- Category: Comm Trailer Build
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Did you happen by and see a utility trailer with sprouted antennas on the top and wonder, "What is this thing?" What is it used for?
I get that question a lot, and the answer is not one that can be given in two quick sentences, so I wrote this article to explain it.
The antennas along the perimeter of the roof are mostly for two-way Ham radio transceivers, a Ham radio repeater, a GMRS repeater, a scanner, a WiFi booster, and a cellular data booster.
Ham radio, also known as amateur radio, is a communications hobby involving two-way radio communications. It involves radio frequencies from the microwave spectrum to the same frequency spectrum used by local government agencies for short distances to shortwave-type frequencies that can be heard at long distances and around the world. You can read more about amateur radio on Wikipedia.
The amateur radio antennas on this trailer and primarily used for the more local type of communications, which include frequencies from 28 MHz to 927 Mhz. Citing the frequency ranges may be getting a bit geeky, but the reason why I mention them is to help explain why the trailer focuses on these frequencies.
These frequencies, especially the higher ones, don't travel very far when talking directly from one radio to another. To extend the range, repeaters are used. Repeaters are automatic relay stations that take a signal from one radio and retransmit it over a larger area. This can allow more users who are further apart from each other to remain in contact with each other. You can read more about radio repeaters on Wikipedia.
Amateur Radio operators set up repeaters. Lots of them. There are more than 23,000 repeaters in the United States and Canada. But unlike repeaters that are set up by governments and local businesses that report the location and parameters of the repeaters to the FCC, amateur radio operators do not. Most amateur radio repeater owners want the amateur radio community to know where their repeaters are and how to access them.
Enter my company, RepeaterBook.com, which is a website and mobile app that serves as a directory to help the amateur radio community find these repeaters. My name is Garrett Dow, and I have been licensed as an amateur radio operator by the FCC since 1992. My "callsign" is KD6KPC. As the owner of the RepeaterBook brand, I work hard to obtain accurate data for the amateur radio community, and this trailer helps me do it.
The antennas on the outside are connected to radio equipment on the inside that allows me to travel and test the operational characteristics of amateur radio repeaters all over the country and report them on my website.
The trailer also includes a portable repeater that travels with the trailer and can be activated to improve local amateur radio communications in the vicinity of the trailer.
General Mobile Radio Service (GMRS)
I am also licensed for the GMRS Service as WREQ745. The GMRS service is limited to frequencies between 462-468 MHz and are similar to the Family Radio Service (FRS) in the same frequency vicinity. GMRS licensees may operate repeaters, just like amateur radio operators can. These repeaters are also tracked and tested by RepeaterBook.com.
The trailer also features a portable GMRS repeater that can be activated to improve local GMRS communications in the vicinity of the trailer.
Government, Marine, and Business Band
I have been trained by the Department of Homeland Security and authorized to operate on frequencies allocated for local government use during emergency situations. This trailer has radio equipment to facilitate field operations in disaster areas. It can also communicate on Marine frequencies and monitor business band channels.
Citizen's Band (CB)
Repeaters are not allowed on CB, but I included CB capabilities. Although the primary purpose of the trailer is to support RepeaterBook.com, it can function as a mobile command center providing communications capabilities in a disaster zone. Having access to various frequencies and modes maximized flexibility.
The additional equipment on the inside of the trailer aid with powering the radios or further supporting the purpose of the trailer. Equipped with the ability to accept electricity from the grid, generator, or solar, its onboard power system can keep the trailer running indefinitely, with or without power from the electrical grid.
I hope this article has helped answer some questions you might have had about this "porcupine trailer." I've added a FAQ below for some short answers to some additional questions you might have.
Q. Does this trailer emit dangerous radiation?
A. All transmitters, including cellular, Bluetooth, and Wifi routers emit energy. If exposed to high radio frequency (RF) energy for long periods of time, the FCC has shown that it can cause negative effects on the body. The equipment in this trailer is thought to be capable of producing the energy amounts and duration to cause ill effects on the body if exposed for many years. The person exposed would have to be within inches of the transmitting antenna continuously for years to experience any illness. Simply walking by the trailer or living next door will not produce the energy required to cause effects on your body. The antennas are also mounted above a person's height, and the radiation is transmitted up and out from the trailer. Besides that, the trailer is not intended for use at home but rather on the road. The occupants of the trailer are protected from RF energy by the metal structure of the trailer.
Q. Can the trailer cause interference to my TV, computers, or phones?
A. The operating frequencies of this trailer are not typically associated with causing any kind of interference. The radios are regulated and tested by the FCC as far as their requirements not to cause spurious emissions that cause interference. In fact, they tend to be more of the victim of interference by other household electrical devices and appliances that are malfunctioning. All of the same frequencies and equipment have been operated for years from the antenna on the roof of my home for the last 17 years without a single complaint from a neighbor. Again, this trailer is not intended to be used at home as the home is already equipped with similar radio systems with better base station antennas mounted at the highest points of the roof.
Q. How can I learn more about the trailer? Do you do tours?
A. If you would like a tour of the trailer next time you happen by and see me working on it, just ask! I also demonstrate the capabilities of the trailer to amateur radio clubs, youth groups, and school classes as a way to expose the science and physicals of electrical theory and radio propagation to all interested parties. For more information, you can contact me here.