Hi All,
I just wanted to give everyone who is waiting for a 3DR 433MHz radio a heads up about a shipping delay. A few days ago I discovered an interference problem with the 3DR 433MHz radios that can cause the range to be much less than expected. We're still investigating the problem, but meanwhile I've suggested to Sam that they delay shipping the 433MHz variant of the radio until we've solved it.
Our current theory is that the 480MHz clock in the USB host controller on some PCs is the source of the noise, and that 480MHz is close enough to the 433 MHz radio band to cause the problem. This theory is supported by testing with the USB host controller forced into USB 1.1 12MBit/s mode ("full speed") instead of the more common "high speed" 480MBit/s mode.
The above graph shows a particularly extreme version of the problem on one of my laptops. This graph was produced with a modified firmware that uses the Si1000 as a simple scanner, looking at the background signal level at frequencies from 420MHz up to 950MHz. The graph shows the background noise levels in "433-scan.txt" (the red dots) for a USB version of the 3DR 433 radio. The green dots are for the FTDI version of the radio connected to the same laptop. Those noise levels are far too high, and would severely limit range when connected to this laptop.
We have found some workarounds - in particular running the USB host controller in 'companion' mode, where it forces the controller to run all ports in "full speed" 12MBit/s mode. That helps, but we are not very happy with the solution, and the noise is still higher than we would like.
So we are still investigating the best solution and meanwhile I've suggested to 3DRobotics that they hold off shipping the 433MHz radios until we have properly solved the problem.
The 900MHz radios are unaffected by this and we've got great range on those with lots of different ground station laptops.
I'll keep you all updated via this forum as we make progress on the noise problem. Meanwhile all I can do is apologise for the delay. We thought it was better to ensure the problem is properly fixed rather than having some people disappointed in the range.
Cheers, Tridge
Replies
Hello,
If 433mhz Ground Modules are affected by noise from FTDI /USB chips and needs some distance between them. this also means the air modules will be affected by presence of any FTDI chip inside the plane electronics. any thoughts ??
thanks
What are the main pros and cons between the 900 and 433 and how do they compare to the Xbee? I am considering buy either the 900 or 433 and here there are no restrictions so I could use either.
So firstly (appart from cost) how do they compare to the Xbee for speed and range.
Which out of the 900 and 433 would be the best choice and why?
Quality first.
Ironically , this order also holds my APM2's - so I am waiting very long now .. and it feels even longer.
A few comments suggseting this wouldn't be an issue with air modules (UART), only the ground module (with inbuilt USB adapter). Is that right? Or is the interference coming from the Bus, rather than the adapter?