I do not need to know the exact location, just the general direction of the jam. (Eg, north, south-east, etc)
So if now i have gotten a mini-SDR, what do i have to do in order to detect the Jam?
Does my method of detecting the jam sounds correct? (Using RSSI and SNR from the mini-SDR's calculations)
And also, how do i detect the general direction of the jam?
What's your skill level? Here are two answers.
The advanced method:
Build an antenna switching system using FET analog muliplexers. and get a set of N magnetic mount antennae. with a triangle of strings connecting them to a common wooden strip. The wooden strip will be your directional reference. The strings are so you can repeatably position them in the same configuration. Use nylon monofilament fish line to get minimum stretch.
Generate a long random sequence either using a true random number generator or the Mersenne Twiser PRNG. The scale the numbers to the range p to q where p is the minimum number of clock ticks between ADC samples. I don't know what q should be. I'd start with 256 times p as an initial choice. Program the multiplexer to select each antenna in turn. Set a timer to go off at the Jth clock tick in your sequence. When the timer goes off, collect a sample of he signal output from the receiver using the ADC and reset the timer to the next interval.
Divide the data into N parts, one for each antenna. This is the y for each antenna. Setup N instances of Ax=y where the A matrix where the Jth row is a Fourier series sampled at the Jth time. You'll need to integrate the delay intervals. Seek an L1 solution for x using the simplex solver in the GLPK package. Because you're using the same random intervals, you can precompute the A matrix and store it. You will solve Ax=y N times for each directional fix.
Evaluate the non-zero coefficients in x at a regular series of sample times which meets Nyquist criteria. Fourier transform and and compute the phase delays for all the channels. Convert the phase delays to direction relative to your reference stick. The farther apart the antennae, the better your directional location. The modulus of the Fourier transform is the waterfall row in the second method.
What I've described is what I call a "sparse L1 pursuit". It also goes by the term "compressive sensing" and is absolute state of the art. If you implement this you have gained a major employment credential, especially with the 3 letter agencies. If it's not been done it's a PhD level project at a major university. Though to get a degree you will have to understand the math rather than just how to implement it. Show it to the faculty and you'll get a full ride through school.
An LPC4370 runs at 204 MHz and has a 12 bit 80 MS/S ADC. In the form of an LPC-Link2 programmer they are available from Digikey for $20 each. You'll need two, one for the MCU and one to program it.
The basic method:
Build a multi element Yagii on a circular piece of PCB so you can rotate it rapidly without vibration.. Rotate the Yaggi and note the direction with the strongest signal. Use a waterfall spectrum display with a reference marker for each rotation. A jammer will have a distinctive spectral signature which will repeat once per revolution.
There are intermediate level approaches. I'll let you investigate those.
Have Fun!
Reg