Correct Antenna Position for 2.4 Gig Transmitter.

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Correct Antenna Position for 2.4 Gig Transmitter.

Postby iflylilplanes » Sun Nov 04, 2012 3:18 pm

Forgetting the brand of radio, on a 2.4 Gig transmitter antenna, I have been given conflicting advice on how the antenna is to be orientated. I have been using my antenna sideways because I was told the waves radiate out as a fat donut, now , I have not had any problems as yet the radio has worked flawlessly with the many different receivers I use. Now I an getting back into thermal soaring which, means greater altitudes. At a recent 2 meter competition I was told I have it wrong, that I should have the antenna straight out from the TX because the radiation field extends out from the antenna still as a donut but as an elongated heart cross-section. Lastly, I have seen other flyer with the antenna pointing strait forward ready to poke yourself in the eye.

Which is the correct radiation field shape and which is the correct transmitter antenna position?
Many Thanks,

Dave W.


Dead Stick Glide Distance: Half the distance from the airplane to the nearest emergency landing field.
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Re: Correct Antenna Position for 2.4 Gig Transmitter.

Postby FlyingTiger » Sun Nov 04, 2012 8:26 pm

Most flyers have the antenna pointed 90°up. I don't know the electronic pattern of the transmission but you will be fine as long as you don't have the tip of the antenna pointed directly at the receiver.
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Re: Correct Antenna Position for 2.4 Gig Transmitter.

Postby iflylilplanes » Sun Nov 04, 2012 9:00 pm

That is my way of thinking because or the way the radiation field emits from the antenna. I have found it difficult to find info on the field shape so I can orient the antenna to get the best cover to the aircraft.
Many Thanks,

Dave W.


Dead Stick Glide Distance: Half the distance from the airplane to the nearest emergency landing field.
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Re: Correct Antenna Position for 2.4 Gig Transmitter.

Postby kaptain_zero » Mon Nov 05, 2012 1:28 am

Transmit and receive antennas should both be oriented in the same direction. WHICH way depends on many things.... orientation of the aircraft, reflectivity of the ground, obstructions between the two antennas etc. Simple things like your own body will influence the radiation pattern of your transmitter, as will anything else near by, so it becomes impossible to say exactly what orientation is going to be *best*, but depending on the antennas you are using we *can* predict what orientation should be used for best range most if not all the time.

When using "rubber ducky" type antennas, keeping them pointing straight up will give the best omnidirectional pattern. The same becomes true for the aircraft... try to keep the antenna in the same orientation. If you have 2 antennas on the aircraft, putting them 90 degrees apart will maximize your chance of having one of them vertical or as close to vertical as possible at any one time.

If one reads what the FPV folks do, one quickly discovers that circular polarization of the signals with the corresponding CP antennas at both ends of the path, improves it's reliability. This would apply equally to the transmit/receive of control signals, but in normal use, as we need to be line of sight when not using FPV, the range is sufficient with the easier to make linear polarized antennas, such as the "rubber ducky" (ham radio term) which is typically a 1/4 wave vertical antenna. The frequency in use is of no significance other than to dictate the size the antenna for the desired frequency. What applies to 2.4Ghz applies to 1.2Ghz or 70Mhz etc. etc.

Keep your antennas pointing UP to maximize your range and try not to point the tip of the antenna at your aircraft as that is the worst possible way of orientating it. Folding the antenna down to the side will require the aircraft to have an antenna to the side and broadside to you. Folding the antenna over to the side creates nulls to both sides of you, but *might* slightly extend the range to the front (in theory), but there are too many unaccounted for factors, such as the effect of your body, the ground etc. However, if your are flying close in... say indoors, or using a multirotor craft or perhaps practicing 3d aerobatics over the runway... hovering and the like, then folding the antenna to the side might get it "out of the way" but other than that, still serves no purpose other than to perhaps look "cool" much like gang movies where you see someone holding a handgun sideways... in real life it would make it far more difficult to hit something with that gun, but it does look "cool".

Antenna and radiation patterns are very complex and influenced by so many things that sticking with the basics becomes the safest course to take... So, keep those 1/4 wave vertical antennas vertical.

Regards

Christian
"I'd like to live as a poor man with lots of money."
-- Pablo Picasso
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Re: Correct Antenna Position for 2.4 Gig Transmitter.

Postby iflylilplanes » Sun Nov 11, 2012 8:17 pm

I used the antenna in the sideways position in a competition Sunday, hooked a few boomer thermals to a 1000 ft without any issues. Most of the pilots have the antenna the same way for the same reason, to keep the strongest part of the signal field on the aircraft.
Many Thanks,

Dave W.


Dead Stick Glide Distance: Half the distance from the airplane to the nearest emergency landing field.
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