I have a question regarding the antenna positioning for the P4P remote controller.

In the manual there are a couple of diagrams which appear to give instruction on how to correctly orientate the RC antenna  - depending on the selected frequency you are on.

At 2.4GHz it appears to show that they should be at 60 degrees.

For 5.8GHz  - 90 degrees.

This is correctly interpreted?

Or....should none of these angles matter in respect to the way in which you are holding the controller? I.E. so long that the antenna is perpendicular to the aircraft - this is the optimum?

Please discuss.

Cheers.

You should follow what is in the manual as it is relevant. If your transmission is set to Auto it can sometimes change between 2.4 and 5.8 and you may not realise  so the best position is probably 60 degrees as the 5.8 will still work ok at that angle. If you are seeing weak transmission messages then you may want to check which band is being used and where your aerials are.

Sorry, an antenna angle of 90 degrees to the aircraft is giving the best signal to the drone, no matter what freq in use. If there is anything else written in the manual, it should be rewritten !!!

Regards Leif.

Landbo Posted at 2018-2-17 23:19
Sorry, an antenna angle of 90 degrees to the aircraft is giving the best signal to the drone, no matter what freq in use. If there is anything else written in the manual, it should be rewritten !!!

Regards Leif.

Absolutely. The antenna angle has nothing to do with frequency, the best angle is one that shows the maximum length of antenna to the aircraft. This is basic radio transmission theory.

Jenee 2 Posted at 2018-2-17 22:11
You should follow what is in the manual as it is relevant. If your transmission is set to Auto it can sometimes change between 2.4 and 5.8 and you may not realise  so the best position is probably 60 degrees as the 5.8 will still work ok at that angle. If you are seeing weak transmission messages then you may want to check which band is being used and where your aerials are.

I thought putting the setting into 'Auto' only lets the app auto select the best channels on that particular frequency not  actual bandwidth?

Okay guys - thanks for the brief discussion...

This is DJIs tutorial on antenna positioning:-

Aardvark Posted at 2018-2-18 03:40
This is DJIs tutorial on antenna positioning:-

https://youtu.be/P7M9JtfVwQE

Yes - I'm aware of this  video, thanks for posting it up though I'm only referring to what the P4P instructions was trying to explain.

The illustration referred to by the OP is on page 41 of the manual.

If one understands wave amplitude, which is the height - not the wavelength - of a radio wave at a given frequency, then one might realize this idea of tilting a multi-frequency antenna for a lesser frequency might be worthy of some considerable thought.  

I don't quite understand how the antenna itself is constructed so that it works best at the two frequencies.  But I do know the 2.4 ghz signal naturally has a higher/lower amplitude than the 5.8.  Put another way, it has a larger profile.  So given that, it seems to make some amount of sense to tilt the antenna down slightly for 2.4 ghz because it's not an optimum 2.4 ghz antenna to start with.  This would potentially produce a better wave profile for 2.4 ghz as the signal meets the AC and as it's received as well.  OTOH, by tilting the antenna, you're also weakening the signal since everybody knows the best strength of the signal would be emitted exactly perpendicular to the antenna.   So it seems to me it's possible DJI is suggesting a compromise between best signal strength and best signal profile by tilting the antenna down slightly relative to the AC when using 2.4 ghz.

Mark The Droner Posted at 2018-2-18 15:07
The illustration referred to by the OP is on page 41 of the manual.

If one understands wave amplitude, which is the height - not the wavelength, of a radio wave at a given frequency, then one might realize this idea of tilting a multi-frequency antenna for a lesser frequency might be worthy of some considerable thought.  

I know you are not going to want to hear any of this, but what you are talking about in terms of tilting the antenna is rubbish, radio waves have no idea what comprises angle, they propagate from the antenna in a pattern that is determined by the antenna design, not the angle it is held at. Reading the ARRL handbook on antenna design might be helpful.

The idea depends on how well the 2.4 ghz antenna is made.  If it's a dedicated 2.4 antenna, then yes, tilting would be silly and accomplish nothing.

I confess I cannot say for sure what a wave looks like when it's transmitted with a bad antenna.  But there's also the receiving aspect of it.  

If you consider the "donut" on a conventional vertical omni-antenna signal, perpendular would be perfect, but straight overhead would have profile of zero or close to zero.  DJI seems to be suggesting a compromise between these two positions, due to the inadequacy of the antenna for 2.4 ghz.  

It's easy to look at the illustration suggesting a 60 degree tilt and quickly conclude that DJI is a collection of idiots.  

One thing I've learned over the years is on the few occasions I suspect DJI is dumb, it usually turns out it's me who's dumb.  

Mark The Droner Posted at 2018-2-18 15:43
The idea depends on how well the 2.4 ghz antenna is made.  If it's a dedicated 2.4 antenna, then yes, tilting would be silly and accomplish nothing.

I confess I cannot say for sure what a wave looks like when it's transmitted with a bad antenna.  But there's also the receiving aspect of it.  

An antenna is a tuned circuit, or should be if it is going to work efficiently, which means it needs to be a multiple or sub-multiple of the working frequency. The antennas on the P3 and P4 are 130 millimetres long, the wavelength of 2.4 Ghz is approx. 125mm, so this seems to correlate, as part of the length of the plastic shroud is probably not actual antenna. The wavelength for 5.8 Ghz is approx 51mm, which does not correlate at all, even for twice wavelength, because it should then be 102mm.

The basic principle of a whip antenna requires it to be a sub-multiple of the wavelength, so it would seem that DJI have chosen a full wavelength antenna design for 2.4Ghz, but an incorrect length for 5.8Ghz. It is possible to correct for an incorrect length by placing an inductor in the antenna to 'tune' it, but it would still not be correct for both bands.

I looked at the P4P manual, and it does specify 90 degrees antenna angle for 5.8Ghz, and 60 desgrees foir 21.4Ghz, but according to the theory I studied, this will have no effect at all on the transmission of a signal from the RC unit, and as far as I am aware, no effect on signal reception. Angling the antenna only serves to til the axis of the 'donut', which in my opinion, is not desirable.