OpenVTX. Open Source. Open Control.
Most VTX firmware is a black box—closed, proprietary, and unchangeable. The OVX300 and OVX303 run on OpenVTX, an open-source project powered by JyeSmith from the ExpressLRS team. The firmware is preloaded. The source code is available. Community improvements are continuous. This is the VTX that evolves with the hobby.
SmartAudio + Tramp. Auto-Detect. No Configuration.
OpenVTX implements both SmartAudio and Tramp protocols simultaneously. Connect to your flight controller. Power up. The VTX automatically detects which protocol your FC is using. No manual switching. No firmware reflashing. No compatibility guesswork. SmartAudio is fully implemented and tested against Rev. 09. Tramp implementation is based on Betaflight information. Either way, your OSD-controlled channel and power adjustments just work.
Five Power Levels. Pit Mode to Full Send.
– 0mW (Pit Mode): Safe bench configuration. Zero interference to other pilots.
– RCE Mode: Race event compliance. Minimal output for crowded heats.
– 25mW: Indoor whoop racing and proximity flying.
– 100mW: General freestyle and park flying.
– 300mW: Maximum range for outdoor toothpick and micro long-range builds.
Switch levels remotely through your Betaflight OSD or via SmartAudio/Tramp commands. No physical button needed on a nano build where every millimeter counts.
Two Form Factors. One Open-Source Soul.
| Model | Weight | Dimensions | Mounting | Best For |
| OVX300 | 0.9g | 14×15×3mm | Direct solder | Ultralight whoops, 1S nano builds |
| OVX303 | 1.5g | 16×16/20×20/25.5×25.5mm | Triple mounting holes | Toothpicks, micro freestyle, standardized frames |
OVX300: The lightest OpenVTX transmitter available at 0.9 grams. Direct solder pads. No mounting holes. Designed for 1S whoops where every milligram matters.
OVX303: 1.5 grams with three mounting patterns—16×16mm, 20×20mm, and 25.5×25.5mm. Drops into virtually any micro or toothpick frame. Standardized mounting without the weight penalty.
5V Input. FC-Powered Simplicity.
Both models require 5V DC input—connect directly to your flight controller’s 5V BEC output. Maximum current draw is <650mA at 300mW. Ensure your FC’s 5V regulator can supply sufficient current. Clean. Simple. Lightweight.
40 Channels. Full 5.8GHz Band.
Standard 40CH coverage across all common 5.8GHz FPV bands. Find a clean frequency in any environment. Configure via SmartAudio or Tramp through your OSD.
Key Features
* OPENVTX OPEN-SOURCE FIRMWARE: Powered by JyeSmith (ExpressLRS team). Source code available. Community-driven improvements. No black-box firmware.
* SMARTAUDIO + TRAMP AUTO-DETECT: Both protocols implemented. Automatically detects FC protocol on power-up. OSD channel and power control without manual configuration.
* 5 POWER LEVELS: 0mW Pit / RCE / 25mW / 100mW / 300mW. Remote switching via Betaflight OSD. From bench to full send.
* 40CH FULL 5.8GHZ BAND: Standard channel coverage. Clean frequency selection in any flying environment.
* OVX300: 0.9G NANO: Direct solder. 14×15×3mm. The lightest OpenVTX transmitter. Built for 1S whoops.
* OVX303: 1.5G MICRO: Triple mounting patterns (16×16/20×20/25.5×25.5mm). Fits every standardized micro frame.
* 5V INPUT: FC BEC powered. <650mA max current. Clean power design. No external regulator needed.
Specifications
| Model | OVX300 | OVX303 |
| Brand | Happymodel | Happymodel |
| Firmware | OpenVTX (Open-Source) | OpenVTX (Open-Source) |
| Frequency | 5.8GHz 40CH | 5.8GHz 40CH |
| Power Levels | 0 / RCE / 25 / 100 / 300 mW | 0 / RCE / 25 / 100 / 300 mW |
| Protocols | SmartAudio + Tramp (Auto-Detect) | SmartAudio + Tramp (Auto-Detect) |
| Input Voltage | DC 5V | DC 5V |
| Max Current | <650mA @ 300mW | <650mA @ 300mW |
| Dimensions | 14 × 15 × 3 mm | — |
| Mounting Holes | Direct Solder | 16×16 / 20×20 / 25.5×25.5 mm |
| Weight | 0.9 g | 1.5 g |
| Antenna | U.FL/IPEX Not Included | U.FL/IPEX Not Included |
Package Included(Optional):
1x Transmitter Open VTX
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