Ionograms are an image of frequency versus time delay (virtual height) of HF echoes from the ionosphere recorded by an ionosonde. An ionosonde is a swept frequency HF pulsed radar used to monitor the ionosphere. Vertical sounding ionosondes normally sweep in frequency from about 1 to 20 MHz.
The location combo-box selects the station (Sydney, Brisbane, etc) from which the ionograms are drawn.
The date (d, m, y) and time (hr, min) combo-boxes select a particular ionogram from that station. Most stations create ionograms on the hour and every 5 minutes thereafter. For some stations (Sydney, Canberra) ionograms start at 3 minutes past the hour, and then every 5 minutes. Some high-latitude stations produce only hourly ionograms.
A blank ionogram is displayed when there is no ionogram available for the specified time. This could be due to a gap in the regular schedule when an ionosonde is temporarily out of service due to hardware problems or power failures.
When the location, date or time is changed, the current list of ionograms is refreshed. The following controls can be used to navigate within the current list.
The Amp Threshold control sets the minimum echo amplitude threshold to be displayed. As you move the scrollbar, the ionogram is refreshed using the new amplitude threshold.
Pressing the Oblique button opens a separate window that shows an equivalent synthetic (ie, not directly observed) oblique ionogram derived from the vertical ionogram. The accompanying combo-box allows oblique ionograms to be generated for several different distances.
Note: SWS operates an oblique receiver from Auckland to Culgoora (near Narrabri NSW). You can see the current oblique ionogram for this circuit and compare it with the synthetic oblique ionogram for Christchurch (the nearest ionosonde to Auckland) or Sydney (nearest to Culgoora, with the distance set to 2000km).
The ionogram viewer is a Java applet. If it does not display properly, there might be a problem with Java in your browser. You can: