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Another Look at Noise Abatement

Alan Applegate (K0BG) on April 23, 2004
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Another Look at Noise Abatement

Foreword

Recent queries from amateurs seeking solutions to the various noises emanating from today's vehicles has spurred me to revisit the noise abatement issue.

Adding insult to injury are several articles recently published in QST. While they're technically accurate, they ignored important noise abatement procedures and/or bypassed common safety practices. For example, one of the articles described how the author designed and built a combination capacitive matching and mounting base for his HF antenna. Nothing was mentioned in this article about DC grounding the antenna which helps eliminate static build up and provides a measure of safety should the antenna come into contact with high voltage lines.

Yet another issue which needs to be clarified is the use of ferrite beads to suppress induced noise in the various circuits in question. Further, too many folks are buying surplus split beads of unknown origin so their results are mixed. When and where to use them (or not to for that matter) is another hotly debated issue which needs readdressing.

A careful reader will note that I have used the term noise rather than RFI. This is because some of the noise we have to deal with is not within the radio frequency spectrum. Alternator whine is an example. The hash generated by modern-day fuel pumps contains both audio and radio frequencies making it difficult to distinguish which is which. Each range of spectrum typically requires a different form of abatement, but not always.

A careful reader will also note that I have not used the term suppression selecting abatement instead. This is because of one simple fact; It is all but impossible to fully remove all of the noise in any given vehicle. I'll agree that some are nearly quiet, but some are so noisy that no amount of abatement will reduce it to an acceptable level. It is also important to note the following facts: Noise levels can vary as much as 30 to 50 db in otherwise identical vehicles; newer models are not necessarily less noisy; engine type has little to do with the level of noise, including diesel engines; modern COP (coil over plug) technology isn't a panacea either; and most importantly, what worked for your buddy's vehicle may not work for yours.

Wiring & Grounding

Proper wiring is the single most important item when installing any radio in any vehicle regardless of the power rating or frequency of operation. It needs to be properly sized and fused, it needs to be protected from abrasion, heat and chemicals, and it needs to be neat and tidy to avoid interaction with passengers and mechanical devices.

In the case of noise abatement, size does matter. I suggest a minimum of #8 awg even if you're running QRP. Keep in mind we're trying to keep the impedance low to minimize induced noise. Secondarily we want to keep resistive losses low as well. As an example, under key down conditions, an Icom 706MkIIG will draw about 22 amps. The factory supplied 6.5 foot (2 meter) cable appears to be #10 awg, but has a voltage drop of .35 volts at this amperage. Using the same size wire to supply power to a trunk mounted 706, and you'd end up with a one volt drop. While this doesn't seem significant, the 706 will shut down if the voltage goes below 11.5. Transmitting while idling with the lights on...well you get the picture.

I personally use two size 6 awg cables in my mobile (I run 500 watts out replete with a second trunk-mounted battery); one for the plus and one for the minus. Why for the minus? You can not rely on the vehicles frame and/or body to provide a low resistance path back to the battery. In my Acura coupe, the resistance between the negative lead in the trunk and back through the body to the main battery up front measures 3 ohms! Sizes larger than #6 awg are seldom if ever needed. If it is, then a second trunk-mounted battery is a better solution.

The type of wire you use is also important. First, NEVER EVER use solid wire in a mobile installation if for no other reason than its inability to withstand vibration. The jacket material should be THHN or one of the newer equivalents. THHN has a scuff resistant outer sheath over a high temperature vinyl rated at 105C, and is impervious to automotive chemicals. It costs about 35 cents per foot.

I'm a stickler about using common grounds. If your rig, antenna control, and DSP speaker all have different ground connections, you're asking for problems with ground loops and induced noise which are two of the most difficult problems to trace and fix. One of the ways to address this issue is to build a control panel for the various components of your setup. In my case, I have an SG235 auto coupler, an SG500 amp, an ADSP2 Speaker, and an Icom 706. All of the power connections are in the trunk. A homebrew remote control head for the coupler and amp also provides power for the speaker, thus all of the power connections are in one convenient spot.

Remember this about the wiring; Neatness counts! Clusters of wire and looms here and there tied back with tyraps are accidents waiting to happen. If a power cord is 6 feet too long, cut it off rather than bundling it up. The liberal use of star washers and OxGard will insure good, long lasting connections. Covering the exposed cable with split sheathing secured with tyraps is also a good idea.

There are a few things to avoid too. The use of RG8 coax to feed power to your radio is not a good idea. Although recently touted by The Doctor is IN column in QST as a way to control alternator whine, the size of the inner conductor is inadequate for any modern HF rig. Personally I've never found that it did one iota to reduce alternator whine or induced RF.

Don't use existing vehicle wiring to power any rig, QRP or otherwise. This includes accessory (cigarette lighter) sockets, and using a modified blade fuse as recently taunted in QST as the perfect solution. It isn't! You run a great risk of burning the vehicle's wiring harness which might start a fire. Either way, it is a great expense you can easily avoid.

Don't rely on crimped connections; Solder those suckers! Avoid using butt splices. If you do use butt splices here's a tip. With a little fiddling you can get the outer cover to slide off the barrel. Crimp and then solder the connection and while it is still warm, quickly slide the cover back on. The heat will reshrink the cover for a snug fit.

Keep power runs short, but use enough so curves are smooth and not kinked. Do yourself a favor, don't use vinyl tape for any purpose. The type of vinyl you see wrapped around vehicle wiring is designed for the purpose. As good as they are Scotch #33 or #66 will not stand up to a vehicle's environment. Instead use good quality, irradiated polyolefin heat shrink tubing and not the stuff you buy from Radio Shack. Fastenal and Digi-Key are good sources.

Fuses

I've put fuses under their own section for good reason. Without their correct use and placement, any mobile installation runs the risk of fire. A good quality automotive battery can under dead short conditions provide upwards of 400 amps for nearly a minute. Or enough time and energy to burn through even a 1/0 cable.

The size, type, current rating, and placement are all important considerations. Up to 30 amps, 3 AGU size fuses (1/4 dia) or ATO spade fuses are adequate. From 30 to 60 amps, 4 AGU (3/8 dia), or Maxi spade fuses are in order. For load over 60 amps it's best to rely on low voltage circuit breakers (don't use household breakers) or blade fuses designed for household use.

For a variety of reasons, power cables should be connected directly to the battery, and the fuses protecting this cable should be as close to the battery as possible. Both the plus and minus leads should be fused to protect the wiring in case the vehicle's wiring fails. Having fuses on the rig end of the power cable is fine, but what happens if the wire gets shorted down stream from those fuses?

It's also important to correctly choose the fuse rating. A good rule of thumb is to use a fuse 20% higher than the continuous current carry capacity of the cable based on 500 CM per ampere. For #10 awg, this is 22 amps plus 20%, equals 26.4 amps. The next larger fuse size is 30 amps which will instantly fail on a dead short. Avoid slow blow fuses. Let me stress an important point. The aforementioned fuses are to protect the wiring you install, not what's powered by the wiring. Quite obviously the correct sized fuse for your equipment should still be included.

Don't forget spares. I always carry two spares just in case. You can find 3 AGU fuses at almost any store, even Walgreens. Radio Shack and most mobile sound shops carry 4 AGU fuses, but Maxi and blade fuses will always be supply problematic.

As before, there a a few things to avoid. Don't use inline fuse holders especially those with pigtails which require butt splices.

As mentioned above, don't use household power panel circuit breakers. They are not designed for DC applications and will fail to provide adequate protection.

Fuse links have there place too, but not in ham radio. Fuse links protect the circuit by getting hot enough to melt and when improperly mounted can cause a fire after the fact.

If your local store doesn't sell high power fuses, holders, and heavy-duty terminal strips look on-line:

Beads

I've written several articles about the proper use of split beads for noise abatement, so this may be redundant for some readers.

The biggest misunderstanding about beads is how they work. Without getting in to great detail here's the basics. Since I recommend using Mix 43 for the best all-around mix, we'll use it for our example. Mix 43 has a nominal operating range of .01 to 1 Mhz. At frequencies over 1 Mhz, they get very lossy. It's like adding a resistor in the flow of RF while allowing audio frequencies to flow unabated. ( For a refresher and more detailed description, the reader can reread the split bead article: http://www.eham.net/articles/7596 )

As I pointed out in the article, it is very important to know which mix you have. Do not rely on surplus sources for your beads. Here are several web sites I recommend. ( http://www.amidon.com or http://www.palomar-engineers.com or http://www.surplussales.com ) When ordering you must specify the mix. Again, mix 43 is the best all around mix to use.

Where and when to place them is also a hotly debated issue. There are three aspects to this and for clarity I want to separate them. The first and most important is placing them on the power cables leading to devices which interfere with you. Good examples are fuel pumps, AC and cooling fans, COP (coil over plug) units, fuel injectors, IAC (idle air control) motors, windshield wiper motors, and ABS motors. In some cases placing them over ignition wiring helps, but it typically takes several on each wire.

The second is their placement over power cables for devices which you interfere with. Alternator control circuits (not the DC power out), ABS control units, cruise controls, AM/FM radios and their amplifiers, traction control systems (a real headache I've experienced), navigation systems, and even some windshield wiper controls. And if you own an Icom 706 and have one of the early extension cables with out factory installed beads, you'll need one on each end as well.

If your vehicle's CHMSL is mounted in a fiberglass wing like mine is, you should bead the lead where it enters the trunk area. This is how I cured the headache I refered to above.

Where not to place them includes low impedance DC power cables. If you adequately size your power cabling, the use of split beads is a waste of resources. Using them in an attempt to cure alternator whine is also a waste. Alternator whine is best cured at the source. Whine usually stems from one or more leaky diodes in the alternator. GM products seem to be the worse for this malady with older model Toyotas in second place. Brute force filters may help, however one large enough to handle a 100+ amp alternator is usually more costly than fixing the alternator.

Bonding

Bonding or strapping is undoubtedly the most important aspect of noise abatement, yet most hams never take the time to do it correctly. Bonding the various bolted on parts together accomplishes two important tasks. It minimizes the leakage of RFI into and out of the various parts, and secondly it enhances what little groundplane a vehicle offers.

The exhaust and tail pipes are good examples of RFI leakers. It is not uncommon to see a 20 to 30 db drop in received noise levels once they're properly grounded. Bonding engines and hoods is also important for the same reason.

Bonding doors and trunk lids have lessor effects on noise, but do aid is maximizing the groundplane. If you doubt this reasoning, here's a little experiment you can try. Install your antenna first and use an MFJ 259B or similar antenna analyzer to measure the on-resonance input impedance of your antenna. Then follow the suggestions below and once you're done, measure it again. The resonant point will drop slightly and the input impedance will drop perhaps as much as 25 percent. This occurs because bonding lessens the groundlosses which are reflected in the input impedance. The better the quality of the antenna, the more noticeable the change is.

Over the years I have developed the easiest and most long lasting method for attaching bonding straps to the various parts, and I offer them here. If not a panacea, at least they're a starting point.

You can buy all sorts of strapping material from the various electrical outlets and hardware stores. However, I've always had a few chucks of old RG8 laying around and the shield makes excellent strapping if it is not corroded or discolored. Just take care when you strip off the outer jacket that you don't cut through the shield itself.

I usually make up several 6 long ones for the doors, 10 long ones for both sides the engine, both hinges of the hood and trunk, and at least three for the exhaust and tail pipes. The end connectors I use are the ones with built in star washers. I purchased mine from Fastenal, but there are other sources. Use a size which will accept #8 awg and with a hole for #10 or #8 self tapping sheet metal screws. I crimp and solder them and you should too. Crimping alone allows moisture to seep into the connection with predictable results. If the strap will be subject to abrasion (like those used on the doors) cover the outside with heatshrink tubing or discarded RG58 casing.

When attaching them to the doors you need to use caution. Keep them away from any interior wiring and away from hinges, door stops, and weather seals. Typically the lower edge of the door is ideal.

Caution is also needed when bonding the hood and trunk. You don't want to end up drilling through the lid! And don't use the existing bolts. Use the self tapping screws which bond better especially with the aid of the star washered lugs. And strap across both hinges, not just one.

Almost without exception nowadays, exhaust systems are make of a good grade of stainless steel. Wire brushing a small area for the lug to bite into and using stainless steel hose clamps to secure the lug has always worked for me. I have never had one come loose or need retightening. The opposite end should be attached to the underframe or unibody strut work. If the car is undercoated you may have to clean a small area. A Dremel tool with a wire wheel works well for this operation.

If your vehicle is body on frame you'll need a bunch of straps to go between the body and frame. As an example, four separate straps (one on each corner) work well for a pickup bed. Incidentally, don't rely on any factory strap to provide a good RF ground. They're meant solely for DC grounding tail lights etc. and are just inadequate for RF grounding needs. The same can be said for factory engine strapping.

There is an old cliche that says an ounce of prevention is worth a pound of cure. If you'll just take the time to do your bonding correctly, you'll be amply rewarded. Short cut it and the results won't be worth the effort. I spent some eight hours making and installing the straps on my vehicle. If it takes you much less, you probably didn't do it right.

Antenna Grounding

High frequency mobile antennas come in about every size and configuration you can imagine and every single one of them is a compromise. Length matters and it would be nice if we could drive around with 20 foot long whips, but alas we cannot. Shortening an antenna lowers its input impedance, poor groundplanes and coil losses raise it, with the end result being the input impedance is closer to 25 ohms than 50 ohms. Literally thousands of articles have been written about matching them to 50 ohms to match our coax feeds. What ever method you use to achieve this match is fine as long as the antenna is DC grounded.

There are two issues with this. First, DC grounding helps control static discharges from the antenna, thus reducing some of the received hash we all put up with. Secondly it is a safety issue. If the antenna were to come into contact with a live overhead power line, DC grounding will help prevent damage to your equipment and perhaps to you as well.

The capacitive matching technique mentioned in the foreword does not provide DC grounding. Inductive matching on the other hand does, and so do ununs. If you're using capacitive matching and don't want to bother with changing it, at least add a 10K resistor across the antenna terminals. While this won't protect you from the overhead wires, it'll help tame the static discharges. An adequately sized RF choke will to the same.

The Bottom Line

Some people just can't resist saving a buck or two even when it costs them $10 to do it. My grandmother used to call this penny wise and pound foolish. What ever you call it, there are a few things in amateur radio you shouldn't scrimp on. One of those is coax. Another is coax connectors. An in my opinion, mobile installations is another. While I hear retorts to the contrary all of the time, I want the readers to remember this: It may very well be a hobby with everyone having their own requirements and levels of satisfaction, but when we're in our mobiles operating our favorite modes and bands, you're also operating a motor vehicle. Any and every thing you do while underway is potentially deadly to you, your passengers, and to those who share the highways and byways with you. The last thing you need is another distraction which might cause you to have a crash. Sloppy installations with a lack of proper safety procedures in place are much more distracting than neat, clean ones. Take your time, do it right, and spend what it takes to be safe.

Member Comments:
This article has expired. No more comments may be added.
 
Another Look at Noise Abatement  
by KB7YOU on April 23, 2004 Mail this to a friend!
 
RE: Another Look at Noise Abatement  
by W1RFI on April 23, 2004 Mail this to a friend!
> Adding insult to injury are several articles
> recently published in QST. While they're technically
> accurate, they ignored important noise abatement
> procedures and/or bypassed common safety practices.

I suggest you write a letter to the editor of QST. If you cc it to me at w1rfi@arrl.org, I will hand carry it to Joel Kleinman and explain why I think it should be published.

For that matter, your article here was very well written. The subject would be great for QSTreet, and it would reach a large number of hams that didn't see it here. I can't speak for the editor, but I can put in a good word. :-)

73,
Ed Hare, W1RFI
 
RE: Another Look at Noise Abatement  
by W8JI on April 23, 2004 Mail this to a friend!
Hi Alan,

Nice article but two things confuse me.


Why is a 43 mix bead the best to use? It may be best for VHF, but it sure isn't for HF!!! As a general rule you want a material with an **impedance peak** on HF. Unless I'm mistaken, 43 material's impedance peaks well up in the hundreds of MHz. It has a Q of unity at about 10 MHz, that's where the XL and Xr are equal.

73 Material has an impednace peak at 10MHz, so would offer the highest impedance over HF. 43 would be up at upper VHF or lower UHF.

# 73 materials would be a better choice for suppression at HF.

Or am I missing something?

I'm also not sure about buying materials from EXPENSIVE surplus houses who get parts second hand or whose primary business is not ferrite materials. I've always found the surplus cost similar to cost from the original supplier, and sometimes even more. I'd recommend searching the web for suppliers, or contacting balun manufacturers. Surely a balun manufacturer would buy in bulk directly from the original source, and I'd bet some are willing to sell cores. Just a suggestion.

73 Tom
 
RE: Another Look at Noise Abatement  
by K0BG on April 23, 2004 Mail this to a friend!
Tom is correct about Mix 77. From 1 to 7 Mhz, Mix 77 is a better choice, and for frequencies over 200 Mhz, Mix 61 is the perferred mix. This said, Mix 43 is still the best "overall" choice, and is more readily available.

Alan, KBG
 
Another Look at Noise Abatement  
by N2XE on April 23, 2004 Mail this to a friend!
Alan, great information here but the tone and tenor of the article nearly turned me away. Let me address one comment specifically:

"For example, one of the articles described how the author designed and built a combination capacitive matching and mounting base for his HF antenna. Nothing was mentioned in this article about DC grounding the antenna which helps eliminate static build up and provides a measure of safety should the antenna come into contact with high voltage lines."

I'm quite familiar with that article. I think you missed the point of what it was about. The article you're criticizing was about mounting and matching a mobile antenna--not noise abatement. The point of the article was two-fold: Short antennas have a low radiation resistance and how to attach an antenna to a car and impedance match the critter at the same time. Not how to abate noise or the proper way to wire your mobile rig. Were the article to include every concern and aspect regarding potential problems and issues, it would be very long and very boring.

You article here doesn't address antenna efficiency, radiation pattern or polarization. Nor does it address how to make an antenna mount with built in impedance matching. Those are extremely important concerns to radio amateurs yet you omit this information?
 
RE: Another Look at Noise Abatement  
by W8JI on April 23, 2004 Mail this to a friend!
Hi Alan,

I still disagree, let me explain why.

Amidon, Palomar, and others are not bead engineering people or manufacturers, they are retailers. They simply repeat information from manufacturer catalogs without fully understanding the end application. The advice is sometimes not good advice, not because they are stupid or trying to be misleading....but because they are not experienced in this application.

As a matter of record, Fair-Rite Corp, and actual manufacturer of beads recommends 43 materials as EMI/RFI suppression from 20-250MHz. NOT for HF.
(page 5 14th edition Fair-Rite Products Corp catalog)

Fair-Rite Corp is a core manufacturer with at least one good real engineer on staff, not a retailer. They understand applications. The material recommended for EMI suppression on frequencies below 30MHz is 73 material! 43 is OK for 20 MHz and up or for use in known resonant applications below 20MHz.

If the core is in a resonant circuit or handles very high flux levels, you want to use a core operating at or close to a Q peak. For mid-HF, that would be a 61 material or other materials that show an XL peak at upper HF and mimimal resistance.

If the core is for suppression or low power broadband transformers, it needs to be operated at or near an impedance peak. For suppression we would like R to be as large as possible, and X to be as low as possible.

Why do we need that? Because we don't know what the impedance of the circuit is. If for example we place a bead with +300j in series with a cable that has a fuel pump on the end, and that pump has a capacitive reactance of -300j, we would actually PEAK the noise current! We would make the wiring series-resonant!

What we want is a material that has very high RF resistance, because any amount of resistance we would add would ALWAYS reduce RFI.

For example?

A #73 Z chip bead has an impedance peak of 40 ohms at 20MHz. The resistive part is 40 ohms at 20MHz! It is 20 ohms Z at 2MHz with an R and L about equal. The Q is only one.

The same construction 43 material bead has an impedance of 28 ohms at 20MHz. R is 20 ohms, XL is slightly less. It has only 5 ohms Z at 2MHz, and the impedance is almost a pure reactance.

We never want to add a pure reactance to an unknown impedance to suppress signals! It might just as likely make things worse as better.

All across HF 73 material has higher impedance, and at some frequencies 4 times as much as 43 materials. Worse yet, 43 material has a high Q, which means it may increase noise coupling in cases where the line has a capacitive reactance where installed.

77 materials would be similar to 73, and would be a much better choice for low power suppression, like computer, ignition, or pump noise. As a matter of fact the impedance ratio advantage is 4:1 at lower HF and it is higher all across the HF bands with 73 and 77 materials having significantly more resistance than reactance across the HF spectrum.

For noise abatement, that's what we want. Inductance, which comprises most of the 43 materials impedance, can actually INCREASE noise levels if the position on the lead you are placing it over exhibits capacitive reactance! A resistance will always decrease noise levels. A reactance might very well increase it.

73 Tom
 
RE: Another Look at Noise Abatement  
by K2WH on April 23, 2004 Mail this to a friend!
OK, I read it all. So, can one use a snap on ferrite beads using all (3) types mentioned in series on the same lines to take care of the entire HF spectrum?

K2WH

 
RE: Another Look at Noise Abatement  
by K4JSR on April 23, 2004 Mail this to a friend!
Only if you admit that the beads are DUDES!
 
RE: Another Look at Noise Abatement  
by AD7DB on April 23, 2004 Mail this to a friend!
K0BG: Great article as always, and much appreciated.

W1RFI: "QSTreet"? A Freudian slip perhaps? :) Treet is Armour's version of Hormel's Spam.
 
RE: Another Look at Noise Abatement  
by WB2WIK on April 23, 2004 Mail this to a friend!
Nice article, Alan!

If gasoline gets any more expensive, it will cost $5 per QSO to operate mobile...here in CA, it will be more like $8.

I've got my own noise level down to "nothing" when I start my engine. Now, what do I do about everybody else on the road? :)

WB2WIK/6





 
RE: Another Look at Noise Abatement  
by K2WH on April 23, 2004 Mail this to a friend!
Hey Steve, can an individual order small quantities from Fair-Rite? Or do you have to buy a kabillion at a time.

Nice instructive website (Fair-Rite).

K2WH
 
Another Look at Noise Abatement  
by N4ZOU on April 24, 2004 Mail this to a friend!
When QST was available in the book stores I would buy one when they had a good article in it... that was about once every two or three years. Not only that but the ARRL only serves a small part of the amateurs licensed here in the states. I have no idea why anyone would want to post an article where so few would see it.
 
Another Look at Noise Abatement  
by K1CJS on April 24, 2004 Mail this to a friend!
Great article, Alan! The only thing you didn't mention is to check the bonding and the wiring at least every 3 to 4 months, and also after your vehicle is serviced anywhere.

It is easy for a mechanic to either break or leave one of the straps disconnected. It is also possible that something may happen to the wiring or one of the fuses in the wiring that you won't know about unless you check them.

It is also easy to overlook corrosion, especially if you're not looking for it. And in New England and northern regions, if one thing is known by people up here, it is that the combination of weather and road treatment chemicals cause corrosion--especially to wiring and connections.

If you see noise levels getting higher in your mobile, check the bonding and wiring--there may be a problem beginning that you may easily fix instead of having to re-do the connections from the start.

Thanks for the pointers and 73!
 
RE: Another Look at Noise Abatement  
by K0BG on April 24, 2004 Mail this to a friend!
Chris, you are indeed correct! This is why I recommend using NoOx or one of the other antioxidizers available. Of course, you can't use them on exhaust systems, but everywhere else is OK.

About the only other thing you could do would be to use a stud welder to attach the straps to. Interesting enough, I just saw one on sale at a local specialty hardware store. I'm almost tempted to spend the $150 for the thing.

All kidding aside, quarterly inspections are the norm for us "died-in-the-wool" mobile types. Huh?

Alan, KBG
 
Another Look at Noise Abatement  
by NC2W on April 24, 2004 Mail this to a friend!
Please remember that fuses and circuit breakers protect WIRE. They don't protect devices. Please correct your article, to include that point. A wire should be one size larger than the fuse protecting it.

(fuses should be smaller than wire.)
 
RE: Another Look at Noise Abatement  
by K1CJS on April 24, 2004 Mail this to a friend!
They are--they are indeed. Even welding won't stop connections from breaking off, and as good as no ox is, it still only slows the damage--not stop it.

And I've seen mechanics even remove bonding straps that they consider unneeded. I've had to tell a mechanic to reconnect them more than once after having my car serviced.

73!
 
anti-ARRL troll  
by KZ1X on April 24, 2004 Mail this to a friend!
OK, I'll take the bait ...

~660,000 licensed US hams, about 1/3 active =
~ 220,000 active hams

ARRL paid annual memberships = ~ 180,000

... or about 82% of active hams. Pretty good coverage, I'd say. US hams who aren't League members "cut their own noses to spite their face."


This mobile installation technique / noise abatement article is top notch. Edited properly, it would make a great QST article. I'm with Ed on this one.

 
Another Look at Noise Abatement  
by VE6XX on April 25, 2004 Mail this to a friend!
Hello All: Alan: Thanks for yet another thoughtful well written article. Thanks also to those who added their $.02 in the form of info or helpful comments.
Tom beat me to the draw on the "mix" numbers for ferrite beads. I also prefer to weld studs to exhaust piping to mount bonding straps, but I have never tried clamping the stainless exhausts so can't comment one way or the other. Tsk Tsk Alan. The world would no longer revolve if it weren't for "black tape", Green string" & of course "duct tape". I understand your aversion to vinyl tape Alan, but there are times.....
Your comments regarding crimped connections & !@#$%^& butt splices should be "required" reading for ALL hams & they mirror my experience as well. The use of co-ax as a power cable has it's roots in antiquity, does NOT reduce noise in my experience & is sadly undersized for modern rigs as you pointed put. I actually use "welder cable" for some installs because of the low "Z". My own install uses a separate "gel-cell" mounted under the rear seat in my Dodge diesel 4X4, & it is charged by a #10 wire running to the batteries, diode isolated. There is a 1 foot lead feeding a box of continuous duty relays that are switched from a panel in the front seat.
There is essentially NO voltage drop to the radios.
A great article Alan, & I would urge you to accept W1EFI's offer to approach the QST tech editor re: publishing it in QST. Finally, permit me to thank everyone who responded for the polite & civilised tone of their remarks. I grow weary in the extreme of "flamers" & the terminally rude.

CHEERS! Brian Hind, VE6XX
 
RE: Another Look at Noise Abatement  
by LNXAUTHOR on April 25, 2004 Mail this to a friend!
- tks for an excellent article... one of the great reasons for keeping up with this site and finding good technical information, experience and advice...

- i still haven't installed an HF rig in the vehicle, but i'm collecting all the good tips published here and am collecting the requisite materials...

- one thing i haven't seen regarding mobile ops is a recommendation on battery connectors? IOW, how to properly tap off a battery with existing connectors? (i'm assuming that a secondary battery is the best way to go, but since my vehicle's battery resided under the rear cargo area, i'm not sure i have room for a secondary)...

- once again, thanks for the info!
 
RE: Another Look at Noise Abatement  
by K0BG on April 25, 2004 Mail this to a friend!
Eric, NC2W; I thought I did just that. Apparently I didn't.

Front mounted fuses are indeed to protect the wiring, not the device(s) connected to it. Secondary fuses (usually supplied by the maunfacturer of the radio) in the supply line are in part designed to protect the radio. They usually don't, however.

The information I posted with respect to the amperage ratings of the fuses comes from the SAE and others.

As for the bead mix, I have not arguement with Tom (W8JI) on this one. It is my intention to rewrite the article with information supplied by Tom with the hopes of having it published in QST. Now all I have to do is purchase about $150 worth of Mix 77!

Lastly, for those who think the QST audience is small should read the publication data appearing twice a year in QST as required by Federal law. And while some will fault their politic, without them there wouldn't be amateur radio.

Alan, KBG
 
Another Look at Noise Abatement  
by AD5GX on April 26, 2004 Mail this to a friend!
Thanks for the detailed information. So often I see "make sure to ground well". Your specific advice has given me a practical checklist to follow.

I'd appreciate something on adding a second battery in the trunk. What does "diode isolated" mean? How does the second battery get charged without overcharging?

Thanks!

73,

Matt
 
RE: Another Look at Noise Abatement  
by N0RF on April 26, 2004 Mail this to a friend!
Bravo!

Timely, concise, detailed, specific, helpful, useful.

Thank you Alan. Please continue with more articles like this.

Also, thank you to the other posters who offer expanded info and other pov's.

What a great forum.
 
RE: Another Look at Noise Abatement  
by W5SO on April 26, 2004 Mail this to a friend!
Good work Alan.
Question: What about the static drain you posted a while back? Wondering if it would help the S6 road noise in my '98 Explorer.
Keep up the good work.
Steve
 
RE: Another Look at Noise Abatement  
by WA1IVB on April 26, 2004 Mail this to a friend!
On the subject of bonding, be sure to bond the pickup truck box to frame and cab as well. In deference to people who don't think a pickup should make squeaky noises, the new trucks are made with polyurethane bushing mounts that do a great job of insulating that mass of metal from frame. I've cleaned up a Ford fullsize, a Dodge Ram 1500 and most lately my Tundra with a couple of straps here, gaining 15 to 20 db of noise reduction without much effort.
 
Another Look at Noise Abatement  
by AB0TJ on April 27, 2004 Mail this to a friend!
I just see two problems... I have installed many high-current stereo amplifiers in many cars (some even draw 120 amps or more) and I'm not sure if the same applies for radios, but these techniques have worked for radio installs in my vehicle also. Anyway, I have never had a problem with using the vehicle body as a ground. Running a ground wire from the battery all the way to the trunk makes ground loops and picks up alternator whine. Both of these can make noise on your received and transmitted signals. I'm not sure why you got 3 ohms, but on most vehicles you can sink quite alot of current thru the body. Sometimes a larger gauge wire is required between the frame and the battery, but that's it.

Just my $0.02
Alex
AB0TJ
 
Another Look at Noise Abatement  
by AB0TJ on April 27, 2004 Mail this to a friend!
I also forgot to add, an extra battery in the trunk is actually not a good idea. The alternator supplies the current when the car is running, not the batter(ies). A large enough alternator and power wire to handle the load is a better solution.
 
RE: Another Look at Noise Abatement  
by AB0TJ on April 27, 2004 Mail this to a friend!
I hate to write yet another relply, but I have found that fusing the ground wire is also not a good idea. No fires are going to happen if the ground wire comes in contat with the body. And if the ground wire blows it's fuse, but not he positive wire, things like coax sheilds that are still grounded end up being the ground wire for your rig. You won't notice the the fuse has blown, because the rig will still be operating. But you will notice when you hit transmit...
 
RE: Another Look at Noise Abatement  
by K7IHC on April 27, 2004 Mail this to a friend!
I'm with Alex on his points. Most (if not all) commercial and public safety mobile radio installations don't use a separate power wire directly to the (-) battery terminal. Good body/frame grounds are just fine, even for 110 watt VHF lowband radio installations. And good quality crimped wiring connectors are fine for 12VDC wiring, when properly used. Vehicle and aircraft manufacturers use crimped wiring connectors in their harnesses. I've found Scotch Super 88 (or the even better 88T) tape to work fine in mobile installations, if applied properly and used judiciously. I'll agree that good shrink-fit tubing is the first choice, but tape can be fine for secondary protection and certain applications.

Also, marine (boat) equipment suppliers can be a good source for top-quality 12 VDC wiring equipment and supplies.
 
NTIA REPORT POSTED  
by KA4KOE on April 28, 2004 Mail this to a friend!
http://www.ntia.doc.gov/
 
Another Look at Noise Abatement  
by KC2MMI on April 29, 2004 Mail this to a friend!
Alan, I'm glad to see I'm not the only one who thinks crimping is nice but crimping AND soldering is better.<G>

I recently completed a wiring job with #4AWG fully tinned machine wire (which is similar to battery wire) and that stuff's a bear to crimp, even with the proper crimping tools. Before I crimp a cable end, I spread it a bit and inject some Solder-It (aka Solder-Weld at Radio Shack) into the cable end. Also, some in the lug cup. After I crimp I only have to apply heat to the lug, and wait for the water-white flux to flow out. I know that the solder has melted from the inside out, and completely filled any voids in the cup. I'll also run some solder on from the outside, to make doubly sure.

But injecting the Solder-It paste before the cable goes in, is cheap insurance to make sure the solder will completely fill any gaps and make a solid bond.

Hey, I'm into overkill. I'm used to working on boats, where there's no such thing as a minor electrical failure.<G>

One thing that baffles me is the lack of proper fuse boxes. If I want to reroute four medoium loads to the end of a heavy cable...I can buy junk from China for $4.95, or an official "marine" grade fuse panel for $80. But there's damned little to found be found in between those two extremes, the few places that show nice little fuse boxes (i.e. preassembled, using ATO fuses and covered) simply never have them in stock. ust a simple source for a simple fuse box, under $20, would be nice.

 
Noise Abatement in general . . .  
by N7CAV on June 3, 2004 Mail this to a friend!
Should I be worried about using beads that would block the 1-30Mhz range? (Using 'any old bead' from dead electronics and the like, and adding them anywhere I can on my station) - and for that matter, if I just randomly add various types of beads to various parts of my station, is it doing any good or evil?

I also pounded five copper-bonded 8' ground rods in the earth, about 4-6 feet apart, and bonded all to the center rod, and to my station. All my gear is grounded to a 3/4 copper pipe, connected to 2AWG wire, connected to the denter external ground. Not sure if this is overkill.

Reading the negative ground schools of thought, I guess I feel more comfortable with a direct battery, or at least frame ground. I'll abandon the idea of fuse protection on the ground side, however- Seems to make sense that if the primary ground is broken, something else WILL take its' place before you realize a positive lead is resting on your radio chassis, or some other disaster . . . :-)

I really enjoy these posts, and even the feedback that is or is not negative- as long as it is helpful and contains good information.

73 - trooper, N7CAV
 
RE: Another Look at Noise Abatement  
by W4MMP on February 19, 2005 Mail this to a friend!
I hope WA1IVB receives this. He wrote:

"On the subject of bonding, be sure to bond the pickup truck box to frame and cab as well. In deference to people who don't think a pickup should make squeaky noises, the new trucks are made with polyurethane bushing mounts that do a great job of insulating that mass of metal from frame. I've cleaned up a Ford fullsize, a Dodge Ram 1500 and most lately my Tundra with a couple of straps here, gaining 15 to 20 db of noise reduction without much effort. "

I have been attempting just about everything to suppress EMI in my 2004 Toyota Tundra V6. Many ground straps, beads everywhere and nothing works.
I hope WA1IVB reads this and perhaps can give me some specfic pointers on how he reduced the noise.
Thanks,
Ron
 
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