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UHF YAGI ANTENNA
UHF 4-BAY ANTENNA
UHF 8-BAY ANTENNA
CHANNEL MASTER 4251
UHF 7-FT. PARABOLIC
CHANNEL MASTER 4251
This site is to report the results of continuing field tests using different types of antennas, comparing them to my reference antenna, the Channel Master 4251, a 7-ft. parabolic UHF antenna, which is known as the most powerful UHF antenna ever made for home use. These tests are for digital UHF reception only.
Three types of UHF digital reception will be tested:
1 - LOS (line-of-sight)
2 - 2Edge (Double edge diffraction)
3 - Tropo (Tropospheric scatter).
Since reception conditions, especially on 2Edge and Tropo, can change by the second, I decided it best to compare two antennas at the exact same moment. It is impossible to get 100% accurate results unless both antennas are mounted at the exact same spot at the moment of reception. Since that is not possible, I have both antennas mounted approximately the same height, approximately 25 feet apart. Each antenna is mounted with a rotator for pinpoint aiming. In addition, each antenna is connected to a different television, again making some error possible because of UHF tuner sensitivity differences. However, since the tests are to compare the different types of antennas using the CM4251 as a reference, these differences in setting should not materially affect the test results. These tests are taking place in Clovis, California, County of Fresno.
For more information on the Channel Master 4251, click here.
You can determine which types of signals are available in your area by going to TV Fool and entering your address and antenna height. After clicking on "Find Local Channels," you will get a list of the stations you may be able to receive along with the type of signal (LOS, 2Edge, Tropo) along with more valuable information to help you get the channels you want. Take that information as a guideline, not as an absolute. You may not be able to get all the stations they list for your area, and yet you may get stations they do not list.
TEST 1 - LOS (line-of-sight)
In this area of Central California, all local stations broadcast a signal strong enough for most any outdoor antenna to receive good reception.
In this test, first a Channel Master 1162A UHF-VHF yagi-type antenna was used. All local stations came in without any problems. Also, two stations from Bakersfield (111 miles away) also came in on a regular basis. For information about the Channel Master 1162A antenna, click here.
Next, the Winegard HD-9032 was used. This is Winegard's highest gain UHF antenna. Results were the same as above.
Conclusion: For LOS (line-of-sight) reception, it depends on signal strength. If you have weak stations, consider a high gain antenna, whether it be a yagi type or a 4 or 8-bay antenna. Consider trees and other obstructions in line with the signal you wish to receive. Generally speaking (but not always), the higher the antenna the better. In my particular area, an antenna mounted on a chimney mount is high enough for all local signals plus two stations 111 miles away.
Before going forward to Test 2, some antenna terms need to be understood.
Antenna Gain: Most antenna manufactuers publish at least an average gain for each antenna. While one may list an average gain of 12db, another may list 12dbd or 12dbi. In most cases, 12db should be the same as 12dbd. This means a 12db gain over that of a dipole. In order to equate 12dbi with 12db(d), you must subtract 2.15 from the dbi figure. Example: 14dbi = 11.85db(d) (14 - 2.15).
I take these gain figures lightly as there are different ways to measure antenna gain. They can be used to compare antennas from the same manufacturer, but I wouldn't trust using gain figures from one manufacturer to compare to another manufacturer. I would treat them as a indication and not an absolute.
Mileage claims are even worse. Use them only when comparing one antenna to another from the same manufacturer and for the same antenna series. Using mileage comparisons between different manufacturers should be used with caution.
Antenna Beamwidth: Most antenna manufacturers publish beamwidth figures for their antennas. The beamwidth is the area the antenna will receive a signal before losing one half the signal. Let's look at an example.
Beamwidth of antenna = 90 degrees.
Given: amount of signal necessary to receive a digital signal without dropouts = 100%. In this example, let's say we have a very weak signal and using a high-gain antenna produces 110% of the signal needed. In this case, every degree off center will, on average, reduce the signal by 2.22%. Let's say the signal is coming 5 degrees off center. 5 degrees x 2.22% = 11.1%. Now take 110% x 11.1% = 12.21%. You start with a signal producing 110% on center, subtract 12.21% for being off center by 5 degrees, which leaves a signal of 97.79% which is below the level necessary to get a digital picture.
Local stations may produce a signal strong enough that even being more than 45 degrees off center will still be enough signal to produce a perfect digital picture. But for marginal signals, it is best to use an antenna rotator to zero in for the strongest signal.
To complicate matters even more, some antennas have a beamwidth that is not symetrical; thus, the manufacturer may list a beamwidth of 90 degrees, but it might be plus 50 degrees and minus 40 degrees, just for an example. Another reason those who are serious about receiving very weak marginal signals need an antenna rotator.
Another specification that many antenna manufacturers give is f/b, or front-to-back ratio. The higher the number, the more the unwanted signals and interference is rejected from the rear. A high front-to-back ratio may be needed if co-channel or other interference needs to be rejected from the rear of the antenna.
Whether you need a narrow beamwidth or wide beamwidth, or a high front-to-back ratio, or a high gain antenna all depends on the particular circumstances. I always say it's better to get an antenna better than you need than one not quite good enough.
Antenna capture area: This is one specification manufactures do not give. There is no standard I know of, so I have invented my own. When you get into double edge diffraction and tropspheric scatter signals, I believe capture area can be a very important specification to consider as you will see from my testing below.
Notice the graphic of the Winegard HD-9032 at the top of this page. At the far left side of the antenna is the "corner reflector." That is used to capture more signal which then is reflected down onto the folded dipole. The corner reflector is 31.5 inches in height and 15 inches wide. My capture area calculation is to take width x height; thus, 31.5 x 15 = 472.5 square inches. The AntennaCraft U8000 shown is 36 inches high and 40.5 inches wide. Thus, it's capture area is 1,458 square inches.
Winegard HD-9032 - Capture Area = 472.5 sq. inches.
AntennaCraft U8000 - Capture Area = 1,458 sq. inches.
My method of calculating the capture area of an antenna shows that the AntennaCraft U8000 has a capture area just over 3 times that of the Winegard HD-9032. The tests below show how important the capture area of an antenna can be. While the HD-9032 has a much higher gain, the antenna will not produce a digital picture if the signal doesn't hit the antenna, while the lower gain U8000 antenna with a larger capture area might capture enough signal to produce a perfect picture.
TEST 2 - 2Edge (double edge diffraction)
2Edge reception presents more of a challenge. I chose marginal reception times for testing purposes. It doesn't do any good to test antennas when the signal is strong.
I tested two different channels over 100 miles from here where reception seems to depend on the weather, or atmospheric conditions. I tested RF Channels 25 and 45. Because these signals were extremely weak, I used the Winegard HD-9032 to see how it compared to the Channel Master 4251 (reference antenna).
The results on this test were mixed. One time the HD-9032 did about as well as the CM4251, but all other testing times the CM4251 held a good signal while the HD-9032 lost the signal, or the signal would come in and out using the yagi HD-9032.
Here is why I think the results were mixed. UHF signals, especially weak and from double edge diffraction, can vary greatly just a few inches up, down, left, or right. A yagi antenna has a very small area to "capture" the signal. Some people walk around on the roof with a signal meter to see where the strongest signals are, and mount the antenna at that spot. The problem is, with 2Edge signals, the location of the signal can vary from minute to minute, or even second to second.
Conclusion: If you are attempting to receive signals that come from double edge diffraction, I recommend an antenna with a large signal-capturing area. I would go with at least an 8-bay antenna. If you are going all out to get whatever is possible, I'd go with the Antennacraft Super-G 16-bay antenna. It is the largest signal-capturing UHF antenna available today that I am aware of unless, of course, you could still find a new or used Channel Master 4251 7-ft. parabolic antenna. The Super-G is 60 inches wide by 60 inches tall. The larger the signal-capturing area, the better chance the antenna will capture this type of signal.
TEST 3 - Tropo (tropospheric scatter)
Troposheric scatter reception presents the biggest challenge. It can present a hit or miss situation.
Once again, I used the Winegard HD-9032 and compared it to the Channel Master 4251.
When the signal was strong and steady, both antennas did well. However, with tropspheric scatter, the signal may be strong but not steady. The signal is scattered, so it becomes more of a challenge.
Results so far indicate the following: The larger the "capture area" of the receiving antenna, the less fading and dropouts occur.
One test you can do with your present antenna is to watch your signal level bars (or percentage, etc.) while receiving tropospheric scatter signals. If the signal level swings quickly between a strong or moderate signal and a weak or no signal, the signal may be hitting and missing the antenna. In this case, a larger capture area would probably reduce the large swings and give a more steady signal level. The larger the capture area, the better the chance of the signal hitting a portion of the antenna.
Recommendation for reception of tropospheric scatter signals: use the antenna with the largest capture area practical for your situation and mount it as high as possible. Many factors may enter into what is practical for your situation. Cost may be a factor. Wind resistance in high-wind areas may limit the size. Antenna heighth may be limited because of many factors.
Most of us have to be willing to compromise. What we want is the best antenna system we can get at a cost we can afford, and mounted as high as practical considering many factors.
Sources for TV antennas:
Solid Signal carries a wide variety of TV antennas at great prices and low shipping. Watch for sales and special free-shipping days. If interested, sign up on their website to get special offers by email.
Summit Source carries a wide selection of TV antennas. Summit Source is the exclusive dealer (as far as I know) for the AntennaCraft Super-G Model 1483 16-bay UHF antenna. To the best of my knowledge, this antenna has the largest capture area and highest average gain of any UHF antenna available today.
About the author: Gary Arnold has been playing around with antennas since the 1950s. His article, HOW TO SELECT THE BEST TV ANTENNA, was published in the AUG 1982 issue of RADIO ELECTIONICS magazine.