Antennas Orientation

[leowagen]

Hello all. Looking for some suggestions on how to install my recievers in order to get the best antenna "coverage". My setup is an Archer Plus R12 as master and an Archer plus R6 as Slave, working on ACCESS protocol. Tx is an ISRM X10 with Ethos OS 1.4.x. Model is a gas powered quarter scale Decathlon.

My idea is to setup each pair of antennas at 90 degrees, so each recieved pair of antennas generates a "plane", so far, so good. Now, how should I install those two planes? perpendicular? i.e. master antennas at 90 degree held on a horizontal surface and slave antennas at 90 degrees, held on a vertical surface, keeping master and slave as apart as wiring and plane structure allow.

Makes sense?

Or I should keep all 4 antennas on the same plane, but covering 2 different orientations, for example 2 looking forwards and 2 looking backwards?

This is my first redundancy setup, so i'm trying to get the most out of it.

Thanks a lot, nice flights and nicer landings to everyone!

 

[jure]

if each pair of antennas defines a plane , set them up so that the two planes ( produced by two receivers ) are perpendicular.
they do not need to be strictly vertical and horizontal , just perpendicular.

 

[Konrad]

I also like to place the elements in a plane (geometric term) as far apart as practical. For this reason I like the longer antennas for larger models. Also try to place the antennas so that you see at least one sticking out from behind a reflective object (motor, battery or carbon and aluminum structure) as you move the model around.

@jure has made some good points about maintaining a ground plane with the coaxial part of the antenna. This has helped me with some of my larger electric aircraft (getting the signal from a round the large 12 cell battery).

 

[thenated0g]

This is a little off topic (long range fpv) but i remember an antenna designer talking about the difference between putting antennas in vertical or horizontal orientations. One was better for long range (horizontal i think) and the other was good for going behind (punching thru) objects like trees. When we had external transmitting modules it was easy to match this with the plane but now with them built into the x20 im not sure which way the antenna is orientated inside. So if you have 2 antennas, like usually you do on 2.4 RX's, make sure they are 90 to eachother, make a V, so you always are close to having matching orientation.

 

[Konrad]

@thenated0g I think the horizontal/vertical orientation of the antennas is a TX concern dominated by earth being a grounding plane.

With the RX this isn’t so much an issue as we (I) spend a lot of time making the aircraft do all sorts of gyration. Now if the aircraft is going to be in one orientation then you can try to match the TX and RX antenna orientation. Looking at a Smith plot of the radiation pattern might help with this visualization. I think the 90 degree orientation is to deal with the fade issues often associated with high frequencies.

While I hold many FCC licenses it’s been close to 50 years since I last took any certification tests. I’m sure @jure can give a better explanation of what is going on. He is a double EE and works with RF transmission issues.

 

[jure]

with model aircraft we need to consider the worst case regarding random orientation of Tx and Rx antennas .
In fixed point to point radio links , the orientation may be optimized ( and kept forever )

 

[thenated0g]

I think for the close range stuff we do with line of site, the orientation stuff is not as important unless you have a bunch of stuff blocking the signals which will just make any problems you have worse. Most of the 2.4 stuff will go way way beyond visual line of site.

Edit - i come from flying mostly foamy's so nothing is really blocking the signal like on the glass/carbon ships.

 

[thenated0g]

One of the interesting thing you have to think about in long range fpv is that for half of the flight the tail is facing you and than for half the flight its now coming towards you. So you want an antenna orientation that will beable to match in both positions. BUT at the half way point, which you dont really know when that will be sometimes as you can never know for sure when you will get to the end of your radio link, at that half way point your ship will transition 180 degrees which means that at the weakest point in the trip your plane will be 90 degrees to you, with probably some roll too, for a few moments. So in that transition you need to make sure that you still have a good connection. Now a lot of this is also covered by your flight controller kicking into return to home on loss of link, but thats never a good feeling to lose control.

 

[leowagen]

What I've read somewhere is that the worst possible link is when the Tx and Rx antennas are parallel and kind of aligned, due to the 3d shape of the emitting signal, which is like a thick donut with the Tx antena going through it. What i can't picture is what happens in the Rx end. But following the great suggestions you guys are describing, i think i can figure out a configuration keeping each Rx pair of antennas at 90°, and into different planes per Rx, plus making sure at least one antenna per each Rx is not parallel to the Tx at any time....

My flying is more sport oriented, trying to get my fingers into Imac precision aerobatics....

Sent from my SM-N986U1 using Tapatalk

 

[Haoyang Wang]

What I've read somewhere is that the worst possible link is when the Tx and Rx antennas are parallel and kind of aligned, due to the 3d shape of the emitting signal, which is like a thick donut with the Tx antena going through it.

I thought that’s the best case. The worst case is when the tips of the rx and tx antennae point at each others.

 

[leowagen]

I thought that’s the best case. The worst case is when the tips of the rx and tx antennae point at each others.

Exactly! that's the real worst thing!