Never going to happen... you well always get interference... 5.8 gives the best picture but Bugger all penetration... as you go down in frequency you get better penetration but lower image quality...

 

VHF, Linear Amp, 25 million tvs cant be wrong! lol...

 

Thanks crash.. i got ya back buddy .. go team crash ..

 

Screw you @HeliGod Father , You are a darker overload in sheeps clothing ! You don't fool me.. MOFO !

 

I'll never come to the side of white light .. Never.. Live life on the edge, Muah ha ha ha ha ...

 

Ok.. So to get back on topic.. What's others advice.

 

There's no cut & dried answer unfortunately, but there are a few key things you need to know so you can get the best out of any system. There'll be a bit of radio theory chucked in so hang on till the end...
Any video link is like any radio link in that the receiver can, and will, adjust itself internally to work with whatever signal it receives to create the best output (picture in this case) that it can. Once a received signal degrades to the point where it's just above the general signal noise floor then the picture will suffer and you will see "snow" or other interference such as lines across the image which indicates a loss of sync. In general the signal needs to be twice as big as the noise floor, but it varies depending on the signal and the receiver itself.
So the only way to get a good picture is to give the receiver a decent input signal to work with and this can be accomplished in a few different ways.
First up always work to reduce the noise floor. This means picking a channel as far away from others as possible and by using an antenna that is as directional as possible (we'll cover this a bit more later) because a directional antenna will block out (well, reduce by a lot really) any signals coming from any other direction whereas an omni-directional antenna won't.
Second, always pick a receive antenna with the highest gain possible. The higher the gain the bigger the signal the receiver "sees". Receiver antenna gain is where you will pickup the biggest differences for the system, it's like free power boosting. For reference every +3db of gain equals a doubling of signal whereas every -3db equals a halving of signal. So a 6db receive antenna will give you 4 times the signal to the receiver. The one problem with high gain antennas is that the gain increase will see a trade off for direction i.e. more narrow focus so you will need to keep that in mind.
That's it for receivers. The next post will be about transmitters.


Citizen #186

 

For transmitters they key thing is all about placement on the multicopter and the antenna selection once again. You can egg great results with very little power if it's set up correctly. I won't be discussing the legalities of power output. We're all grown ups so you can make your own decisions on whether you follow the law or not and there's plenty of info about what's legal & what's not.
Any transmitter should be setup with enough voltage & current to run it properly. Self evident I know, but I've seen lots of systems with piddle little wires feeding the transmitter.
Secondly the antenna should ideally be mounted straight onto the transmitter, or at the very least any cables should be kept short as this limits not only power loss, but power reflections that occur due to mismatch.
The transmit antenna should be oriented so that it is vertical (assuming you have an omni-directional antenna fitted) so that the transmitted signal shape is radiating evenly in all directions.
Perhaps the biggest difference you can make is to mount the antenna high enough away from anything else remotely metallic. The reason for this is that we want the antenna to be able to radiate evenly without the signal bouncing off anything close around it. This bouncing back is a reflection of the transmitted signal and it will be out of phase and either partially or completely cancel the signal out producing dead spots around the antenna.
How far away is far enough? Ideally you should aim for 4 times the wavelength, so for 5.8gHz that will equate to roughly 200mm. If you can't get 4 times then 3 times should still work ok for the majority of cases.
The other thing to think about is that you will be banking & turning the multicopter as you fly it so whenever the antenna disappears from direct line of site behind the frame for example then the signal to the receiver will suffer. Another reason to get the antenna nice & high/ we'll away from the frame.
That's about it for now & should give you something to work with. Don't be scared to experiment with antenna placement by setting your multicopter up on a stack of plastic milk crates and walking 100 metres away with your receiver to see how it goes. Better still if you can walk all around the multicopter to find the dead spots.
If you have any questions fire them back & I'll attempt to answer them.


Citizen #186

 

Thanks very much @mr_squiggle , that's some awesome info to work from .. I appreciate the time taken. Cheers

 

No problem at all @TheDude, hope it helps.


Citizen #186