A CODAR advent

Over the last few days, I have been recording CODAR on 4463kHz to produce images of the ionosphere. I started on Friday 15th and the plan was to leave the recording running until Christmas Day, thus producing some kind of “CODAR advent” images. Unfortunately, there seems to be a problem when the receiver runs for several days that results in the sudden loss of the CODAR signal. This problem can be seen at the bottom of the image below. Thus, I have finished the recording on the morning of the 24th. The equipment and software used is the same that I detailed in a previous post.

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Respuesta al artículo “¿Por qué asociarse?” por EA1URA

English summary: This is an opinion post discussing the reasons given by EA1URA to join URE, the National Amateur Radio Spanish society. My main point is that the services offered by the society do not justify the fees and that the society doesn’t properly represent the interests of Amateurs with a profile similar to mine.

Normalmente no escribo artículos de opinión ni tampoco escribo en español en este blog, pero en este caso he creído conveniente hacer una excepción. Recientemente, EA1URA (URE Asturias) publicaba un artículo titulado “¿Por qué asociarse?” en el que da una lista de razones por las que merece la pena asociarse a URE. Ayer, en Twitter, @ea1ura me pasaba directamente el enlace del artículo. Tras una breve lectura, yo contestaba que ninguno de los puntos que exponen me parecen económicamente interesantes para un Radioaficionado de mi perfil y que no consideraba que URE defendiera adecuadamente mis intereses.

En este post intento extender y justificar mi respuesta, con la esperanza de que quizás sirva como crítica constructiva. Durante el artículo incluiré algunas comparaciones con la situación en Reino Unido: la RSGB y su normativa. Esto es simplemente porque es el único país extranjero donde conozco bien la situación, al haber residido allí. En general, considero que la situación en Reino Unido está bastante mejor que en España y deberíamos intentar copiar algunas cosas de allí. Imagino que cualquiera que tenga un buen conocimiento de la situación en otros países europeos como Alemania u Holanda puede tener una impresión similar.

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Using CODAR for ionospheric sounding

CODAR is an HF radar used to measure surface ocean currents in coastal areas. Usually, it consists of a chirp which repeats every second. The chirp rate is usually on the order of 10kHz/s, and the signal is gated in small pulses so that the CODAR receiver can listen between pulses. The gating frequency can be on the order of 1kHz.

CODAR can be received by skywave many kilometers inland. Being a chirped signal, it is easy to extract the multipath information from the received signal. In this way, one can see the signal bouncing off the different layers of the ionosphere, and magnificent pictures showing the changes in the ionosphere (especially at dawn and dusk) can be obtained. For instance, see these images by Pieter Ibelings N4IP, or the image at the top of this post, which contains 48 hours worth of CODAR data.

Here I describe my approach to receiving CODAR. It uses GNU Radio for most of the signal processing, and Python with NumPy, SciPy and Matplotlib for plotting.