The Pip

Yes and no. At short range there are devices like doppler direction finders [1] that are remarkably affordable and can make quick work out of locating some signals. This is for signals that arrive over a straightforward single path, though.

These shortwave transmissions do not have that convenient property. HF transmissions at high powers will duct through at the atmosphere, bounce off of the geography, and in general propagate in all sorts of strange ways that result in them arriving simultaneously via multiple paths to any given position. This means that standard direction finding methods will not be very effective. Because of the long wavelengths of these signals, very large antennas are also required to even attempt direction finding, usually circular structures hundreds to thousands of feet across, a common type being a Wullenweber antenna [2].

Very few organizations possess substantial HF direction-finding capability. The FCC has monitoring stations that can do this in many cases, and they use it for enforcement purposes, I believe primarily when public safety users report jamming problems. As a fun fact, one of these monitoring stations is located in Livermore, although I believe that station is remote-control and has no staff. The FCC is not very public about how these monitoring stations operate, I believe their positioning is based on differential analysis of the reports from all of their 14 stations across the country though. Most of what I know about them is from a rather outdated source [3] although their locations are listed in 47 CFR s. 0.121 since they are afforded special protections against interference.

On the international scale, if you looked at the Wikipedia article on Wullenwebers you may have noted that that was originally a code name. Various militaries and intelligence agencies operate large direction finding stations, but because of the challenges of locating HF signals even these large facilities have limited efficacy. Nonetheless, I assume that the NSA has confirmed transmitter locations for these signals (probably by a combination of direction-finding and good old fashioned on the ground tradecraft) and has simply chosen not to share.

[1] http://kn2c.us/ [2] https://en.wikipedia.org/wiki/Wullenweber [3] http://blackradios.terryo.org/documents/publications/e-FCC.p...

I suppose the most likely scenario is that these are part of some long-running experiment or are used for some fairly mundane purpose like radio navigation or calibration. My first thought was that it might be for a military or intelligence fail-deadly system (e.g. to mount an attack, perform subterfuge, deploy suitcase nukes across U.S. cities, or check in with a handler).

"The Duga systems were extremely powerful, over 10 MW in some cases, and broadcast in the shortwave radio bands. They appeared without warning, sounding like a sharp, repetitive tapping noise at 10 Hz, which led to it being nicknamed by shortwave listeners the Russian Woodpecker."

https://en.wikipedia.org/wiki/Duga_radar

http://www.brogers.dsl.pipex.com/Wpecker5.html

They have a nice dossier on it as well:

http://priyom.org/media/56944/the_pip_dossier.pdf

That's going to be terribly off-topic, sorry for that, but I have to: I hoped the article was about "Pip pan" from amazing kids book "Kastrullresan" ("The Saucepan Journey" in English) by Edith Unnerstad.

If anyone of you have kids (6+) don't miss that one (and others from that author too)!