Update on Ottawa Experimental DTV Transmitter

Experimental DTV Transmitter

As of the date of this report, the construction of CDTV’s experimental DTV transmitter in Ottawa is still underway.

An experimental authorization for high-power operation on Channel 67 has now been issued by Industry Canada.

The installation of air conditioning, ventilation and ac power systems was completed in September, more or less on schedule. The transmitter delivery was delayed somewhat but the 2.5 kW Larcan unit was eventually delivered in late September and has now been installed and tuned by the manufacturer. The remote control system is being installed, which will allow Communications Research Centre (CRC) personnel to monitor and control the transmitter from their offices, or even from a mobile location. When completed, the test facility will be of a professional calibre and will even include provision for emergency diesel power.

Still to be completed is the adjustment of the channel 65/67 antenna combining device. This process has run into a snag. Although Dielectric Communications said that it will be possible to use the existing CITY-TV Channel 65 Constant Impedance Filter (CIF) as a combining device, recent measurements reveal a very poor impedance match for the Channel 67 transmitter at the point where it is to feed into the CIF. This problem is now being discussed with Dielectric and they are planning a site visit to help resolve the problem. It is still hoped that the facility will be ready for operation in November, barring any further unforeseen problems.

A preliminary test plan has been developed by the CRC staff . This plan is was reviewed and accepted by the CDTV Technical Working Group at its 21 October 1999 meeting in Ottawa. One of the key concerns at this time is that the first generation of DTV receivers has not performed well in field tests conducted in the USA. The CDTV WG does not want to undertake extensive field tests with these inferior receivers, since important decisions about required operating parameters for DTV are expected to result from its testing. Steps are being taken to obtain early copies of improved receivers that are better able to adapt to signals that are subject to ghosting (multipath). In the meantime, testing that does not require the higher-quality receivers will be undertaken.

So far, it seems that the $200K of funding that was obtained from Industry Canada will be adequate to get the transmitter project up and running. The very high level of co-operation that the project group has received from equipment suppliers, both in Canada and the US, has made it possible to undertake this installation with no infusion of funds from CDTV’s own budget up to now.

W.A. Stacey, P.Eng
CDTV Test Transmitter WG
26 October 2021


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