If you are ever listening on HF and hear a very fast "Zwoop" that can be startling, it might just be a chirpsounder, an electronic device that evaluates ionospheric conditions. Chirpsounder signals look like vertical lines going across the waterfall screen. Pic below.
Have heard these up as far as the CB band, but you'll find them scattered around the HF band, some move slow, others are lightning fast.
Sponge
Have heard these up as far as the CB band, but you'll find them scattered around the HF band, some move slow, others are lightning fast.
Sponge
