Final Word On Range Extenders?

[Droning on and on...]

According to Alientech team the DJI RC antennas are not omnidirectional... See this: https://ae01.alicdn.com/kf/H0fea13e2fc8d4b019632c8d32f23654c3.jpg

Thats true, but it would simply make things worse.

A directional antenna must be pointed precisely at the aircraft to get the peak power to it – which is the whole point of an amplifier - get more power to the target to extend range.

The farther away the target is, the smaller the allowable error in pointing the transmitter.

In any case, the cheap antenna design on the RC2 and N1/2/3 certainly aren't ideal omnidirectional radiators (no antenna is), but they're laughable as directed beam antennas. Without even looking at a power plot, from what I learned in microwave antenna design way back in college, those antennas will have several lobes, and leak tons of signal outside them.

 

[AZDave]

I think the OP needs to look up what signal-to-noise ratio means and how RF works. S/N is what determines how well the receivers in BOTH the drone and the controller can decode transmissions. For a given signal strength, the background noise determines the signal-to-noise ratio and therefore the reliability of contact. The noise in an urban location at microwave (i.e., WiFi) frequencies is generally far greater than it is out in a quiet environment with flat open terrain where DJI almost certainly did their tests. Not to mention that signal reflections from buildings can cause lots of interference problems irrespective of the noise.

Amplifiers can boost the signal from the controller but generally not from the drone. Proper directional antennas on the controller work for BOTH sides of the transmission, both by boosting gain and also by discriminating against noise coming from a direction other than where it is pointed. They do, however, require making sure that the antenna is always pointed at the drone ... otherwise they will work worse than the stock antennas because they will discriminate against the signal coming from the drone.

 

[AZDave]

Thats true, but it would simply make things worse.

A directional antenna must be pointed precisely at the aircraft to get the peak power to it – which is the whole point of an amplifier - get more power to the target to extend range.

The farther away the target is, the smaller the allowable error in pointing the transmitter.

In any case, the cheap antenna design on the RC2 and N1/2/3 certainly aren't ideal omnidirectional radiators (no antenna is), but they're laughable as directed beam antennas. Without even looking at a power plot, from what I learned in microwave antenna design way back in college, those antennas will have several lobes, and leak tons of signal outside them.

The stock antennas in the controller are actually two antennas fed in phase which results in a broad bidirectional pattern ... forward toward the drone and backward toward the pilot. The theoretical pattern from that kind of two element array has no additional lobes if the spacing is correct, but I'd bet that the antennas are some sort of compromise and I'd bet that there are all kinds of internal reflections and interactions that additionally compromise the pattern.

The yagi addon antennas redirect the backward energy forward, as well as focusing some of the side energy into a narrower pattern. They work.