Consumer-Grade DTV Receivers Lack Consistency
In this month's Journal I wanted to share some observations I have made over the last few years regarding DTV receivers. I guess I should qualify that by saying terrestrial DTV receivers since over-the-air broadcasting to receivers is what we're trying to accomplish here in Iowa.
I have had some concerns about receivers in a couple of broad areas. The first area of concern is the professional grade receiver. These are the units we'll be installing at our transmitter sites and studios for monitoring the quality of our transmission signals.
I've had the opportunity to look at several different manufacturers' products for use in the professional marketplace. The unit I am most familiar with is the Zenith ATSC Professional Demodulator that I have seen at several VSB seminars, including one that we hosted at IPTV several months ago.
The other unit is the KTech DVM-100 VSB reference receiver. Although I am not as familiar with this unit as I am with the Zenith model, it was the topic of a review in the June 13, 2001 issue of TV Technology.
What I like about both of these receivers is that they are very straightforward and easy to operate and both provide easily discernable indications of the basic quality of the received signal. I must confess that I especially like Zenith's digital S/N readout that provides an immediate indication of how much headroom is available before the signal goes over the digital cliff. The I/O connectors on the Zenith are divided between the front panel and the back panel that makes the unit a little more difficult to install in a non-laboratory type environment like a transmitter site. The KTech unit has all of the I/O's on the rear panel and is designed to be placed in a rack and dressed - either of these units is an excellent choice for use in the role of a precision demodulator.
DO THE RIGHT THING
The area I am really more concerned about is the consumer end of the receiver business. I seem to spend a lot of time talking about the consumer side of this conversion but that is the area that will ultimately determine the success or failure of DTV. Let's face it, as broadcasters we're not going to spend ten grand on a precision receiver and then hook it up to rabbit ears or a piece of 25 year-old RG-59.
On the other hand, the consumer at home may do just that or worse.
This probably won't be the early adopter of DTV. We have them even in Iowa and when we put our Des Moines station on line for tests, we get e-mails from these folks telling us that they receive our signal and it is rock solid. These people tend to do their homework and ask the right questions.
My concern is the next wave of buyers that have waited for the price point on DTV sets to drop and are going to start buying. These people have the expectation that DTV is going to work better than analog. Doesn't everything digital work better than analog? Isn't that the market hype? So when these people cannot get the signal from the terrestrial broadcaster but their satellite signal is fine, they will be calling.
I suggest that you start looking at the consumer marketplace and conduct some tests. The reason I suggest this is that you may be surprised by some of the inconsistencies that are out there. During our DTV Symposium last October, IPTV's DTV station in Des Moines was on the air. In Des Moines, we broadcast on analog channel 11 and digital channel 50. We were broadcasting a long loop of program material that showed HD, SD and upconverted analog with basic PSIP information and used a number of different receivers and displays at various locations to show the signal. Seems pretty straightforward.
On our Zenith 64" at the studios, our digital channel was displayed as 11-1, which I believe is correct according the standard. Our analog service on channel 11 sets the base channel number and shows up as 11-0 and our first digital service is 11-1 and so on.
On our first generation Sony tuner, we were 50-1 - evidently the Sony tuner used the actual DTV RF signal as the base channel but did recognize that the digital service starts at 50-1. We have a couple of RCA DTC-100 set-top boxes and one of them also displayed 50-1. The DTC-100 that I use in my office displays our DTV channel 50 as 106-1 and I haven't yet been able to figure out where that comes from, especially since the tuner locates all of the analog channels and displays their assignments properly.
Just getting the consumer market to recognize and accept that the receiver may not be an integrated part of the television is a challenge. The TV set in the mind of the consumer is an appliance that you buy and use until it wears out or you decide to buy a bigger one and move the old one to another room. Getting them to see the display as the appliance part and the receiver as a component that may need to be upgraded from time to time - especially during the early days of DTV when the details of the standards are still being finalized and implementation is creating some bumps in the road - won't be easy. And the real challenge in the receiver world will be when there are over 3,000 analog and DTV stations operating in the U.S., all crowded into the spectrum between channels 2 to 51.
Unfortunately, because of budget constraints, IPTV has not been able to keep our DTV channel on line. However, we have already begun working with as many consumer electronics vendors in the area as possible to develop a knowledge base of what various makes of receivers will do when confronted with terrestrial DTV signals, analog signals, noise and interference. It is in the best interest of our viewers and our own to make sure that as DTV rolls out, the terrestrial component has a place and works as well as the myriad other digital television services available to the consumer.
Bill Hayes is the director of engineering and technology for Iowa PBS and a SMPTE Fellow. He is also a member of SBE, IEEE-BTS and SCTE and a recipient of Future’s 2021 Tech Leadership Award.
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