Pat Spencer

Our local Amateur Radio club is building a Radio Direction Finding TDOA (Time Difference of Arrival) detector that has LED's to indicate the direction (Left or right) of the fox.  Here are the build instructions.   (Note: this project was originally presented by NZ1J.  See his video:   https://www.youtube.com/watch?v=mNqUKYkifOo&t=68s   ) Here is the completed project: We start with the schematic:   Note that you either install PIN Diode pairs s D3 and D2, or Diodes pair D1 and D4.   The difference between these is the packaging.  If you are ok with Surface mount, then install D1/D4.  If you want discrete components use D3/D2. Next is the PCB.   The PCB can be ordered using the GRBR files available from the author.  The BOM for the electronic parts is as such: Doppler Direction Finder Bill of Materials   11/12/2021        Qty Part Digi-key Part Number References 1 PIC Pocessor PIC16F18324-I/P-ND U1 1 14 Pin Socket ED3114-ND U1 1 78L05 497-7268-ND U2

This article describes a few projects that I built from plans for Amateur Radio Fox Hunting. Basically, the hobby/sport is for someone to hide a few low power "Foxes", which are small transmitters that beep or send Morse Code, and then have a bunch of HAM's try to find them. The first project that I built was a Yagi Antenna (Directional receiver) and a 4MHZ Offset Attenuator.  The attenuator is needed when you get close to the fox and you need to reduce the power of the received signal.  I struggled with this setup because, on my first 2 fox hunts, there was too much reflection and multi-path interference.  This causes false direction detection and if you are not mentally prepared for this, you want to throw all of your equipment into a garbage can and take up a different hobby.   There are some truly strange individuals who find this frustration fun and enjoy making other people suffer, but I will leave that discussion for another day.  Anyway, in one particularly frustr