Mounting the F9P rover inside the fuselage

Hello!

I want to use two Sirius RTK GNSS F9P rovers to get a heading estimate from PX4. Ideally, both the modules would be placed inside the fuselage, to protect them from rain etc. However, I am worried that this might cause a problem with EMF or the fuselage blocking the signals.

I am using a FoxTech BabyShark 260 VTOL, which is a composite frame: https://www.foxtechfpv.com/foxtech-baby-shark-vtol.html.

Do anyone have experience with something similar? Will I likely be experiencing problems when mounting a RTK GNSS unit inside of a composite frame, together with the electronics?

Thank you in advance for you help!

No problem, you can put Sirius RTK GNSS F9P inside the airframe, the signal quality degrades a bit and it’s negligible. (You will easily get the RTK FIX because you are attaching the antenna on an aircraft, not a car or lawn mower, signal interference problems, multi-path reflection, … will not be a problem).

Just try to place the antenna at the top inside and just below the top shell of the aircraft.
Of course, you can still remove the plastic outer shell of the Sirius RTK GNSS F9P if that helps.

I see, thank you! How much would you say that the signal degrades? Will we lose any accuracy, or will it not be possible to notice the difference?

Signal averaging around 37-40dBi is good enough for RTK.
Maximum signal level can reach above +50dBi.
The attenuation level of just 1-3dB has almost no effect on RTK. Because of the fact the F9P can operate at less than 30dBi.
With an antenna mounted on the body of the aircraft, there is no need to worry about signal strength.

I see, and mounting the module inside the airframe will only cause an attenuation level of 1-3 dBi?

Really appreciate the help.

Yes. With flexible foam, ordinary plastic (without metal coating), PVC, … with a thickness of less than 5mm, the degradation is only 1-3db.

Will it be different for an airframe made of composite materials? The airframe I am using is a composite frame consisting of glass fiber and Kevlar.

WIFI band is in the range of 2.4Ghz.
The GNSS band is between 1.1Ghz and 1.6Ghz.
VHF / UHF bands are in the 0.2Ghz to 0.5Ghz range.

The degree of reflectance and absorption depends on many factors, from the distance to the source, frequency, … and the properties of the material itself.
You can refer to more information in these 2 documents :