The buzz around ExpressLRS Gemini Mode is undeniable, yet there’s a lack of true diversity receivers on the market that support this awesome feature. Enter the RadioMaster RP4TD – marking a significant upgrade from its predecessor, the RP3, which only offered antenna diversity. Let’s dive in to see what it offers.
Learn more about ExpressLRS in our comprehensive tutorial: https://oscarliang.com/setup-expresslrs-2-4ghz/
What’s Gemini Mode? https://oscarliang.com/expresslrs-gemini/
Table of Contents
Where to Buy?
Get the RP4TD Receiver from these vendors:
- Radiomaster: https://oscarliang.com/product-ptxv
- AliExpress: https://s.click.aliexpress.com/e/_DEIWSY9
- RDQ: https://oscarliang.com/product-910o
The package includes a set of silicone wires for connecting to the flight controller, and three pieces of clear heat shrink, enhancing the durability of the setup.
Technical Specifications
- MCU: ESP32
- RF Chip: Dual SX1281
- Antenna: Dual 65mm 2.4GHz T Antennas
- Frequency Range: 2.4GHz
- Maximum Refresh Rate: 500Hz / F1000Hz
- Telemetry RF Power: Max 100mW (x2)
- Working Voltage: DC 4.5-12.0V
- Weight: 1.4g (excluding antennas)
- Dimensions: 23.7×16.3×4.0mm
- Pre-installed Firmware: ExpressLRS V3.3.0
- Firmware Target: RadioMaster RP4TD 2400 RX
- Bus Interface: CRSF
- Extend Interface: UART
The standout feature of the RP4TD is its two separate SX1281 RF chips and TCXO (Temperature Compensated Crystal Oscillators). This design means the receiver is better equipped to handle a wide range of temperatures and challenging environments. With dual RF chips, the RP4TD offers two telemetry outputs at 100mW each, a significant upgrade for long range flying. For those looking to push the limits of 2.4GHz FPV flying, this receiver seems like an ideal choice.
Build Quality
The receiver itself is compact and well-built.
The top side features a boot button and two U.FL connectors for the antennas. The four soldering pads are accessible on both sides of the receiver with clear labels: 5V, GND, RX and TX.
Although the RP4TD is notably larger than single-antenna EP1 receivers due to its dual RF chains, the design remains impressively compact.
However, the inclusion of longer antennas could have enhanced its appeal for larger builds, such as 7″ or 10″ drones. Nonetheless, extended antenna wires are readily available for those in need:
95mm / 120mm / 240mm antenna:
- Radiomaster: https://oscarliang.com/product-vwxx
- AliExpress: https://s.click.aliexpress.com/e/_DmbG8IH
Installation
Installing the RP4TD is as straightforward as any ExpressLRS receiver. The key is to ensure optimal antenna placement. To ensure the best reception, positioning the antennas to avoid getting blocked simultaneous by any part of the quadcopter is crucial. This separation is vital for maintaining a consistent and reliable connection.
Conclusion: Is the RP4TD Right for You?
Note that true diversity doesn’t necessary increase range but intended to boosts reliability and link quality, particularly with Gemini mode enabled.
The RadioMaster RP4TD Diversity ELRS Receiver is a significant upgrade for FPV pilots seeking the utmost in reliability and performance. Its dual-chip design and robust build make it a top choice for demanding flight conditions.
Get the RP4TD Receiver from these vendors:
- Radiomaster: https://oscarliang.com/product-ptxv
- AliExpress: https://s.click.aliexpress.com/e/_DEIWSY9
- RDQ: https://oscarliang.com/product-910o
For those building larger drones, consider getting some longer antennas for the best setup. For those who push their FPV flying to the extremes, the RP4TD is a worthy investment, ensuring that your drone remains in constant, reliable communication with your transmitter.
95mm / 120mm / 240mm antenna:
- Radiomaster: https://oscarliang.com/product-vwxx
- AliExpress: https://s.click.aliexpress.com/e/_DmbG8IH
9 comments
Hey Oscar, couple of questions if I may?
1. Is the ideal position to have one antenna angled vertically, so during flight it’s vertical, and have the other antenna on plane with the quad? Your tutorial / article on antennas mentioned this kind of antenna setup. Where do you recommend placing each respective one?
2. Currently antennas are on opposing arms, at 90 degrees, and on place with the quad. I’ve noticed that the rasi dbm osd consistently shows, about 99% of the time, the second channel as the one that’s used. I’m referring to the number after the colon on the rssi dbm. I’ve checked telemetry logs, again by using your artical, and it confirms that the 99% of the time, it’s one channel used over the other. Btw, OSD shows either number 1 or 2 after the colon but Logs show either 0 or 1 for the ANT. Thoughts?
Thanks for all the great knowledge, I’ve basically learned everything through your Site.
1. How often is your quad at 90 degrees? Sure it happens when you do acrobatics, but that happens in a fraction of a second I don’t think it matters really. The main advantage of diversity antenna is to have them cover as much reception angle as possible so nothing on the quad can block the signal during flight. When it comes to antenna angle, personally I’d place it vertically to how the quad’s cruising position because that’s how your quad would be 95% of the times. And if you configure Failsafe and Rescue Mode same as me, your quad would be in this position also if you have a failsafe.
2. non-programmers count from 1, but programmers like to count from 0, so perhaps just inconsistency in the OSD and log coding.
Hi Oscar!
Have you find an useful manual? The one published in Radiomaster website doesn’t say a lot. What is the T and R pads (at the side) for? Thank you!
The extra T & R pads on the side are another set of UART. For more information see The ExpressLRS Lua Script Wiki under the section Reciver Options/Protocol2
expresslrs.org/quick-start/transmitters/lua-howto/#protocol:~:text=Receiver%20Serial%20Protocols-,Protocol%202,%C2%B6,-The%20Protocol%202
Hi what the difference between radiomaster r81 and rp4td
R81 uses Frsky protocol while the RP4TD uses ExpressLRS.
How to solder RP4TD with regular servo cable plug i mean there would three wire one goes for(+) and one goes for(-) and remaining one to RX or TX? I am doing it so to connect it to my Hex orange cube plus.
thank you
So how does that receiver work without a gemini module? Does it just use one antenna or does it use antenna diversity?
Yes, it works with non-gemini transmitter modules.