Published: TV Technology

Issue:  10/23/97



Viacom Seeks Equalization Over Replication

by Joe Fedele



MIAMI--Viacom, owner of 11 television stations nationwide, has filed a petition for partial 

reconsideration of the FCC's 6th Report and Order (6th R&O) that, among other things, identifies 

specific DTV power levels.  In its petition, filed on August 22, Viacom is seeking to raise the 

minimum power levels specified in the 6th R&O for all UHF stations. 

 

Although no one at Viacom would comment publicly for this article, the company contends in its 

petition that "the particularly egregious power disadvantages suffered by [some of] its UHF 

stations" will seriously compromise its ability to compete against other stations in these markets 

that have been allocated much higher power levels.  Consequently they're asking the FCC to 

increase the specified minimum power level for all UHF TV stations from the current 50 Kw limit 

to 250 Kw.



Viacom is requesting that the FCC reconsider its philosophy of issuing DTV licenses on the basis 

of "comparable coverage."  The FCC, in its 6th R&O, has proposed to allot DTV channels using 

a "service replication/maximization" concept that was developed by a variety of broadcast 

industry interests and representatives. 



Using this approach the FCC sought to establish DTV allotments which allowed stations to 

provide digital service that matched their existing NTSC grade B contours. 



Under existing rules, a majority of NTSC VHF stations were assigned UHF allotments with 

authorized power levels at or near the maximum allowable limit for that channel.  UHF stations 

assigned a UHF DTV frequency (U-to-U), on the other hand, have generally seen power 

allocations far below the maximum limit of 1,000 Kw.



In Miami, for example, all three of the low-band VHF stations assigned UHF DTV channels were 

allocated with the maximum of 1,000 Kw of Effective Radiated Power (ERP). Conversely, none 

of the five U-to-U stations in the market were authorized with ERP's above 193 Kw.   One station 

was allocated only 57 Kw. 

  

This pattern seems to be consistent across virtually every market in the country.  The inequality 

of coverage areas has been a sore spot for UHF broadcasters since the inception of the band in 

1952.  VHF stations have always enjoyed an increased coverage area when compared to UHF 

stations. In effect, nothing has changed in the DTV allotment schedule that would remedy this 

situation.



Prior to the publication of the DTV allotment table in April, UHF licensees found it difficult to 

convince the FCC of their disadvantageous positions. But the obvious inequities in power levels 

provide an easy means of assessing the wide rift in coverage between VHF and UHF band 

licensees. 



The Viacom petition seeks to narrow the disparity between VHF and UHF stations by raising the 

allotment table "floor" by 7 dB across the board.  This would raise the minimum ERP level 

assigned to all UHF DTV stations to 250 Kw. 



This issue of disparity between UHF and VHF stations is discussed in some detail as part of the 

6th R&O. Comments filed by several groups argued that the "power differences [in the table] 

would increase the existing disparities between UHF and VHF stations." The FCC has countered 

that they "continue to believe that [their] service replication proposal is the appropriate approach 

for implementation of DTV.



"This approach," the Commission continued, "will ensure that broadcasters have the ability to 

reach the audiences that they now serve and that viewers have access to the stations that they 

can now receive over-the-air.  At the same time, we recognize that the service replication 

approach could lead to increased disparities among stations."



Aside from the "replication" approach, the FCC has specified coverage areas for DTV stations 

based on interference factors.  In the 6th R&O the Commission states that they would "entertain 

requests for increases in power by DTV stations above the 1000 kW level where such additional 

power would be required to provide service to the station's Grade B contour and would not result 

in additional interference."  This would, for the most part, only exacerbate the disparities between 

VHF and UHF stations.



The Commission also agreed in the 6th R&O to allow DTV licensees assigned ERP's less than 

1,000 Kw to "serve an area up to the Grade B contour of the largest station in the market." 

However, they further stipulated that this would only be allowed "provided that such increases in 

power would not result in additional interference."  



This is good news for UHF stations because it tends to equalize coverage areas.  But the 

question of what constitutes "additional interference" remains a stumbling block for coverage 

equalization proponents such as Viacom.



In the 6th R&O, the FCC used a computer model to predict both station coverage and 

interference factors.  The methodology for making these calculations is outlined in the Office of 

Engineering and Technology (OET) bulletin 69.  "OET-69," as it is called, utilizes the Longley-

Rice radio propagation model to make predictions of radio field strength.  (see sidebar for more 

information on OET-69)



Viacom notes in its petition that after the release of OET-69 on July 2, 1997 they "are more able 

to accurately study the ability of U-to-U stations to maximize their power within the confines of 

the table allotment."



But "maximizing their power" would also increase the interference levels induced by Viacopm's 

stations to other licensees.  In the 6th R&O the Commission noted that their allotment procedure 

minimized the amount of interference that would be caused to both existing TV services and the 

new DTV service alike.



"The DTV Table," the order continued, "will fully protect 98.8 percent of existing geographic 

service area and 98.6 percent of the population now served within the Grade B contours of 

existing stations."



The exact measure of a station's coverage area has been specified in OET-69 by defining the 

predicted field strength when using an F (50,50) curve.  And while the 6th R&O does not directly 

specify any absolute level of interference as its defining measure of acceptability in the 

maximizing of such coverage, its acceptance of approximately 1 percent interference could 

appear to some to have become a de facto standard.

  

Viacom was quick to grasp this, as its petition cites studies performed by Hammet & Edison, a 

San Francisco-based consulting firm. The studies show that "raising the power level floor to 250 

Kw would result in 93 percent of all 3,190 NTSC and DTV stations experiencing only 1 percent or 

less increased interference." It also found that only 3.7 percent of all stations would experience 

between one and two percent increased interference, while only 2.3 percent of all stations would 

experience between 2 and 5 percent increased interference.  



Overall, the study concludes, "raising the power of the 964 UHF DTV stations to 250 Kw would 

result in calculated interference on average of 0.19 percent of the existing Grade B population."

        

Viacom, in their petition, claims that approximately 3.1 percent of all stations will actually 

experience a reduction of at least 1 percent from the levels of interference adopted by the FCC.

        

The petition justifies its conclusions by saying that "this minimum level of interference, balanced 

against the ability of the U-to-U stations to better compete with their Grade A contours with 

increased power levels, warrants Commission adoption" of their power increase plan.  As of this 

writing the Commission has not acted on the Viacom petition.