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"Blinky" TDOA RDF Detector

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
      • 2 2N3904 2156-2N3904-FS-ND Q1, Q2
      • 2 PIN Diode 568-1922-1-ND D1, D4
      • 4 Green LED C503B-GCN-CY0C0792CT-ND D5, D6, D8, D9
      • 1 Red LED C503B-RCN-CW0Z0AA1-ND D7
      • 4 1k Resistor 1.0KQBK-ND R3, R6, R13, R17
      • 8 4.7k Resistor 4.7KQBK-ND R2, R5, R10, R11, R12, R14, R15, R16
      • 2 470k Resistor 470KQBK-ND R1, R4
      • 1 220pF Cap 399-14053-1-ND C6
      • 1 0.01uF Cap 399-9772-ND C5
      • 3 0.1uF Cap 399-4264-ND C1, C3, C4
      • 1 10uF Cap 493-17435-1-ND C2
      • 1 1uH Inductor 78F 1R0K-TR-RCCT-ND L1
      • 1 Slide Switch 450301014042-ND SW1
      • 1 9V Battery Clip 36-232-ND TP+
      Assembly Overview:

      Radio Frame parts:




       

      Comments

      1. RobMay 24, 2023 at 10:43 AM

        how is the coil connected to the board, do you have to solder a wire to each end of the coiled wire?

        ReplyDelete
        Replies
        1. AeroBatGeekMay 24, 2023 at 11:43 AM

          Yes, The simplest way is to solder the coiled wire to the PCB. If you wanted to add a jack or terminal strip you could.

          Delete
      2. AdamJanuary 30, 2024 at 2:17 PM

        Good idea, congratulations. In my case, there are always several signal sources (GSM, high-power TV and others), so I must to expand the antennas to one frequency :(
        Is there a chance for the system to work at 1.6 GHz? Theoretically, this is possible for any frequency. Has anyone tested at high frequency?
        73' de SP4IZK

        ReplyDelete
        Replies
        1. AeroBatGeekJanuary 31, 2024 at 9:36 AM

          This device was designed by NZ1J. He could perhaps help you with this question. For me, I would build a simple TDOA (without the blinking lights) which would work at any frequency. The Simple TDOA that I am thinking of is just a 555 timer that switches the antenna using pin diodes. It is up to you to attach a radio and process the signal. This works great and I find it much easier to use.
          See https://aerobatgeek2.blogspot.com/2022/03/radio-direction-finding-tdoa.html and http://www.146970.com/PDFs/TDOA%20Phasenpeiler.pdf .
          .

          Delete
      3. AdamFebruary 1, 2024 at 9:03 AM

        Thank you for the quick reply.
        The amplifier in this scheme amplifies low-frequency signals. TRX is used to obtain the signal. Have there been any attempts to use a simple signal detector (Ge diode + capacitor)? Then TRX is not needed. If there is only one source nearby.
        There remains the problem of eliminating other sources. SAW filters are still expensive :(
        73' de SP4IZK

        ReplyDelete

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