Antenna Gain & Manufacturers Performance Ratings

[Jellyby]

I'm a bit confused by different manufacturers performance claims of their antennas.

The Antenna Craft HBU44 has a 116" boom, 44 elements, and a db gain of only 8.2, yet they rate it good for 80 miles VHF, 60 miles UHF.

The Channel Master CM-2020 has a 90.6" boom, 41 elements, peaks at 10.3 db gain on channel 35, and they rate it good for 60 miles on both UHF and VHF.

The Winegard HD 7696P has a 110.75" boom, 41 elements, Peaks at 13 db gain on channel 14, and is rated good for 60 miles VHF, and 40 miles UHF.

Even though the Winegard has the most gain your performance rating is more conservative (and maybe more realistic) than the others. The Antenna Craft sounds especially over optimistic. Isn't more decibels gain the most important factor in reception?

[winegard]

Good morning Jellyby -

You've hit the nail on the head. All we can do is make the best antennas possible and post the most accurate information available by our in-house testing range and give the consumers the facts. Internally these 'mileage ratings' are something we struggle with every day. It's very hard to tell someone an antenna is good up to X miles when it is completely dependant on the individual's circumstances.

[KNP 2516]

A few facts to think about.

UHF is line of sight. Even over the horizon, the line of sight for a tower 3000 feet high - while looking over the ocean might be about 48 miles if the sea's were calm and there was no fog or other obstructions between you and the light on the top of the tower.

I'm sure that at this point, you are going to wonder - isn't the horizon about 26 miles from one side to the other?

The answer is that the light refracts - bends around the curvature of the earth - which extends the line of sight - if you get a object high enough.

Then you also have to remember that most television transmitter towers are less than 1000 feet in height.

The height of the transmitter antenna is factored into the power output of the transmitter.

So by knowing all this knowledge - you can put it to the test.

If you had your television antenna 1000 feet above average terrain - not height above ground, and you had the transmitter antenna 1000 feet above average terrain. You could get a signal from a range of about 40 miles. If you were ever driving down the road and you saw 3 big white or blue convex antenna's on the top of a tower - they are usually for microwave transmission - telephone.

The next tower would be somewhere around 20 miles away, due to the fact that the tower is only a couple of hundred of feet high and they need to maintain a direct line of sight. If you climbed up there and moved one of the antenna's a couple of degrees, your home telephone probably wouldn't work - if you dialed the right area code or area, due to the fact that the one antenna couldn't see the other antenna and all telephone communications that that particular antenna carried would not work.

So we know that UHF will work to a range of about 40 miles - line of sight in a ideal situation.

Then you get into diffraction, reflection and refraction, where the characteristics of the signal changes due to the fact that radio waves bends - just like light waves. You have to be able to understand these things in order to be able to build a modern communications facility and be able to compute how far the signal is going to go at X amount of frequency with Z amount of power.

So with everything in a ideal condition, UHF will travel to a distance of about 65 miles maximum.

Then you have to remember that not all antennas are 100% efficient. The most efficient antenna's are the ones with the most elements. The more surface area you have on your antenna, the more gain you can achieve - due to the fact that the antenna uses the driven element to receive the signal and all the other elements reflect the signal back to the driven element. On the VHF side, the antenna might only use 3 sets of elements at any one time. The higher you go in frequency, the further from the driven element the antenna uses its elements to tune the antenna for the best performance. That is the main reason why the good VHF antenna's were so large.

Because the UHF signal is shorter in length, the elements on the antenna are also smaller to properly tune the antenna to receive the signal. That is the reason why most UHF / VHF antenna's uses a YAGI type antenna and a reflector on the receive end.

The front to back ratio is nothing more than how well the antenna receives the signal from the side which is not pointed in the right direction.

In the old days, VHF analog, you could point the antenna in one direction and still get a good signal off the back side of the antenna. With UHF digital - if the signal is too far away and you have the antenna pointed in the wrong direction by even 10* - you will not get a signal.

Manufacturers can put anything they want on the outside of the box, but most times, if the antenna is junk, you will know it in just a couple of days. How many times have you heard someone say - I took down a 25 year old antenna and the new antenna didn't perform as well as the old one?

That is usually due to the fact that the old antenna was large and had lot's of gain.

About the best combo antenna on the market is the 8200 U Winegard.

It will receive a signal from a range of about 60 miles maximum, as long as you have a clear line of sight between you and the transmitter, most times of the day without a amplifier - if the run of wire is good wire and the run is not more than 40 feet long.

Some of Winegard's antenna's are nothing more than one half of the 8200U - UHF antenna and something else, or nothing else.

Pre amplifiers usually only helps overcome loss from long lengths of wire and splitters in the system.

They cannot amplify a poor signal.

With digital, the signals are all 1's and 0's, either you have a signal or you don't!

I won't install a Antenna Craft antenna.

The quality of materials in a Winegard antenna is several times better than most other antenna's and will give you years of reliable service. Some other manufacturers antenna's fails after just a couple of months.

Even if the antenna is good, if the transformer fails, then you have no signal.

The thing that I like best about the Winegard is that it uses a cartridge box that converts the 300 ohm signal to a 75 ohm F terminal directly, which eliminates the problems with the transformers.