N7XSQ PropaGator Interpretation

The NCDXF/IARU HF Beacon System consists of 18 beacon stations spread out all across the world that transmit beacon signals on a designated frequency in each of five amateur bands between 14 and 28 megaHertz. The schedule of these transmissions is interleaved in such a way that each station transmits on only one frequency at a time, and there is only one station transmitting on a given frequency at any one time. Each beacon transmission consists of a ten second time slot containing the station's call sent at 100 watts at 22words per minute, followed by a four one second dashes sent at 100w, 10w, 1w, and 100mw.

The N7XSQ beacon monitoring station consists of a HF receiver connected to a computer that tunes the radio and monitors the received beacon signals via a sound card connection. The computer time is synchronized to an internet time server. The beacon signals thus received are analyzed and displayed by the BeaconSee application.

The BeaconSee display consists of a grid of 18 columns, representing a station location, and 5 rows, representing a frequency. Each cell displays graphically the beacon transmissions that have been monitored over a period of time for that station and frequency, in a horizontally scrolling waterfall type of display. BeaconSee monitors one beacon transmission (10 seconds) in each cell in turn, and adds a small display slice on the right hand side of each cell. It thus takes 15 minutes to monitor all stations on all frequencies and add one display slice to each cell. Within each cell, the vertical axis represents a small frequency band centered on the beacon frequency. Horizontally, each cell contains a series if 10 second observations, each separated by 15 minutes, with the most recent on thr right. A cell holds approximately two hours of observations.

The strength of the signal at any point is shown by the color and brightness that is displayed. Any signal received within the passband of the display will be shown, and not all are beacon signals. Within each ten second time slice, a beacon signal starts out at 100w and decreases sequentially to 100mw. Therefore it will tend to show up on the display as a series of triangular shapes that point toward the right, or as a series of dots if the signal is weaker. Each different beacon station tends to transmit on a slightly different frequency. Since BeaconSee scans all the stations on a given frequency one after the other, a signal that extends horizontally across several cells can be recognized as interference on the channel. Lightning and similar types of iterference will produce a signal that extends vertically the entire height of the cell. The general noise level of the band can be estimated from the amount of snow in the background of the cell. Finally, there is an artifact from the sound card that is currently in use that appears as a perfectly straight horizontal line across the center of all the cells in a particular row.

Beacon analysis by BeaconSee
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