Suggestion for Antennas

[Mr. Know it all]

Can I say something - without sounding to crass?

Almost none of your suggestions for a outdoor antenna are a good choice.

Most all of those antenna's has some sort of limitation which keeps them from being good choices.

Without going too deeply into this subject, the first point to ponder is that UHF television signals are line of sight. That means that unless you can see the tower or unless some sort of refraction, diffraction or reflection momentarily sends the signal your way. There is no way that you are going to receive it much past 65 miles.

Two way that I explain line of sight is if you put up a transmitter tower 1000 feet above average terrain and you put up a receive tower and antenna 1000 feet above average terrain, you would get a good signal.

The other way I can explain line of sight is if you put a transmitter 1000 meters tall ( 3280 feet tall) out in lake Erie and you stood on the shore 46 km away ( 28 miles ), you could still see the light on top of the tower.

In telecommunication, radio horizon is the locus of points at which direct rays from an antenna are tangential to the surface of the Earth. If the Earth were a perfect sphere and there were no atmospheric anomalies, the radio horizon would be a circle.

The radio horizon of the transmitting and receiving antennas can be added together to increase the effective communication range.

Antenna heights above 1 million feet (1966 miles, or 3157 kilometres) will cover the entire hemisphere and not increase the radio horizon.

VHF and UHF radio signals will bend slightly toward the Earth's surface. This bending effectively increases the radio horizon and therefore slightly increases the formula constant.

Line-of-sight propagation refers to electro-magnetic radiation including light emissions traveling in a straight line. The rays or waves are diffracted, refracted, reflected, or absorbed by atmosphere and obstructions with material and generally cannot travel over the horizon or behind obstacles.

Radio signals, like all electromagnetic radiation including light emissions, travel in straight lines. At low frequencies (below approximately 2 MHz or so) these signals travel as ground waves, which follow the Earth's curvature due to diffraction with the layers of atmosphere. This enables AM radio signals in low-noise environments to be received well after the transmitting antenna has dropped below the horizon. Additionally, frequencies between approximately 1 and 30 MHz, can be reflected by the F1/F2 Layer, thus giving radio transmissions in this range a potentially global reach along multiply deflected straight lines. The effects of multiple diffraction or reflection lead to macroscopically "quasi-curved paths".

However, at higher frequencies and in lower levels of the atmosphere, neither of these effects apply. Thus any obstruction between the transmitting antenna and the receiving antenna will block the signal, just like the light that the eye may sense. Therefore, as the ability to visual sight a transmitting antenna (with regards to the limitations of the eye's resolution) roughly corresponds with the ability to receive a signal from it, the propagation characteristic of high-frequency radio is called "line-of-sight". The farthest possible point of propagation is referred to as the "radio horizon".

In practice, the propagation characteristics of these radio waves vary substantially depending on the exact frequency and the strength of the transmitted signal (a function of both the transmitter and the antenna characteristics)

 

[Mr. Know it all]

Again,

Television antenna's are usually tuned to receive certain frequency's well and all other frequency's withing the spectrum of television at a semi ok level.

Local channels with a clear line of sight, will come in with little resistance as long as you use a antenna that is higher than average terrain.

Beyond that point, it is a crap shoot.

There is no such thing as a HDTV antenna. Any UHF antenna will receive UHF signals and any VHF antenna will receive VHF signals and any combo UHF / VHF antenna will receive both.

Some people seem to think that a HDTV antenna is cut to receive channels from 7 to 59. That myth is a lie. There are still television signals in the range of channel 2 - 6 in many markets and a good antenna will receive all the frequency's, unless you live somewhere - where there is no VHF signals present, then all you need is a good UHF antenna.

If you had a UHF / VHF antenna and live within the service range and your antenna was still good, it might still work.

There is only one thing that you have to remember, that is that UHF digital signals are line of sight and your antenna needs to be pointed in a direct line with the transmitter to get the best reception.
That can only be done with a antenna rotor.

The VHF digital signals are now low power and does not transmit well over long distances as did ANALOG VHF.

The best antenna's are the ones that are manufactured with a cartridge box that directly connects the RG 6 wire F type terminal to the antenna.

Cheap commercially made transformers usually fail within one year in any environment where there is cold weather, wet weather, high temperatures and UV light. Many antenna's are junked - just because the terminals corroded on the lugs on the antenna or the transformer went bad.

The only two options is to use a Winegard type antenna that has a cartridge box that seals the phasing lines from the weather and directly connects the antenna to the 75 ohm RG 6 wire.

The other solution is to use a Channel Master type pre amplifier that directly connects the leads of the pre amp to the lugs on the driven element on the antenna which then eliminates the need for a matching transformer.

A little bit of anti seize on the threads of the lugs and terminals and some RVT silicone sealer on the outside of the terminals and some good 3M electrical tape will keep the moisture out of the wire and give you years of service.

RG 6 Wire does not wear out, it just gets moisture inside of it and then it deteriorates the signal inside of the wire.

All television antennas in fringe areas should use Quad Shield due to it's low loss and better shielding against outside noise.

 

[Aaron62]

Can I say something - without sounding to crass?

Almost none of your suggestions for a outdoor antenna are a good choice.

These aren't recommendations, they're reviews or informational links.

 

[Piggie]

At low frequencies (below approximately 2 MHz or so) these signals travel as ground waves, which follow the Earth's curvature due to diffraction with the layers of atmosphere.This enables AM radio signals in low-noise environments to be received well after the transmitting antenna has dropped below the horizon.

AM radio is vertically polarized and a very low frequency giving it the ability to create a ground wave out to a fairly good distance. But ground waves are not due to diffraction. Ground waves are formed by a Marconi type radiator (normally a 1/4 wave above a ground plane). A Marconi is only half a dipole since it's 1/4 wave not a 1/2 wave like a dipole. The second half of the dipole is made by the earth. It's called a ground wave because since the second half of the dipole is the earth, it radiates outward along the ground. The wave sees the ground as part of other half of the antenna for many miles in all directions, in the range of up to 50 or more miles with enough power. The part of the wave in the air follows the curve of the earth because it's the other half of the wave in the ground. A ground wave is not reflected or diffracted off of anything. Ground waves also travel farther in earth that is a good conductor.

Ground waves play an important role in communication up through low band VHF. Every vertical antenna puts out a ground wave. But much above 50 to 60 MHZ it's not very significant. The lower the frequency the more range a ground wave has. This is why they use VLF to talk to submarines under water. It is also one of the advantages (when there is no skip) for low band 2 way radio in rural areas. Though just about all companies that used low band VHF and police have moved to high band or vhf due to the skip problem. I used to work on Florida State Trooper radios around 40 MHz that talked to 150 ft towers out as far as 40 miles, well beyond the radio horizon. All the cars ran 100 watt FM transmitters and the base stations were normally a 1/4 KW.

But also on AM radio the radiator being a vertical 1/4 also puts a lot of energy up at at the sky at very steep angles. If the MUF or solar indexes are high enough, radio waves in Medium Wave band and lower Shortwave will reflect almost straight up and back down from the F layers. This can add or subtract from the ground wave from an AM station depending if it's in or out of phase. Normally the ground wave is so much stronger for the first 10 to 200 miles (depending on power) it is stronger than any skywave reflected and the station comes in clear as you move down the road. Being the MUF is normally so high above the AM radio band, this reflection happens almost all the time and often helps a station's range a little past it's ground wave range in the daytime. But at the same time there is another layer seldom discussed call the D-Layer. It's useless to enhanced radio propagation and actually has a negative effect. During the day it ionizes the atmosphere all the way to the ground. It actually blocks signals up to about 3 MHz most days by adding electrical noise. Much of the daytime F-Layer bounce is negated by the D-Layer, hence most daytime propagation of AM radio is ground wave. You can think of the D-Layer as one that absorbs radio waves as well as adding noise.

Now, as the sun sets, the F-Layer "cools off" and the MUF drops. The D-Layer disappears about sunset. The F-layer can then reflect waves at lower frequencies at shallow angles, extending AM radio to thousands of miles on some nights.

Hence why AM stations have to cut power at night.