Hacking, HAM Radio (EA1IYR), DSP, physics and more

BatchDrake's blog

SigDigger 0.2 - Using suscli

As the latest SigDigger 0.2 release included lots of new features that are difficult to summarize in GitHub’s release notes, I will write a series of posts about typical use cases for this features. It will not have a regular schedule (I am still writing down my master thesis, plus other duties far from my computer).

This first post will be dedicated to suscli, a command-line front-end for Suscan that does not depend on a graphical environment.


Amateur radioastronomy in 4 GHz (II)

The Titanium C1-PLL

Alright, so earlier last summer I managed to gather all the necessary parts for my DIY C-Band radiotelescope. My initial goal was to buy a primary focus dish somewhere near Madrid. Unfortunately, those are extremely difficult to find in Spain because reasons, at least at a reasonable price. I had to switch to plan B, this is, a medium-sized 110x120 cm offset antenna that was eventually purchased from diesl for an extremely reasonable amount (65€). Since the LNB is designed for primary focus dishes, I had to buy a conical scalar ring so that the dish was completely illuminated (hence reducing spillover losses to a minimum).


Amateur radioastronomy in 4 GHz (I)

Hi, everyone! It’s been a while since my last blog post here. I couldn’t help it: I began a master’s degree in Astrophysics in the UCM last year, and a lot has been going on since then. In particular, I had an assignment for the subject Extragalactic Astrophysics, consisting on a scientific poster based on a freely chosen paper out of a list provided by the teacher.

One of the papers in the list was Measurement of the flux density of Cas A at 4080 Mc/s by Arno Penzias and Robert Wilson. This paper is particularly interesting for two reasons: first, this is the paper that led to the discovery of the Cosmic Microwave Background. Spoiler alert: they measured Cassiopeia A flux at 4 GHz successfully, being ~1 kJy, overestimaing its secular dimming to 1.1% per year. Second, it talks about radioastronomy in 4 GHz, and as we all know, radio is inherently fun.

The Holmdel horn antenna, whose calibration by Arno Penzias and Robert Wilson led to the discovery of the CMB. Image courtesy of Wikimedia Commons

Release of cccrack, the convolutional code cracker

On April 6th-7th 2019, the second edition of the STARcon 2019 congress took place in the ETSIT, in which I gave a talk about the state-of-the-art of reverse engineering of convolutional encoders, and provided a proof of concept of the ideas behind the work of Mélanie Marazin, Roland Gautier and Gilles Burel to guess the encoder polynomials of the Meteor MN2 LRPT signal.


Making an old VFD glow for the last time

Years ago (2008?), in the middle of an outburst of interest in electronics, I decided to dismantle my aunt’s old VHS recorder, a Sanyo VHR 7100EE, which she replaced by a generic uninteresting DVD player days earlier.

It was not the first time I disassembled a VCR. I did it multiple times in the past for minor repairments (like a worn out pinch roller that wrinkled the tapes), but back then I wanted to go a bit further. I extracted the main PCB, the head drum, the power supply and a couple of things more, being the 24-pin VFD display the only piece that remained with me until today.

Testing the VFD after more than 10 years.

VFD displays are particular cases of warm cathode vacuum tubes, in which (usually) 7-segment-shaped anodes are coted with a phosphorescent substance that light up when they are hit by an electron flow coming out of the heated filament due to thermionic emission (also called Edison effect).