WSPR setup - RPi - no filter

Don't do this at home... it may brick your Pi

First experimental setup. Just to see how it works.
No band filter. So a lot of harmonics... and QRM.

No buffering on GPIO4 pin, so it may brick the Pi. These GPIO pins work on 3V3 and are directly extracted from the Broadcom BCM chip. This is a so called  SOC (System On a Chip) .

For this experiment I used a Raspberry Pi 2 model B. WSPR signal set to 40m.

    WSPR Pi No filter EndFed setup
    Experimental setup. Antenna End-Fed for 10/20/40/80m multi band


      WSDPR Tx - Rx antenna setup
      WSDPR Tx - Rx antenna setup

      Calculating output power

      Signal measured on the Raspberry Pi pins (7, 9). Loaded with End-Fed antenna 50Ω.

      WSPR 40m EndFed Scope signal
      WSPR 40m EndFed Scope signal

      Scale 1V/div. The signal is about 2V top-top = 0.707V RMS.

      So the output power is about (0.7V * 0.7V) / 50Ω = 20 mW.

      Signal strength

      As the Tx and Rx antennas are in parallel and far to close ... the signal is booming ;-)
      And ... producing a lot of QRM... ;-(

      WSPR 40m EndFed Rx signal
      WSPR signal at close range

      WSPR signal report

      After five minutes and two Tx cycles the signal is reported !!

      WSPR 40m RA9ROB after two Tx cycles
      WSPR 40m RA9ROB after two Tx cycles (WSPR world watch by G4SWY Android app)

      And on over a longer (one hour) period.

      WSPR 40m map 20171027
      WSPR 40m map 20171027

      Not bad for 20mW on 40m at daytime...

      Next step ... adding buffering for GPIO4 and a low pass or band filter.

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