Omega - End of an Epoch

Well, I got a nice recording of Omega's last beeps and also two nights of nice whistlers too, especially this morning, 01 October, between 1100-1330 UT. There was also some intermittant dawn chorus starting at about 1230 UT and going until after 1500 UT - I had not yet caught chorus this summer or fall until now, so I was really glad to hear some chorus even though it was not very strong, and overall a really nice 2 days of whistler listening. Many whistlers this morning (October 01) had echoes too. The whistlers seemed to be generated by fairly nearby lightning - not too local but within 1000 miles.

I have found that indeed (and this is shown in a more recent book on magnetospheric physics), whistlers don't follow exact paths and congugate points AT ALL(!!!). Often, loud whistlers at any locale may be generated by lightning somewhat far away (1000-2000 miles perhaps) while more closeby lightning is NOT generating the loudest whistlers (which may be loud 1000 miles away somewhere ELSE!) Listening since mid-august has given me quite a bit of observation in this regard and countless examples on tape. I mentioned this somewhat subjectively in my VLF STORY I wrote a few years back and I'm even more sure of this. As such, Mexican or Montanan lightning may make LOUD California whistlers, and at the same time California lightning may make for loud whistlers in Colorado or even Kansas (to use a scenario). Certainly, there are times when nearby lightning does make for the loudest whistlers, but this is more infrequent in my observations than the scenario above.

Anyway back to Omega's shutdown--I started recording at 0257 UT 9/30. I made a WWV time check at 0259 on the tape and then let it run with the WR-4b whistler receiver set to high-pass--lots of Omega into the tape recorder. At about 0259:30, Omega D (North Dakota) shut down, leaving Omega-C Hawaii going for about 2-3 more of its cycles. About 0300 (or within a few seconds) and after its two 11.8 kHz beeps, Omega C went off. Both D and C did not shut off abruptly, but did a sort of 'fade-out' over a 1-2 second period. Interestingly, going over the tape in slow motion revealed a third, very weak Omega station running on until a minute or so later - the 10.2 kHz beep was noticed. Probably H-Japan, the next strongest station here in Califirnia usually.

By 0301 UT, all that was left was the Russian Alpha system - short beeps in clusters of three beeps, a pause, then three beeps again in downward frequency steps. Russian Alpha is much weaker and higher up in frequency (up to 14.1 kHz) then Omega was and has a far lower duty-cycle, and so the natural radio band is really MUCH cleaner sounding suddenly! It's also fun to observe Alpha propagation - I guess the strongest one I get is from Siberia (KO - see ALPHA article below)--it is stronger toward sunrise than at any other time of the day by 3-6 dB or so.

The spectrogram above shows Omega Station "D" North Dakota, and Omega Station "C" Oahu, Hawaii with their last beeps. Recorded on my van-based WR- 4b VLF receiver with 2 meter whip antenna up 3 meters high. The tape was made on a Marantz PMD-212 with cromium tape and the WR-4b in high-pass/emphasis mode.

The tape was copied into a sound file at 44.1 kHz/16 bit. Then it was FFT filtered in Coolwave 1.5 and 9 to 14 kHz was emphasised by 15 dB. Then I ran a spectrogram on it and then edited the spectrogram adding the labels.

Stations:

1) KO - Komosomolskamur (north of Khaborovsk), 50N/137E

2) NO - Novosibirsk (master station, Central Russia), 54N/83E

3) KR - Krasnodar (Black Sea), 45N/38E

Time Schedule: Cycle period 3.6 seconds, 6 time slots at 0.4 sec. duration, 0.2 sec. spacing

Estimated radiated power in wattage 50 kW to 100 kW

Beukers Laboratories, Inc.: VLF and LF for Navigation, Summer 1974, Vol. 21, No. 2

Kerckhoff, Manfred; Bremen, Germany - narrow-band and wide-band receiving observations (Manfred also supplied the article above)

McGreevy, Stephen P.; Lone Pine, California - In-field observations with wide-band receivers