A beautiful location for an FM antenna

BOSTON — The beautiful mountain vista seen above is an excellent location for an FM station, don’t you think? But what do you do when your leased tower site falls through and no new tower construction is allowed?

This was my mountaintop challenge!

In early 2012, I set out to complete construction of an FCC CP for a new station, WUMV(FM), with less than two months before expiration. No big deal, I thought, until the tower owner we had been dealing with for two years informed us that the tower couldn’t accept any additional antennas, and he offered us no options. So I got to work — I like a challenge!

I found a nearby neighbor who has a love for public radio, and some land on the side of the hill the previously-mentioned tower sits atop of. I made a deal with him to install a temporary antenna on a tree in his back yard! See the picture on the next page for the eventual resolution.

With this arrangement, we would still provide full coverage of the city of license. There was one problem: our effective radiated power and our transmitter power output would have to be double what we had planned at the first site, so I couldn’t use my spare 250 watt exciter as I had planned.

If there’s no tower, there’s always a tree!

The station is associated with University of Massachusetts Boston so I didn’t have a large budget to work with. I started looking for cost-effective options. One potential problem — the transmitter had to be small enough to fit into a weatherproof equipment cabinet I already had, along with all the peripherals needed, and be efficient enough to need only exhaust fan cooling.

Solutions

Our Shively 6810-2-SS-DA antenna mounted easily to a 4-inch pipe, which mounted to the tree with a special arrangement of custom mounting brackets and straps designed by Chris Loycano of Broadcast Tower Co. of West Bridgewater, Mass. We chose a nice, fat beech tree, and being a directional antenna, the orientation stake was located by the surveyor, according to Shively’s measurements. Chris’ mounting arrangement of rope and wood lattice allows the tree to breathe and grow, and doesn’t damage its sapwood layer or bark, while permitting the antenna to be aligned to its required azimuth.

At a New England Radio Engineering Luncheon (hosted by Broadcast Signal Lab), I saw one of Elenos’ cute little Indium series transmitters put through its paces and fell in love. The 1,000 watt unit is only 2 RU high, and its high efficiency results in little waste heat. Unfortunately, the transmitter was a couple of inches too deep to fit within the donated enclosure with the doors closed.

Securing the Shively antenna to a tree — landscape fabric under a wood and rope lattice protect the tree from the mounting chains.

So I fabricated special brackets that allowed the transmitter to be installed at a steep angle, with the front near the bottom front of the cabinet and the back near the top. This sleight of hand can be seen in the picture to the right. It provides a natural path for the air to flow, because the transmitter exhaust heat appears near the exhaust fans in the top of the cabinet.

The equipment enclosure sits comfortably on two pressure-treated wood, 6-by-6-inch boards staked into the ground with standard ground rods. Even though there’s no steel structure in the air, I didn’t skimp on grounding. The antenna, transmission line, and the enclosure and its contents are well grounded, tied into the ground rods anchoring the enclosure.

The author and his transmitter box. Note the steeply angled Elenos transmitter: Its exhaust fans on the backplane are at the top of the box to vent excess heat.

The site is fed with power from the landowner’s garage, using 400 feet of 10-3 SO cord. All communications with the site are through a Verizon USB wireless data dongle. That includes program audio, remote control and TCP/IP management. The tower we planned to be on is only half-a-mile away, and I’ve got four bars of signal strength on the wireless router. We get around the lack of a static IP address by setting up an SSH tunnel from the site back to the studio, checking for existence of the tunnel every few minutes, and rebuilding it if it collapses — a great idea from Rob Landry, well known in these parts for his extensive bag of computer tricks.

Setup of the transmitter was a breeze, taking less than five minutes to set frequency, power output and modulation level directly from the front panel.

The site has been on-the-air for nearly six months now, and we’ve been very impressed with the operation.

Unique transmitter site challenges sometimes require out-of-the-box thinking. This project was no exception!

For information about Elenos, contact Mary Ann Seidler in Florida at (855) 353-6670 or visit www.elenos.com.

For information about Shively Labs, contact Bob Surette in Maine at (207) 647-3327 or visit www.shively.com.