By akh, a month ago
Today I'm releasing Gozim a side project written in Go.
It's a set of tools to serve ZIM files, (compressed copy of Wiki articles), use it to run your full copy of Wikipedia off the grid.
It runs great on a small computer as the Raspberry Pi or your own laptop.
It could be a solution to give access to knowledge in countries without stable internet connections.
By akh, 2 months ago
hamradio airspy linux
Airspy is an SDR with amazing specs, but drivers are slowly coming to your prefered os.
This apply to Arch but should apply to any recent Linux.
I've first compiled libairspy but always had the error
"usbfs: interface 0 claimed by airspy while 'airspy_info' sets config #1"
Since Linux 3.17 comes with an airspy v4l autoloaded driver making impossible to use it with libusb: no airspy_info and no gqrx.
Simply get rid of it with a modprobe config like /etc/modprobe.d/airspy.conf
Here are my Arch AUR pkg that will build airspy-git, gr-osmosdr-git and gqrx-git (note that you need to uninstall the packages from community to avoid conflict).
By akh, 3 months ago
First you need to create a VirtualBox FreeBSD install using a 10G qcow format, use an SCSI controller for the install as the disk will be visible as da0 inside GCE.
On FreeBSD 10.1 I had to load virtio manually, so set this in /boot/loader.conf
Copy your ssh key in your home user .ssh/authorized_keys, be sure to be in the wheel group.
On a Mac you need to install GNU tar (brew install gnu-tar), shutdown your VirtualBox vm and upload your image to GCE
VBoxManage clonehd -format RAW ../VirtualBox\ VMs/FreeBSDGCE/BSDGCE.qcow ~/Downloads/disk.raw
gtar -Szcf freebsd.tar.gz disk.raw
gsutil mb gs://bsdimage
gsutil cp freebsd.tar.gz gs://bsdimage/gce-bsd.tar.gz
gcutil addimage freebsd gs://bsdimage/gce-bsd.tar.gz
You should now see "freebsd" as available install image in your console
By akh, 7 months ago
APRS is a tactical digital communications system used between amateurs radio, to exchange positions & messages, here I blog my experience decoding/encoding APRS with a small Arduino as it may help some of you too.
Some transceivers are incorporating this functionalities but most of them don't, a lot of new technicians start with cheap Baofeng radios (30$) which don't provide advanced functionnalities but here is a way to solve that.
I've first looked at Bertos project, a realtime os for micro controllers as Atmel 328p (Arduinos), you can see my 1st attempt there:
This was the receiver only, a simple divider, the "hard" part was to understand the Baofeng/Kenwood mic jacks.
It takes me a long time to figure out that the Baofeng was too slow to trigger the squelch, so the Arduino missed the beginning of the message, hopefully I have a Kenwood too ...
So for a Baofeng using this kind of APRS decoder, you have to disable the squelsh completly, and set the volume very high it has to reach a proper signal on the arduino around -3v/+3v.
For the AFSK modulation, the Bertos project use a DAC made with 4 resistors.
Later, I've discovered the wonderful work of Mark Qvist MicroAPRS, mostly the same circuit as the Bertos project but with an awesome documentation of the code, it's a pleasure to read & learn.
So I've started to work on a circuit using a Bluno Nano an Arduino Nano with Bluetooth Low Energy, as an iPhone developer, this piece of electronics is just incredible and gives me the capabilites to connect my circuits to iphone Apps.
It's working but hardly a mobile solution :)
I'm currently designing a PCB for that.
I'm using Frizting to design and then export to OSHPark for the PCB manufacturing, it's far from perfect but I will improve the circuit and publish it soon !
This plus an iPhone app and you'll rock APRS !
73 de KK6NXK
By akh, 7 months ago
hamradio radio radio amateur
When I was a young child, I remember listening to an old radio receiver with my grandfather, looking for morse transmission.
30 years later, I take the opportunity to get my radio amateur license in the US, it was not difficult (Technicial license is easy), especially cause US radio amateurs are using the metric system (almost all the time ...), the only difficulties were to learn some terms and simple formulas from french to english and to know some parts of regulation by heart (I have never been able to learn by heart).
A lot of people keep asking me why are you doing this? Do you want to speak to a microphone to a stranger?
First why not, it's not the craziest thing I've ever done :)
Then they probably have forgotten that every single piece of technology today are using radio waves, from your 4G phone to wifi to Bluetooth, learning and understanding that is really useful.
For example Radio amateur bands overlap some of the "civil" bands, it gives some extended privileges to a radio amateur to experiment with long distance wifi transmissions.
So it's not just about voice but data too.
Another aspect is electronic, a lot of radio amateur are sharing hardware and electronic circuits to build your own receiver/transceiver, before it was cool on the Internet.
Learning electronic to build something real is a lot more rewarding than it was at school...
Even without a license this is a brand new world to explore, receiving satellite images of the Earth is one of the many possibilities you can get entering radio world.
This is the beginning of a new knowledge branch to conquer !
See my work on an APRS bluetooth Modem
73 de KK6NXK
By the way in french it's radio amateur and not amateur radio :)