CBS KYW-DT Philadelphia 8-VSB Field Test Report: Outdoor and Indoor DTV Reception Results
Summary
CBS conducted comprehensive 8-VSB DTV field tests at KYW-DT (Channel 26) in Philadelphia, measuring outdoor reception across 60-mile radials and indoor reception at 42 sites. Results showed 99% of outdoor sites and 94% of indoor sites with marginal NTSC signals achieved full-quality DTV reception.
CBS DTV/HDTV FIELD TEST REPORT
KYW-DT, PHILADELPHIA, PA
EXECUTIVE SUMMARY
Introduction:
The FCC goal was to develop a Digital Advanced Television Transmission System which would provide an improved quality DTV/HDTV terrestrial television service within the existing 6 MHz television channelization plan. An additional goal was to replicate the present NTSC analog service area with minimal interference utilizing the 8-VSB transmission system. These tests have been conducted to determine if this goal was being achieved in a major television market by a full power 8-VSB DTV station.
The tests were conducted in Philadelphia using the CBS-owned station KYW-DT on Channel 26 comparing the DTV coverage to NTSC station WTXF-TV on nearby Channel 29 to ensure that the tests were made using stations with frequencies as close to one another as possible, and, therefore, with similar propagation conditions. Since the coverage of the NTSC station, WTXF-TV, on Channel 29 substantially replicates the coverage of KYW-TV on Channel 3 FCC allotted Service Contour of KYW-DT, the technical accuracy of the tests is maintained.
Both outdoor and indoor reception tests were made. The objective of the outdoor reception tests was to verify the predicted extent of the stationís DTV coverage. The objectives of the indoor tests were to determine the extent of the impact of multipath distortion of the DTV signal on indoor reception, to evaluate the performance of three types of indoor antennas, and finally, to field test the third generation 8-VSB receivers for the DTV/HDTV service. This field test did not include testing of mobile reception of the DTV/HDTV signals.
Outdoor tests:
For these tests, a fully equipped test truck, based on the ATSC Field Test Vehicle Design, was used. The test sites included those situated on eight equally spaced radials centered on the transmission site. Testing began at points on the radials 10 miles from the transmitter and extending outward at test points spaced 5 miles apart on each radial, up to a maximum range of 60 miles.
In addition to these radial sites, a grid of an additional 28 sites spaced one half &Mac189; mile apart was selected in Reading, PA, 40 miles from Philadelphia. Reading is a large town, surrounded by high ground with limited line-of-sight from the transmitter. Reading was chosen to determine multipath transmission effects caused by natural terrain obstacles.
At all these sites, measurements of reception quality were made for the NTSC signal transmitted by a UHF television station, Channel 29. Subjective quality assessments were made using the ITU CCIR Grading system for interference, in which:
Grade 1 is considered to be "very annoying" and unacceptable,
Grade 2 is "annoying",
Grade 3 is "slightly annoying",
Grade 4 is "perceptible, but not annoying",
Grade 5 is "imperceptible".
In assessing the results obtained, it is important to note that while an analog NTSC signal deteriorates gradually in quality as the receiving distance from the transmitter is increased, a digital signal will retain its full quality as the range is increased until the ìcliff effectî is reached at which point, no reception is possible.
Indoor Tests:
For indoor reception tests, homes and commercial structures were selected on a random basis, and were located at points between 5 and 35 miles from the transmitter. At these sites, commercially available receiving antennas of three types were tested: Log Periodic, Double Bow Tie, and Loop antenna with an amplifier. Third generation DTV decoders supplied by Zenith, Motorola / Sarnoff and NxtWave/ST were used in the receiver. The quality of the received signal from the Channel 29 NTSC transmitter was graded, using the CCIR Quality scale.
Outdoor Test Results:
Good reception was obtained at sites on 8 radials extending out to 60 miles, the service limit of the NTSC service area, except where reception was limited by natural terrain. Good reception was also obtained for a set of grid measurements taken in a terrain limited city 40 miles northwest of Philadelphia (i.e. Reading, PA). Importantly, full quality reception of the DTV/HDTV signal was obtained, even when a marginal NTSC signal was available (i.e. CCIR 1.5 or greater)
Of the 105 outdoor sites that had even a marginal NTSC signal (i.e. CCIR grade 1.5 or greater), 104, or 99%, had full quality DTV reception.
Indoor Test Results:
Indoor tests at sites in downtown Philadelphia, consisting of commercial structures and homes, showed that both DTV and NTSC reception is impeded at some locations. The limiting factor at most locations was multipath not signal strength. Nevertheless, for all 42 indoor reception sites, if even a marginal Grade 1.5 NTSC quality picture was observed from the NTSC transmission, a full quality DTV/HDTV picture was obtained at 94% of the sites.
Of the 33 indoor sites that had even a marginal NTSC signal (i.e. CCIR grade 1.5 or greater), 31, or 94%, had full quality DTV reception.
(For symmetry with the outdoor tests, we need to add a parenthetical at this point noting xx of the 42 indoor sites.)
Of the three indoor antenna types tested, the Log Periodic antenna was clearly superior for indoor reception.
Conclusions:
The outdoor testing in Philadelphia shows that if even a marginal analog NTSC picture was viewable, then a perfect DTV service was available. The field measurements of over 100 sites indicated a 99% success rate. Perhaps more important, when testing indoor reception, if even a marginal NTSC picture was viewable, DTV service was available 94% of the time.
This field test strongly suggests that 8-VSB DTV/HDTV transmissions do in fact can service replicate the current NTSC the FCC allotted Noise Limited Service Contour service area in Philadelphia.
Given the continuing refinement of the improved 8VSB receiver designs as tested, it is clear that the goal of the DTV/HDTV reception replicating the NTSC service area has been met, and exceeded, for both indoor and outdoor DTV/HDTV reception.
Thus, the goal of implementing a fully operational U.S. advanced digital SDTV, Multiplex TV, and HDTV service with digital data capability using the 8-VSB transmission system replicating the NTSC service area has been met. Moreover, as is always the case with new technologies, further rapid development and its consequent improvements in technical quality, flexibility, and reliability can be expected and will be forthcoming.
Following on this test, CBS also also looks forward to the upcoming MSTV testing of 8-VSB and COFDM, to which CBS will contribute financial and technical support, in order to further the knowledge of RF transmission characteristics.
Further Detailed technical information on these this DTV/HDTV reception test is available in a CBS Technical Report entitled: ìKYW-DT, DTV Field Test Report. Requests for copies of this technical report should be addressed to CBS Engineering at 524 West 57th Street, New York, NY 10019.
CBS DTV/HDTV FIELD TEST REPORT
KYW-DT, PHILADELPHIA, PA
EXECUTIVE SUMMARY
Introduction:
The FCC goal was to develop a Digital Advanced Television Transmission System which would provide an improved quality DTV/HDTV terrestrial television service within the existing 6 MHz television channelization plan. An additional goal was to replicate the present NTSC analog service area with minimal interference utilizing the 8-VSB transmission system. These tests have been conducted to determine if this goal was being achieved in a major television market by a full power 8-VSB DTV station.
The tests were conducted in Philadelphia using the CBS-owned station KYW-DT on Channel 26 comparing the DTV coverage to NTSC station WTXF-TV on nearby Channel 29 to ensure that the tests were made using stations with frequencies as close to one another as possible, and, therefore, with similar propagation conditions. Since the coverage of the NTSC station, WTXF-TV, on Channel 29 substantially replicates the coverage of KYW-TV on Channel 3 FCC allotted Service Contour of KYW-DT, the technical accuracy of the tests is maintained.
Both outdoor and indoor reception tests were made. The objective of the outdoor reception tests was to verify the predicted extent of the stationís DTV coverage. The objectives of the indoor tests were to determine the extent of the impact of multipath distortion of the DTV signal on indoor reception, to evaluate the performance of three types of indoor antennas, and finally, to field test the third generation 8-VSB receivers for the DTV/HDTV service. This field test did not include testing of mobile reception of the DTV/HDTV signals.
Outdoor tests:
For these tests, a fully equipped test truck, based on the ATSC Field Test Vehicle Design, was used. The test sites included those situated on eight equally spaced radials centered on the transmission site. Testing began at points on the radials 10 miles from the transmitter and extending outward at test points spaced 5 miles apart on each radial, up to a maximum range of 60 miles.
In addition to these radial sites, a grid of an additional 28 sites spaced one half &Mac189; mile apart was selected in Reading, PA, 40 miles from Philadelphia. Reading is a large town, surrounded by high ground with limited line-of-sight from the transmitter. Reading was chosen to determine multipath transmission effects caused by natural terrain obstacles.
At all these sites, measurements of reception quality were made for the NTSC signal transmitted by a UHF television station, Channel 29. Subjective quality assessments were made using the ITU CCIR Grading system for interference, in which:
Grade 1 is considered to be "very annoying" and unacceptable,
Grade 2 is "annoying",
Grade 3 is "slightly annoying",
Grade 4 is "perceptible, but not annoying",
Grade 5 is "imperceptible".
In assessing the results obtained, it is important to note that while an analog NTSC signal deteriorates gradually in quality as the receiving distance from the transmitter is increased, a digital signal will retain its full quality as the range is increased until the ìcliff effectî is reached at which point, no reception is possible.
Indoor Tests:
For indoor reception tests, homes and commercial structures were selected on a random basis, and were located at points between 5 and 35 miles from the transmitter. At these sites, commercially available receiving antennas of three types were tested: Log Periodic, Double Bow Tie, and Loop antenna with an amplifier. Third generation DTV decoders supplied by Zenith, Motorola / Sarnoff and NxtWave/ST were used in the receiver. The quality of the received signal from the Channel 29 NTSC transmitter was graded, using the CCIR Quality scale.
Outdoor Test Results:
Good reception was obtained at sites on 8 radials extending out to 60 miles, the service limit of the NTSC service area, except where reception was limited by natural terrain. Good reception was also obtained for a set of grid measurements taken in a terrain limited city 40 miles northwest of Philadelphia (i.e. Reading, PA). Importantly, full quality reception of the DTV/HDTV signal was obtained, even when a marginal NTSC signal was available (i.e. CCIR 1.5 or greater)
Of the 105 outdoor sites that had even a marginal NTSC signal (i.e. CCIR grade 1.5 or greater), 104, or 99%, had full quality DTV reception.
Indoor Test Results:
Indoor tests at sites in downtown Philadelphia, consisting of commercial structures and homes, showed that both DTV and NTSC reception is impeded at some locations. The limiting factor at most locations was multipath not signal strength. Nevertheless, for all 42 indoor reception sites, if even a marginal Grade 1.5 NTSC quality picture was observed from the NTSC transmission, a full quality DTV/HDTV picture was obtained at 94% of the sites.
Of the 33 indoor sites that had even a marginal NTSC signal (i.e. CCIR grade 1.5 or greater), 31, or 94%, had full quality DTV reception.
(For symmetry with the outdoor tests, we need to add a parenthetical at this point noting xx of the 42 indoor sites.)
Of the three indoor antenna types tested, the Log Periodic antenna was clearly superior for indoor reception.
Conclusions:
The outdoor testing in Philadelphia shows that if even a marginal analog NTSC picture was viewable, then a perfect DTV service was available. The field measurements of over 100 sites indicated a 99% success rate. Perhaps more important, when testing indoor reception, if even a marginal NTSC picture was viewable, DTV service was available 94% of the time.
This field test strongly suggests that 8-VSB DTV/HDTV transmissions do in fact can service replicate the current NTSC the FCC allotted Noise Limited Service Contour service area in Philadelphia.
Given the continuing refinement of the improved 8VSB receiver designs as tested, it is clear that the goal of the DTV/HDTV reception replicating the NTSC service area has been met, and exceeded, for both indoor and outdoor DTV/HDTV reception.
Thus, the goal of implementing a fully operational U.S. advanced digital SDTV, Multiplex TV, and HDTV service with digital data capability using the 8-VSB transmission system replicating the NTSC service area has been met. Moreover, as is always the case with new technologies, further rapid development and its consequent improvements in technical quality, flexibility, and reliability can be expected and will be forthcoming.
Following on this test, CBS also also looks forward to the upcoming MSTV testing of 8-VSB and COFDM, to which CBS will contribute financial and technical support, in order to further the knowledge of RF transmission characteristics.
Further Detailed technical information on these this DTV/HDTV reception test is available in a CBS Technical Report entitled: ìKYW-DT, DTV Field Test Report. Requests for copies of this technical report should be addressed to CBS Engineering at 524 West 57th Street, New York, NY 10019.