Unknown purpose Pips, multiple frequencies, April 18, 2012

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Premium Subscriber
Jun 18, 2010
Mojave Desert, California, USA
Last night an unusual signal was reported in IRC. Not an uncommon occurrence ;)

A CW “Pip” was reported on multiple frequencies at the same time first noted about 0247z. These pips were CW bursts about 70 milliseconds long occurring every 3.00 seconds. They were on multiple frequencies all in synchronization and simultaneous transmissions. The frequencies ranged from below 6 MHz to above 12 MHz. The frequency spacing of the signals were clearly defined and changed as the frequency increased, from each 90 kHz at the low end to each 150 kHz at the high end. All frequencies were not found, as the signal terminated while I (and others) was trying to define all the frequencies. All frequencies terminated transmission at the same time (0339z).

They were heard all across the USA, from New York to California, and Washington to Florida.

Video of one frequency as received at my location here:
Oddities Station, CW pips, multiple frequencies, 6720 kHz, April 18, 2012, 0333 UTC - YouTube

The known frequencies were:
5670, 6150, 6240, 6330, 6420, 6720, 6820, 6920, 7020, 7130, 7240, 7460, 7570, 7680, 7800, 7920, 8040, 8160, 8280, 8400, 8530, 8660, 9050, 9190, 9900, 10200, 10350, and 10510 kHz. 28 defined frequencies in my log. Reports were received of it operating above 12 MHz, but the signals stopped when I had only found them up to 10510 kHz and unfortunately I did not note in my log the specific frequencies others were reporting. If you note the pattern of the frequency spacing you see that:
6150 to 6420 was spaced each 90 kHz
6720 to 7020 was spaced each 100 kHz
7020 to 7680 was spaced each 110 kHz
7680 to 8400 was spaced each 120 kHz
8400 to 8660 was spaced each 130 kHz
9050 and 9190 was spaced at 140 kHz
10200 to 10350 was spaced at 150 kHz
10350 to 10510 was spaced at 160 kHz.

Several frequencies that fell on the correct spacing were occupied by SW BC stations, so it is quite possible they were also used by the Pips, but not able to be received at my location.

I have seen these pips in the past, on discrete frequencies, but never realized they were on more than one frequency at a time. I will be watching for them in the future, to see if they always use the same frequencies and what the upper and lower frequency limits might be, as well as if the frequency spacing stays predictable at all times.

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