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Antenna Vendors Anticipate Another Wave

The time to plan for full power is nigh

Washington: Antenna makers and tall-steel teams are gearing up for a spike in business as TV stations prepare to crank up the power on digital transmitters.

"Another bottleneck is expected," said Jay Martin, vice president of sales and marketing for Dielectric, a manufacturer of towers, antennas and related peripherals in Raymond, Maine.

The first bottleneck occurred just prior to the first DTV broadcast deadlines in 1999. Manufacturers scrambled to meet the increased demand, because no one keeps 1,500-foot towers or two-ton antennas in inventory. Each one has to be made to spec, said Alex Perchevitch, president of Jampro Antennas in Sacramento, Calif.

"These are not companies that produce things like Dell computers," he said.

Then in late 2001, just six months before all commercial stations were supposed to replicate their analog coverage area in digital, the FCC changed the rules to allow stations to meet the deadline with low-power transmitters. Demand for high-power transmission equipment dwindled and manufacturers again raced to meet a new demand for low-power gear.

Now, stations broadcasting at low power will most likely need further structural modifications to meet the final full-power deadlines. The first of these deadlines hit July 1, when the top four stations in the top 100 markets had to transmit DTV at full throttle. (Stations that didn't change their DTV channel in the current channel-election process have to hit maximum power; those with a tentative DTV channel assignment have to replicate their 1997 analog coverage area.) All remaining stations have to maximize, or replicate at least 80 percent of their '97 coverage by July 1, 2006. And that leaves just about enough time to make it happen, according to Perchevitch.

"This is not a 30- to 60-day project," he said. "Somewhere between six to nine months is more realistic."

Both Martin and Perchevitch said most large-market stations have made the necessary modifications, but that those in smaller markets appear to be in wait-and-see mode. Just as with the on-air DTV deadlines, the FCC has allowed for six-month waivers on the full-power deadlines.

Martin said "The majority of people have things budgeted, but all of them are watching the commission's actions."

Based on records kept at Dielectric and those in the FCC's database, Martin has identified at least 400 stations that will likely have to replace existing DTV antennas with high-power units. Dielectric, one of the nation's largest makers of broadcast antennas, has the capacity to manufacture around 400 antennas a year, Martin said.

"We're sending out a notification to stations that we know will need to do improvements," he said.


Antennas are custom crafted according to application, power level, gain, coverage pattern and so forth. Each is slotted for a specific frequency. A Channel 22 antenna does not work for Channel 24. The manufacturing cycle for a single broadcast TV antenna can vary from 30 days to as long as four months, depending on the type of unit. That timeframe doesn't take into account several mitigating factors--399 other simultaneous orders, for example. More imperative, however, is where that two-ton piece of steel is ultimately going to sit--i.e., the tower.

The next full-power deadline may not spur a huge rash of new tower construction, but existing structures will likely need modifications. And not everyone in the tower business is qualified to do the type of modifications necessary to tack a digital stick onto a tower, said Bill Harland, director of marketing for Electronics Research Inc. (ERI), a Chandler, Ind.-based manufacturer of antennas, towers and peripherals.

"When you're talking about DTV, you winnow out the guys that are running around changing light bulbs," he said.

Harland noted that the process of reaching full power merely begins with identifying what type of antenna is necessary.

"From there, the next step is the structural analysis," he said. "The tower is often fine for the load, but many times, the tower can't handle the erection stress of having the antenna installed."


The standard for tower construction and modification is also about to change. As of Jan. 1, 2006, all new towers and modifications of existing ones must meet EIA/TIA/222-G 2005, the most exhaustive revision of the standard since the mid- to late-'80s, according to John Erichsen, former vice president of engineering for Plymouth, Ind.-based tower manufacturer, PiRod (now owned by Valmont). Erichsen is now principal of EET Llc., a structural engineering consulting firm in Granger, Ind., and was a member of the editorial committee that drafted "Rev. G."

"If you're modifying or adding an antenna--anything but regular maintenance, you'll have to bring the tower up to the new standard," Erichsen said.

Tower structure is pretty much defined by wind, and Rev. G calculates wind load differently than the previous standard. The American Society of Civil Engineers developed numerical models for wind and ice loads in the late '90s, and these are now incorporated into tower construction/modification standards for the first time, Erichsen said.

Rev. G considers several factors, such as how the tower will be used, e.g., for ham radio, 911 relays, television, radio or cellular antennas. The "exposure factor" considers "whether a structure is in the middle of a cornfield, or in an urban environment or near a large water body," Erichsen said. "It helps the designer determine if wind will be disrupted by the structures around [the tower]," he said.

All tower modifications will require a "rigorous structural analysis on the entire structure and everything that's on it," which could take anywhere from a week to a month, depending on the availability of information, Erichsen said. "On an old tower, you may have to go out and measure. It could take more time, depending on what's going to be done to the tower."

Erichsen suggested that "antenna manufacturers have to get their hands around this, because their antennas essentially define the parameters of tower structure." Rev. G is available from Global Engineering Documents at