Yes, these are the signals that Hugh Stegman called the “Snake Charmer Flute” or the “Magic Flute” in the August 2013 Monitoring Times. Others have called it “Pipes of Pain” and “Pipes of Pan”. I typically call it “Drifty MFSK”, or “Pipes”, in my notes, or sometimes the “HEB/WLO/WPG Oddness”.
This set of signals were originally associated with HEB in Europe and WLO in Alabama. Later it was determined that the majority of these frequencies were licensed to WPG, Indiana. I have bearing cuts on the signals at different times that support all three possible locations, so not much help there
These signals, or ones related to them and on the same frequency set, showed up in my logs in Nov of 2012, however others had been watching them a few months by that time. Between that time and now several waveforms have been used, the stepped MFSK is the currently used most common, however 22819 kHz most frequently shows what appears at first glance to be a swept signal, but is most often not actually swept.
The frequencies I have been able to tie together are (USB, to yield roughly the same audio frequency excursion for each signal, the actual “proper” tuned numbers are probably +/- 100 Hz):
14756
16926.5
16929
17299
17383
19281.5
22483.5
22819
The signals are often up on more than one frequency at a time, with 14756, 19626.5, and 17299 kHz being the most common. Sometimes the audio on multiple frequencies are identical and in sync, other times it is unique audio on each freq and they are not in sync. I generally find one or more of these frequencies in use every day.
This image shows an example of 4 of the frequencies in sync with the Drifty MFSK. 16926.5, 16929, 17299, and 17383 kHz are all shown here. I have miss tuned each to result in a different audio frequency, so that the signal from each did not end up on top of the others.
If you build a spectrum with max hold of the Drifty MFSK signal you will find that most often it contains 32 steps, on well defined frequencies. While it wanders around without apparent pattern it ends up hitting all of these freqs over time. The following image is a 15 minute max hold, showing each frequency hit in that 15 minutes, all frequencies were hit many times in that time.
As I said, there is also what appears to be a swept signal that sometimes appears on all of these frequencies. Very occasionally it is actually swept, the vast majority of the time it is simply stepped like the Drifty MFSK, but in sequence, low to high, and quickly, to give the illusion of a sweep to the eye and ear.
The “swept” signal looks like this on a waterfall:
But as I said, most often when seen like this it is not truly swept, but rather it is stepped quickly. The same “swept” signal in the image above, when doing an audio histogram and a max hold, appears to have the same 32 steps that the drifty MFSK most often has. The below is a 15 minute max hold of the swept signal above, ignore the note about the 4 dB of ripple, that turned out to be an artifact of the receiver used. Note the sweep covers the same bandwidth (allowing for tuning errors) as the Drifty MFSK signal, and has the same number of steps.
This 32 step Drifty MFSK and Swept signal are not the only ones that might be seen on these frequencies, but they are currently the most commonly seen. There is also a 64 step version of each (not seen in months now), and one of the swept signals is actually swept and not stepped. There are also some more “data like” modes with faster FSKs and sometimes PSK components.
In my opinion few, if any, of the transmissions I have seen actually are data, I don't know what it is, but it probably ain't data. The Swept signal is almost certainly no data, and is sent for hours at a time. The Drifty MFSK does not seem to have any structure to it other than the 32 freqs it will hit. It is hard to believe that these signals are on the air every day, and do not contain usable data, but it really does seem that way to me. Just an opinion though, if someone finds something repeatable and convincing I will be glad to change my opinion.
T!
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