Why has CDTV built an experimental digital TV transmitter?


Canadian broadcasters will soon start building their own DTV transmitters.  They require practical information about how such facilities should be planned and operated.  Moreover, the service assumptions applied during the development of Canada’s channel allotment plan need to be verified by practical measurements and observations.  At present, CDTV operates the only DTV transmitter in Canada.


      What are the specific test plans?


The facilities are intended to be used for:


        Verifying DTV coverage prediction methods;


        Assessing DTV coverage at the fringe of the service area and under difficult receiving conditions;


        Assessing the quality of DTV reception in the urban and most populous areas, where reception with an indoor antenna is prevalent. 


        Comparing the coverage and service reliability of the DTV facilities versus the co-sited NTSC facilities;


        Assessing various techniques for re-broadcasting DTV signals.


        Assessing reception and modulation conversion of the off-air 8-VSB DTV signals by cable, MDS and DTH satellite distribution undertakings;


        Experimenting with the transmission of multiple standard-definition (SD) and single high-definition (HD) video signals, combined with audio and possibly auxiliary data services.


        Possible public demonstrations of both SD and HD DTV signals.



      Who is doing the testing?


The majority of the testing is being carried out by the Broadcast Technologies Research Branch of the Communications Research Centre (CRC), under a contract issued by Industry Canada.  Signals from this facility may also be used by others (e.g.  cable,  MDS and DTH services) to experiment with signal pick-up and carriage.



      What transmission facilities has CDTV built?


The DTV transmitting facilities assembled by CDTV are similar to those constructed by broadcasters in the USA.  Equipment is professional-grade and of high quality.  The facilities are located at the Rogers Broadcasting Ltd tower site near Manotick, ON.  The signal from the DTV transmitter has been combined into an existing antenna, currently used for NTSC service on Channel 65 by CITY-TV-3.



      What TV channel is being used?


The transmitter operates on Channel 67 (788-794 MHz), a DTV allotment for Ottawa, ON, listed in the Canadian TV Allotment Plan.



      What are the operating parameters?


The antenna consists of an 8-bay panel array using four RFS Broadcast UHF-TV panels per bay.  The antenna is nominally omnidirectional but in fact has a slight horizontal gain variation of 1.7 dB.  The RMS vertical gain of the antenna is 13.8 dBd.  A 2.5 kW Larcan solid state, air-cooled Channel 67 DTV transmitter is being fed to the antenna through the existing CITY-TV-3 constant impedance filter, acting as a combiner.  The maximum ERP of the facility is 44.2 kW and the average (RMS) ERP is 29.9 kW.  The antenna EHAAT is 215.4m.



      Over what range can the signals be received?


Off-air reception of the DTV signals should be possible within the existing Grade B service contour of CITY-TV-3, or a radius of about 70-80 km.



      What type of DTV signal is being transmitted?


At present, the system transmits mainly an 8-VSB signal, complying with Canada’s transmission standard for DTV (ATSC A/53).  Input to the transmitter will be SMPTE 310M, 19.39 Mb/s transport layer.  Other test signals may be transmitted from time to time, as required.



      How long will this facility be in operation?


At present, 18-24 months of experimental transmissions are planned.



      Where can I get more information:


Please contact:       Wayne A. Stacey, P.Eng.

Vice-Chairman, CDTV Technical Working Group

c/o Stacey, Lawson Associates Ltd.

5-1420 Youville Drive, Ottawa ON K1C 7B3

Tel (613) 830-6985

Fax (613) 830-8124

E-Mail:                                                                                     2021-02-16