Very Distant TV stations and Antennas

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I was wondering if it would be possible to get an antenna that would pick up a network station in a town about 140 miles from the transmitter. This is also in a mountainous area of Virginia. The rest of the channels would be arriving from a town about 50 miles to the north. I am trying to set up an antenna to get the networks and not have to get cable. Would it even be remotely possible to recieve such a signal? Thanks in advnace.
-at
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a.t. wrote:

140 miles is a long way, but if the local conditions are correct and if the station is powerful enough and if the frequency is right (UHF tends not to carry so far) then it might. Ask around locally and see if anyone else can get that station. I might add that an antenna tuned to just that station and designed for weak signals would be your best chance.
--
Joseph E. Meehan

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In addition try this site for information on the type of antenna needed. http://www.ve3gk.com/stacked.htm
--
Joseph E. Meehan

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Throw enough money at it, you can do almost anything. A tall, tall tower, with a very directional antenna and a rotator, you MAY be able to bring it in, at least part of the time. As a kid, I used to DX distant city TV stations when it got cloudy, and the signal would bounce on the cloud layers. (one night I got several Tennesee stations clear as a bell in Bloominton, IN.) But unless you happen to be on a tall ridgetop, a tower tall enough may be more expensive than several years of satellite service.
Suggest asking your question over on the rec.radio.amateur.antenna group. They may not like a non-HAM question, but they actually know what they are talking about over there, unlike me. Alternative- are there any (non-radio-shack) antenna companies in your area? Cable TV has made most of the yellow page ads for them go away, but whatever company in your area that sells antenna towers (look under 2-way radios) may still have an old-timer around that remembers when tall TV antennas on rural homes were dirt-common.
aem sends....
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Back in the 1950s in NE Misissippi, folks routinely received broadcasts from stations in Memphis, TN, 109 miles away. The quality of the reception varied from almost perfect to almost non-existent, depending on the height of the tower and quality of parts. My aunt and uncle had a 35 ft. tower and excellent antenna with rotator. Their reception was almost always very good.
--
Wayne in Phoenix

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yes
one of these inline with a good 75 ohm antenna system and an electric antenna rotator might do it http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F003%5F010%5F001%5F000&product%5Fid %2D1170
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a.t. wrote:

The old "radar range" approximation is that the horizon in nautical miles is the square root of 2 times the antenna height in feet. 140 sm is about 122 nm. So you need an antenna height of 7391 feet to see the horizon.
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I'm confused
122 =1.414x x feet?
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Greg,
When converting math into English sometimes the words aren't enough. "the horizon in nautical miles is the square root of 2 times the antenna height in feet.140 sm is about 122 nm." Consider that 122= 1.414X fills the bill but so does 122=(2X)**(1/2). The second equation gives Mr. Plummer's height. I do not vouch for the correctness of the second equation since I don't know this field.
Dave M.
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David Martel wrote:

d[nm] = sqrt(2 * h[ft])
d[nm] = d[sm]* 5280 / 6080 122 = 140 * 5280 / 6080
from above, d**2 = 2 * h or, h = d**2 / 2
For d2, you need a 7442 foot tower to have line-of-sight to the horizon. But the Earth's curvature could peak halfway between the sender and the receiver. So, with no diffraction or other effects, you might get by with an 1861 foot tower.
BTW, here's derivation of the "radar range approximation". Draw a circle of radius R with center E. This is the Earth. Draw a radius and label it S (for sender). Where S meets the circle is the horizon. Draw a second Radius and label it T (for tower). Extend T out beyond the circle by h (tower height). Draw the tangent from T (tower) to S (sender). There is a right angle at S between the tangent and the radius by definition. R+h is the hypotenuse of the right triangle. The length of the tangent is our d, distance to the horizon from the tower.
By Pythagorus, (R+h)**2 = R**2 + d**2 . We need to get every thing into feet, starting with d in nautical miles.
(6080*R + h)**2 = (6080*R)**2 + (6080*d)**2 (6080*R)**2 + 2*6080*R*h + h**2 = (6080*R)**2 + (6080*d)**2
Now, h**2 is very small compared to the other terms and can be dropped. (6080*R)**2 + 2*6080*R*h = (6080*R)**2 + (6080*d)**2
Divide by 6080**2
R**2 + 2*R*h/6080 = R**2 + d**2
Subtract R**2 from both sides
2*R*h/6080 = d**2
Now approximate the radius of the Earth R as 6080 nautical miles, 2*h = d**2
or, d = sqrt(2*h).
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You might want to look into how far a digital TV signal can go, I think they might work better.
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I can't see digital/non-digitial having anthing to do with it. TV signals are RF, whether the modulation is digital or not.
However, not being an expert, I could be wrong.
--James---
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James Nipper wrote:

I'm no expert on digital either, but I do recall a newspaper article a while back, from the early days of digital in Chicago; people three miles from the transmitting antennas were having a great deal of trouble getting any usable signal. I get the distinct impression that digital needs a MUCH cleaner signal than analog.
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Dropped "bits" in analog is just snow. Dropped bits in digital, beyond what ECC can reconstruct = garbage.
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There are people receiving signals at over 60 miles (both digital and analog). See:
http://www.avsforum.com/avs-vb /
Then any of the HDTV forums.
--
Bob in CT
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wrote:

miles
I agree; our experience with both analog and digital inspires this comment which generally agrees with the "MUCH cleaner signal" requirement. Without getting into too much detail of the different technologies to any extent I offer this; TV, especially digital has got 'better quality' over the years since it was first introduced as simple black and white, non stereo etc. So the signal now transmits more bits of information, colour, five channel sound, program schedules, text of the voice and other information! Also there is a basic difference in the nature of digital versus analog signal modulation. The simplest radio transmission of all was the dot/dash (morse Code). All that was needed was to able to 'hear' the transmission going on and just a little bit.. Even with severe noise; noise that perhaps could be stronger than the radio signal itself, it was only necessary to detect the slight change in order to be able to read the message! Very slow limited information but could often be the best or method of last resort! Next came AM (amplitude modulation) or analog, where the signal strength is modulated up and down in time with speech music or picture. Again even with noise as long as it is possible to 'hear' the variation it is usually possible to read the signal. When TV was introduced analog was used; noise due to a weak signal or otherwise can interfere with analog TV and may cause everything from a hissing noise, slipping or rolling of a TV picture or 'snow' on the picture. But in many cases as long as the picture can resynchronize itself fairly quickly the human eye and ear can tolerate the slight interruption. Airlines still use AM modulation for some frequencies because it is still considered that there will be a better chance of hearing a weak or interfered with emergency signal from a flying or downed aircraft! FM, frequency modulation was introduced especially for the sound part of TV and also for 'FM' stations. Better quality but using much more bandwidth and it has gained a reputation for 'When it works well the quality is good; very good, allowing stereo and other high quality sound transmission etc". FM also used for many VHF police, taxi and military radios systems with the channels packed much closer together than TV. Finally digital, where the signal is sort of turned on and off many millions of times per second, works very well and allows a lot of information to be transmitted provided there is good bandwidth (bandwidth has to do with speed of transmission available that's why you can't receive a TV programme over a telephone dial up on the internet!). This provided the signal is not interfered which means good clear signal from the digital transmitting TV station or from a satellite. When all the digits are received the TV receiver reconstructs the picture and sound etc. perfectly. However if digits are lost or interfered (due to noise or weak signal or interference) the receiver lacks the information to reconstruct the picture. We also have digital satellite and it very frustrating when the screen breaks up into a series of meaningless rectangles! Interference with the digital signal sometimes makes loud noises on the sound! Heavy rain with a certain size of rain drops causes more trouble with our received digital signal than does snow! Getting a clear signal path between you and various TV stations which may be in different directions from your location is important. Also your TV antenna has to cope with several different frequency channels; so most TV antenna are a compromise! The biggest current issue that is IMO worth mentioning to posters is 'interference'; it appears that the profusion of electrical devices we use today, everything from a Christmas Tree light flasher, microwave oven, light dimmer switches, our personal computers, hair dryers/shavers, blenders etc. etc are not manufactured or regulated to standards by the FCC (or other regulatory authorities in other countries) so they do emit interference or radio energy, which they should not? The most current of these is some trials of sending digital and internet signals over the power lines; commonly called BPL. BPL trials in a number of countries have been cut short because of interference with critical services such as ambulance, police and aircraft to ground communications! The problem with BPL being that the overhead wires are carrying not only the electrical energy they were designed for, which doesn't radiate to any great extent. But for these other radio/digital signals; the overhead wires are in effect a very large and very extensive transmitting antenna! So if you get 'interference' complain to your political representative for proper regulatory enforcement of electrical/radio standards! If you have a weak signal, well that's what you have to work on! Better antenna for that channel, pointing the right way (remove any hills or skyscrapers that are in the way!), don't live under a landing flight path or with a busy highway with metal vehicles whizzing by right in the sight line between you and the TV station and you should be OK analog or digital. Good luck.
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William W. Plummer wrote:

Well, the old radar range calculation isn't very accurate at VHF/UHF frequencies, but it is close enough to give you a rough idea of the heights involved in line of sight distances. However, don't forget that both the TV transmitter and the OP's receiver are going to be elevated, not 'at the horizon'. You also need to worry about the height of the obstacles that may be in the path between the transmitter and receiver (the Fresnel zone), the path loss associated with the frequency used, tramitter power, receiver sensitivity, antenna gain, and a whole host of other factors.
Here is a rough approximation that may be useful and/or informative. IF the TV transmitter's antenna was on one of the Virginia mountain tops at 4200 feet ASL (re: http://americasroof.com/highest/va.shtml - the OP can check with the station or the FCC records for exact height) and there were no intervening obstacles in the path then it would take a receiving antenna at 1200 feet ASL in order to be able to "see" (LOS) the transmitter. Then you have to take into account all the other factors mentioned. So, if the OP is also on a mountain ridge then it might be entirely practical to receive the desired TV station.
More information on long distance TV reception: http://www.geocities.com/toddemslie/UHF-TV-DX.html
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Bottom line after all the previous "stuff": At 60 miles from the transmitter, you're over the horizon...unless of course you're way higher...like on a mountain top. Sure, you might get signal bounce and reflection depending on atomospheric conditions, but nothing dependable. Just like it "might" snow tomorrow.

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I guess that is why those TV stations put up those big towers huh? I used to watch Richmond TV from DC when the Redskins were blacked out and that is over 100 miles. I had a 20' mast on the roof of a 2 story house (45' or so).
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As stated in a prior reply, you have to have the height, if you are more than about 50 miles from the desired station. That height can come from a TALL tower (not likely) or from a high location.
I am in a mountain location in North Carolina, at 4200 feet above sea level. Every day and night, I get signals in the 150 mile range. On occasion, I have received tv stations from the coast of NC, nearly 400 miles away. But under routine and normal conditions, I get clear signals from 150 miles and more.
I have a large antenna, on a 40 foot tower ( just to get out of the trees and well off the ground), and I also use an antenna pre-amp.
Good Luck !!
--James--
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