Quick Answer
The cable you need depends on your Pixhawk version and RFD modem. Pixhawk 1 uses DF13 connectors; Pixhawk 2 and later use JST-GH. RFD x-series (RFD900x, RFD868x) and ux-series (RFD900ux, RFD868ux) modems need different cables that are not interchangeable. Use a straight telemetry cable for basic MAVLink, or a multi-cable if you need external power and SBUS/PPM output.
Pixhawk 1 vs Pixhawk 2: The Connector Problem
The most common mistake when buying telemetry cables is getting the wrong connector type. Pixhawk 1 (FMUv1/v2) uses Hirose DF13 connectors. From Pixhawk 2 onwards, including the Cube, Pixhawk 4, 5, 6, and 6C, the standard changed to JST-GH.
Despite the same pitch, DF13 and JST-GH are physically different. A DF13 plug will not seat in a JST-GH socket. If you have an older Pixhawk 1, you need a DF13 telemetry cable. For Pixhawk 2 or newer, you need a JST-GH telemetry cable. Adapter packs are available if you need to convert between the two.
RFD x-Series vs ux-Series Cables
RFdesign makes two families of long-range telemetry modems. The x-series (RFD900x and RFD868x) uses a 16-pin 0.1" pitch header on the board itself. The ux-series (RFD900ux and RFD868ux) uses DF13 connectors instead. Because of this, the cables are not cross-compatible. An x-series multi-cable physically cannot plug into a ux-series modem.
| Cable Type | Compatible Modems | Connector on Modem End | Connector on Pixhawk End | Extra Connections |
|---|---|---|---|---|
| Straight Telemetry Cable (Pixhawk 2) | RFD900x, RFD868x | 0.1" pitch socket | JST-GH 6-way | None |
| RFD900x Multi Cable | RFD900x, RFD868x | 16w header | JST-GH 10-way | 2-pin power, 3-pin PPM/SBUS |
| RFD900ux Multi Cable | RFD900ux, RFD868ux | DF13 | JST-GH 10-way | 2-pin power, 3-pin PPM/SBUS |
| RFD 8-way Socket Cable (ux) | RFD900ux, RFD868ux | DF13 | 8-way socket | APM/FTDI interface |
Straight Cable vs Multi-Cable
A straight telemetry cable carries the essentials: serial TX, RX, and ground. This is enough for MAVLink communication between your flight controller and the modem. It plugs into one of the TELEM ports on your Pixhawk for mission planning, live telemetry, and firmware updates.
A multi-cable adds more connections on top of the serial link. It uses a 10-way JST-GH connector instead of a 6-way, giving you extra pins for external 5V power and a PPM or SBUS output. The external power feed is worth using if you want the modem to transmit at full power. The RFD900x multi-cable and RFD900ux multi-cable both provide this, but they are not interchangeable between modem families.
Cable Length Considerations
Telemetry cables come in 15cm, 30cm, and 75cm lengths. Longer cables give you more flexibility in positioning the modem, which helps with GPS interference and antenna placement. Serial UART signals degrade over distance though. Beyond one metre you can see corrupted packets. Stick to the shortest cable that works for your build. The 75cm Pixhawk 2 cable suits larger airframes where the modem needs to sit further from the flight controller.
Pin Orientation and Installation
Several of these cables have a specific orientation. The RFD900x multi-cable has a black triangle that must align with the PIN 1 marker on the modem's 16-pin header, with the red wire on pin 4. The ux 8-way socket cable has an arrow indicating which way is up. Inserting cables backwards can short pins and damage the modem. Always check orientation before powering up.
What to Buy
- RFD Telemetry Modem to Pixhawk 2 Cable (15cm) - basic MAVLink link for Pixhawk 2+ and RFD900x/RFD868x
- RFD Telemetry Modem to Pixhawk 2 Cable (75cm) - same as above but with more routing flexibility
- RFD900x Multi Cable (30cm) - for RFD900x/RFD868x with external power and SBUS/PPM
- RFD900ux Multi Cable (30cm) - for RFD900ux/RFD868ux with external power and SBUS/PPM
Browse the full range in the RFdesign long-range telemetry collection. If you need to adapt between DF13 and JST-GH connectors, see our JST-GH to DF13 adapter cables.
Frequently Asked Questions
Can I use a Pixhawk 1 cable on a Pixhawk 6?
No. Pixhawk 1 uses DF13 connectors and Pixhawk 6 uses JST-GH. The physical shapes are different and they will not plug in. You need a JST-GH cable for the Pixhawk 6, or a DF13-to-JST-GH adapter.
Are x-series and ux-series cables interchangeable?
No. The x-series (RFD900x, RFD868x) uses a 16-pin 0.1" header, while the ux-series (RFD900ux, RFD868ux) uses DF13 connectors. Using the wrong cable will not fit, and forcing it can damage the modem. For help choosing between the two modem families, see our RFD module comparison guide.
Do I need a multi-cable or is a straight cable enough?
If you only need MAVLink telemetry (live data, mission uploads, firmware updates), a straight cable is fine. If you also want to supply external 5V power for full transmit output or pass through SBUS/PPM, get the multi-cable. For a full walkthrough of connecting everything, see how to set up RFdesign telemetry radios with ArduPilot and PX4.