Sunday, March 01, 2009

The Great WebSDR Tour - Part 3

3589.7 (Dial, listed 3588.0)
This is an output frequency for an interesting European data network called PSKmail. Those who have used "packet" mailboxes get the concept, except that this one is in PSK250. This is a much faster, and much wider, version of the PSK31 that everyone's probably heard on 14070 kHz. It works better than HF packet, and you don't need a US $1500 modem to receive it, like you do for Pactor-II and III. The shareware MultiPSK program does it just fine, even over the grungy webSDR.

The station on this frequency identifies as DK4XI-8. It seems to dump large files of amateur callsigns and coordinates on the hour. I don't know if these are APRS or obtained in other ways. Many of the stations are afloat. At hour +15, it dumps an even larger file of Deutscher Wetterdienst WX and NAVTEX Hamburg, both in German. This contains weather observations and maritime safety information from the German weather and hydromet offices.

I've also copied another PSK250 station, DA5UWG, on 3588.5. This is also PSKmail.

3592.6 (listed, dial can vary all over)
This is an interesting world propagation spotting net using a semi-automated amateur mode called WSPR (Weak Signal Propagation Reporter, aka "whisper"). WSPR is implemented in another small computer program resembling WSJT. Look and feel are similar, since both are written by K1JT, but WSPR is even less intuitive if that's possible.

This mode is designed for very bad HF circuits. It is precisely timed, with transmissions beginning exactly 2 seconds into each even UTC minute and lasting around 110 seconds. DEFINITELY sync your computer to an Internet time server if you're going to use THIS mode.

The information rate is very slow, around 1 baud. The signal is only about 6 Hz wide. It uses a very narrow 4PSK modulation and a lot of redundancy (FEC, etc). Therefore the dedicated WSPR software decoder can extract very weak signals, well below the noise.

Even when it's audible, WSPR is easy to confuse with just another dirty carrier or more local computer grunge. This makes it easy to miss, but if you park WSPR on the SDR at or near 3592.6 USB, you'll hear it eventually. At home, try this one and 10138.6 USB.

So far my only successfully decoded hit is:

0622 -4 1.7 3.594074 0 OE1SMC JN88 30

and yes, the actual transmitted frequencies are between 3594 and 3594.2 kHz.

Our tour comes to an end with the Russian Navy SLHFB Single-Letter HF Beacon cluster. Like all these clusters, this one consists of several CW Morse beacons spaced 0.1 kHz repeating one letter forever. These have been on the air for a very long time, and they are thought to be propagation beacons. It's possible to tune in the whole range at once and see where the band's open to.

So far, on 80, we have nailed:

3593.7 "D" Sevastopol 02/04/09 0431
3593.8 "P" Kaliningrad 02/08/09 2142
3593.9 "S" Severomorsk 02/04/09 0431

(Thanks to Ary Boender for the locations).

There should at least be "C" (3594.0, Moscow) audible at some point, and also an "A" on 3594.1 and maybe a "K."

Well, that's the 80 meter part of our tour. Sure a lot more to hear than around here.

For those who want to do the WebSDR thing, there's a list of these here. Note that K7UEB has just brought up a new one at his US location near Walla Walla, WA. It covers 14000-14095 kHz (or most of the 20 meter digital band).

Happy decoding!