On a whim I brought out my SDR tonight for a bit of low frequency exploration. I found a wonderfully odd signal at 157 kHz and decided to look it up on sigidwiki - only to discover that the page was intensely unstable. Now, an hour later I saw this post on the front page of HN, Fermi’s exclusion principle must work for hobbies as well it seems.
The website appears to be having trouble. Here is a description
This wiki is intended to help identify radio signals through example sounds and waterfall images. Most signals are received and recorded using a software defined radio such as the RTL-SDR, Airspy, SDRPlay, HackRF, BladeRF, Funcube Dongle, USRP or others.
Such a perfect page for nerd sniping. Too bad that I couldn't find a signal that I heard in the 90s on an FM radio and have never been able to identify. From what I can remember, I didn't hear it on other FM radios, which makes it even more mysterious. In frequency ranges where there was no radio station transmission, I didn't just hear the typical static noise but also some strangely melodic tones changing frequency multiple times a second. The tones weren't very pure like most examples on the page, but with lots of strange harmonics / distortion.
It could be heard just at the edge of the normal FM range. Most FM radios cut off before you could reach the frequency, however.
The signal was used for something like an early pager service. The early receivers were rather large, making them only suitable for cars. The service was also very expensive, so pretty much only businesses used it for management or sales people.
Yes, I think that's it! It certainly was more distorted than in this capture but it matches the "melody" that I remember. Mystery solved 25 years later. Thanks :)
