ELRS AirPort vs SIK

yrjobjorkqvist · December 10, 2023, 8:18am

Hello all friends.
Does anyone have experience replacing SIK radio with ELRS AirPort?
Happy flying //YB

Awsmits · December 23, 2023, 2:56pm

Not yet, but I’ve ordered the new 915 MHz ELRS Tx and Rx from Radiomaster and plan to give it a try in the next month. I fly my planes with the 2.4 GHz ELRS now, so the 915MHz should give good radio separation.

c.rieger · January 17, 2024, 11:59am

It is much nicer. Better range and higher speed. (2.4ghz)

I managed over 7km instead of a few hundred meters with EU-SIK at highest data rate.

adcam · January 17, 2024, 6:50pm

I plan to switch to ELRS
Is ELRS Airport full mavlink ? I mean how many data drop

c.rieger · January 17, 2024, 7:24pm

it is a transparent serial port like SIK radios. → standard mavlink.

Awsmits · January 18, 2024, 12:53am

Just following up on trying ELRS Airport on 915MHz while using 2,4 GHz ELRS for the RC link. It works, but I have been disappointed in the lag time between the attitude and sensors of the plane and how it is displayed on Mission Planner. I’ve mad a number of tweaks to MP parameters and Telemetry rates, but I still get a 2-3 sec lag time, so I’m very disappointed so far. If I can’t resolve this, I’ll be trying Bluetooth between my transmitter and my PC.

acoolguy · October 17, 2024, 9:06am

Did this ever improve for you?

I’m on the fence about purchasing another SiK radio pair vs. Radiomaster bandit micro + Bandit BR3 diversity Rx. The price for the SiK radio is $103.50 vs. $103.87 for the bandits. I’m willing to pay $0.37 more if it works better. But it seems like it’s worse(?). I think there’ve been some firmware updates this year. Has it gotten better in the last 9 months?

geofrancis · October 17, 2024, 12:24pm

you can use the mLRS firmware to do the same thing if your hardware is supported.

github.com

olliw42/mLRS-docu/blob/master/docs/SETUP_SIK.md

# mLRS Documentation: Setup as SiK Telemetry Replacement #

([back to main page](../README.md))

This page describes how to use mLRS as a bi-directional MAVLink telemetry link similar to a SiK telemetry unit. This setup doesn't require a radio and will only transmit and receive MAVLink data.

<img src="images/mLRS-docu-setup-sik-telemetry-02.jpg" width="800px">

## Setup

The configuration for this mode is similar to others, except that one can ignore the RC settings on both the mLRS Tx module and receiver.  The RC input and output pins on the devices are not used.

For this setup, the mLRS Tx module should having the following settings:
- Tx Ch Source = none
- Tx Snd RadioStat = 1 Hz

Note: Tx Snd RadioStat sends the RSSI of the Tx module to the ground station software.

There is no specific configuration of the mLRS receiver neccessary.

This file has been truncated. show original

LupusTheCanine · October 17, 2024, 3:28pm

MAVLink over ELRS is pretty much fully supported right now, there are minor changes that will arrive with Ardupilot 4.6 (new dedicated MAVLink message for RX inputs to FC, some fixes for MAVFtp). The only real issue is that Yaapu’s Telemetry Script isn’t supported.

IMHO external ELRS modules are better suited for use with MAVLink thanks to the built-in USB port.

acoolguy · October 18, 2024, 1:58am

Thank you for the replies.

I have to be honest: I’m still not clear on the difference between ELRS Airport and mLRS. Do the same rules apply, such as: AirPort - ExpressLRS

Frequency band

If you plan to use two side-by-side ELRS links on the craft (one for RC and one for telemetry), it is HIGHLY recommended to use different frequencies for each link. For example, you will see good results with RC on 2.4GHz and AirPort on 900MHz. The range will be severely reduced if both RC and AirPort are on the same frequency band.

And also, is it fast? I’ve read anecdotes of people saying there’s a 2 second delay between rotating the vehicle and the mission planner artificial horizon displaying it. I don’t get lag with SiK radios.

geofrancis · October 18, 2024, 2:39pm

mlrs has about 3x the bandwidth. Basically ELRS uses a lot of very small packets, thats how they can do the really fast RC update rates but it means that mavlink packets have to get split into a lot of packets to get sent slowing it down and adding latency, mLRS uses a lower number of larger packets, so you get more bandwidth at the expense of update rate and a little less range but unless your racing or freestyle 30hz or 150hz RC makes no difference, the 10-15% reduction in max range is due to it needing to receive more data to make up a packet. It also has mavlinkX, basically mavlink compression that gets you more bandwidth than you actually have.

mlrs doesn’t support as much hardware as ELRS so you would need to look at what’s supported, most ELRS receivers work. the ESP32 TX modules are still a work in progress, stm32 modules work.

acoolguy · October 18, 2024, 4:44pm

Thank you for the information. The Radiomaster bandit I was looking at seems like a bad choice at the moment; it has an ESP32 module. Instead, the Mateksys mR900-30-TX looks like a better choice. That’s the ground station solved.

Rx question; which is better: Full diversity @ 100mW, or zero diversity @ 1000mW? I can’t decide between the Mateksys mR900-30 and the Bandit BR3 ExpressLRS 915MHz Receiver.

geofrancis · October 18, 2024, 4:46pm

1000mw is going to go much further than diversity.

the mR900-30-TX are not compatible with the ELRS receivers, they use more modern RF modules so you will need to use a pair of the MR900-30 modules, they get about 30% faster data rates than the older modules ELRS use that run at 19hz on mLRS that’s essentially the same chip from the frsky r9 modules.

yapuu telemetry is also supported.

https://www.mateksys.com/?portfolio=mr900-30-tx
https://www.mateksys.com/?portfolio=mr900-30

acoolguy · October 18, 2024, 8:18pm

Thank you for the insight. mLRS all the way it is!