Aeronetworks sro - Airborne Linux

Not Enough Spots Thanks to the current low sun spot cycle, the 40 meter band arguably provides the best HF radio propagation.  The problem with this band, is that a half wave dipole wire antenna is 20 meters long.  If you string that from a mast or a tree, you may need 30 to 40 meters of space for the wire and ropes.  Most modern backyards are not that large. One solution is to upgrade to a Country Manor House, but for most radio amateurs, that would be too much lawn to mow.  On the other hand, fitting a 40 meter band dipole into the attic of a regular sized home or cottage, certainly seems impossible, but it is actually quite easy: Curl the dipole up into a helix! Clue Up On Helices The following NEC card stack defines a dipole made from two helices, wound around a 5 meter length of "Two by Four" lumber, for a 75% overall size reduction, which should fit into the attic of most homes. "Two by Four" lumber is actually 1.5 by 3.5 inches, or 38 by 89 mm in s...

RIP WPA2 I can never remember how to set up a Socks proxy to my Digital Ocean Droplet, so here is a simple little how-to guide. Using a secure proxy server to somewhere else in the wild wild world, to get through a local insecurity suddenly got added urgency, since the WiFi WPA2 protocol is now officially broken. Using a secure proxy in this way, will prevent local script kiddies from looking over your shoulder on a WiFi connection. The most fun you can have with your socks on! Note that the cheapest Digital Ocean Linux or BSD virtual server costs only $5 per month and that is all you need.  You don't even need to change or install anything on it, since it comes with sshd running by default.  So, just sign up for one, start using socks over ssh and relax. On the laptop: Add nameserver 8.8.8.8 to the top of /etc/resolv.conf Start the socks proxy: # killall ssh # ssh -fND 2222 -p 22 root@w.x.y.z Firefox: Open Menu Preferences, Advanced, Network, Sett...

Would you like to know the scattering Radar Cross Section (RCS) of your RC or UAV quadcopter toy?  If you are a Real, Card Carrying Geek, then of course you would... The Boeing RAH-66 Was Designed for Low RCS I have done some more work on this problem and decided to revisit this article, so if you think you have seen it before, keep reading.  Search Radar Two types of radar need to be considered. Long range over the horizon radar is used to tell whether there is an aircraft and where it is heading. Short range targeting radar is used to track an aircraft and direct an anti-aircraft gun or missile. The Radio Frequency modelling of the aircraft skin is done using a vast number of triangles, called a surface wire frame, or a mesh.  The maximum size of the triangle wires, need to be <1/10th of a radar wave length.  A computer program then calculates the interaction of every wire, with every other wire, iterated over the whole skin - a tremendous comp...

I am an ex Army Signals officer and also built military HF radio equipment for a period of about ten years - man pack, ground and airborne, so when I saw the new BitX40 radio kit, I just had to get a couple to play with. These kits are made in India, are good quality surface mount, built up tested and aligned.  For the princely sum of $59, one can get two or three and have fun: http://www.hfsigs.com/ Bread and Circuses Here is my breadboard setup.  Yup, it is a real olde skool bread cutting board.  Wood is a good insulator and some blue ticky-tacky keeps things down: BitX40 7 MHz SSB HF Radio The BitX40 is an analogue radio, with a digital synthesizer tuner - so it is a throwback to some time before the dinosaurs, circa 1985 - nice and simple. The default setup is for the 40 meter band, but one can tune it for any HF band, by using switches and coils.  They are so cheap, one could get multiple radios and configure each for a different band of inter...

I had a look at radio amateur Slow Scan TV and noticed that it is analogue, so I wondered whether I can create a digital version using gstreamer. Here is an example script that will play one video frame every ten seconds.  This could very well form the basis for a digital SSTV system. The first part of the script are commented tests that show how I worked my way up to the super slow method that uses the videorate plugin to drop most of the frames. Note that due to the long time between SSTV frames, everything will always be different, so motion jpeg will likely work better than h.264 compression. #! /bin/bash echo Slow Scan TV example with a laptop PC camera and gstreamer # Install all the plugins including v4l2src: # dnf install gst*plugin* # Play the laptop PC camera the simplest possible way using the system defaults: # gst-launch-0.10 v4l2src device=/dev/video0 ! autovideosink # Play the camera and scale it smaller at 30 frames per second # gst-launch-0.10 v4l2src dev...

The Numerical Electromagnetics Code (NEC) is a powerful and efficient program for the analysis of the electromagnetic properties of antennas and other objects. It is a Method of Moments type of successive approximation program and dates back to the time of the dinosaurs.  In theory,  practise and theory are the same,  but in practice not. To measure, is to know! NEC was developed on a CDC 7700 in the mid 1970s to early 80s at Lawrence Livermore by Burke and Poggio for the US Navy and it was paid for by the friendly US tax payers - free for use by anyone now. Dipole Antenna Example CDC - Control Data Corporation, became Computing Devices Canada, which became General Dynamics Canada - I worked there through all the name changes - but you don't need to go hunt in a museum for a CDC 7700 to run NEC - an Intel PC will do.   The NEC documentation amusingly still refers to stacks of punch cards, but these have been replaced with simple text fi...

For a few years, it has been possible to launch tiny educational satellites - for free - to fill up some of the unused payload space on big rockets.  http://www.asc-csa.gc.ca/eng/satellites/cubesat/default.asp This opportunity has been used by many universities and radio amateur groups: http://www.asc-csa.gc.ca/eng/sciences/canadian-cubesat-project.asp A few months ago, the American University in Sharjah also launched a cubesat called NAYIF-1: http://www.arrl.org/news/nayif-1-cubesat-to-have-funcube-transponder .  It has been passing overhead many times and I was a bit miffed that I did not know about it before the launch, had no idea how to connect to it and to my knowledge, the radio amateur law in the UAE did not allow foreigners to operate.  The NAYIF-1 satellite is a CubeSat-5, which is a little different from the CubeSat-1.   Here is the AmSat data warehouse for the NAYIF-1 (EO-88), which shows all the pertinent information on the satellite in re...