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Author Topic: position of circular polorized antennas?  (Read 357 times)

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Offline greggmaN

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position of circular polorized antennas?
« on: February 16, 2017, 22:31:54 »
how do you position circular polorized antenna? i had a dys one connected to my aomway vtx and i just bent the stem so i pointed upwards....is this wrong if so how do you posistion it im looking for a new one as i had a crash and bent the metal bits :( mines this one http://makeitbuildit.co.uk/index.php?route=product/product&product_id=859



Offline Cheredanine

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Re: position of circular polorized antennas?
« Reply #1 on: February 16, 2017, 22:53:49 »
Best circular polarised I have is manacerc raptor.
Hands down recomend them.

They use the pagoda design by Maarten Beart. There are some antenna using this design that are less good but the menace Ines are brilliant.

As for placement, imagine you took a donut and fitted it over the antenna physically. That is how it transmits, the donut from the antenna and the donut from your rc need to occupy the same space to work, the more if the donuts that overlap the better the signal.  So best if they are at the same orientation at the same height and actually some distance appart

If you use a patch antenna that picks up a tear drop shape out the front of the antenna, again it needs to overlap as much of the donut from the cp antenna on the quad as possible.

So the antenna, or the part of transmitting being upright is the ideal orientation. Since quads usually fly nose down, this means the antenna should be tilted backwards

Antennas mounted on or through the top plate have a nasty habbit of breaking at the basem generally it is accepted that it is best for the antenna to exit the back of the quad in the middle and then be bent upwards

(There are two frames that are actually superb for this: the scx200 and the dquad obsession, I have examples of both builds in the 250'build section, go take a look :)

Offline Bajadre

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Re: position of circular polorized antennas?
« Reply #2 on: February 16, 2017, 23:01:34 »
Yeah mine fitted like yours matey straight out the back pointed up (seems to save the connector in a fall better I found)ideally you want the mushroom pointing upwards and above the frame etc
Emax nighthawk 280,Blade 350qx3,dx6 (gen2),fatshark doms v2.

Offline iRobot

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Re: position of circular polorized antennas?
« Reply #3 on: February 16, 2017, 23:32:56 »
Tilted back gives best results. Before I fitted the new vtx and antenna on my quad, I always had it directly out of the top of frame, reception was OK but not fantastic. The new position (in the picture) is spot on.
I'm no expert, but this is what I have been advised,,,, it works  :smiley:

Offline greggmaN

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Re: position of circular polorized antennas?
« Reply #4 on: February 16, 2017, 23:34:40 »
no...mine comes straight out of the back horizontally...i then thinking im doing good...bending the antenna so it points up! is that bad...should i just screw it in and leave it horizontally....i see what you mean as quads fly nose down so it would be pointing up

yeah like yours in that picture thats how mine is now

Offline greggmaN

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Re: position of circular polorized antennas?
« Reply #5 on: February 16, 2017, 23:38:42 »
also whats the difference between left and right antennas?

Offline Cheredanine

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Re: position of circular polorized antennas?
« Reply #6 on: February 16, 2017, 23:43:08 »
I robots picture is about right, it kind of depends what angle you mostly fly at but that is quite variable, if you have it like his then I would say jobs a good one

If the Rx and tx have the same polarisation then you are good
If the Rx and tx are opposite then you are not gonna pick up much

So at racing meets they may use alternate polarisation for quads on adjacent freqs so they don't interfere with each other

Also in reflective environments, for example indoor drone races or places with a lot of big hard surfaces the signal will reflect off the walls/roof/other surfaces, when it does this it reverses polarisation so the reflected signal does not interfere with the origional


Offline greggmaN

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Re: position of circular polorized antennas?
« Reply #7 on: February 17, 2017, 09:48:53 »
so let me get this right...if on your quad you have a right one...your rx should be right aswell? as having and left and a right wont get you a good signal?

and at race meets people use left and left and right and right to and use different freq to avoid interferance?

Offline Cheredanine

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Re: position of circular polorized antennas?
« Reply #8 on: February 17, 2017, 09:53:14 »
To first bit - yes

To second bit, not all race meets, but where they want more pilots in the air
Let's say (and these freqs are not right:
Pilot 1 is on 5800
Pilot 2 is on 5820
Pilot 3 is on 5840
Pilot 4 is on 5860 etc

Then they would have all the odd number pilots on one direction (say RHCP) and all the other pilots on the other (LHCP)

Offline greggmaN

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Re: position of circular polorized antennas?
« Reply #9 on: February 17, 2017, 10:10:21 »
got it,

just to go off topic a sec im looking at eventually getting some fatsharks...was hoping for the dom v2 or v3..i currently have the cyclops eye 5hd and the picture is good, my rx for the goggles is a FR632 diversity receiver....a hell of alot of youtube vids for fatsharks have a great deal of interferance and i must say with my headset i get none at all whys this? for the money i expect to get a really good image but im failing to see if i will get a better image than im seeing now and i aint getting interferance...i just like the style of fatsharks but may think twice if i know im not going to get a better image :/

Offline Cheredanine

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Re: position of circular polorized antennas?
« Reply #10 on: February 17, 2017, 13:41:31 »
The image is largely unrelated to the goggles other than ratio and resolution. What you are poking at is a product of vtx, reciever, antennas and environmental factors

I got sent a set of box style goggles to review. I compared them to my fatshark dom v2s and then I got my missus who has never flown fpv to sit in them one at a time whilst I flew

Her opinion, and I agree with it but she was really the blind test, was the fatsharks were much more immersive, it felt more like you were int he quad, rather than sitting behind it
(She used the box goggles first and was perfectly happy with them but then when she tried the fatsharks she much prefered them)

May be due to 2 screens and I don't imagine it is any different for similar goggles such as skyzone, but I am sticking to my doms, and when they die I will be buying another pair.

If the price delta is justified is a different, and subjective matter

You got no one around you flying with fatsharks who would let you try them?