.com/Antenna grounds.htm

and here for mobile stuff

Http://www.k0bg.com

 

Your website recommendations are spot on. I have to ask about why you think the bungee cords hitting the ground have any effect.

The effect of static in your radio may be caused by static electricity being present somewhere on the antenna system whether on the antenna itself or within the coax feedline. It may also be within other components in your trucks electrical system. Most often the issue is taken care of by ground strapping either using tinned copper braid or solid copper flashing from the mount to part of the framework on the truck.

The bungee cords have absolutely nothing to do with fighting static on your radio. If you think about it, rubber is an INSULATOR and not a CONDUCTOR. In other words, any static electricity CANNOT get discharged or make it's way to ground via bungee straps hung on your steps.

The bungee idea is simply a horrible roadside myth. The BASIS of the idea though comes from earlier trucks in the 50-70's A lot of trucks would have a METAL strap hung from the trailer or hung from a mudflap that dragged on the ground in the belief that any static charge buildup or even energy from a lightning strike would be channeled to the pavement via the METAL strap. The idea, while seeming sound, has little merit as a truck driving 600 miles per day simply grinds off the metal strap as it drags on the ground. You would have to change out the drag strap on an almost daily basis.

 

So did I on page one "Almost forgot to add consideration to the OP's problem. Look at the ground or lack thereof from the added mirror mount to the cab body. Is the bracket mounted on an arm insulated from the body? Common in newer trucks with the large diameter mirror arms. Something to look into anyway."

All of my other comments were directed to your disbelief of Rabbiporkchop's statement about Al VS Cu, i.e., explanation as to the reason and also a breakdown of the various components of static related noise sources and explanations thereof. Common in the art is a non sparking Be-Cu braid dragging the ground behind the differential to bleed static back to the earth, alterations in tire composition, a Be-Cu spiral in the front wheel grease caps, and mildly conductive organo-Lithium based wheel gearing grease. Previously on this site I have mentioned keeping a spray bottle of 50/50 water/liquid Downy softener to spray the tire sidewalls every week or so when the static problem is very severe.

As well examination of the sound of the 'static' the OP mentions, since from experience many describe very different noises with similar words. Example a 400 HZ whine from the alternator varying pitch with engine RPM is not 'static' but I have heard the word used in description before. Other examples exist.

 

I understand why you posted the info, and appreciate the reminder about aluminum oxide.

I just disagreed with the idea that the antenna was the problem right from the start.

There are millions of aluminium antennas on vehicles without issues as many more sit on towers and on roofs without issue. to many of us it not the right road to travel down.

Grounding is important as you know and as you mentioned, it should be the first thing anyone needs to look at. But other stuff needs to come into the picture when grounding is not solving the issue.

It is really really simple, there is only a few things that matter with cbs, and phsyics haven't changed yet. ....

I'm trying to figure out how does one hermetically seal an antenna coil.