Meeting SHVA measurement requirements
Aug 1, 2004 12:00 PM, BY DON MARKLEY
 Stations sometimes must conduct field-strength measurements to verify coverage. This truck is operated by WRAL-TV, NC. Photo courtesy Potomac Instruments. |
Many TV viewers choose to use satellite service to receive signals other than their local stations. Viewers who cannot receive their local stations' terrestrial broadcasts can request that the satellite service provider offer the main network signals. There are two sets of legislation that allow such viewers to request this service: the Satellite Home Viewer Act (SHVA) of 1988, 17 U.S.C. Section 119, and the Satellite Home Viewer Improvement Act (SHVIA) of 1999, PL 106-113. But, for the viewer, it's a confusing mess.
First, the viewer has to request network service. The satellite service provider then checks the viewer's zip code to see if a local station claims service to that area. That is where the first abuse of the system happens. Some stations claim service to zip codes where their signal could only be received on a tethered balloon. If a station claims service to the viewer in question, the satellite service provider may then request a waiver so it doesn't have to provide network service.
Here's the second abuse of the system. Naturally, the television station in question is reluctant to admit that there is any area it doesn't serve or to relinquish claim to a household as part of its viewership. While the legislation specifies the time allowed for the station to act on the waiver request, stations routinely drag out their denial for as long as possible in the hopes that the request will simply go away. If at all possible, a station will try to justify a denial of the waiver request.
The first thing the station has to do is calculate the predicted field strength at the viewer's location. SHVA has defined rigid criteria using the Longley-Rice Propagation Model, Technote 101 and OET Bulletin 69 for this calculation. For a single location, the FCC states that stations must use the Individual Location Longley-Rice (ILLR) model. This is basically the same model applied to other broadcast-oriented calculations, with some small variations. For example, the ILLR calls for running the model in the individual mode instead of the broadcast mode. In addition, the station must consider terrain elevation every 0.1 kilometers, use a confidence-variability factor of 50 percent, ignore any error codes and consider the antenna height to be 20 feet above ground level (AGL) for single-story buildings or 30 feet AGL for buildings taller than one story. The Cable Services Action CS 99-1 contains this specification. OET 69 gives the elevations as six and nine meters. Section 73.686(d), for measurements as opposed to calculations, specifies the elevations as 6.1 and 9.1 meters.
If any reader thinks that there is going to be some significant difference between 6 and 6.1 meters or between 9 and 9.1 meters AGL, he should seek a different field of endeavor. Yet, that is one of the complaints raised in Petitions to Deny the First Report and Order in this matter, ET Docket No. 00-11, 15 FCC Rcd 12118 of 2000. Again, this is an abuse of the system. That type of action is obviously an attempt to delay enforcement of the act for as long as possible. It is easy to pick on the commission's decisions because it often seems to do dumb things. But it's a pity the commission seems to have no authority to simply throw out nuisance petitions. Our good vice president would know what to tell them, but the commission can't use that type of language.
To predict the eligibility of the viewer to receive the satellite signal, the station must run the calculations using ILLR. At least one of the popular software services includes this ability in its program. While a station would naturally be hesitant to purchase all that software for one calculation, the station's consulting engineer should be empowered to do so. A big difference shows up at that point in the individual study. Normally, the station would perform the study only for a small area where the viewer is located. To do the study with points at 1/10 of a kilometer all the way out to the edge of service would cause the poor computer to slog away for hours for no good purpose. The predicted field-strength value is required only at the viewer's location — not everywhere in the service area.
If the station, based on ILLR, does not grant the waiver, the viewer can request field measurements. The satellite service provider then selects an independent signal-intensity tester from a list provided by the American Radio Relay League (ARRL) — the same organization that we hams have belonged to, off and on, for many years. It is considered to have the right people and the right technical skills to perform the measurements. Right. While some members are hams who could design and build excellent TV field-strength meters, others are truck-driver CBers who have upgraded to technician class to get away from the noise. In other words, the technical ability of these people varies greatly. The commission does touch on a rough technical requirement for field-strength meters in Section 73.686, but there are no real criteria to judge the accuracy of the meter, the ability of the operator or the calibration of the antenna, feed line and meter.
But that's enough complaining. If the measurements reveal that the viewer does not receive a signal sufficient for off-air viewing, the television station gets to pay for the measurement. It seems, to this humble author, that there's a lot of wiggle room here. For example, the cost of doing the measurement seems to be closely related to the experience and qualifications of the person doing the work. If a ham operator — using a meter of unknown brand from the last ham fest — does the work, the cost would probably be minimal. On the other hand, if an experienced professional engineer in the business does the work with the latest model UHF field meter, freshly calibrated, then get ready to face the equivalent of a few hours time for a good attorney.
Don Markley is president of D.L. Markley and Associates, Peoria, IL.
Send questions and comments to: don_markley@primediabusiness.com
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