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Stable, high quality telemetry and RC link options for proffesional aplications

#1

Hello.
I’m building and Arduplane based vehicle and it’s time to choose telemetry and RC link. I’m a bit stuck here since there are a lot of variables to take into account. I’m looking for a long range (up to 10-15km) potential. I’ve read a lot of the threads here and I got some favorites. I’m EU based so the main frequencies I’ allowed to use are 868 MHz and 433 MHz (and 2.4GHz, 5.8 GHz). But lets start from the beginning. Right now, the prototype is TBS crossfire based (got a lot of experience with their systems from drone racing) but from what I’ve read here, crossfire isn’t stable, reliable link for my application, especially for telemetry and ground control functionality.
Here are my options (and questions):

  1. TBS crossfire - mavlink RClink and telemetry, connection to Ground Station via over bluetooth or Wifi - concerns as above - probably buggy, not stable enough, especially GS connection.
  2. TBS crossfire as RC link + RFD 868X-EU as telemetry for Ground Station - the main concern here is interference between those two systems. Not sure how problematic that might be, but in theory it’s not a good idea.
  3. Dragonlink RClink + telemetry - heard a lot of good things about this system. Telemetry seems to be very prone to interference though.
  4. Dragonlink RClink + RFD 868X-EU as telemetry for Ground Station - interference between the systems shouldn’t be as bad as in option 2, what do You think about this setup ?
  5. RFD 868 TXMOD V2 as RClink and telemetry - this thing looks very good. I can’t see any cons here, but is it reliable ? I’ve heard and read a LOT of good things about RFD 868X-EU as a telemetry system, but never heard anything about using it as RClink What about range ? Any potential problems with RClink using this ? Like lag, stability or any other thing ? Looks like the main advantage here is no interference between link and telemetry.
  6. TBS crossfire + SiK radio telemetry 433Mhz (Holybro or mRo, since 3DR isn’t available/supported anymore) - this is a cheap option which may work well, and it’s inverse of option 4 in terms of possible interference.
  7. Herelink for everything - don’t know anything about it’s reliability and cons of this system. Price is the obvious one of course… But If it’s absolutely the best - let me know.

Please share Your opinion, which of this configurations is the most professional, reliable and has the greatest potential. If You know any other, better options, feel free to suggest anything You think is worth considering.

Thanks!

#2

Hi @BennetEown, I had been looking at exactly the same issue as you have, and have tested just about every combination of RC and telemetry. I do have and tested Herelink, R9M (Interfered with SIK Radios), Crossfire, RFD, etc. My conclusion is that the RFD900x at this time is my best option. If you are testing on the ground and looking at surfaces move, you will notice some lag in the response in the control surfaces, but this is not an issue in flight for controlling at least a fixed-wing at all. It was hard to figure out how to get everything working, and when I did, I wrote a post about it to share and document for my own purposes as well. Here it is for your reference. Combined RC and Telemetry on a single link (TXMod v2, RFD 900x, TX16S, GCS, Matek H743)

Enjoy and good luck, let me know if you have specific questions I’ll do my best to adress them.

#3

Thanks for Your response @jimenezlee. I’d definitely check out Your thread, looks like You’ve been through hell of a travel with all those links.
You say You got some interference on R9M and SiK - what was the frequencies You were using on those systems ? Was it like 2x 915 MHz or 868 MHz + 433 MHz ?
I feel like every scenario with mixing systems will be prone to interference here. Not entirely sure about 868 and 433 mixing, 868 is super close to half wave length though, it really doesn’t look good on paper for this combination.

How were Your experiences with Herelink ? Was it any good ?
You haven’t tested the dragonlink though, and it’s a choice of many long range operators. Would be cool if somebody with experience with this system could share his opinions here…

#4

@BennetEown, you are right, I have not used dragonlink myself. R9M and SiK were both at 915MHz.

868 and 433 should have harmonic interference with each other.

Herelink was not bad, but I was using it with a large hexacopter and honestly my one gripe with it is that it has no switches, and if you get anything like a gps glitch it will be near impossible to switch modes quickly enough. I put the Herelink on the back burner for a little while for that reason, and once I finish another project I’m working on, I’ll come back to it. I’m planning on getting everything setup and working reliably using a std radio (TX16S) and then will go back to setting it up with Herelink when I plan on only needing one or two modes on physical buttons and then any other mode changes would be done through QGC on the tablet display. The deal here is that things need to be working really well and stable so you have time to fiddle with the tablet and changing modes/etc through those drop down boxes. I’m used to being able to make quick changes on switches right now.

#5

Running both, Rclink and telemetry as two different systems on the same bandwidth (in Your case 915 MHz) isn’t a good idea for sure… The 868 and 433 though might not be that bad, I’d really like to hear an opinion of someone’s who were using it like this.
As for Herelink - how was the connection reliability and range ? Was it as good as RFD ?

#6

@BennetEown, I never had any problems with the reliability of the connection, but have not done range testing.

#7

For professional use, RFD, if you need all-in-one solution then Herelink. (especially once the module only ground version will be available).
All other solutions mentioned are for hobbyist. Most of them are unbalanced (TX on ground is more powerful than TX on air, therefore not good for bidirectional telemetry) Bonus: none of them are legal because of power output, bandwidth, duty cycle. RFD can be setup to be legal, and Herelink also FCC/CE compliant.

#8

I’ll also vote for the RFD900x. The setup has some challenges but the link is solid. I’ve only a few KM with it but looking at the log values afterwards tells me I’ve got more than enough range to get me into plenty of trouble. :slight_smile:

I have used DragonLink. Admittedly it wasn’t the latest version so I needed to modify the RX to get the wifi link for my GCS. It was functional but I was never satisfied with the GCS link. I can’t pinpoint a reason but I was never truly confident in it. Once the RFD system arrived the DragonLink was pushed aside and I’ve never looked back.

#9

Thanks guys. Really appreciate Your help. I think I know what I wanted to know.

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