Radio Frequency Interference
Screen videos are in Windows WMV format and are best played in Windows Media Player.
Click here for a screen video of a "sweeper" in the HF band near 20 MHz. These are thought to be from Over-the-Horizon Radar (OTHR) transmitters. The screen video was taken from SpectraVue running with an RFSpace NetSDR. The sweeper starts in the upper-right corner of the spectrogram and marches across the screen. The audio is from two R75 receivers, one tuned to 19.612 MHz and the other tuned to 20.024 MHz. Both receivers are set to LSB mode. Squeaks are heard as the sweeper passes through the R75 passband. WWV at 20 MHz is clearly seen. Spectrogram center frequency is 20 MHz and displayed bandwidth is 3.0 MHz.
Click here for a screen video of an unusual pattern of HF RFI. The spectrogram center frequency is 20 MHz and displayed bandwidth is 0.5 MHz. The screenshot below shows the same indications just below 20 MHz but with a much wider displayed bandwidth of 3.0 MHz. The same equipment setup as above was used for these recordings.
The screenshot below shows unusual emissions at around 19.1 MHz at 0214 UTC on 10 December 2011.
Click here for a screen video of RFI from a Hewlett Packard 15 inch CRT monitor. A few seconds after the video starts you will see a series of combs about 50 kHz apart on the upper-left side of the spectrogram. The monitor was turned on for 20 seconds and then turned off.