Antenna Performance Analysis

I came across an interesting page analyzing antenna performance - The author has what is considered the best all-time antenna ever designed and manufactured for the home - the Channel Master 4251 (no longer available). Here are some of his thoughts. See especially his discussion concerning “antenna bandwidth” and the losses incurred when pointing away from the broadcast tower.

“Given: amount of signal necessary to receive a digital signal without dropouts = 100%. 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.”

"Antenna capture area: This is one specification manufactures do not give. There is no standard I know of. When you get into double edge diffraction and tropspheric scatter signals, I believe capture area can be a very important specification to consider.

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.

The 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."

"2Edge reception (categorized in TVFool reports as “path”) presents more of a challenge. 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. The larger the signal-capturing area, the better chance the antenna will capture this type of signal."

Some of these considerations should provide a wider context to the Tablo’s reporting of signal strength… Things to take into account when the Tablo cuts in and out due to signal fluctuation and LPWs.

BTW it is every antenna hunter’s dream to get their hands on an old 4251 -

1 Like