SDR for Direction Finding

I need a solution more than an answer.

I am in need of a quick and easy way to find a signal source (think foxhunting) but I need to make it pretty much dummy-proof.

Looking primarily at 121.5Mhz and 243.0Mhz

I would like to use a Raspberry pi with a mini tft screen. Pseudo-doppler or 4 seperate antennas, either one. I would like to build a handheld and a vehicle mounted system

Thanks!
Tony

https://archive.org/details/RashawkAocChallenge

I was actually hoping to see something that uses 4 RTL-SDR's (and switch totally in software) rather than the traditional hardware antenna switching matrix. The RTL's a cheap enough. It might just be a matter of small USB hub. But there would need to be software developed, and that is always my weak area.

kb9mwr said:

https://archive.org/details/RashawkAocChallenge

I was actually hoping to see something that uses 4 RTL-SDR's (and switch totally in software) rather than the traditional hardware antenna switching matrix.

Click to expand...

That's not going to work very well because of PLL phase jitter and the difficulty of syncing multiple PLLs for the 4 SDRs. It also requires processing 4x as much data with zero benefit. The switched antenna array is used because it is the best tool for the job.

https://www.rtl-sdr.com/pseudo-doppler-direction-finding-with-a-hackrf-and-opera-cake/

https://www.rtl-sdr.com/more-information-on-the-android-rtl-sdr-direction-finding-implementation/

https://www.rtl-sdr.com/gr-con17-ta...nding-with-rtl-sdrs-on-android-and-much-more/

https://www.rtl-sdr.com/tracking-wildlife-with-tdoa-direction-finding-and-rtl-sdr-dongles/

https://www.rtl-sdr.com/a-multi-cha...-for-passive-radardirection-finding-and-more/

EDIT: A link to all RDF tagged articles on rtl-sdr: https://www.rtl-sdr.com/tag/radio-direction-finding/

GLOBAL TSCM GROUP, INC. - Radio DF DDF2020T

You can use any SDR as the FM receiver.

jonwienke said:

GLOBAL TSCM GROUP, INC. - Radio DF DDF2020T

You can use any SDR as the FM receiver.

Click to expand...

Page says out of stock.

jonwienke said:

That's not going to work very well because of PLL phase jitter and the difficulty of syncing multiple PLLs for the 4 SDRs. It also requires processing 4x as much data with zero benefit. The switched antenna array is used because it is the best tool for the job.

Click to expand...

I guess I never thought of that. Thanks for the info.

For the OP, here are some more common dopplers units that I have built/used:
http://www.silcom.com/~pelican2/PicoDopp/PICODOPP.htm

DDF2020T

now sold as MFJ 5005
https://www.mfjenterprises.com/Product.php?productid=MFJ-5005
demo
https://www.youtube.com/watch?v=ePVnTUU0M1c

I too am interested int doing RF DF with an SDR

I am looking for something I can mount in a fixed wing SUAS, to track wildlife collars for research.
I was thinking an SDR with a raspberry Pi or Intel Watson board computer that would be a payload in a small fixed wing or hybrid s/UAS. It would have to accept GPS location data from a Pixhawk, (which I am sure it puts out in some form of serial data stream), and would scan a set of frequencies and derive bearings for each at multiple locations along a set path, allowing triangulation.

I think you would be creating something that would be so complex that it would only work on the ground as you would be too busy to fly the plane. As mentioned, a doppler with switched antenna array is simple and effective needing only a receiver and its audio output.

I have a DDF2020T and its the best thing you can get for the money and interfaces to GPS and will give basic headings to the source signal or will also triangulate on a map with a laptop running Google Earth.

melyash said:

I am looking for something I can mount in a fixed wing SUAS, to track wildlife collars for research.
I was thinking an SDR with a raspberry Pi or Intel Watson board computer that would be a payload in a small fixed wing or hybrid s/UAS. It would have to accept GPS location data from a Pixhawk, (which I am sure it puts out in some form of serial data stream), and would scan a set of frequencies and derive bearings for each at multiple locations along a set path, allowing triangulation.

Click to expand...

I think you misunderstand or I was not clear

I am looking at a system small enough to be used on a under 10lb fixed wing RC Aircraft with a Pixhawk flight controller that has a GPS Build in. The Item you show is way too big for this application, is manually operated and takes a Laptop to plot in real time, I don't want real time, I want it recorded.

I am looking for something that runs a single SDR dongle, and utilizes as you say "antenna switching" run by something the size of a pack of smokes. I want the computer to run the SDR, tune the freq, and take/record the bearings cross correlated to the current location supplied via the Pixhawk autopilot.

I don't need said computer to fly the sUAS, with the pixhawk it flies itself with GPS accuracy to each and every way-point and executes whatever maneuver I need done, be that a circle or if I am flying a hybrid like a Firefly 6 I could execute a hover, (though at great cost to battery life and range).

I know folks out there are using Raspberry Pi to drive SDR, I am looking for a way to enhance that capability via the Pi 3 to gather the data we need. I don't need the raw data, I just need the bearing from that location at that time for a set of maybe 30 frequencies.

Hope I made that a little clearer. Thanks for the reply and look forward to yours.

M

You were quite clear; I had no trouble figuring out what you wanted. Problem is, what you want probably does not yet exist and someone has to create it. Also, I suspect that given how large storage capacities are these days, it might make sense to create a device that just records GPS data and raw SDR I/Q data for later analysis, as this could greatly reduce the amount of processing power and battery power required for the task.

Aah, there are two separate posts here and two different wants. Something to consider for the RC aircraft is once you have switched antenna array with doppler interface to a radio, the end result is usually an audio tone that designates a phase angle or direction. You can then send that audio from a simple DF receiver or SDR dongle to a small transmitter and broadcast that back to the ground to feed the real time heading display.