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Circular polarized antennas - left or right hand?

#1
Hi guys,

I am just getting into FPV, and recently got my FPV equipment. It came with the stock antennas which is of no use at all, so I have decided to make my own circular polarized antennas, but I have a question.

I have made the Clover Leaf Antenna for the TX which is a left hand antenna, should the Skew-Planar Wheel Antenna for thr RX be left hand or a right hand antenna?

Thanks for the help

Arno
 

MudMan

Junior Member
#4
Just a noob question..... can you use these guys for your tx/rx? i just dont see anyone doing it? why not? why only for fpv signal?
 

lobstermash

Propaganda machine
Mentor
#5
You *could* use them for your control system. However, the control system transmits a very small amount of data (a few bytes) numerous times in a single wave, so if a signal is incomplete the rx ignores it and waits for the next one. However the video system transmits a lot more data per wave and therefore data loss through partial transmission or multipathing is much more significant to the outcome (video feed).

The simpler way to get around signal loss for the control system is diversity, for example two antennas on the rx mounted perpendicular to each other.
 

MudMan

Junior Member
#6
That makes sense :)
so when you say diversity does that mean I need one of those active double adapter signal selector thingys or are they for the video stuff as well? could I just whack a second antenna on at right angles? can i use a rediculously huge antenna like of a 4X4 radio?
Thanks heaps for your help! :D
 
#7
Does the length of the antenna matter? I know the length of the actual cloverleaf part does but what about the length of the coax? If so where do I find specifications? I'm on 900Mhz... Thanks!
 

lobstermash

Propaganda machine
Mentor
#8
Sorry MudMan, missed your reply. Some control receivers come with 2 antennas. You would have to add some components to a receiver with one antenna to make it work with two. For the video system, you can get diversity controller, which allow you to plug in two video receivers of any frequency, and it will pick the best signal.

Antennas perform best when their length is matched to the frequency being used. Bigger is NOT better.

Coaxial cable does lose some signal, so the shorter the better. However if you must have some length (which practically is almost unavoidable), ideally it should be on a quarter length multiple. It'll still work on any length (unless a few km long or something silly like that), but with reduced performance.