NOAA 15 made a pass over my QTH this morning with a maximum elevation of 35 degrees.
Not ideal but I was surprised to start receiving the satellite’s signal on the very minute of its rise above the horizon. At this point, it was being received 2.5 kHz above the onboard transmit freq of 137.620 MHz due to Doppler. Total shift during the pass was 5.7 kHz.
The receiver was a FunCube Dongle Pro+ using the homebrew QFH antenna that I mounted to my chimney yesterday. Software was SDR#. Compensating for Doppler was a simple matter of setting SDR#‘s tune steps to 100Hz and then clicking periodically to keep the signal centered in the 40 kHz bandwidth. With a slightly wider BW, I doubt any compensation would be needed at all. SDR# allows the recording of both an audio file and the I/Q data – all I needed here was an audio file, which was recorded at a 48 kHz sample rate. After the pass I reduced the sample rate to 11025 Hz in Audacity for compatibility with the WXtoIMG software that converted the audio file to the image below.
A map overlay is also provided based on home QTH input during the software’s set-up. I still have a bit to learn about all this but am happy with initial results of such a small receiver, a $6 antenna and a lower-than-ideal pass. One thing I need to find out is whether or not I can configure the WXtoIMG software to accept the audio directly from the FCD+ during a pass and then spit out an image afterward without me having to manually go through the Audacity detour.