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Questions about patch antennas.

PostPosted: Mon Jan 23, 2012 10:41 am
by rogueqd
Quick question about the patch antennas, do they allow any omnidirectional flying at all? As in do you have 50 or 100m around you to land and stuff? How far behind the antenna can you fly before you lose signal?

I guess this comes from IBCrazy's Antennas101 video. He had blue shapes radiating out from his antennas and said that as long as the shapes touch you've got signal. I used to think of it more like light with a patch antenna being like a torch and the plane being like a light sensitive diode or something. The diode is only going to react if the torch like falls on it. Can the omni antenna on the plane kind of reach out and pick up a bit of signal from the patch even if the patch is pointed away from it?

Re: Questions about patch antennas.

PostPosted: Mon Jan 23, 2012 8:55 pm
by Shotglass
any anytenna no matter hot directional will radiate backwards to some degree
with a single patch antenna realistically youre looking at something in the range of -20dbi to -30dbi of gain behind it or about 100 to 1000 times less power radiated in that direction compared to some theoreitcal antenna that radiates in all directions identically (and about 1000 to 10000 time less power radiated in that direction than to the front)

anway off the top of my head iirc the range factor is the square root of the power factor
no assuming the 2.4km the frsky system allegendly can achieve with its usual monopole antenna (for simplicity and as a safety factor well assume that thing has a gain of 3dbi or factor 2) we get that the power radiating to the back of the patch antenna is 2000 times less than that of the normal frsky antennas
take the squareroot of that invert it ans multiply it with 2.4km and unless i made a mistake somewhere i get ~50m of range

i wouldnt really trust a large expensive plane with that calculation though
either way point is its not like your plane will immediately crash the moment you fly behind the patch antenna
it will however severely limit your range

Re: Questions about patch antennas.

PostPosted: Tue Jan 24, 2012 1:59 am
by kaptain_zero
Here's a typical patch antenna pattern: http://goo.gl/k3ZiA

Re: Questions about patch antennas.

PostPosted: Fri Apr 20, 2012 1:38 am
by zann68
I've noticed on these directional antenna's they refer to some as "Patch" and some "Panel" are these the same antenna or is there a real difference? Ohh and lets not forget some say Vertical , Horizontal or even Vertical & Horizontal polarization. dBi looks to be just as bad on choices as well, however it seems around 10 to 12dBi may be a winner, don't really know either. From what I gather dBi determines how tight the pattern is that the antenna will see "How much directional it really is". I have the Eagle Tree system and 5.8ghz CP antenna's. I ask this because I want to add a directional antenna to my setup for my tracker. I also have a Pan/Tilt kit coming. I have been looking over and over at antennas what a dizzying mess.

Re: Questions about patch antennas.

PostPosted: Fri Apr 20, 2012 7:20 am
by RCModelReviews
If you're running CP antennas then you don't want a patch, you want a helical.

The helical will maintain the benefits you've already experienced from your CP antennas but can also give you lots of gain.

A 5-turn helical will probably give you about 9dB of gain and an operating angle of around 60 degrees. They're also pretty easy to make.

Re: Questions about patch antennas.

PostPosted: Sat Apr 21, 2012 2:22 am
by zann68
RCModelReviews wrote:If you're running CP antennas then you don't want a patch, you want a helical.

The helical will maintain the benefits you've already experienced from your CP antennas but can also give you lots of gain.

A 5-turn helical will probably give you about 9dB of gain and an operating angle of around 60 degrees. They're also pretty easy to make.


Can you point me to a recommended guide for making a helical 5.8ghz.

Re: Questions about patch antennas.

PostPosted: Wed May 30, 2012 1:17 pm
by francoishaha
Check on rcgroups ibcrazy helical antenna thread

Re: Questions about patch antennas.

PostPosted: Thu May 31, 2012 12:32 am
by pldb64
Do you have a specific link in mind? ... my search of RCG didn't find a 5.8GHz related thread? ... but very interested :-)

Re: Questions about patch antennas.

PostPosted: Thu May 31, 2012 12:54 am
by francoishaha
Yes, sorry i was with my phone and it's so long seeking a link, so here it is for the helical antenna tutorial by IBCrazy
http://www.rcgroups.com/forums/showthread.php?t=1377791