Top Shields for Horns - Idea

Tom DeReggi

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What would be the viability to make/add optional top shields / visors for the 30deg horn antennas to reduce top side wasted energy?

Currently the horns deliver a uniform round equal in all directions of its 30 deg beamwidth. 15 degs to the right, left, up, down, etc. Although that design could be ideal for many applications where the customers are at higher and lower elevation, its not ideal for traditional application where the AP PTMP antenna is mounted high on a tower above the elevations of most of its its subscribers. In a horn's case, the 15 degs going upward becomes just wasted lost energy.  But worse, it complicates down tilting. In congested areas, Downtilt is essential to create coverage zones, to reduce coverage distance, to avoid interfering with neighboring towers.  We observed, our past 5.x deployments to interfere with our other towers even 20 miles away, without using downtilt.  Although Horns can be downtilted 15+ degrees to enable reducing coverage, that will also spread out to much energy downward to near field obstructions (especially in more urban areas with tall buildings) that could potentially reflect back to the tower at higher harmful signal strengths to cancel out the transmission signal due to out of phase or multipath signals.  But worse, excessive downtilt, drops the signal 6db to the frontal core desired coverage area, because its being served by the top edge of the beamwidth. Without downtilt, the 15 degree offered in the downward direction is already plenty enough to accommodate any nearfield coverage.  The above is one reason, rectangular sectors antenna with minimal vertical beamwidth (4 - 12 degrees) or electronic downtilt are often used.

With that said, there are many other exciting benefits to the symmetrical Horn antennas, that make them favorable to utilize. For one, the small size foot print. And second the excellent front to back ratio  and side lobe isolation.  In my case, Im using the horns at one tower with very limited space, because we were forced to switch our colocation agreement to a price per square foot of antenna front panel surface area. Three 30deg horns have less than 1 sqft of frontal surface area, saving me a ton of money on colocation, at 4x to 6x saving over other traditional sector designs. (Yes, Im very pleased with Rfelabs!) 

So back to the original question.... a top shield or visor !?  Sorta like a anti-glare or rain shield used on traffic lights.  Having a shield, curved to attach to the Top 90deg-120deg rim, and extending straight out horizonatlly 6-12" (not at the slope of the horn).   This could potentially block the upward beam radiation and reflect it downward to increase the TX gain at the core frontal focal point of the antenna, with less physical downtilt.    In many cases, the symmetrical horn pattern is only needed in the lower 180 degrees

Or would the shield, cause harmful reflections to degrade the signal more than the benefit of such? 

Is that something rfelabs has already experimented with? 















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thank you very much for your feedback. We are glad that our Symmetrical Horn antennas work great for you. We really like their compact size with all their great features :) It will be amazing if you can post here some photos of your installation.

Symmetrical horn antennas bring many benefits that are very useful in different scenarios, however there are certain cases where you need to use our Sector Carrier class antennas. Adding a top shield or visor to Symmetrical horns will be more harmful than beneficial. Such a shielding usually just reflect the signal causing a lot of reflection, changing the whole radiation pattern of antenna and thus significantly degrades performance of the antenna. Same what happens if you put RF armor on a traditional sector antenna. The only way how to reduce the coverage of symmetrical horns is to use downtilt (up to 25 degrees) and lower the output of the radio to reasonable level. The output power of the radio is very important and often overlooked factor. The fact that you hear your sector 20 miles away might signalling that you are using too much output power. 

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"Adding a top shield or visor to Symmetrical horns will be more harmful than beneficial" - very likely.

" changing the whole radiation pattern of antenna and thus " -  well, that was sorta the idea, to purposely change the radiating pattern :-)

Sounds like I'll need to experiment some to determine the best downtilt for our application.

I will definitely post picts of the completed install, as we progress..

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