Going Computer Mobile in Today's Electronic World

Going Computer Mobile In Today's

Electronic World

I have lived long enough to see the world come from AC/DC tube radio sets and small black and white TV to the world of Wifi Internet radio and HD 70” flat screen digital TV. With everything being controlled by computer chips and connected to the world wide web. With all the innovation few have addressed the issue of interference or mobile power supply.

The government has given manufactures an out with a small label they place on the back of everything they manufacture. Go to the FCC web page and read “Title 47 CFR Part 15” and you will soon realize that anything that has been labeled “certified to comply with” label attached will interfere with at least 15 other appliances that carry this label.

Now with the above in mind, think about all the electronic components that operate your vehicle. I am sure that vehicle manufacturer's have considered your use of computers, printers, and other RF (radio frequency) producing device, and have come up with their own label, commonalty knows as a “warranty”. I haven't read all warranties, but the few I have have given the vehicle manufactures an out. “The installation and/or use of electronic devices or radio frequency producing products will void this warranty” or something similar.

I have Ham radios, CB radios, Scanners, FRS/GMRS, and computers with printers in my vehicle and use them without interference on a regular basis. I use cell phones and GPS with better than average results.

First Thoughts

Before the advent of the cell phone and mobile computing the number of people using electronic devises in their vehicles was relative few. There was a small number of Ham radio mobile, and CB operators. The biggest problem that face them was interference and noise. It was more noticeable because they typically used AM (amplitude Modulation), or SSB (Single Side Band). Ignition systems were quickly identified as the major problem, with the charging system a close second. The paramount problem was contact points opening and closing. Along with brushed running on a commutator. Add to this long runs of wire from front to rear of a vehicle and you have numerous possibilities of broadband RF (radio Frequency) interference problems.

The least obvious problem is what automotive service technicians call the “hard start condition”. This is when under the right condition the starting circuit will draw power from any power source. This means the starting of the vehicle will draw power from a cell phone, computer, or memory battery connected to the vehicle electrical system.

What has changed

We have had an explosion of new technology and most of it uses or produces an RF (radio Frequency) signal, and requires power from the vehicle electrical system. Cell phones, and computers with printers, along with all types of mobile radio systems.

The vehicles themselves have computer controlled everything build into them. The computer control module that runs the vehicle, and control's the electronic fuel injection and fuel system. Air conditioning, back up cameras, GPS just to name a few.

Count the antennas on a police cruiser, note the antenna on commercial buildings. Ask a aircraft pilot about the amount of electronics in his air plane. I have seen wifi on city buses. This all is to work together without problems? Right!

Where Do I start

I will always start with grounding everything. I will make ground straps that will go between all doors and the hood and trunk lid. Not only will this go a long way in fighting interference, it is the best thing you can do for any radio or wifi antenna's you may have. I will add ground straps between the engine and the frame of the vehicle. I put a ground strap at the end of the exhaust pipe. Don't forget the fuel door, add a ground strap there also.

Get self tapping screws, star washers and braided flat strap from your local electronic surplus house. Look for it at a ham fest or order it. You may want to use crimp connectors, but I have found that just adds to the cost and they are prone to come loose. Just screw the self tapping screw threw the braided cable with a star washer between the braid and vehicle. You can sometimes put ferrite beads on wires to tame noise.

I have found that fuel pumps emit broadband noise that almost covers the complete radio spectrum. And have built a filter that will eliminate the problem. I found this filter also works on the heater and defroster blower motors. You can build this from parts found at electronic supply and surplus stores. It is basically a coil with capacitance and none of the values are critical. Check out the ARRL (American Radio Relay League) Hand Book for information on building electronic filters. The Internet can help you on this by Googling electronic filters.

Windshield wiper motors are a thorn in the reception wifi and other radio receivers. They always make noise at the precise time some one says something important. And You cannot always ask for a repeat of the information. They can be tamed with a coil and some capacitance, you just need to spend the time when it is nice and dry outside to get the job done. Don't wait until it is raining, it won't get done.

Powering Everything

Now comes the fun part, powering your computers printers and radio's. Over the years I have come up with a method of powering my radios, and computers in my vehicle that I think is unique and actually very simple. While at the same time it accomplished several things all at once.

I install a secondary 12 volt automotive battery that will be charged by the engine, but never used in the starting of the vehicle. This prevents the vehicle from drawing voltage from the radio/computer memory battery or cell phone battery under a hard to start condition. Thus always having a reliable starting battery to get things going.

This also allows me to always have a well charged 12v automotive battery ready for any reason. I use a dry cell battery so I do not have the problem of corrosion, or spillage or leakage of acid into any thing. I can pull this ready to go battery out of the back of my vehicle and with a small inverter run almost anything I may need to run. This saved the day at a Christmas parade my family participated in. It ran the lights and music on the float that night.

The secondary battery can be set up several ways to keep it charged and yet not in the vehicle start circuit. I use diodes, capacitors, and a switch to separate the secondary from the primary battery. The diodes and capacitors prevent any AC voltage that may be coming from a bad voltage regulator from reaching the secondary battery. A switch of high enough amperage separates the secondary from the primary on the start of the vehicle. I have seen a voltage controlled solenoid used to separate a secondary battery from a primary on many RV's but this dose not achieve what I found necessary in the operation of computers, printers, and radios in my vehicle.

I use small aluminum project boxes to house the coils, diodes, capacitors, switch, and mount all the hardware. I use banana connectors on one end and a SO-239 coaxial cable connector on the other end. I run RG-213 coaxial cable underneath the vehicle to the read where the secondary battery is. I terminate the coaxial cable into another project box that has the diodes in it. The box mounted at the primary battery has No 12 wire to a in-line fuse box and large connectors to allow quick disconnect. I wire the switch into the positive wire and mount the switch in the passenger compartment.

This is to charge the battery that will operate any DC powered device, and it will run an inverter to power 120 volt AC device. I have placed the secondary battery in the bed of my truck, and behind the drivers seat of my truck, which I think actually works better for me. This allows me to place the separation switch at the secondary battery shortening the wire to the switch.

This makes for a nice neat installation and fights interference. It keeps the secondary charged and allows me to add or subtract things quickly and cleanly. I can add a cigarette lighter receptacle, or other connector quickly. I keep spare fuses inside the project boxes as a precaution. I normally keep an inverter attached to run laptops and printers. And it can run a CPAP machine all night for those that have sleep Apnea. I used this on my truck when I was trucking and need computers, and printers for the job. I have kept the local surplus suppler in business without busting my own bank account.