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Old 31-Mar-2011, 4:24 AM   #1
retired17
Junior Member
 
Join Date: Mar 2011
Location: anaheim, ca
Posts: 13
Impedance matching, directionality, and gain

Quote:
Originally Posted by No static at all View Post
I agree as well. Just a few inches can make a world of difference, even with a strong signal. UHF can be very fickle.
Just registered. I was using a CM4228 8-bay antenna to get the UHF channels because I believed it would help my reception plagued by multipath. Some channels were strong and some were weak. I would move the antenna a few inches and the weak ones became strong but the strong ones became weak. I could never find a spot where all stations were strong. I read on HDTVPrimer that a large antenna (which has a narrower beamwidth) could actually be more lossy than a smaller antenna. Thus I tried the CM-4221 4-bay antenna and to my surprise all the UHF channels were strong (high S/N), some even stronger than before. Didn't have to move the antenna at all.

My theory of why I got better reception is that the radiation pattern across the smaller antenna was more uniform than across the larger antenna. According to the reciprocity theorem, the multipath signals received creates a very complex signal that is not matched to the transmission line thereby causing reflection which is loss. The losses must have been greater than the 3 dB increase in gain. The received signal from the smaller antenna better matched the transmission line resulting in less loss.

Sorry for being long winded. Your comments or thoughts are welcomed.
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