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So go forth and attempt to tame the black magic of RF! Some other DIY antennas we covered recently include a hybrid helical for using a geosynchronous ham radio repeater, an off-center dipole, and a directional antenna made from coat hangers. Although the tests weren’t perfect, it is impressive how much practical data was able to gather with low-cost hardware. He also discovered that the inverted-L appeared to be “deaf” in one particular direction. Where the same transmission was received by both antennas, the signal-to-noise ratios was compared.įrom all this data, was able to learn that the inverted-L antenna performed better than the T3FD antenna on three of the four frequency bands that were tested. Using the recorded data and Python he compared the number of received transmissions, the distance, and the heading to the transmitters, using the location information included in many FT8 transmissions. Between the two antenna setups, more than 100,000 FT8 transmissions were logged. also modified GQRX and WSJT-X to give him all the remote control features he needed to automatically change frequencies. GQRX, a software receiver, converted the signals to audio, which was then piped into WSJT-X for demodulation.ĭata for each received FT8 transmission was recorded to a log file. These were set up to receive FT8 transmissions, a popular digital ham radio mode, which allowed to automate data collection completely. first gathered performance data for each over few days, connected to separate PCs with RTL-SDRs via low-pass filters. The two antennas in question was a single band inverted-L and smaller broadband T3FD antenna. Using cheap RTL-SDR dongles and Python, was able to compare the performance of two shortwave/HF antennas, and documented the entire process. For practical applications, especially when building antennas, comparing performance in relative terms is more practical. Measuring the performance of antennas in absolute terms that can involve a lot of expensive equipment and specialized facilities.
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