Many thanks to SWLing Post contributor, Bill Patalon, who shares a link to the following article on Extreme Tech:
Last Tuesday at 1744 UTC (1:44 PM EDT) UR3RM, a ham radio station in Ukraine blindly sent out a message on 7040.138 kHz. It was automated. It was text. Maybe someone would hear it. Maybe not.
The “maybe not” part is easy to understand because UR3RM’s transmitter was putting out one milliwatt, .01 watts. To put that in perspective, a Class 2 Bluetooth transmitter, the ones good for around 30 feet, run 2.5 milliwatts.
UR3RM was using a mode called WSPR for Weak Signal Propagation Reporting. Unlike most of ham radio, this is a one-way mode. Not only is there little expectation anyone will be listening, but there’s even less that the signal would make it back. Radio propagation isn’t always a two-way path.
WSPR’s biggest selling point is you can do it on the cheap. It’s easy to set yourself up for not much more than $100 and often a whole lot less. And, though a ham radio license is needed to transmit, anyone can put up a receiver. And the US ham license test is multiple-choice, all published and online.[…]
Post Readers: How many here have received and/or transmitted using WSPR? Please comment!