Motorola DTR Radio Review |

By "T"
The first warning I heard was Rambo asking Jimmy Dean "Want me to play 'Bubba Shot the Jukebox?'" Looking like a more worn version of Willie Nelson, Rambo is a feral, slightly unhinged Army veteran of both Vietnam and Desert Storm. He's really useful at getting broken equipment working again in the field, and when you need a bodyguard when visiting such entertaining locales as Hartford and Bridgeport. At any other time he's best kept out of sight of the customers. He was in a foul mood today as he was getting sued by the families of a group of Norwalk youths who thought he was a homeless person when they tried to assault him. The police dropped the charges as it was five against one and self-defense, even if three of them are still in a coma. He was just finishing up his lunch with a copy of Edward Abbey's "The Monkey Wrench Gang," and listening to The Doors on his iPod at a volume that would bring Jim Morrison back from the dead. Having been exposed to too many loud noises while serving his country, Rambo needs to crank his iPod's volume up full bore despite having the earbuds jammed so far into his auditory canal that Jacques Cousteau couldn't find them. Jimmy, not being the brightest of bulbs, made the mistake of telling Rambo "Yea, that's a good song." That's when I dived over the workbench, as Rambo was in the process of pulling his .45 out from his toolbox in an attempt to silence Jimmy's annoying noise source. Afraid that the round would overpenetrate the boombox and fly off to hit some innocent person or piece of test equipment, I knock Rambo off his chair, and wrestle the .45 out of his hands while he's cursing at me in Vietnamese.
It started out innocently enough and with the best of intentions (much like a Warren Zevon song). How was I know what started as a simple exercise in boredom-induced technological funkenspiel would introduce me to the next quantum leap in portable personal communications systems. That's one of the more interesting things about this hobby. I was at the shop and had just been asked to stop harassing my co-worker Jimmy Dean. Jimmy likes both types of music, and therefore keeps his radio tuned to the local FM station that plays his particular genre of acoustical entertainment. Sometimes he likes to play his music at excessively high volume, and his co-workers are forced to defend themselves. In this instance, the implement of defensive destruction was an iPod playing Cruxshadows and E Nomine hooked up to a service monitor. After several loud inquiries of "What the heck is that?!", the boss comes in and asks me to play nice. I actually was playing nice, as I made sure all the songs from The Mentors were not on my defensive playlist.
So I soon found myself on this slow day surfing Motorola's product website when I came across them. I'm always keeping an eye out for neat exotic communications equipment at hamfests, and when I saw the Motorola DTR portables I thought to myself "I have to check these things out!" The DTR series are one watt license-free handhelds operating in the 902-928 MHz band along with other Part 15 and ISM devices. Unlike other license-free radio services such as FRS, MURS, and CB that operate on a single analog FM or AM frequency per channel, the DTR series use digital frequency hopping spread-spectrum modulation (FHSS). This means they are less susceptible to interference, can't be received by police scanners, and have a longer communications range than analog single-frequency radios running a watt. Motorola in fact claimed a two-mile range with these units. FRS radio manufacturers also claim a two-mile range with their little half-watt 460 MHz handhelds, and anyone who has played with them knows that at best you can get is a half-mile to a mile tops, under most circumstances. How well would the DTR handhelds operate under a variety of circumstances? I would soon find out. After a few inquiries and a trip into the back storeroom, I soon found myself in possession of a pair of Motorola DTR650s. Jimmy went back to playing both of his favorite types of music. As I walk out into the shop floor, I hear someone with a Texas accent sing about the differences between divorces and horses, Jim Morrison telling everyone "This is the end. My only friend, the end." and Rambo asking Jimmy "Want me to play 'Bubba Shot the Jukebox?'"
Frequency hopping spread-spectrum is nothing new. The military has been using it for years with their SINCGARS (Single Channel Ground/Air Radio System) radios. Instead of staying on one frequency when transmitting, the radio "hops" through a number of different frequencies in a pseudo-random sequence. This reduces the vulnerability of the communications to interference and interception. Frequency hopping is also used on the ISM bands such as 902-928 MHz for telemetry and control, a.k.a. "SCADA" (Supervisory Control and Data Acquisition) systems. Many cordless phones operating in the 902-928 MHz and 2.4 GHz bands also use FHSS. In the latter two instances, it i used for spectrum efficiency as well as interference reduction. You may also find certain cutting-edge amateur radio operators experimenting with spread-spectrum communications on UHF and microwave ham bands, and the ubiquitous 2.4 GHz band. WiFi systems use spread-spectrum as well. While spread-spectrum communications are commonplace in industrial, government, military, and wireless networking applications, until the release of the DTR series radios there simply was not a unit that offered spread-spectrum voice communications in an inexpensive license-free package.
These radios are comparatively priced with less expensive portable radios and give a significant measure of privacy over handhelds operating on a "dot" frequency. If you were putting together a new portable radio system from scratch, it would be worth your while to invest in DTR radios. From a management standpoint, these radios have some neat features not found in similarly priced conventional portables that will enhance your communications system. These features will be addressed later in this article. These radios are license-free and truly plug-and-play. Their operation is uncomplicated. Scanning receivers cannot monitor them, and it is extremely unlikely that will change anytime soon. The DTR is a FRS radio on steroids, and just like FRS, MURS, and CB does not require a FCC license. Until now there was really no way to inexpensively experiment with spread-spectrum voice communications. A pair of DTR410s cost less than a digital trunk-tracking scanner.
Motorola makes three models of DTR radios for the U.S. market. The basic entry-level model is the DTR410. This features six "public talkgroups." For the purposes of keying-up and talking consider them the same as a channel on a FRS or CB radio. The other two are the DTR550 and DTR650. The DTR550 and DTR650 can operate in a private "unit-to-unit" mode, and the DTR650 can act as a supervisor radio enabling the user to do remote monitoring and disabling of other DTR units. Other than these firmware differences, they are all the same one watt 900 MHz FHSS radio.
The first thing I absolutely had to do with these things was to try a scanner on them. Ok, I used more than a scanner. To be more specific, I used a "Signal Stalker" scanner, frequency counter, spectrum analyzer, and an old Optoelectronics R-10 Interceptor on them. I started with the Signal Stalker. This little $100 scannist's friend has, since its appearance on the scene, totally changed the way hobbyists look for frequencies. I turned it on, made sure the 800/900 MHz band was selected, and keyed up the DTR. Nothing. Nada. Zip. I then did a more traditional frequency search of 902-928 MHz and found a donut shop's drive-through, a couple baby monitors, and some ham radio operators on a local 927 MHz repeater. No test transmission from the DTR though. Neat! Next in line was the Optoelectronics R-10 Interceptor. Finally I heard something. Yes, this deceptively capable piece of intercept gear masquerading as an innocent piece of test equipment heard something! What did it hear? A popping "digital" sound that sounded nothing at all like audio. Not only is the DTR a frequency hopper, it also uses digital audio! After that test the frequency counter and spectrum analyzer results were anticlimactic. They confirmed what I already knew about the units. The frequency counter attempted to lock onto the signal, but didn't have a quick enough gate time, and just gave random readings around 900 MHz. The spectrum analyzer gave me a nice view of a FHSS signal.
One aspect of operation I noticed about the units was that they needed a fellow unit on the same "channel" in order to key up. Otherwise they give an error message when you attempt to key them. This is a neat feature, as if the radio keys up you can generally be assured that at least one person you are talking to is within range. It also allows you to do solo communication range tests if you're lacking a fellow hobbyist to play with you. In this case, I had help from a number of friends with these units.
First among them was Hank Frost. Hank is a fellow veteran with a similar interest in electronic communications who is my usual co-conspirator in playing with things technological. Hank is much like a technological spider sitting in a big electronic web (that is, if you can imagine the spider looking like an Alaskan Brown Bear). Hank has the disturbingly cool ability of taking common consumer electronics equipment and modifying them into interesting pieces of what he refers to as "test gear." It makes me wonder what he actually did in the Army, but when I ask him he just shrugs and says "Oh, this and that." After running the gauntlet of electronic security that separates his residence from the rest of the world, I present a DTR unit for his examination. He breaks out this piece of equipment that looked like it was put together from spare parts found in a TV shop. I ask him what it was and he replies "It was originally a satellite receiver." Further questions as to the "test equipment's" origin only elicit that it was originally from "a dude in Green Bay." After checking out the DTR for a few minutes, he hands it back to me and says "Nice for something off-the-shelf." I ask him if he wants to help evaluate it, and he replies "New Hampshire sounds good about now." The next Saturday, we're in a two-vehicle convoy heading up Interstate 91 on our way to Keene and parts beyond. This is a well-known route to us, being the way to get to the famous and now-defunct Hosstraders Hamfest that was held in Hopkinton, NH. Talking car-to-car, we were able to achieve about a two mile range between radios, thus living up to Motorola's range claims. Bouncing around the towns of Southern New Hampshire, the units consistently gave us a range of about a mile to a mile and a half. Hiking in the region's mountainous terrain, that range went down to about a half to three-quarters of a mile.
After playing with them a while up North, I gave The Lone Gunmen a call. The Lone Gunmen are a group of three friends and fellow electronics hobbyists who share my interest in exotic communications equipment. We decide on the most RF-intense, interference-plagued, radio-unfriendly proving ground that's equidistant between the two of us: New York City. If they can perform there, they'll perform anywhere. With Frank Sinatra crooning in the iPod, I hop a train south and meet them at Grand Central Terminal. Soon were walking down Park Avenue looking for a suitable place to do a distance test. Motorola claimed an in-building range of 25 stories, and we wanted to see how they actually stacked up. There are few, if any, tall buildings in Manhattan you can just walk into and start ascending in order to do a radio test. We notice the tallest thing on the New York skyline, and figure "Why not?" I would have loved to take one of these up to the observation deck and attempted a 33 cm band DX record, but the line to the observation deck was oppressively long and we were carrying way too much interesting shit on our persons to deal with a security checkpoint. We walk into the "office" entrance and look around. Despite being one of New York's premier tourist attractions, the Empire State Building has a more mundane function of being home to thousands of law offices, accounting firms, and other businesses. Byers asks me for one of the radios and goes in. A few minutes later he keys up from the 25th floor with perfect audio quality. Then he keys up from the 30th floor with perfect audio quality. After the 51st floor the audio was getting "digitized" and unreadable. Impressed by the performance so far, we went on to have some fun. By this time it was getting close to 5 O'Clock, and it was first Friday.
For those of you who are unaware, a very well-known and infamous hacker magazine has held get-togethers on the first Friday of the month in New York City since 1987. The location is Citicorp Center on Lexington Ave. At this get together, you get computer hobbyists of all stripes, including a contingent of radio ninja wannabes with dual-band ham handie-talkies that like to screw with the security guards. The last time The Lone Gunmen and I were there, we sported VHF Saber handhelds and ran DES-XL on 151.88 MHz. The wannabe radio ninjas thought we were Feds as their Optoelectronics frequency counters could lock onto our signals, but all they heard was the open-squelch noise of an encrypted signal. We figured that tonight would be no different, and we were correct. We walked in with these radios on our hips, and the intrepid group of hamsters in training reach for their Signal Stalker police scanners. Their smug looks changed to that of utter confusion when they discovered that this time they couldn't lock on our signal. Langly yells at them "Try a spectrum analyzer!", to which they reply "What's that?" Soon the word spread around the meeting that "The Feds are back!" Our mission of inducing paranoia completed, we proceed to sit down at a chair and loudly talk about our other favorite subjects: firearms and alcohol. And they all moved away from our table.
Why would you be interested in a proprietary frequency-hopping radio when there are other license-free radios available that cost less? From a hobbyist standpoint, these radios offer a very inexpensive means to play with practical spread-spectrum communications. Since these radios are still relatively new, experimenters have yet to work with them. Much like hobbyists have done with WiFi and other electronics gear, I expect to see a whole host of "mods" to become available for these excellent little radios. From the point of a group of individuals looking to implement a small portable radio system, the cost of these radios is the same as any medium-grade business band radio, but with the superlative quality that Motorola products are known for. Their use of FHSS provides a higher-level of privacy than a handheld operating on a "dot" frequency, and the added features of the higher-end units offer better functionality for a small business. In a similar vein, the higher privacy level would be valuable for such users as CERT, search and rescue, and disaster response teams for relatively private communications when mobile phone service is unavailable for whatever reason.
A few years ago, communications at this level would have been out of reach of most individuals and small businesses. The Motorola DTR series represents the next step on communications, and are a good value for a small group wanting some extra privacy and management ability for their communications or a hobbyist wishing to experiment with the new generation of wireless communications. If you fall into this category, the DTR series radios are highly recommended.
While scanner hobbyists may as expected decry the advent of such technology as the end of their voyeuristic hobby, the advantages of such technology as represented by the DTR series of radios outweigh such fatalistic rants. The communications hobby is a beautifully diverse pastime represented by intelligent and forward thinking individuals. Such individuals will see the DTR series of radios as having the potential to add new excitement to their hobby, and embrace it with open arms much the same way 802.11 wireless networking was embraced. Individuals and groups with a need for inexpensive private communications will likewise see the DTR radios as a useful tool for whatever their mission happens to be. As crowding becomes more of an issue on the RF bands, I expect to see more equipment utilizing spread-spectrum communications. So no matter where you might be in the wide world of radio, I would recommend you take a look at these radios. They are the future.

"Damn it! Don't scare away the teenaged boys!"