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Discussion Starter #1
I live in a relatively small TV market (Champaign, IL) which probably won’t have HDTV OTA for at least a couple more years. Though there have been some delays in getting HDTV on the air in Chicago, obviously they’ll have it a lot sooner than we will.


Though a definitive answer is probably impossible, I wonder if some of you HDTV pioneers can tell me whether it’s worth the effort to try to pull in a HDTV signal from the Chicago stations.


My situation is this: As near as I can figure, my house is about 125 air miles from the Loop (where I assume the antennae reside on tall buildings). Having driven to the city many times, I know there are no mountain ranges between my house and Chicago, in fact it’s as flat as a billiard table. My house sits up very high and I could get an antenna mounted about 50' above the ground, on a mast with a rotator.


Using the highest gain antenna reasonably available , along with a low noise, high gain signal amplifier, and the most sensitive receiver I can find, do I have a shot at getting HDTV signal from Chicago on a reliable basis?


As a kid, I remember my dad getting fairly decent VHF signals at 125 miles from the transmitter tower, though I realize that’s an entirely different situation.


Thanks for any advice.


MIKETextf>
 

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It's worth a shot. Some folks in the southern California area are DXing the stations in Los Angeles from San Diego, and vice versa. That path is over 100 miles.


I have received steady DTV signals from New York City over an obstructed 65 mile path with modest antennas and preamps. You'd need a lot of gain - possibly stacked antennas with phasing lines - and a preamp to pull it off.


KC
 

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You probably will be able to get intermittant nighttime reception and perhaps some daytime reception. It will depend on the weather.


I am in a similar situation. I am 124 miles from the raleigh NC stations and get intermittant reception. Sometime I get 90-100% signal strength. Other times i get none at all. I am using a CM4251 with Titan 7777 preamp. It is mounted on a mast above my roofline about 30-40 feet above the ground.


Good luck. It is fun to try.


Scott Burns
 

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Champaign-Urbana is my original hometown. I can tell you that bringing in Baltimore from Northern Virginia is not easy. Possibly from an elevated site, you could negotiate that kind of distance, but in Illinois ~ I don't think so. Tom
 

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BTW,


Stable reception really depends on line of sight. With a good antenna, gain is less of an issue.


Multiple the height of the transmit antenna by 2 and take the square root. Multiple the height of the receive antenna (in feet) times 2 and take the square root. Add the two together. This is your max stable range in miles.


Ex: transmitter at 2000 ft. Receive antenna at 40 feet. Range is SR(2000*2)+SR(40*2) = 63.25 + 8.95 = 72.2 miles


Hope this helps.

Scott
 

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BTW, the FCC deadline for your local stations to be on the air is May 1, 2002 (not years as posted). There is some debate about what is going to happen in small markets as this deadline nears.


Scott
 

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Mike,


You can judge probability of Chicago DTV reception by comparing to analog TV reception from Chicago.


For example, here in South Bend at my home I have a 12.2 dB gain Blonder Tongue model BTY-10-U ch. 50 yagi antenna and B-T model SCMA-U 24 dB gain preamp with 2.5 dB noise figure to pull-in WPWR from Chicago 75 miles away and I usually get an acceptable signal (except for occasional atmospheric problems). As a bonus I get great reception from WLS-DT ch. 52 most of the time, too.


(The same holds true for ch. 32 WFLD & WMAQ-DT ch. 29 and WFLD-DT, ch. 31; and other analog Chicago U's.)


The trick is for you to have line-of-site between your receive antenna and the Chicago transmit antennae (to "see above" the 4/3 radius "bulge" of earth over the 125 mile path), which would mean your receive antenna would have to be up pretty darn high.


(From the antennae atop Sears at 1600-ft their "radio horizon" is about 56.6 miles. To have line-of-site from them to a receiver 125 miles away, the receive antenna would require a "radio horizon" of 68.5 miles, which would require a height of about 2300-ft...plus a few more to clear any obstructions that may occupy the intersection of the two radio horizons.)


Applying that line-of-site theory to my location, you'd expect a receive antenna height of about 175-ft, although I'm getting acceptable results from only 40-ft.


Anyway, I can say from experience that if you can receive watchable signals from the Chicago UHF analog channels then you should be able to get the Chicago digital channels as well (but I'd expect a lot of fading and atmospheric outages over a 125-mile path).




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George at WNDU
 

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Denver only has one full power digital station on the air. Two stations broadcast low power digital TV with another expected to come on line in September. Only people living close to downtown get the low power digital signals. I do receive the digital signals from downtown Denver. However, KUSA our NBC station is not planning a low power transmitter. Denver's full power tower has been blocked by local politicians in Jefferson County.


I have a Channel Master HDTV antenna on a rotator on my roof. I can point it to Colorado Springs about seventy miles away and currently get a fuzzy NTSC signal. However, when Colorado Springs goes digital next May, I expect to be able to receive my digital NBC and Jay Leno from Colorado Springs and not Denver.


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Discussion Starter #9
Thanks for everyone's advice. It doesn't sound too promising for something that's likely to cost a thousand bucks or more to try. My main interest in HDTV is sports, which are as often as not broadcast during the day.


I wasn't aware that the FCC's deadline for stations in my area was less than a year away. I e-mailed the engineering offices at a couple of local stations a few months ago and none had any plans in effect to implement the digital changeover. I'd assume by now that the process is more of a turnkey operation than it was for the first stations. And of course, it's much easier to find a site for a new tower here in the cornfields than it is in a big city.


Having been wowed by a number of HDTV demos, I continue to be amazed and how little enthusiasm the industry has generated for this great new technology. I don't think it's unreasonable to assume that at least 25% of US household has at least one resident whose a fairly intense sports fan. Sell one HD set to each of these households and you've sold a lot of new TV's. I'm old enough to remember the switch from black and white to color sets and everyone back wanted a color set and got one as soon as they could afford it.


MIKE
 

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Mike,


As I'm typing this, I'm watching your locals-15,17,23,and27(183mi.).Quite common here during Spring and Summer.Last Friday KDSM Fox-17 (Des Moines) blew through WAND-17 for about a minute(456mi.).If the enhanced propagation is bi-directional you could turn an antenna towards Indy,which is closer than Chicago(108mi.) from you,and pick up DT's 25,45,46 and 9.


With a good first-class install,you might be suprised what you can receive,especially after dusk!


[This message has been edited by MAX HD (edited 07-31-2001).]
 

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There are several types of reception conditions that can yield over-the-horizon reception conditions.


Tropospheric scatter. Signals may be available a great deal of the time but to implement a system requires very high gain antennas with a large capture area (multiple arrays). The signals are scattered from the uppermost layer of the troposphere and range can be several hundred miles, or more. The same concept was used to create early warning, over the horizon radar systems before the use of military satellites, etc. Expensive to implement and to say the least, unsightly.


Tropospheric ducting. Changes in weather conditions at the lower levels of the troposphere create ducting paths which can extend VHF and UHF signals several hundred miles beyond the normal reception boundaries. Unpredictable and the path conditions can change rapidly allowing the signal to arrive from several paths at once, out of phase, creating multipath like reception problems.


Sporadic E and F Layer Ionespheric Skip. Ionespheric skip takes place most often during the peak of the sunspot cycles. E Layer skip occurs mostly in late spring, summer and fall months, affecting usually frequencies up to just above the FM band. High band (7-13) is rare. The distances typically are as short as 400 miles to 2,000+ miles. I once received WCBS, channel 2, from NYC in Ashland, Oregon via E layer skip. Reception can last from a few minutes to several hours.


F layer is a winter phenomena and under certain conditions low band VHF channels can travel via multiple hops up to 10,000 miles. The record, prior to the migration of the VHS channels to UHF frequencies, was reception of the BBC from a British transmitter by a hobbyist in Longview, Washington.


Meteor Scatter. As a meteor passes through the atmosphere it leaves an ionized layer of particles which will reflect VHF frequencies for several seconds. TV DXers, in the days when TV stations often transmitted test patterns with station call letters, use to take advantage of meteor scatter to ID stations. A meteor scatter signal comes up from nothing to a strong signal in less than a second, lasts about 1-2 seconds and then fades just as rapidly.


That is my shortcourse on TV DXing! I did it as a hobby when I was in high school (yes, I was a nerd!) and logged nearly 500 television stations over a period of about 6 or 8 years.


[This message has been edited by cwood (edited 07-31-2001).]
 
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