dipole_antenna_board.pdf

PCB with two BNC connectors and two PIN diodes connected with a resistor for a DC path.

Adobe Portable Document Format - 10.39 kB - 07/31/2019 at 04:40

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ddf_v_04.pdf

Controller board schematic with Teensy, jacks and rotary encoders. All filtering and heading measurement is via DSP unlike the Roanoke systems using zero crossing measurement.

Adobe Portable Document Format - 102.96 kB - 07/14/2019 at 03:53

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DDF_DSP_display_0.ino

This contains computation of the Doppler tone magnitude and phase and first harmonic magnitude. A crude "quality" metric is computed and displayed on the neopixel.

ino - 7.50 kB - 06/13/2019 at 15:48

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ddf_HW_v0.2.pdf

Updated hardware with overkill analog band-pass filter from the 1999 WA2EBY article. I thought it would be an interesting test to see if system performance could be improved with additional filtering.

Adobe Portable Document Format - 125.27 kB - 04/15/2019 at 07:15

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antenna_switcher.png

Selects an antennas based on input at P1. By selecting one of the four antennas in a rotating fashion a pseudo-Doppler tone is added to the received signal. The Doppler frequency is set by the rotation rate.

Portable Network Graphics (PNG) - 25.93 kB - 02/19/2019 at 21:42

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switched_antenna_board.png

Antenna board with sma input connector and BNC antenna connector. Diode D1 conducts VHF when biased on with DC.

Portable Network Graphics (PNG) - 41.03 kB - 06/28/2019 at 04:45

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display options.jpg

The VFD is beautiful but I worry about washing out under sunlight. E-ink is really slow and not a good fit. Probably go with 4 digit LED or LCD. Any tips for getting better LED pix? I turned the ISO to lowest setting to get this.

JPEG Image - 2.93 MB - 04/07/2019 at 22:39

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DDF Scope Display.mp4

The upper trace is one of the antenna bias drivers turning on one of four antennas. The lower trace is the demodulated Doppler audio tone DSP filtered. The comparator output is overlaid showing Doppler zero crossing. You can see the lower signals wobbling around which I believe is me interacting with the RF reflections.

This is a terrible test lash-up and all of my signals are noisy. Must clean up.

MPEG-4 Video - 41.31 MB - 03/03/2019 at 23:57

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