Proposal for Frequency Allocation

We have had occasions where some pilots have experienced swamping of their video during our races, most likely due to insufficient frequency separation and perhaps in a few instances high TX power settings. This is a proposed solution to help alleviate future issues. Below is a standard 40-channel frequency chart for most TXs sold:


I charted all the frequencies in ascending order to visualize the spread between all the frequencies. The plus number indicates the MHz difference from the previous frequency:
E4 5645
R1 5658 +13
E3 5665 +7
E2 5685 +20
R2 5695 +10
E1 5705 +10
B3 5711 +6
A8 5725 +14
R3 5732 +7
B1 5733 +1
F1 5740 +7
A7 5745 +5
B2 5752 +7
F2 5760 +8
A6 5765 +5
R4 5769 +4
F3 5780 +11
A5 5785 +5
B4 5790 +5
F4 5800 +10
A4 5805 +5
R5 5806 +1
B5 5809 +3
F5 5820 +11
A3 5825 +5
B6 5828 +3
F6 5840 +12
R6 5843 +3
A2 5845 +2
B7 5847 +2
F7 5860 +13
A1 5865 +5
B8 5866 +1
F8 5880 +12
R7 5880 +0
E5 5885 +5
E6 5905 +5
R8 5917 +12
E7 5925 +8
E8 5945 +20

As you can see, many of the frequencies are very close and can interfere with each other. Most of the bands use a 19-20MHz spread, and Raceband has a 37MHz spread but there may still be some TXs without Raceband. MultiGP races use a channel lineup named IMD6C for up to 6 pilots:

Pilot 1 - R1 5658
Pilot 2 - R2 5695 +37
Pilot 3 - F2 5760 +65
Pilot 4 - F4 5800 +40
Pilot 5 - R7/F8 5880 +80
Pilot 6 - R8 5917 +37

IMD is intermodulation distortion, which is what happens when two frequencies broadcasting together cause interference at additional frequencies. This can occur within each band when frequencies are equally spaced apart, so for example, frequencies F1-F4-F7 would create interference for each other as they are equally spaced 60MHz apart. The IMD6C works as they are not spaced equally.

We can use IMD6C but it is limited to 6 pilots and we have more than 6 in our group, so some of the frequencies would be assigned to different pilots who can't fly together, but we rarely have 6 pilots in the air, so this could work but would involve changing of frequencies which can be inconvenient if you don't have smart audio.

I culled what I believe are the most usable frequencies with the best spread possible, and found 11 usable frequencies. I considered IMD in selecting these frequencies.

R1 5658
E2 5685 +27
B3 5711 +26
A7 5745 +34
R4 5769 +24
F4 5800 +31
B6 5828 +28
F7 5860 +32
E5 5885 +25
R8 5917 +32
E8 5945 +28

These can be divided further into 2 groups for an even greater spread:

Group 1
R1 5658
B3 5711 +53
R4 5769 +58
B6 5828 +59
E5 5885 +57
E8 5945 +60

Group 2
E4 5645 (this frequency was added just to equalize the groups into 6 each)
E2 5685 +40
A7 5745 +60
F4 5800 +55
F7 5860 +60
R8 5917 +57

We could assign each pilot a frequency for his fleet, and theoretically it should be fine if we ever decide to all fly in a swarm. Obviously this only deals with frequency interference, but TX power and transmission distance can also affect susceptibility to interference. Let me know your thoughts and share your inputs, suggestions, or corrections.

Comments

  • 4 Comments sorted by Votes Date Added
  • Waiting for assigned channel, so I can set my fleet,,,, (OR ARE WE CALLING DIBBS)
  • maybe not a specific channel/frequency. but maybe choose a band to stay in.

    from the data provided above, it seems like R, E, and F are the bands with the most usable channels.

    i'm sticking with R(ace) band. i can bounce from 1, 4, and 8 depending on what group is going up. Unless your running smart audio or some other OSD changeable VTX changing bands can be a pain, but channels is usually just a couple quick clicks.

    also, smart audio you guys, welcome to flavor country.

    also, interactive 5.8 frequency graph

  • At out next flying session, we can see where everyone's frequency is, and assign or change then. Some of us are already on the frequencies with the wider separation.

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