Hello,
I am looking for more information about what the “Unhealthy GPS Signal” Pre-Arm signal means? I have a good HDOP, 4 satellites, good mag field, GPS Fix. Not quite sure what is causing this. Is the baud rate for the gps not high enough? Default 38400. I have tried setting GPS_GNSS_MODE to 1 and 67 but that did not help. I appreciate any suggestions to check.
4 sats good? …hardly.
I wouldn’t take off unless at least 6 sats when just using regular GPS (US-Satellites) and perhaps at least 12 or more when using multiple satellite systems.
There are many reason why you get “Unhealthy GPS Signal” messages.
Besides just 4 sats, you might be indoors, you might get interference from other equipment (if in doubt show us a photo of your setup), the wiring could have issues, poor GPS receiver,…
Some more info:
https://ardupilot.org/copter/docs/common-gps-how-it-works.html?highlight=unhealthy+gps
https://ardupilot.org/copter/docs/gps-failsafe-glitch-protection.html?highlight=unhealthy+gps
Here is some more practical testing in regards to shielding
Some practical comparison of receivers:
In the bottom corner of the map screen it has the sat count. In this case there’s 19. It’s the GPS Status that says 4.
All that aside, it could be a interference issue. The links from @Karl_Schoelpple should offer some ideas. Are you near power lines or indoors? Is the compass calibrated?
My tests were done outdoors in two different spots away from power lines. Compass has been recalibrated at the beginning of each test. I read through the articles and I’ll play around with some fine mesh. I’ll send a picture of my setup when I get the chance to see what you think about the interference. But wouldn’t that come up on the HDOP? Thank you for the help.
Difficult to comment without see the set up. It could be many different issues possible.
I understand that battery power wires are some of the worst for interference but the gps is well over 15cm away. RX(Antennas go out the back) and Telem are also pretty well spaced. I can always move it farther away if you think that would help.
A simple, yet effective way of greatly reducing interference from wires is to twist them wherever possible.
That’s why good ESC’s have the control wires twisted already.
Also please move that antenna away - But I believe you intend to do that anyway.
Here is the outcome of a very basic test I’ve been doing a couple of years ago:
Regular, neat wiring:
Twisted wiring:
As you can see the amplitude (strength of signal) was reduced by just twisting the wiring.
PS: you can also twist those GPS wires in order for them to be less susceptible to RF interference and / or if you want use a bit of household aluminium foil and wrap this around the GPS wiring. - Especially where it passes under other electrical equipment.
@Austin_Lee,
You really should have a metal ground plane around 3-4 inches in diameter under the BN-880.
1 Like