What VTX Tables Are (and Why Wrong Ones Break Everything)
You’ve wired up a new VTX, picked a frequency in the OSD, and then… nothing. Your goggles scan right past your quad. Or worse — you think you’re on Raceband 4 at 5769 MHz but the VTX is actually blasting 5945 MHz because the table doesn’t match. This happens to nearly every builder at least once, and the root cause is always the same: the VTX table in Betaflight doesn’t align with what the VTX hardware expects.
A VTX table is a JSON structure that maps human-readable names (like “R-4” or “F-2”) to specific frequencies in MHz, and ties those frequencies to band/channel/index numbers that the VTX’s internal firmware understands. When the table is wrong, every frequency selection you make becomes a gamble. This guide walks through the full setup chain — from finding the right table to wiring SmartAudio to troubleshooting the most common failures.
Where to Find Correct VTX Tables
You have four reliable sources for VTX tables, in order of preference:
- Manufacturer website or product page — Rush, TBS, AKK, and Matek all publish JSON VTX tables for their products. Search “[VTX model] Betaflight VTX table” and look for a .json file or a copy-paste block.
- Betaflight VTX Table Presets repository — In Betaflight Configurator 10.9+, go to the Presets tab and search for your VTX model. Many popular VTXs (Rush Tank, TBS Unify, Caddx Vista) have community-maintained presets that load the table, power levels, and SA protocol in one click.
- Community sources — Sites like OscarLiang.com and IntoFPV.com maintain VTX table databases. The IntoFPV forum has a sticky thread with tables for hundreds of VTX models.
- Build the table manually — If all else fails, use the VTX’s manual (which lists actual frequencies per band/channel) and construct the table yourself in Betaflight’s Video Transmitter tab. This is tedious but guarantees accuracy.
Never copy a VTX table from a random YouTube video comment or an old Reddit thread without verifying against the manufacturer’s specs. VTX firmware revisions can change the frequency mapping, and a table from firmware v1.2 won’t necessarily work on v2.0.
Loading a VTX Table in Betaflight Configurator: Step by Step
- Step 1: Connect your flight controller via USB and open Betaflight Configurator. Go to the Video Transmitter tab.
- Step 2: At the bottom of the tab, click “Load from file” and select the .json file you downloaded from the manufacturer. If you’re using a community preset, skip to Step 4 and use the Presets tab instead.
- Step 3: Verify the table populates correctly. Check that band names (A, B, E, F, R, L), channel counts (usually 8), and frequencies match what the VTX manual says. Each row should show a unique frequency. If you see duplicates or frequencies that don’t match, the table is wrong.
- Step 4: If using a presets-sourced table, go to the Presets tab in Configurator, search for your VTX, click it, review the changes, and hit “Apply”. The preset will load the table and often configure SmartAudio automatically.
- Step 5: In the Video Transmitter tab, set the Protocol dropdown to match your wiring. If you wired VTX data to a TX pad on the FC, you’re using SmartAudio (TBS protocol) or Tramp. Select the correct one.
- Step 6: Click “Save” at the bottom right. Reboot the FC. After reboot, confirm the VTX table is still populated and the protocol is set correctly.
SmartAudio vs. Tramp: Wiring and Protocol Differences
| Feature | SmartAudio (TBS) | Tramp (ImmersionRC) |
|---|---|---|
| Protocol developer | Team BlackSheep | ImmersionRC |
| Common VTXs | TBS Unify, Rush Tank, AKK, RDQ Mach | ImmersionRC Tramp HV, AKK X series, Matek |
| Wiring | Single wire: VTX SmartAudio pad → FC TX pad (any UART) | Single wire: VTX T (Telemetry) pad → FC TX pad |
| Power level control | Set via dBm values; supports Pit Mode (0 dBm or off) | Set via enumerated levels (25, 200, 600, etc.); Pit Mode as separate mode |
| Frequency setting | Via band/channel index OR direct frequency in MHz | Via band/channel index only |
| SA 2.0 vs 2.1 | SA 2.1 adds device status polling (temp, lock status) | Single version, no major revisions |
| Best for | Most modern VTXs; better OSD integration | Older VTXs; simpler protocol, slightly less overhead |
The wiring is identical for both: one wire from the FC TX pad to the VTX’s data pad. On a TBS Unify, the pad is labeled “Audio.” On a Rush Tank, it’s “IRC” or “SA.” On a Tramp, it’s “T” or “Telemetry.” The wire carries UART serial data — it’s not analog audio. Use any free UART TX pad on your FC; SoftSerial works too if you’re out of hardware UARTs, but it’s less reliable at high baud rates.
SA 2.1 (SmartAudio 2.1) is the current standard. It added device-status polling — the FC can query the VTX for its temperature, PLL lock status, and current power level. This enables better OSD warnings (like “VTX overheating”) and more reliable power-level reporting. Most VTXs manufactured after 2020 support SA 2.1. If your VTX only supports SA 2.0, it’ll still work — you just won’t get status telemetry.
VTX Power Levels and Pit Mode
Your VTX table must include accurate power level definitions, because Betaflight uses these to decide what power to set during disarmed vs. armed states. A typical power configuration for a 1W VTX might look like:
| Power Level Label | Power Value (mW) | dBm Equivalent |
|---|---|---|
| PIT | 0 | -∞ (effectively off) |
| 25 | 25 | 14 |
| 200 | 200 | 23 |
| 500 | 500 | 27 |
| 800 | 800 | 29 |
Pit Mode is a low-power state (often 0-0.1mW) that lets your quad sit powered on at a race without blasting everyone else’s video. In Betaflight, the Low Power Disarm feature sets the VTX to a low power level (or Pit Mode) whenever the quad is disarmed, then ramps to your chosen power level once you arm. This is invaluable for long-range: you can sit on the ground with GPS acquiring lock without cooking your VTX.
Configure it under the Video Transmitter tab: set “Low Power Disarm” to “On” and choose which power level to use while disarmed (typically 25mW or Pit Mode). The VTX switches to full power the moment you arm — no delay, no steps.
OSD VTX Control: Channel, Band, and Power Through Your Goggles
Once your VTX table is loaded and SmartAudio (or Tramp) is wired correctly, you can control the VTX from your OSD — no need to land, plug in USB, and use Betaflight Configurator. This is enabled by default in Betaflight 4.3+.
In your OSD (accessed with stick commands: throttle mid + yaw left + pitch up), navigate to Features → VTX. You’ll see options for Band, Channel, Power, and Pit Mode. Changes apply in real time — you’ll see the frequency update immediately. This is how you coordinate frequencies at a race or between pilots without pulling out a laptop.
Add the “VTX Channel” OSD element to your display. It shows the current band and channel (e.g., “R4” or “F2”) so you always know what frequency you’re on. If you’re running a DJI O3 Air Unit or Walksnail system, VTX control works differently (those systems manage their own channels via the goggles), but the Betaflight OSD can still display what’s configured.
Common VTX Table Errors and Their Fixes
| Symptom | Likely Cause | Fix |
|---|---|---|
| No video at all after changing channel in OSD | VTX table frequencies don’t match hardware frequencies | Reload correct table from manufacturer, verify each frequency |
| Video on wrong channel (e.g., selected R4, video on R6) | Channel index offset in table (table indexes start at 0, hardware at 1) | Check if table uses 0-based or 1-based indexing; adjust in table editor |
| Power level changes don’t take effect | Power dBm values don’t match VTX power table, or SA protocol mismatch | Verify power labels and dBm values against VTX manual; confirm protocol is SA, not Tramp |
| VTX control works sporadically | Loose wiring, wrong UART, or SA baud rate mismatch | Resolder VTX data wire, confirm UART TX is set to “TBS SmartAudio” in Ports tab |
| VTX stuck at one power level | Low Power Disarm is set to “On” and you’re testing while disarmed | Arm the quad or temporarily disable Low Power Disarm for bench testing |
| “VTX not detected” in Configurator | Wrong protocol selected, or VTX not powered (needs battery, USB alone won’t power it) | Plug in battery (with antenna attached!), verify protocol, check UART assignment |
SA 2.0 vs. SA 2.1: What Actually Changed
SmartAudio 2.0 was the standard for years and handles basic frequency and power commands reliably. SA 2.1 adds a polling mechanism — the FC can periodically request status from the VTX. This brings three practical improvements:
- Temperature monitoring: The VTX reports its internal temperature, which Betaflight can display on the OSD. Useful for long-range flights where the VTX is running at 1W+ for extended periods.
- PLL lock status: The FC knows whether the VTX has successfully locked onto the requested frequency. If the PLL isn’t locked, the VTX output is unstable.
- Current power level confirmation: Instead of assuming the VTX set the power you asked for, the FC confirms it. If there’s a mismatch, you’ll know.
Most pilots won’t notice a difference between SA 2.0 and 2.1 in daily flying. The upgrade matters most for long-range, where knowing your VTX temperature and lock status can prevent a lost signal 3km out. In Betaflight, select “TBS SmartAudio” in the Ports tab — the protocol auto-negotiates to the highest version both devices support.
FCC and HAM Compliance Note
VTX output power is regulated. In the United States, FPV video transmitters operating on 5.8 GHz require an FCC license for output power above 25mW — and even then, only on frequencies allocated for amateur radio use (Ham bands). If you’re flying at 200mW, 600mW, or 1W+, you need a Technician-class amateur radio license in the US. The test is straightforward (35 questions, multiple choice) and the license costs about $15. In the EU, CE regulations cap at 25mW on most 5.8GHz frequencies. Know your local rules — flying at high power without a license can result in fines and gear confiscation at organized events.
Quick Setup Checklist
- Wire VTX data pad to an FC TX pad (SmartAudio or Tramp)
- In Ports tab, set that UART’s “Peripherals” to “TBS SmartAudio” or “IRC Tramp”
- Load the correct VTX table JSON (manufacturer source preferred)
- Verify band/channel frequencies match the VTX manual
- Configure power levels (including Pit Mode if available)
- Enable Low Power Disarm to run 25mW while disarmed
- Add “VTX Channel” element to OSD for in-goggle frequency display
- Bench test: plug in battery with antenna, verify OSD channel control works end to end
Get the table right, and VTX control is one of the most reliable systems on your quad. Get it wrong, and you’ll chase phantom video problems for hours. Ten minutes of verification at the bench saves you from a day of frustration at the field.