Calculate safe, IMD-free frequency layouts, channel assignments, and heats for multi-pilot events.
📡 Digital System Reference
Based on RotorHazard Frequency Reference Chart (Rev. 2024-12-11) by Michael Niggel / Hazard Creative.
| System | BW | Channels | Notes |
|---|
| Analog | ~25 MHz | All bands (A,B,E,F,R) | IMD is the only concern |
| HDZero | ~27 MHz | R1-R8, F2, F4 | No public broadcast |
| DJI O4 Race 20M | 20 MHz | R1-R8 (actual raceband) | No public broadcast, no data carrier |
| DJI V1/WS 25M (HAM) | ~20 MHz | D1-D7 (avoid D8 = public) | D8 = 5839 MHz public broadcast |
| DJI V1/WS 50M (HAM) | ~40 MHz | J1-J3 | Only 3 channels |
| DJI O3 20M | 20 MHz | O1-O7 (CE: O3-O5 only) | Wide data carrier ~5720-5850 |
| DJI O3 40M | ~40 MHz | Q1-Q3 | Data carrier + huge footprint |
| DJI O4 20M (HAM) | 20 MHz | O1-O7 (same as O3) | HAM unlock, data carrier |
| DJI O4 40M (HAM) | 40 MHz | Q1-Q3 (same as O3) | HAM unlock, data carrier |
| DJI O4 60M (HAM) | 60 MHz | Q1-Q3 (same centers) | HAM unlock, Goggles 3, wider BW |
Key IMD-Free Presets:
R1367 (4P): R1, R3, R6, R7 | IMD5C (5P): R1, R2, F2, F4, E5 | IMD6C (6P): R1, R2, F2, F4, R7, R8 (industry std, minor 3-way)
O3 safe analog (center + ~25 MHz BW outside carrier): E4(5645), E3(5665), R1(5658), E2(5685), R2(5695) below | F7(5860), R7(5880), E5(5885), E6(5905), R8(5917) above. Note: R7/E5 overlap each other, cannot use both!
O4 (HAM): Same as O3 channels (O-band / Q-band) + 60M mode on Q-band. Requires HAM unlock.
ⓘ How It Works
Bandwidth: Analog VTX occupies ~25 MHz of spectrum per channel (FM trapezoid), not just the center frequency. Two channels must be far enough apart that their bandwidth footprints don't overlap. This limits how many pilots fit per heat.
IMD: When VTX signals mix in a receiver, they create phantom signals at sum/difference frequencies (2f1-f2, f1+f2-f3). If a 2-way phantom lands on an assigned frequency, that pilot gets interference. 3-way products are weaker and shown as warnings. Never use equal spacing for 3+ pilots.
O3/O4 Data Carrier: Uses OFDM with a wide data carrier (~5720-5850 MHz). Other systems must keep their entire bandwidth footprint outside this zone. Note: Q-band channels (40 MHz) like Q1(5677) physically overlap R1/R2 - it's not just the carrier, the channel itself is that wide.
O4 vs O3: DJI O4 (HAM unlock) matches O3 frequencies exactly, plus adds 60M mode (Q-band). O3 uses O-band (7ch) or Q-band (3ch), no 60M. Both V1/WS and O4 require a HAM license for race use.
Auto-splitting: When too many pilots for a clean IMD-free set, the tool splits into heats A, B, C, D. Each heat flies separately with its own clean frequency set.