Hello People

[Peter Brown]

I built a hexacopter some years ago but it fell by the way side. I have just bought a heavy lift RC Timer F800 hexacopter frame which I am building up.

I intend to buiild some slightly more sophisticated antennae for both the control transmitter and for the FPV side (both RX and TX) but would like to improve on the control receiver antenna. It has the usual single wire antenna that I would like to replace with a coax ending with an sma connector onto a 4 lobe helical antenna. Can any of you learned people out there advise me if this is feasible?

 

[John Doecliff]

Yes it is and its pretty much the standard of what everybody is using for FPV. As for the radio and it's receiver no one is doing that, mainly because its not really needed and wouldn't increase reliability enough to justify it.

 

[Peter Brown]

Thank you for replying John, I know next to nothing about radio control law in California and only marginally more about those laws in the UK. What I understand is that the two public frequencies most in use are 2.4 GHz for the aircraft control and 5.8 GHz for the FPV side of things. Unfortunately, the majority of Britain is urbanised and the 2.4 GHz band is extremely crowded by Wifi, Cell phones and various other uses. The 5.8 GHz band is beginning to be quite crowded too with the proliferation of wifi equipment trying to escape the crowding of the 2.4 GHz band.

As I understand things, transmitting equipment for radio control in the UK are limited to 100 mW radiating power and occurred to me that the stock equipment in terms of antennae are prone to quite heavy losses and although my RC equipment uses frequency hopping, even the smallest loss can have a considerable effect on the signal leaving my antenna and being received at the other end.

In fact, from what I have read, 2.4 GHz, 'cloverleaf' antenna are quite popular items for sale in places such as ebay and HobbyKing. Apparently, there are more and more mods being carried out on the transmitter that I currently have (Turnigy 9X) to try and improve range. I am not yet ready to hack into the innards of my transmitter and so as a first step, I thought to improve on the antennae. Although the transmitting antenna is usually pointing towards the aircraft by the operator, it occurs to me that a simple strip of bare wire in the stock receiver coax is at somewhat a disadvantage because of directionality as the aircraft manoeuvres and would benefit from a more omni-directional antenna. From watching various Youtube tutorials, the consensus appears to be that semi-rigid, RG402 coax has quite a small loss and I thought to remove the existing length of light antenna and replace it with a shorter length of RG402 terminating in an sma connector onto a helical antenna would improve reception at every aircraft aspect.

I would appreciate any feedback on what I have written.

 

[John Doecliff]

Our sky's are probably just as crowded with 2.4 and 5.8 ghz as well although I suppose it would be worse in some areas than others. Its my understanding that there isn't much difference between radio transmitters in the UK, Europe, Asia and the US (besides mode 1 and mode 2). Manufactures rarely publish transmitter power levels but I have been told that most 2.4 ghz radios are about 60mw but put out the equivalent of 100mw by using a high gain antenna. I would personally not change my radio antenna unless I was going to a long range system but that's an entirely different thing. The radio manufacturers are putting out a pretty good product that will get you a kilometer of range or better with the stock antenna. Interference with other 2.4 ghz signals is reduced and or eliminated altogether by using spread spectrum technology (frequency hopping) and the fact that your receiver is bound to that transmitter. I guess one big indicator that changing your radio antenna is not necessary is that you don't see any aftermarket antennas for transmitters. If it could be improved then someone would be doing it and trying to make a buck off of it. On the other hand you could do it but I would want to have the equipment to prove that it's working better than the stock antenna. That would mean an SW meter to measure standing wave ratio and some sort of power meter to measure output. One of the guys in my radio club has an antenna analyzer that will perform both those functions and more so what your talking about could be done. You could also make the argument that the transmitter is designed and functions correctly and its the receiver reception that needs improving. But then that's why they make satellite receivers and the little 3D printed antenna holders that hold the 2 receiver wires at 90 degree angles to each other, kind of like a poor mans diversity receiver. FPV of course is a different story. You can by a 5.8 ghz FPV transmitter that is above the legal power limit but it's allowed if you have a technicians class amateur radio license which is pretty easy to get. Although no one is checking license's you are supposed to have one.