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Old 25-Jan-2016, 6:10 PM   #45
ADTech
Antennas Direct Tech Supp
 
Join Date: Jan 2010
Posts: 2,942
Quote:
Well I found it odd with channel 10 because it is mounted on the same tower as Fox (channel 23)
Doesn't matter. Each frequency will have it's own signal path which can be filled with minor anomalies which, when the signal finally arrives at any given random point in space (where you happened to put the reception device), can result in the signal getting pushed off the edge of the "digital cliff". When using a simple dipole, the issue can be aggravated by the dipole's reception pattern which can easily admit either reflections or other interfering signals. It is a mistake to assume that all signals from any given area or tower, even from the same antenna on a tower (there are transmitting antennas which broadcast multiple channels simultaneously) will arrive at any give point is space (where you planted the antenna, for example) with uniformity, there are always differences which are frequency-specific and those differences are the reason we put in big red letters at the top of every installation sheet the phrase "Before attaching the antenna to any surface, TEST RECEPTION in that area." Such peaks and nulls on UHF frequencies can be as little as 6-12 inches apart.

Quote:
So removing the reflectors would effectively give me the same gain as a C2V?
Peak boresite gain will drop as indicated. The reception patterns will also change, especially side lobes, but I've never seen any simulations that show it, I just know it will happen. My guess is that the pattern of a reflector-less C4 would look something like a typical bidirectional antenna with observable side lobes fore and aft.

Quote:
I also wondered why the C4V wasn't vertical stacked like the DB4E?
It depends on the design goal. Stacking two double loops vertically would indeed increase the peak boresite gain by about the same as stacking them horizontally while maintaining the ~70° HPBW instead of halving the HPBW as does the implemented design.. However, you would have to have a much longer mast to accommodate the vertical stack and this particular products was designed with retail (B&M) store shelf space in mind. It would also make assembly more complicated.
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Last edited by ADTech; 25-Jan-2016 at 7:25 PM.
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