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Old 11-Aug-2014, 7:07 PM   #1
stvcmty
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Join Date: Mar 2013
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Objects in close proximity to the back of an 8-bay antenna

Objects in close proximity to the back of an 8-bay antenna
Does an object behind the reflector of an 8 bay antenna impact the reception pattern of the antenna?

I use 2 UHF antennas where I am to get all the UHF channels I want. http://www.tvfool.com/?option=com_wr...ec2f149c73e9d6
Right now I have:
1. A winegard HD-8800 at 10’ pointed at 217 degrees true for Baltimore/DC UHF stations.
2. A winegard HD-8800 at 20’ pointed at 356 degrees true for WGCB, WLYH, and WPMT.
They each have their own preamps and come into my house on separate coax’s. I have separate tuners on my WMC computer for the Baltimore/DC stations and for the North stations.

I want to move them onto a tripod/mast on my roof. I would like to put both at 30’ by mounting them on a frame, but before I do that, I want to know if putting two 8 bay antennas in close proximity aimed 139 degrees apart with separate down-leads will cause them to degrade each other’s patterns.

What I envision doing is make a rectangular frame with two vertical bars to mount the two 8800’s on. There would be 2 horizontal bars connecting the vertical bars. At the middle of each horizontal bar I would put a mount to tie the horizontal bar to the mast in the tripod on my roof. Then I could aim the two 8800’s independently, but they would both be at 30’.
Each 8800 would be one side of a triangle. One side (the north 8800) would be perpendicular to 356 degrees true. One side (the DC 8800) would be perpendicular to 217 degrees true. If I remember geometry right, that means the angle between the backs of the two 8800’s would be 41 degrees. (The third side of the triangle would be open.)

The HDTV primer model of the 8800 shows back lobes. http://www.hdtvprimer.com/ANTENNAS/w8800.html Will putting a big metal object (another 8800) behind the 8800 hurt its forward gain? The main lobe of either antenna will not be aimed at the other antenna in any way, both antennas will have their backs facing each other at an angle. There will be no electrical connection of the down leads from either antenna.

Thank you for your help.
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Old 4-Sep-2014, 12:32 AM   #2
tripelo
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Location: Dallas, TX
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Quote:
Originally Posted by stvcmty View Post
Objects in close proximity to the back of an 8-bay antenna
Does an object behind the reflector of an 8 bay antenna impact the reception pattern of the antenna?
Stvcmty, your idea will probably work fine.

Normal reflectors, to a large degree, isolate the active antenna elements from external effects, in rearward directions.

Your having antennas sorta back-to-back is unlikely to affect the main lobes in any noticeable way.

Any metal in an antenna beam affects the pattern more or less.

In your case the main effects would probably be on the rear or sidelobe magnitudes or positions. For the 8800 it seems you are probably not much interested in minor changes of rear or sidelobe levels.

In some few cases, objects behind or beside an antenna can be helpful to reduce particular sidelobes.
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