Hi all, I’m planning a project to detect and geolocate signals in the L-band (roughly 1100 to 1600 MHz) using a KrakenSDR mounted on a mid-sized fixed-wing UAV.
I’m currently looking at the SPK-6E Helical Triband Antenna, weight and aerodynamics are a big concern for this airframe.
Is there any fundamental reason why these antennas wouldn’t work well for direction finding in this band?
Has anyone done something similar on a UAV and can share suggestions for antennas that worked for them (or models to avoid)?
Also, to clarify on the hardware setup: Other options I am considering are active antennas, to use them correctly, do I just need to enable the Bias-T power for each channel in the software, or is there anything else I’m missing?
One concern with a UAV is that Kraken expects the platform to move in the direction of antenna 0 on the array. So it expects it to move more like a vehicle or airplane, which is contrained to move forwards only. So you’ll need to fly the UAV in the forward orientation always to get proper data.
Active antennas could work - you’d just need to activate the bias tee (assuming the ative circuitry is deisnged for 3-5V input), but they have a higher chance of introducing phase errors, which could be a big deal in the L-band.
Great, thank you for the info. The UAV I refer to is a fixed wing VTOL, so I can mostly ensure that antenna 0 is at the ‘front‘.
As for the antennae, I’ll likely buy a set of passive too and compare bearing results. I’m now more concerned about what the effect of the UAV banking will have as I have no easy way to gimbal the antenna rig…
The UAV I am using is very detuned so the bank maneuvers will be very gentle, but they will always occur at the end of each ‘mapping run‘ or in high wind, thoughts on the effect it will have? I could consider pausing the data collection while it is in a bank past x degrees.
I suppose the ideal would be to gimbal the antenna rig, or to be able to feed in attitude information, but that could get complicated for the calculations I imagine.
Yeah I thought as much. An amount of banking is guaranteed due to the nature of fixed wing flight, so I think just pausing the data collection when past a certain angle will be the easiest for now, gimbal later.
However I don’t see an obvious way to ‘pause‘ and ‘continue‘ via the API, just to start and stop. I suppose I could hijack the logic around the ‘pause data collection while stationary‘?
Also I don’t see any obvious documentation around the API running in krakensdr_doa, I’m happy to work it out from the source code, but before I do that is there a guide somewhere I am missing?
For context, I will be creating a python script that runs on the Pi as a ‘companion script‘, which will be connected to the UAV, occasionally pausing and unpausing the data collection, and continually monitoring the status of the KrakenSDR.
There’s no real API for krakensdr_doa, as it is simply an output system.
It outputs the raw DOA data, and it is up to downstream programs like the App to do something with the data.
You can control krakensdr_doa settings by having a downstream program change values in the settings.json file. The code will automatically pick up any changes and apply them.