KV4PC

TDOA DF: UI Idea for quick location determination

Let me preface this by saying I dont have the IT or programming skills to implement what follows. But I do have the communications experience to know what follows is do-able with a dense enough sensor network.

Firstly, I will say I experimentally went through the process defined here: https://www.rtl-sdr.com/kiwisdr-tdoa-direction-finding-now-freely-available-for-public-use/ in order to try to determine the source of some intentional QRM on the 40m band. I found the process cumbersome in extreme, and the target signals were gone after I spent 30 odd minutes manually hunting for sites that could detect them.

Here is how I would lay it out.

1) I would capture the location of the user. Simply ask them or do a locate using the usual internet libraries for determination of approximate geographical coordinates. This is based on the simple assumption that a signal of interest may be received at the users location.

2) I would accept a frequency from the user.

3) Using the frequency provided, the user's location, and the Solar Flux Index of the moment, I would do a VOACAP calculation to get high probability propagation bands from the user in order to automatically select some likely KiwiSDR receivers, TDOA-capable preferred, but for the first pass, any receivers in the high probability band will do. Alternatively, the user can select 1 receiver where the signal is present in lieu of their own location if they are hunting a signal that is not available at their location. Do VOACAP analysis from the selected receiver.

4) I would generate a list of 5 or 10 receivers showing a 1 inch high waterfall maybe 5 kHz wide centered on the frequency selected. Preferentially select receivers that are a single-hop from the user's location or initial receiver. I would show them muted by default, and allow the user to select receivers by listening to them one at a time independently based on whether the signal is present or absent in each (visualized modulation will also suffice). When some receivers are locked in, if enough TDOA receivers are present in the selection, go do the rest of the TDOA calculation.

5) If not, repeat the VOACAP analysis from receivers that do detect the signal to provide further replacement receivers in the select list for any receivers that do not. At this level, there are probably enough propagation rings to select only TDOA capable receivers to add to the list. The user does another pass through the list identifying good receivers. Again, if enough are selected, do TDOA.

6) Repeat 5 until there are enough receivers, dropping single hop limitation, or until it is obvious that there arent enough receivers to do a successful computation.

7) A receive array configuration developed as described above could be saved for future use to bring on line instantly in case favorable propagation appears at a later date, or to repeatedly police troublesome frequencies and/or emitters. Having a partial solution ready to go might significantly improve the efficiency.

8) The manual selection process could be automated to a degree by use of correlation. A user selects the best example of the target signal, and correlation with other receivers could autoselect receivers that are good and then go through the total process of selecting further receivers.

A few ideas that might improve things from an operator's perspective...

73;

Bob KV4PC