Switching to COFDM modulation for DTV would cost many times previously estimated $50,000 per station , DTV transmitter maker Harris Corp. warned in report issued Tuesday. Harris, which makes transmitters for both COFDM- and VSB-based DTV systems, said COFDM also has several other performance disadvantages, and it "makes not sense" to trade more efficient current DTV technology for "short-term" indoor reception benefits.
Harris released study in part to "rally the troops," Bruce Allan, gen. mgr.-broadcast, acknowledged. He said some stations have begun delaying DTV equipment purchase decisions pending resolution of dispute over COFDM: "This has the potential to slow the whole process, and that shouldn't happen." He said budding controversy has been partly result of fact that "a lot of half-truths and partial pieces of information" have emerged.
"Enormous cost implications" of COFDM, Harris said, include: (1) Increasing power consumption costs 4-5 times, as much as $227,000 per year per station, in order to achieve similar coverage area. (2) As much as $1 million per station additional cost for facilities capable of handling higher power level. Harris said that at least 166 stations to date have either begun DTV broadcasting or bought transmission equipment.
"Any temporary difficulty with reception is being addressed by multiple manufacturers," Harris said, including adding better adaptive equalizers for 2nd-generation DTV sets. Paper also said several companies are developing "inexpensive" active antennas that would be controlled by DTV receiver. Harris said that such improvements "promise to reduce to insignificance any current ATSC indoor reception problems" and that "whatever marginal difficulty the ATSC standard may have with regard to indoor reception can be mitigated through the use of an outdoor antenna."
Improvements in DTV receivers are well on way, Allan told us, based on Harris's meetings with half-dozen set makers. Most of changes are in adaptive equalizer circuitry, he said, with some to be on market this year and others to be demonstrated within next month. Allan said sets used in Sinclair demonstrations were "almost laboratory toys" and predicted "vast improvements" beginning in fall. Tradeoffs between VSB and COFDM were "pretty well understood and accepted" when selection was made, he said, and, even though it makes both, Harris remains convinced that VSB is "the right system for the U.S."
Harris said other COFDM disadvantages include" (1) Broadcasters could lost hundreds of square miles of coverage area if they didn't boost power level. (2) COFDM doesn't provide protection against co-channel and adjacent channel interference as well as VSB does, and problem would get worse if power were increased. (3) VSB provides better protection against impulse interference. (4) VSB's data throughput is 19.4 Mbps per 6 MHz channel, vs. 14.7-17.9 Mbps for COFDM.
Sinclair Broadcast Group. demonstrations of DTV indoor reception "prove nothing about indoor reception of ATSC generally" because they use "selective" circumstances, Harris said. It said those wanting to reopen DTV standard issue have "extremely high" burden of proof, and Sinclair demonstration "falls far short of warranting the delay, disruption and confusion that would accompany reopening this debate."
