RF Coverage Test and Radio Classes

On Monday night I got back from a trip to the desert. As part of my volunteer job, I helped test the radio coverage on a road near Las Vegas. This was fun and exciting.

My involvement with this test started in early February when my supervisor called me. I had not been into my volunteer job since October. However, he wanted me to manage their radio field strength testing. In the past there were some issues because the person who developed everything in the lab and the people who ran the test in the field did not communicate in person. After my supervisor explained his plan for the test, I proposed a better one. My plan required less work and gave us the information we really needed a lot sooner. He liked it, and three weeks later we were in the field running my test.

I helped with a test like this last year, but this was a lot better for a few reasons. First, I had a much better idea what we were doing. I understood the steps of the test. Next, I watched or was involved with the construction and testing of the test setups. I was in the R & D Lab soldering wires into a radio to get test points, calibrated a gain curve for individual radios, and learned how to program radios with a code plug. Lastly, it was my responsibility to setup and fix all six of our test units in the field. I had to find a way to make the software work when it was not cooperating and tell everyone how the equipment worked.

This is exciting because I know enough of what is going on to realize problems, propose solutions, and sometimes implement them myself. I realized inventory control gave me the wrong power adapter, even though the number matched what I asked for. This saved a laptop from being fried. I noticed some radios did not have simplex operation programmed for a channel, so I played with the software and corrected the programming on ten radios. Without this we would have been unable to communicate during a lot of the test. During the field test I suggested a change to how our team was driving and the supervisor immediately implemented it.

For the test itself we had five test vehicles with receive units that drove at 30 MPH and were spaced 1/10 of a mile apart from each other. There was also a transmit unit that sent a test signal every minute. Each setup had a laptop, a radio, a GPS antenna, a BASIC Stamp microcontroller, and a fuse block with way too many wires to power everything. The laptops ran a LabVIEW program that logged the signal strength and vehicle location every minute.

I drove in on Sunday night and stayed at the Gold Strike Hotel and Gambling Hall in Jean, Nevada. In the morning we set up the systems and drove into Las Vegas. We had a 30 mile area to test. The entire trip was 627.0 miles.

Thanks to my troubleshooting abilities, all five of the test units we deployed collected good data. Last year only one unit of three had usable data. The data consisted of thousands of numbers for radio field strength measurements and GPS coordinates. I wanted to look at it in a better way, so I created this map.



The transformation from a bunch of numbers to this map was done by GPS Visualizer, a great online tool anyone can use for free. I had to manipulate the fields to get a good result. Our file had coordinates in minutes and North/South/East/West directions, while the program only accepted degrees and no directional identifiers. After some trial and error, including a map showing China, I produced a great file.

Everyone is impressed by this map. The person who made the test setups taped it to the wall where he works. My supervisor will present this map at a meeting this week where he has to explain the value of the volunteer program. Above is just a screen shot, the actual map can be zoomed in and the data points read. The city at the top right is Las Vegas. As the colors get cooler, the signal strength drops. From our test, we learned the entire area is covered.

Now we are planning our next text trip. A few days ago I said I did not want to overstep my bounds by making too many important decisions. My supervisor told me to go ahead and make decisions. It seems my responsibilities and authority are expanding.

Radio Classes, Round II
On Friday I started teaching two amateur radio license classes. These are like the class I taught a few months ago. I only have three people in the beginning class and three in the intermediate class. However, the people look very interested. Someone is even taking both classes at once. My teaching is immensely helped by KB6NU. He publishes an excellent guide to help people learn concepts and what they need to know to pass the FCC license test. If you want to get into amateur radio, I highly recommend his guides.

A couple of people have told me I need to teach another class for the third level of amateur radio license (the Extra). Apparently I am the only person there who has this highest level of license. A couple of people have a similar older licence (which is now obsolete) they got before I was born. I am concerned if I start teaching that class people might think I know everything I am talking about. As it is, there are a few electrical concepts I cannot fully explain or do not completely understand. I am worried if one of my professors walked in and heard me talk he would have me retroactively failed in a couple of my classes. I can cover part of my ignorance with the different sign convention between engineering and electronics.

It seems every time a question I cannot easily answer comes up someone jumps in and explains it. I am blessed to be surrounded by people who have practical experience that fills in all the holes my academic background has. Here is a great example I learned from someone.

FM broadcast radio in the United States has frequencies ranging from 87.5 to 108.0 MHz. These frequencies are centered around 98 MHz. A wave at 98 MHz would have a wavelength of 3.06 meters (speed of wave = wavelength x frequency). If you measure the antenna on your car, it will be just over 30 inches. This is one quarter of the wavelength, since radios get their best reception when an antenna is the length of the wavelength, half the wavelength, or a quarter of the wavelength.

When our team goes out next month for the race, we will be using amateur radio frequencies to talk. Four of our people will have their amateur radio licenses because they took a class I ran.