The aim of this site is to inform/educate in the context of HF radars, though I also include notes on some areas of physics I find interesting but not necessarily related to HF radars.


None of the information here is guaranteed in any way to be fit for any purpose.
Feedback is welcome at the email address "dan.meehan@ddhfradar.com ".
Most Recent Update: August 2nd, 2024



There are two figures on this page. The first figure shows a Lissajous Figure and the second a backscater ionogram.

Why are Lissajous figures important--the interested reader is encouraged to do some research.
Originally (before they became known as Lissajous Figures) these might have been drawn by suspended bags of sand leaking their contents as they swung back and forth.

A French chap Jules Lissajous, in the mid 1800's, used pairs of tuning forks with mirrors stuck on their prongs to draw thee figures on a screen.

The Australian Broadcasting Corporation (the ABC) is a publicly owned broadcaster and has a nice web page describing why its logo is a 3:1 Lissajous Figure.



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The delta F slider is set to a small value because I wanted the figure to move a bit. The phase slider is so you can "rotate" the figure. i.e. if you set the and Y frequencies to be the same you might get a straight line depending on the phase of the two inputs. If they are 90 degrees different in phase you get a circle.



A Backscatter Ionogram

This is an example of a backscatter ionogram, one of the fundamental real-time measurements of ionospheric propagation crucial to the operation of High Frequency Over The Horizon Radars.
What is measured and how does it show in this display?
What might this image look like if there had just been a solar flare?


Bagpipe Music