Sunday, March 01, 2009

The Great WebSDR Tour - Part 1

The WebSDR in the Netherlands just keeps getting more popular. Maybe it's too popular. The server is getting pretty hammered.

It's easy to see why, because this box gets everything. Maybe it's the full size antenna. 20 is dead, but 80 and 40 sound like old times, with stations from one end to the other of the SDR's little segments. Back here in The Land That Shortwave Forgot, I haven't heard the low bands this active since I was a small boy with a big antenna.

Let's begin our tour on 80 meters. This band is shared in Europe. Amateurs co-exist with military utilities and even weather faxes.

The SDR coverage begins around 3576.0 kHz. Frequencies are corrected to documented listed ones where available, otherwise it's the reading of the SDR "dial."

This is a JT65 working frequency range. Stations pick frequencies plus or minus QRM. JT65 is part of a computer program named WSJT which has several digital modes designed for EME (Earth-Moon-Earth communication, aka "moon bounce"). This is done on VHF and UHF, making 80 meters an unlikely place to find these extremely slow polytone-like transmissions. However, a quick session with WSJT decodes them, proving that's what it is.

Here's one morning's decoding done here. It's right off the Internet, rubbery timing and distortion and all:

1836 CQ UT0TV KN39
1843 CQ UA1ZFL KP67
2024 CQ TF3HZ HP94
2025 TF3HZ UA1ZFL KP67
2027 TF3HZ UA1ZFL R-20
2033 GM0AXY
2034 GM0AXY UT0TV -06
2036 CQ RA4NCX LO49

JT65 has three submodes, A through C, depending on the amount of frequency shift made by the single sine wave tone. On receive, WSJT can pick the right one. The sound in your speaker really does slightly resemble the slow preamble sent by the Russian polytone numbers stations (XP and XPH). It's a steady beep changing frequency at regular intervals.

This net sounds weird, which might explain why it seems to have picked up some jamming. Maybe the jammers don't know what it is, or maybe they want them to do it somewhere else. Since the jamming (manually swept carriers) follows the stations around, we know there are people sitting at radios turning knobs. It's definitely a ham turf battle.

3577.0 IZ3DVW Italian Propagation beacon, ~1 watt. Always loud and right in the middle of all the JT65 fuss. Sends long carriers and the callsign plus "BEACON" in CW Morse.

Break, more to follow.