I didn't use my homebrew AT5 clone very often on 80m, but on one occasion when I did, my CW QSO was interrupted by an S9 station purporting to be "GPO monitoring station Gxx" ordering me to go QRT.
I imagine it was because it's not just the frequency that gets doubled on 80m, so does the chirp!
I fully expected a visit, or at least a letter, but neither came.
It's been over 50 years now, do you think it's safe to retrieve the TX from under the bed