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Saturday, Oct 25 2014 11:55 UT

HF Communications

HF Prediction: Upper, Recommended, Second best and Lower frequency (URSL)

Product Description

A common problem facing an HF communicator is to choose one, among several frequencies to establish a communication link. This tool can be used to assist in this task. There is a help screen explaining the various inputs needed (available HF frequencies, level of solar activity, and time of day/year, receiver and transmitter locations). The output is a table of frequencies to use ranked according to upper, recommended, second best and lower frequency.

The map seen on opening this window shows the location of the solar terminator and the auroral oval. If the radio path between the two terminals intersects either of these, there is a possibility of further signal degradation due to excess absorption, near the auroral oval and steep electron density gradients, near the dawn terminator.

Target Users

Anybody using HF for communications on a single link. Typical users could be travelling in remote locations and be setting up a radio link back to base (from peace-keepers to tourists, including mineral prospectors and small boat owners).

Data Source

IPS F-region model; NPOES auroral oval

Cadence

F-region model on demand, auroral oval updated hourly

Australian regional T index time series

Product Description

This time-series plot shows the trend in the observed Australian regional T index over the past 30 days. The daily values can fluctuate during disturbances. The dashed blue line represents the median of these daily values and is an indicator of the quiet level of ionospheric support over the period plotted. The forecast daily T index for the current UT day is shown as the unfilled rectangle. The T index is an equivalent sunspot number and is what the sunspot number would have needed to be to best match the observed ionosphere with the empirical model of the ionosphere used for Australian ionospheric predictions.

Target Users

Any HF frequency manager using software requiring an improved sunspot index for input to manage an HF system.

Data Source

Australian magnetometer network

Cadence

Daily

Global T-index departures from monthly predicted levels

Product Description

This image shows the difference between current observed hourly conditions and predicted monthly conditions for the global ionosphere. The colours blue, green, yellow, red, correspond to "enhanced", "normal", "mildly depressed" and "depressed" conditions respectively. Depressions and enhancements are with respect to the IPS predicted monthly T index for that month. Thus if the monthly predicted T is far too high, the entire global map will be red, which will warn a communicator that any frequencies scheduled using the monthly index are likely to be too high. This situation can occur due to a poor monthly prediction or an ionospheric storm.

Target Users

Any HF frequency manager using software requiring a sunspot index for input to manage an HF system.

Data Source

Global ionosonde network

Cadence

Hourly
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