Tracking antenna systems

If you've been building electronic bits or modifying stuff you've bought then tell us all about it here. A good place to discuss the installation of 2.4GHz DIY modules too.

Tracking antenna systems

Postby Pader » Sat Nov 12, 2016 1:15 pm

Hi folks<
I have been toying with the idea of building a tracking antenna for my multicopter. I have pretty well decided on using two pairs of very directional (slightly splayed) antenna each for the tilt and pan operations perhaps using the simple 'diversity' circuit recently published on the youtube site to power stepper motor drive circuits. The idea being of using the signal strength difference from the returning 5.8GHz FPV signal from the aircraft. I am reasonably sure that I can sort out the electronic side of the apparatus but I have little idea about the receiving antenna themselves. With the little knowledge that I have, I was considering using printed circuit 'yagi' antennae inside two slightly divergent metal wave guides for very fine directionality to give me only a very limited overlap on the incoming 5.8GHz signal then using detector diodes passing through a differential circuit to the motor drive logic.

Another problem that I would have would be to feed the 2.4GHz transmitting signal into a revolving table that would otherwise twist the cable to destruction. I had two possible ideas: one is that I have a small slip ring device (12.5mm) with 3 circuits (6 wires at each end) but am concerned that I would not have sufficient shielding. The other idea that I had was to again use a metal wave guide tube fitted with a bearing inside another tube to feed the 2.4GHz antenna. I know that I am clutching at straws with these ideas as I don't really have a clue. Do any of you folks have any ideas and perhaps give me some pointers?
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Joined: Sat Dec 01, 2012 2:21 pm

Re: Tracking antenna systems

Postby Goratrix » Mon Oct 29, 2018 3:36 am

I see a little problem with 'yagi' antennas, I am no expert but as far as I know, 'yagi' antennas have, depends on how you turn it, an horizontal or vertical polarization. I do not know which kind of transmitter antenna (in your multicopter) you use, the common cloverleaf antenna has a left or right rotating polarization. The properly best directional antenna for a rotating polarization is a helix antenna, you can make these antennas very pointy by using 8 or more loops (remember I am no expert for antennas).
If I understand it right you want to have a directional antenna for your RC, that might be difficult because in that case you need a cable from your RC to the antenna which, this cable makes an attenuation that might cancel out the gain from the antenna. (The next lines are high theoretical) If you mange to separate the HF part from your RC you can connect the antenna directly to the HF part and the HF than via a high flexible cable to your RC. In my opinion slip rings for an antenna signals are bad , you get more problems than you solve.

Although I live in the USA, English is not my mother tongue so please excuse me if my English is sometimes a little bit hard to read.
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Joined: Mon Oct 29, 2018 12:10 am
Location: Mesa AZ USA

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