VTX JHEMCU RuiBet Tran-3016W, 5.8G 40CH, 1.6W, integrated microphone, 7-26V

The tutorial uses the JHEMCU RuiBet Tran-3016W VTX as a standalone module, without a development board and without a program. After it receives power from a LiPo battery and a video signal from a camera, it transmits the image on 5.8 GHz to FPV goggles. It is adjusted with the button and the three LEDs on the board.

You use it in FPV drones, planes and other models that need real-time analog video, with adjustable power between 25 and 1600 mW. In this tutorial we connect it to an analog Caddx Ratel 2 camera, a 5.8 GHz antenna and a 3S 11.1 V battery, without an OSD from the flight controller.

How it works:

The camera sends the analog composite video signal on the Video pin. The VTX modulates it in frequency onto a 5.8 GHz carrier and sends it through the antenna. The goggles have a receiver tuned to the same frequency, demodulate the signal and display the image. If the frequencies differ, the image does not appear or is full of noise.

The frequency depends on the band and the channel. In the Raceband, channels are spaced 37 MHz apart, so the frequency of channel n is 5658 + 37 x (n - 1) MHz. For example R4 = 5658 + 37 x 3 = 5769 MHz. In the Fatshark band the spacing is 20 MHz, so F4 = 5740 + 20 x 3 = 5800 MHz. The default value 5733 MHz is channel 1 of band B.

Power is expressed in mW or dBm, according to the formula dBm = 10 x log10(P in mW). The board levels correspond approximately to 14 dBm for 25 mW, 23 dBm for 200 mW, 26 dBm for 400 mW, 29 dBm for 800 mW and 32 dBm for 1600 mW. Each doubling of the power means 3 dB more, and part of the electrical energy turns into heat, which is why the board heats up more at 1600 mW.

Power enters on the DCIN pin at 7 - 26 V, and the board produces a 5 V output of at most 1 A on the +5V pin, which powers the camera. A 3S battery has a nominal 11.1 V and 12.6 V when fully charged, so it is within the accepted range.

Connection:

Before applying any power, connect the antenna to the VTX through the MMCX - SMA cable, because powering it without an antenna can destroy the VTX. The cable in the package is not an antenna, so mount a 5.8 GHz antenna on the SMA connector, for example an RHCP antenna. The camera is powered from the +5V pin of the VTX, so it does not need another source. Check each wire of the 6-pin cable according to the markings on the board, because the wire colors may differ. On the Caddx Ratel 2 camera, the red wire is VCC, the black wire is GND and the yellow wire is VIDEO, and the OSD wire is not used.

Buttons, settings and indicators:

Changing the channel: press the button briefly. Each press moves to the next channel in the current band, from 1 to 8, and the blue Chan LED shows the selected channel.

Changing the band: hold the button pressed for about 2 seconds and release it. The band moves to the next one in the order A, B, E, F, R, and the green Band LED shows the selected band.

Changing the power: hold the button pressed for about 5 seconds and release it. The power moves to the next level in the order 25, 200, 400, 800, 1600 mW, and the red Power LED shows the selected level.

Unlocking the channels: hold the button pressed for more than 10 seconds. This activates the channels that do not transmit by default, for example 5705, 5685 and 5665 MHz. Use them only where local regulations allow it.

After any adjustment, check the result in the goggles, where the camera image must appear clean on the chosen frequency.

Setup:

Power on with the antenna connected. At the first power-up the VTX transmits on 5733 MHz (B1) at 1.6 W. For bench work, first change the power to 25 mW and only then the other settings.

Step 1: after power-on, switch to the minimum power of 25 mW by holding the button pressed for 5 seconds and repeating until the red LED shows the 25 mW level.

Step 2: choose the band with 2-second presses, until the green LED shows the desired band.

Step 3: choose the channel with short presses, until the blue LED shows the desired channel.

Step 4: tune the goggles to the same frequency, using the frequency table, and check the image. After restarting the VTX, check the LEDs and the image again, to see which values it has kept.

Usage example:

The goal of the example is a freestyle drone with a 3S battery, a Caddx Ratel 2 camera and analog FPV goggles tuned to Fatshark F4 (5800 MHz).

Mount the VTX on the frame with four M3 screws at 30.5 x 30.5 mm. Connect the camera to the +5V, GND and Video pins, then the battery to DCIN and the second GND, with the 5.8 GHz antenna already mounted on the MMCX - SMA cable.

Power up the VTX, set the power to 25 mW for the bench tests, then choose band F with 2-second presses and channel 4 with short presses. Tune the goggles to 5800 MHz and check the camera image.

Before flying, raise the power to 800 mW or 1600 mW with 5-second presses, without leaving the drone on the bench at high power. In flight the airflow cools the board and the image must remain stable.

Common problems:

No image appears in the goggles. The most likely cause is a different frequency between the VTX and the goggles. Check the band and the channel on the VTX LEDs and on the goggles, then check the connection of the Video wire and the antenna.

The image is full of noise or is lost quickly. The cause may be a loosely connected antenna, a polarization different from that of the goggles, or mounting near wires and motors. Check the MMCX and SMA connectors and move the antenna away from noise sources.

The camera does not start. Check the +5V and GND wires of the camera, the polarity and whether the battery is connected to DCIN and the second GND, with a voltage between 7 and 26 V.

The VTX gets very hot on the bench. The cause is high power without airflow. Reduce the power to 25 mW and use 1600 mW only in flight or with a fan.

A desired channel does not transmit. Some channels are disabled by default. Hold the button pressed for more than 10 seconds to unlock them, if local regulations allow it.

The OSD adjustment does not work. In this setup the IRC pin is not connected. Connect IRC to a free TX of the flight controller and configure the IRC protocol with the frequency table of the VTX.

Limitations and tips:

The VTX transmits only analog video on 5.8 GHz and needs goggles or an analog receiver. The 5 V output supports at most 1 A, so do not connect large consumers to it other than the camera. At 6S a fully charged battery has 25.2 V, close to the 26 V limit of the input, so power it with care.

Never power the VTX without an antenna connected. At high power use a suitable antenna and ensure cooling. Respect the local regulations regarding frequencies and transmission power.

In the next project you can connect the IRC pin to the flight controller to change the channel and power from the OSD menu, without touching the button on the board.