Field Report: Comrex Matrix GSM module

One morning this summer, our adult contemporary FM station, WHMS, took the morning show out for a remote. But this particular broadcast hardly stood still for one minute -- literally. By the end of the show, we had traveled more than 130 miles, from our Champaign, IL, studios to downtown Chicago, broadcasting live all morning from a train car.

The idea for this mobile remote had been brewing for weeks. One of our salesmen had made a deal with Amtrak and was looking to promote the rail line connecting Champaign to Chicago. He came up with the idea to broadcast live from the train on a cell phone.

I had heard about the new GSM wireless module for the Comrex Matrix and thought it might be our answer. When I ran this idea by Comrex, they discouraged me from risking the broadcast. Being conservative, they don't recommend traveling while the Matrix is connected, as switching between cell towers at 80mph may drop the connection. At least the network coverage was in our favor: the train tracks connecting Champaign-Urbana to Chicago parallel a thick line of coverage on the GSM maps. With nothing to lose — the hand-held phone was our only other option — we decided to try the Matrix.

Performance at a glance
Fully compliant GSM connectivity
Completely mobile operation
Accepts standard GSM SIM
Increased power output
7kHz audio response
Useable worldwide
Getting ready

Bench testing the Matrix at our studio was difficult because our two transmitters in the building generate enough RF interference to block phone calls from the Matrix or any GSM phone. But leaving the building, we didn't have to go farther than the parking lot to make a successful connection.

On the morning of the remote, we woke up early and arrived at the Champaign-Urbana train station armed with two headset mics, a battery, a backup cell phone, a blank steel rack panel to be used as an antenna ground plane, and the Matrix. Most of our fellow passengers were still asleep when we boarded at 6 a.m. Many had traveled all night from New Orleans, so we had little competition for a table in the lounge car.

We mounted the three-inch antenna on the rack panel, powered the Matrix and dialed the studio. Once we connected, our morning team went live from the train car. Mike Haile and Steve Kelly followed the normal talk-heavy format from the train car. Despite the manufacturer's warning, the connection was stellar all morning, with only one disconnection in more than two hours. Once we got into downtown Chicago, however, our connection faltered again as the train passed through tunnels and under buildings, so we temporarily gave up.

Steve Kelly, left, and Mike Haile during the remote in progress at 80mph.

The remote concluded from a park outside the train station.

Leaving the train in Chicago, we found ourselves underground in Union Station, so we went outside on the patio for the end of the show. I remember how long and tedious it was to use RPU antennas, but in Chicago we were reconnected within seconds, and Mike and Steve finished the morning show there, sitting on a park bench in the sunshine.

As the flagship station for University of Illinois athletics, as well as many other local sports games, our AM station carries a heavy remote schedule. While the university arenas typically have ISDN lines available, many local high schools do not even have regular phone lines at the fields. We have relied on bag-type cell phones for years, but with the GSM Module, we will be able to deliver high sound quality from those venues as well.


We are also looking into the sales potential of this technology. We have a monthly remote from a local cell phone store, which is a perfect candidate for a tie-in. This flexibility allows us to be more creative, so our sales team is busy brainstorming ideas for exciting new remotes. We've already purchased the GSM Module for our own Matrix units; the module just arrived and we are already dreaming up new ways to use it.

Bond is chief engineer of WHMS, Champaign, IL.

Editor's note: Field Reports are an exclusive Radio magazine feature for radio broadcasters. Each report is prepared by well-qualified staff at a radio station, production facility or consulting company.

These reports are performed by the industry, for the industry. Manufacturer support is limited to providing loan equipment and to aiding the author if requested.

It is the responsibility of Radio magazine to publish the results of any device tested, positive or negative. No report should be considered an endorsement or disapproval by Radio magazine.

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