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Old Apr 17, 2015, 09:03 AM
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Interested:, very much so:
What Telemetry are you using ? X8R ? How did you do it ?
I have a quad with L9R and missing telemetry VERY much on it, but still have an X8R lying around here...
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Old May 11, 2015, 10:15 AM
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Everybody seems to agree that the 2 antennas should be set 90 deg apart.
But I wonder if having them positioned as a V is really the best solution?
Let's say your TX antenna is vertical. The best possible situation is that the RX antenna is also vertical. So the V config means you get less than perfect alignment when flying level, and get perfect alignment when banking at 45deg.

Take the same 90deg RX antenna mount and rotate it so you have an L rather than a V.
Now, when flying level you have totally perfect alignment. When banking at 45deg you still have the same alignment you would have in level flight if they were in a V position.

When people suggest the V mount, are they suggesting that you should have a 'less than perfect' signal most of the time, so that when you turn you are improving signal? I can understand this logic.

For me though, if we are talking about how to achieve absolute maximum range, then an L is better than a V... how could it not be? I fly fixed wing and have a RTH failsafe. So I'm not worried if I fly out to my maximum range then banking causes the signal to drop.
Without having RTH you may well prefer a V so if you are on the very edge of your range, a steep turn to come home will actually improve signal.

My point is there is a difference between the 'best' antenna position in terms of what will achieve the best range and the most 'practical' in terms of what happens when you are pushing things.
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Old May 11, 2015, 10:35 AM
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I've had a skin through and didn't see this mentioned (so sorry if it has been)... but what about the actual rotational position of the PCB antenna? The fact they are flat adds a dimension that never existed before with coax antennas.

Forgot the V - L thing, whichever you go for, these antennas have a face and an edge. The signal received must vary depending on if the antenna is facing you or not?

I have seen V mounts with on antenna 'face front' and the other 'edge front'.
To me, this must introduce an imbalance between how the 2 antennas perform.
Let's just say they work best when they are 'face front'.. the 'edge front' antenna becomes best when you are flying across yourself (rather than towards or away). but if that antenna is the left one and you are flying right to left and are also banking left, then the Antenna is now pointing directly at you.... which is bad. The opposite one will now be vertical but that one is facing the front/rear of the aircraft.

So, rather than go on about it I am going to try and test this by doing a range test with both antennas in the same vertical position, side by side. I will see what's best, receiving from the face or the edge. I can;t see how there can;t be a difference.
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Old May 11, 2015, 03:59 PM
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See posts 12 and 14 (on page 1). Signal is strongest with the thin edge of the antenna facing towards the TX.
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Old May 14, 2015, 06:56 AM
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"Less than perfect signal" misses the point. We don't care how "good" the signal is as long as it's good enough to provide the required information with an acceptable error rate. The question is not about best case scenarios but worst case. In other words, a configuration that prevents the signal degrading below the minimal functional level is needed, not one that provides maximum signal some or even most of the time. Thus, if a V is inferior, on average, to a vertical antenna but less subject to even occasional drop-outs, it's preferable.
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Old May 15, 2015, 03:45 AM
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Quote:
Originally Posted by Daedalus66 View Post
"Less than perfect signal" misses the point. We don't care how "good" the signal is as long as it's good enough to provide the required information with an acceptable error rate. The question is not about best case scenarios but worst case. In other words, a configuration that prevents the signal degrading below the minimal functional level is needed, not one that provides maximum signal some or even most of the time. Thus, if a V is inferior, on average, to a vertical antenna but less subject to even occasional drop-outs, it's preferable.
I agree, That's what I was asking (kind of)... I thought that people probably use a V because the worst that can happen when turning is the signal actually gets better : )

I suppose then using the advice that the signal is stronger with the thin edge pointing towards the transmitter then I should mount these on my plane so that the wider face of the antenna is facing front/back. Then if the failsafe was to kick in, as the plane starts to turn the thinner edge would be facing me and you should get signal back. (Rather than having them as i have them mounted now which was done to reduce drag).
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Old May 15, 2015, 04:22 AM
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Has anybody ever tried to make a device that keeps an RX antenna vertical / horizontal (whatever you want)... a bit like a gimbal but not as complicated. I'm thinking more like a single servo.

I fly fixed wing but i have a stabilizer on board and all the mutli-rotors obviously have kit on board that is aware of the aircraft's level in relation to the horizon. I don't know a lot about electronics (or i would try this myself) but I can't imagine it would be difficult for somebody with the right skills to get the level info from a flight controller board and use it to control a servo to point vertical as the plane banks.
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Old May 18, 2015, 04:24 AM
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Hello. If i may interupt i have a related experience and question. I am using the X9D-X8R with the PCB antennas to control a Radian Pro glider. I had both paddles zip tied flat side down to the inside of the servo door which is on the bottom of the fuselage under the main wing. I have been having troubles with spotty telemetry with this arrangement so i moved one of the paddles to a vertical servo wire passage within the fuselage with the wide face of the paddle pointed towards the nose and tail of the plane. Telemetry reception was noticeably better if the nose of the plane was pointed at me or away, but could be spotty from the side. After reading this thread I plan to rotate the horizontal paddle 90 degrees so that it sits on its edge with the wide flats pointed out at each wing. I won't be certain till i test this arrangement, but i am thinking this will give me the best possible coverage with this antenna design. Does this sound like good logic or might there be a better solution? Do the whisker antenna offer better reception at the cost of distance?
http://www.alofthobbies.com/15cm-receiver-antenna.html
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Old May 18, 2015, 10:41 PM
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You wouldn't notice any difference in useful range with whiskers and they are a lot easier to mount properly in a Radian. I've had mine at the limit of my vision many times with no range issues.
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Old May 19, 2015, 04:03 AM
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Thats what i was hoping someone might say. Thanks. If i may ask where did you mount the whiskers?
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Old May 19, 2015, 08:53 AM
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Both are stuck to the outside of the fuselage with cellotape. One runs down towards the tail along the fuselage, the other runs up the fuselage, basically at right angles, from the Rx/servo port underneath to the top just behind the canopy. In each case I keep the exposed section and an equivalent length of coax in a straight line.
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Old May 19, 2015, 09:39 AM
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Thanks. If the PCB antenna doesn't work out in the last configuration I mentioned I will mount a set of whiskers as you specified.
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