The configuration is: F550 frame, Radiolink Pixhawk PX4, RadioLink SE100 NEO-M8N GPS, RCmall ‘upgraded’ (NOT) 3DR 500MW (NOT) Radio Telemetry Kit 915Mhz, FrSky X8R receiver with FLVSS battery monitor and a Teensy Mavlink protocol converter for FrSky SmartPort.
I have tried everything to get the GPS SAT Count and GPS ground speed to stabilize and stop jumping all over the place. It will not let me switch to Loiter until the SAT counts and GPS ground speeds stabilize which it never does as long as the telemetry module is plugged in. As soon as I disconnect telemetry everything appears to stabilize as I can switch to Loiter to takeoff or while flying. I have moved the telemetry unit from the bottom of the frame to the furthest leg and still have issues. Not sure if there is anyone else who has had these issues. Any help/suggestions would be greatly appreciated…
I’m experiencing the same issue with F450 quad frame. When the radio telemetry receiver is off I get the GPS lock and can fly in Loiter mode. When the radio telemetry receiver is on I experience the same issue. Will also be interested in how to avoid such interference.
I’m having the same problem.
As soon as I connect 500mW 3DR Radio Telemetry 433Mhz I get messages “Prearm: GPS speed error xx (need 1.0)” and I can see that multirotor is jumping all over the map.
Did anyone find solution for this?
I’ll try to power telemetry module from separate power supply and report if it makes any difference.
I found source of problem.
Antenna of telemetry module was close to GPS antenna and looks like they are interfering.
Here you can see how strong interference is:
It is also helpful to read THIS thread. It contains lot of helpful information for solving this issue.
I have the same issue at 915 mhz. There is a bunch to read in this link & I can only follow parts of it as I am not a radio technician. I have tried all types of shielding & I suspect the data link may be radiating to the power wires through the FC to the GPS. I have been troubleshooting this over a month and for the $30 or $200 it would cost for new radios, I am willing to spend whatever it takes. The question is what brand is working for people who do not see this issue?
For my copter I have no intention of somehow powering the telemetry through a separate battery and wrapping it in foil (by the way I did wrap it in foil & grounded similar to the video link with no results). I also do not want to cut the manufactured cables that plug into the FC and power my telemetry with a separate battery. These radios are designed to plug it and work but somehow, I have radios that will radiate through a metal roof to the base GPS antenna. They just are worthless if I want GPS, It is not a 550 frame or 450 frame issue I am seeing this with a 800, 680, 550 and at the base.
So what brand works for us lay people?
We use the RFD900 radios and have never experienced this problem.
Looks like these cheap (probably clone) 3DR 500mW telemetry modules don’t have any filtering at output. Using RFD modules will probably fix these problems. I never experienced this problem with RFD telemetry modules.
Have used the 3DR modules for years without any real issues.
Still have half a dozen lying around I use for odd projects.
Are they original and marked as 3DR?
I bought them from Banggood and they come with 3DR logo.
After shielding telemetry module with aluminium tape I reduced interference a lot.
Wire was soldered on ground plane inside module and connected to shield.
As you can see, interference is noticeably reduced:
thanks! that is what I was wondering.
I did use RFD900 900+ and now using 900X. Never , never had such problem. This is on many drones. I do however have separate power for Rx, GPS, Telemetry, Lidar, FC, AND opto isolated ESC No need to send hundred of millivolts of noise from esc 5Volts output to sensitive electronics.
Using opto ESC (No 5V output) insure galvanic insulation in between High power high noise environment and low power sensitive electronics.
Henrik, I do appreciate the detail you included.
on my quad, I am using no BEC just ESC motor combo’s (1 black & 1 white wires out no red 5v output wires).
On a gas plane Yes, I need 2 separate batteries for RX and ignition but never had an issue with electric motors flying planes or copters. So I have a question.
Do you have separate batteries for all 6 components? How many batteries and in what configuration?
ALSO: Just bought the RFD900x ( will get them in 2 days) not cheap but I thank you for the information.
Hmm… my last test was pretty conclusive, the M8N GNSS is not effected by the cheap radios just my M8P.
I did solve this and spent the day testing. I was wrong about the HERE GPS (SORRY!!)
The issue is the cheap tx antenna not the radio, here me out.
For this test I recorded the sv# and S&R ratio for the top 3 sv’s
I used a Trimble R8 and a HERE+ M8P
ANTENNA 1 (DIY)
ANTENNA 2 (STOCK)
ANTENNA 3 (TRIMBLE R8)
I tested 10 cm away 2- 100 & 2- 500 MW (cheap radios) (average of all 4 test shown)
antenna 1 -16 sv 52,51,49 sn
antenna 2 - 18 sv 50,49,48 sn
antenna 3 - 13 sv 53,53,53 sn
then I moved the TX just under 10 cm and saw a slight drop in readings.
antenna 1 -12 +/- sv 43,43,42 sn
antenna 2 - 13 +/- sv 35,34,34 sn
antenna 3 - 13 sv 48,45,44 sn
I had real trouble duplicating the issue then I switched the 915mhz antenna back to stock and immediately saw the GPS loss.
at 30 cm apart
antenna 1 - 5 sv 33,33,32 sn
antenna 2 - did not test
antenna 3 - 3 sv 42,40,34 sn
Moved to 40 cm and it got slightly better.
I tried 3 stock 915MHZ antennas all 3 killed the GPS even on the Trimble R8 at 40 cm.
on the 500 MW radios I used a leica 915 MHZ (2 inch rubber ducky) antenna off some of my survey equipment with 100% good fixes down to 10 CM.
I also had no issue using a 5.8 ghz antenna on the cheap 915 MHZ radio. Obviously your link will suffer at some point if you go that route.