I’m mostly interested in direction finding of HF/shortwave signals. KrakenSDR doesn’t support frequencies below 24 MHz but my question is if it would be possible with upconverters.
I’m sure that 5 separate upconverters will not work, but a set of 5 coherent upconverters might do. It would require 5 mixers with a shared local oscillator. Might not be very hard to build, but before spending money on any serious attempts, what is your opinion, is there a chance to make it work?
It would also require suitable antennas that are located far enough from each other, but these are not big obstacles.
Yes a coherent upconverter could work.
But really I think the upconverter is not the challenge here. The challenge is creating a circle of HF antennas with a huge radius, and carefully managing the cabling.
At 24 MHz you’d need a radius of about 2 - 5m. At 12 MHz 4- 10m. At 6 MHz 9 - 20m, and 3 MHz 17 - 42m. If you have a large field though, then it could work.
Secondly because of the long wavelength HF might not be received directly from the source. If you’re not line of site with the transmitter, then It’s likely that it would be bouncing off the ionosphere in the sky, and appear to be coming from perhaps an odd direction.
TBH, I think the TDoA method of direction finding makes a lot more sense for HF. Then you only need a single antenna at distributed stations.