8 replies to this topic

[TriBum]

Antenna tracking and diversity seems to be the new "magic bullet" for resolving all the woes of FPV. What antennae will be best suited to this setup and how should they be positioned? Is the idea to always have the patch/yagi pointed at the plane? At what point does cross polarization when the plane is overhead, with a vertical antenna, and the RX patch is horizontal pointing at it, become a problem?

[Mr.RC-Cam]

Antenna tracking and diversity seems to be the new "magic bullet" for resolving all the woes of FPV.

I expect there will be a rush for many to get one. But unfortunately, most of the "antenna problems" that I help troubleshoot would not be fixed with a tracking system (the common issues are solved with RF education). My practical advice is that a tracking system should be added only after the stationary Rx antenna based system is working well. And plan on building a mechanism that can hold two antennas since best performance will involve a diversity antenna setup.

Is the idea to always have the patch/yagi pointed at the plane?

That's the goal. Auto-Tracking antennas are essentially convenient tools for supporting long range. With Yagi's and other extremely high gain aerials, auto-tracking will be very desirable. With lower gain antennas, such as the popular 8dBi patches, the Auto-Tracking advantage becomes a coin toss.

At what point does cross polarization when the plane is overhead, with a vertical antenna, and the RX patch is horizontal pointing at it, become a problem?

Any time cross polarization occurs you will be hit with a -20dB to -30dB (100X - 1000X) RF signal loss. You can plug those numbers into your RF system's link budget and see that this will reduce the reliable range a lot. A circular polarized Rx antenna will prevent that, but it penalizes the system with a constant -3dB loss. So, it is not a perfect solution. In long range applications, it is usually best to use a pair of linear polarized antennas, or mix a linear polarized Rx antenna with a cross-polarized Rx antenna. But, every flying site is different, so the best advice is to carefully experiment with different configurations.

A year from now we should come back to this thread to discuss the impact of Auto-Tracking antenna's.

[Jimmy_Z]

So we're now two years on... and I happened to visit this thread randomly.

Be interested in the response now that there are so many folks working towards tracking and directional antennae

[Mr.RC-Cam]

Not much has changed. There are satisfied antenna tracking users and there are those that are happy without it. One thing you can say is that it looks cool in use!

I've noticed Rx diversity is still more popular / fortunately the EagleTree tracker includes that function. There's also been some very interesting DiY antenna designs that are reportedly offering noticeable improvements even without tracking or diversity. So in the end, the antenna is still the most important component to concentrate on, then the gadgets come next.

[Terry]

Well for me I dont use anything else. I have been using an rssi based 5.8Ghz system with 14dBi v patch for a long time now, I dont give it a second thought.


Terry

[Asomaro]

I'm pretty very new on this forum but I play about quite a bit on other heli (eg rcheliaddicts)and FPV/UAV (eg FPVUK) based forums so I hope you will forgive my "jumping in"

Whilst randomly searching I came across this thread - good timing!

I'm just building a 5.8ghz base station with an Eagle tree logging system along with an Eagleeyes diversity and tracking system. I'm just looking into how to set up the tracking and diversity bit. I have the 5.8ghz tx on the plane with a Skew Planar (RH) antenna which is matched to a cloverleaf antenna on one of the base station rx's. (I'm actually using the "blue beam" antennas). I'm trying to decide what sort of antenna to use on the second rx, so I've been looking at a reasonable dbi (about 12+) but I don't know enough (actually I know very little and pretend to know more - if you know what I mean) to make a good decision about using a Circular Polarisation patch panel antenna versus a vertical polarisation antenna.

I'm not looking for huge range but I am looking for a reasonably good and stable video link.

Terry, I see that you are using a 14 dbi patch with no issues, could you tell me a little more about your set up.

Oh, and does anyone know where I could find a UK based supplier of CP patch antennas - budgets are tight as always, so I'm up for paying one of the experts on this forum to build one for me if that's a reasonable request. I'd rather keep it in the "family" if possible!

Thanks for your indulgence.

Cheers,

[Terry]

Hi, the thread with the details is here http://www.rc-cam.co...racking-aerial/
I have not found the need for CP as I tend not to fly overhead or do steep turns so video is pretty solid


Terry

[Asomaro]

Hi Terry,

Thanks for your response. I'm going to try a vertical polarisation panel antenna (12 dbi) to start with and see how I get on!

Cheers,

[Terry]

I wonder how he got on?


Terry