HFU HF Underground
Loggings => HF Mystery Signals => Topic started by: Vizero on November 05, 2026, 0928 UTC
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Hi everyone!
I'm fairly new to HF monitoring, so please bear with me.
I've been observing an unusual signal around 26.150 MHz using the University of Twente WebSDR.
The signal consists of short bursts, apparently emitted in pairs. The intervals between bursts are highly irregular, and the transmission can disappear completely for several minutes before returning.
I've also noticed two distinct received signal-strength states, with seemingly instantaneous transitions between them. These changes appear independent of the frequency shifts I've observed.
The audio sounds automated, with no intelligible voice or obvious data transmission that I can identify.
The signal has been observed repeatedly in the same frequency area.
I noticed that 26.150 MHz appears in Dutch RDI documentation concerning paging frequencies. I don't know whether this is relevant, but I thought it was worth mentioning.
Could this be some kind of automated signalling system, equipment testing, or possibly a military-related transmission?
I'm not claiming any particular origin; I'm simply trying to identify it.
Any ideas or suggestions would be greatly appreciated!
Thanks!
Frequency : 26150.00 / 26150.95 kHz
Hour : ~06:30 UTC
Mode : AM/CW
Video : https://youtu.be/Mkhga-DzBv4?feature=shared