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wrote: Well, considering that there really is no such thing as an HDTV antenna per se, yes. HDTV in the U.S. (ATSC) uses a subset of the same frequencies used by ATSC television, and so all the same considerations apply. With 2 to 4 stations on the same frequency allotment as the old analog in some instances. At any rate some squeeze 4 in the space that used to be used by one. They do this at the expense of bandwidth (IE resolution) They're actually multiplexing two or more digital data streams into a single RF transmission, coming from a single transmitter and tower. No matter whether they're sending one HDTV program, or four independent SDTV digital signals, it's all just one digital bitstream being sent to the modulator, and sent out in a single 6 MHz slice of the spectrum (the same slice of spectrum that a single NTSC transmission would have used). You're correct, the extra programs are sent at the expense of the main program... it must reduce its bit-rate, which means either switching down to a lower resolution, or having more motion artifacts, or sticking to programs which have relatively little motion on-screen and are thus easier to compress via MPEG. If you wanted to tune up only one (or a few closely-spaced) HDTV stations with an omni, you could probably build yourself a turnstile antenna... a crossed pair of bow-tie elements, and a 90-degree phasing harness cut for the middle of the band would probably work. I doubt that'll work as a general-purpose solution for the full band, though. It does here at least out to about 40 or 50 miles from 40 feet. Very good to know - thanks! BTW these antennas are about 30 feet below a pair of 12L, vertically polarized yagis and about 12 feet above the tops of a pair of Diamond repeater antennas. The tribander is about 8 to 10 feet above the TV antennas and the 7L 6-meter yagi is about 15 feet above the tribander. I run the legal limit to the tribander and a 1000 to 1200 PEP on 6-meters. So far no problems. My complements to your filters and amplifiers and your care in setting up the whole system! Only problem I ever had was one neighbor having a foot ball party out in his garage using rabbit ears for an antenna about 120 feet from the base of my tower. "Hello Test" with 50 watts to the 12L pair at 130 feet would give him a blank screen on Ch 12. I gave him a directional TV antenna and from then on I was invited over to the parties and free beer. Now *that* is the kind of QRM-resolution situation we should all strive for! -- Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads! |
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