There are more than 40 channels you can choose from in a video transmitter (VTX), some times even up to 72 channels. It can be confusing for a beginner as which VTX channel is best to use. The choice comes down to if you fly with other people.
Best VTX Channel for Flying Alone
If you fly solo, you can basically use any channel you want, as long as it’s legal in the part of the world you are flying.
Some channels output more power than others. To find out which channel is the most powerful in your VTX, try to search my reviews.
Just based on my past experience in VTX testing, lower frequency channels usually have higher output power. For example, on Raceband, R1 usually has higher output power than R8.
Another thing to take into account is the tuning of your transmitter antenna and receiver antenna. Assuming they are both tuned to 5800MHz, then the performance is going to be better on channel F4 (Fatshark 4) or R5 (Raceband). If they are tuned to 5700MHz, then the best channels would be E1 or R2.
It’s hard to know the exact tuning of the antennas, unless you have the expensive equipment to test them. So really I wouldn’t worry about it too much. If you have time, test all the channels and find the ones that work the best for you. Otherwise just pick the first channel in a band, like R1 or F1.
Flying in Groups
If you often fly with clubs, then you have to choose your channels carefully. Most of the times, your choice is down to what’s available, and you will probably have to change it quite frequent. You have to work this out with your fly buddies if you want to be able to fly together at the same time without giving each other too much interference.
When you arrive at the spot, the first thing you should ask is what frequency everyone is using, so you know what channels are free to use. Pick a channel that is as far away as possible from the occupied channels, wider channel separation minimizes interference.
Also make sure everyone flying in the group set their output power as low as possible, e.g. 200mW, or even better to 25mW.
You will get much cleaner signals if one person uses RHCP antennas, and the neighbouring pilots are using LHCP. This is because opposite polarisation will result in as much as 20dB signal reduction, reducing interference between pilots. We discussed how dB can be related to FPV range in this post.
When choosing FPV antennas, pay attention to Axial Ratio. It’s a measurement of how good an antenna can reject opposite polarized antenna signal. This property is not only important for flying with others, it’s also useful for rejecting multi-path interference, because a bounced signal has reversed polarity.