



Monday, August 2, 2010

Data bursts near UVB-76 frequency

There seems to be a lot of different broadcasts trying to allocate the same spectrum as UVB-76, as this would be the only frequency on a shortwave band .. At the moment, I can spot at least 4 additional carrier frequencys distorting the signal!

Two of them are, however, of special interest. Previous posting already covered the morse code, but even more sophisticated transmission is happening on a lower sideband of the signal. Something somewhere is transmitting very dense data bursts on 4.623325MHz, what are audible as scratching sound on UVB-76 signal. It happens once or twice an hour and is never more than about 10sec. long, so it is a telemetry data of sort.

What makes this signal spectacular are three things: First, it has relatively high-speed data rate for a shortwave band. Second, it has chosen its existance at the same frequency spectrum as UVB-76. Although UVB has lower sideband seriously supressed (i.e. most of the signal is radiated above 4.625MHz frequency, as opposed to regular AM signals what radiate equal amount of energy on both, upper and lower the base frequency), it has still a reasonable amount of signal there to give headic to whoever is trying to use it. And third, the signal itself is asymmetric, i.e. upper and lower sidebands are transmitting different data!

This is what the spectrum on WinradHD screen looks like:


  1. This comment has been removed by the author.

  2. Do you have any theory why this exists?
