Install scrot (if not already installed): sudo apt-get install scrot
To pick a window, run ‘scrot -s’ and then click on the window that you want to capture. Screenshot is saved in your home dir by default.
AngularJS form validation and ng-messages
I’ve been working on a simple example AngularJS app uses ng-messages. Code so far is on my github here.
This is part of my ongoing activity learning AngularJS. You can see my other posts and progress so far here.
To get up to speed with ngMessages, there’s a great tutorial here, and online docs here.
TAPR QRPi: QRP Raspberry Pi WSRP transmitter – 100 mW output on 20m
I finally got my TAPR QRPi shield on a Raspberry Pi 2, setup with WsprryPi software to transmit WSPR (Weak Signal Propagation Reporting) signals, and the results from just 100 mW output on the 20m Amateur Radio band are nothing but amazing. Here’s a screenshot from the WSRPnet.org site this evening over the past couple of hours showing stations that have received my 100 mW signal to a roughly cut dipole wire antenna (zipcord electrical wire split into two) for 20 meters plugged directly into the TAPR QRPi board:
When I got my first spot from VA7MM in Vancouver I was pretty happy with that. 744 miles on 100 mW is pretty good going. But then in the following couple of hours spots from stations even further afield started popping up on the map, including K9AN in Illinois, that’s 1784 miles from here in Davis, California, on just 100 mW. That’s absolutely incredible! (thanks to everyone that spotted my signal!)
This is my second attempt to get this working. My first attempt on a Raspberry Pi 1 Model B didn’t get any spots over a several hours period one weekend, so I wondered if something was not working right on the original Pi model (remembering I’d read somewhere what the WsprryPi software was updated to run on the 2 and 3 recently). This afternoon I installed WsprryPi and the QRPi board on a RPI 2, and the reports started rolling in!
My antenna is just a wire dipole, strung between two bushes in the back yard at roughly 5ft above ground, with the broadside aiming roughly north/south.
Update: it’s 7:30pm local and my signal is being received almost all the way over on the East coast!
Adding and removing cron jobs on Raspbian
crontab -l : lists current crontab
crontab -e : edits the currently scheduled jobs
You can temporarily disable a job from running just by commenting out the schedule line for the job.