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Corey

Proper placement of patch antennas

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I've got some new equipment to try out this weekend and was hoping to get some info to make sure that I'm at least thinking in the the right direction as far as set up is concerned. The equipment is on the 5.8 frequency. I have two Yellowjacket pro diversity receivers feeding into one Oracle diversity receiver. My Trex 500 heli has a 250mw Stinger Tx with the stock whip antenna pointing straight down, several inches away from the radio Rx and the speed controller near where the tail servo is. Then I've got four 8dBi patch antennas for the Yellowjacket receivers with specs of 75 degree horizontal beam and 60 degree vertical beam.

For the "theoretically ideal" antenna placement to get maximum coverage would I be putting each antenna at a 75 degree angle to the adjacent antenna? Then I'm thinking that each antenna should be angled upwards at least 30 degrees so that the bottom of the beam is parallel to the ground, or higher. Is that the right way to approach this? I don't anticipate needing a 360 degree coverage area for this project. I just want a clean video for the entire area in front and to both sides of where I'm standing for a half to three quarters of a mile and at vertically for probably a quarter mile or a bit more.

I also have four 11dBi patch antennas with narrower beams, and also two large 19dBi omni "pole" antennas that I bought before joining this forum and finding out that I probably got the wrong thing. Should I consider trying them for anything with this type of a set-up? I've also read some seemingly conflicting info on whether or not patch antennas should be placed close to the ground or higher up. Is there a right or wrong way?

This particular project is really more for my neighbors than for me. I'm not flying FPV for this, but rather feeding the video output to a couple pairs of FatsShark video goggles for my neighbors and thier kids to pass around while I fly in the park next to my house. It keeps them happy and then they don't bother me when I fly other rc models there!

Thanks in advance for any comments or suggestions.

Edited by Corey

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I just want a clean video for the entire area in front and to both sides of where I'm standing for a half to three quarters of a mile and at vertically for probably a quarter mile or a bit more.

Overall, you've described two different ways to use the Oracle. That is, it can be used to widen the beamwidth (by allowing you to append the beamwidths of your antennas), or it can be used to reduce multipathing (which requires significant beamwidth overlap of the antennas). These are vastly different configurations and the one you use depends on what you want to achieve, the environment you are in, and other factors.

wo large 19dBi omni "pole" antennas that I bought before joining this forum and finding out that I probably got the wrong thing. Should I consider trying them for anything with this type of a set-up?

Try three overlapping patches with one pole antenna. If it was me, I'd dump the pole antenna and get a 3-6dBi dipole omni ducky instead.

I've also read some seemingly conflicting info on whether or not patch antennas should be placed close to the ground or higher up.

In some environments, mother earth can reflect the RF too and cause multipathing. Getting the patch antenna close to the ground can mask some of it.

Bottom line: There isn't one antenna configuration for everyone or every environment. So experiment at each flying site to determine what delivers the best performance for you. Be flexible.

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Thanks for the info. Regarding the patch antenna orientation and to make sure I understand correctly, if I overlap the beam coverage it should reduce mutlipath interference but reduce the overall coverage area?

Also, would it be worth trying to significantly separate the patch antennas from each other or is that not an issue? I was thinking about putting one of the Yellowjacket receivers with its two patch antennas a couple hundred feet or more away from the base set-up and then bringing the output signal back to the base station Oracle receiver via a separate Tx and Rx on a different frequency. Any thoughts?

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As you are not flying FPV I guess you will be overhead or at high angles so I would mount the patches at high angles say 45 deg.

Terry

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if I overlap the beam coverage it should reduce multipath interference but reduce the overall coverage area?

That is correct. You can also try a compromise approach and overlap about 50%, so you get a little of both advantages.

Also, would it be worth trying to significantly separate the patch antennas from each other or is that not an issue?

A few inches separation is usually adequate.

I was thinking about putting one of the Yellowjacket receivers with its two patch antennas a couple hundred feet or more away from the base set-up and then bringing the output signal back to the base station Oracle receiver via a separate Tx and Rx on a different frequency.

I would be concerned about using another RF link to connect to the Oracle. The video signal will probably become too degraded for Oracle to do it's job.

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Just remember the beam coverage is not solid, it is the 3dbi or half signal that is quoted. You can still get a good signal beyond the beam edge but it drops off the further you go.

Terry

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You can still get a good signal beyond the beam edge but it drops off the further you go.

Yes, and that is another slogan T-shirt I need to have made. :) There is a common misconception out there that antenna beamwidth is like a brick wall and once you go beyond the rated specs the signal is totally gone.

On the contrary, some folks have commented that their narrow beamwidth rated patch antennas work for nearly 180 degrees; it causes them a lot of head scratching. But, all it takes is a look at the plots in the antenna's data sheet to realize that there is signal beyond the 3dB points that determines the advertised beamwidth numbers.

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