Flux densities are computed in one of two ways. If an effective radiated power is available, it is used as a starting point assuming, in effect, that a directional antenna has its maximum gain in the direction of the Observatory, thereby giving a "worst case" flux density. If no antenna information is listed, it is assumed that the transmitter output power is radiated by an isotropic source. In both cases, the simplest possible propagation model is used, corresponding to a flat earth with no terrain shielding effects.
For illustrative purposes, second and third harmonic radiation from licenced transmitters are also plotted. When harmonic levels are plotted, it is assumed that emission levels with respect to the carrier are at levels of -40 dB and -60 dB for second and third harmonics respectively.
RFI Characterisations for the various Rx bands:
(2nd harmonics are presented as blue data points and 3rd harmonics are presented as yellow data points)
70 cm (440 MHz) Flux density plot around the centre frequency
70 cm (440 MHz) Flux density plot around the centre frequency with 2nd and 3rd Harmonics present
50 cm (660 MHz) Flux density plot around the centre frequency
50 cm (660 MHz) Flux density plot around the centre frequency with 2nd and 3rd Harmonics present
20 cm (L-band) flux density plot
20 cm (L-band) flux density with 2nd and 3rd Harmonics present
13 cm (S-band) flux density plot
13 cm (S-band) flux density with 2nd and 3rd Harmonics present
6 cm (C-band) flux density plot
6 cm (C-band) flux density with 2nd and 3rd Harmonics present
3 cm (X-band) flux density plot
3 cm (X-band) flux density with 2nd and 3rd Harmonics present
The Worst-case satellite density plots below, are based on the minimum distance each satellite approaches the site in the current month. These plots are updated on the first of the month.
When the downlink bandwidth is known, the spectral flux density is calculated for that satellite. When the bandwidth information is not known, the power density is calculated only (hence the greater number of satellites plotted).
Many satellites operate over a range of frequencies (such as IRIDIUM), so these are plotted as horizontal lines.
Worst-case Satellite Spectral Flux Density Plot
Worst-case Satellite Power Density Plot
MDS S-band interference in the direction of Orange (measured from the top of the aerial cabin)
20cm (L-band) spectrum taken from within the control room.
Land Mobile Service 3rd Harmonic Interference (1398.15 MHz).
Animated GIFS of multibeam scans showing the GPS L3 beacon (on red line)
Low level signal present throughout the ~8 minute scan (beam 1A).
Strong signal present only for ~2 minutes (beam 1A).
Extremely strong signal present for <1 minute (beam 13A).