Wednesday, June 27, 2007
Back in the late 80s through the 90's, two-tone paging was pretty popular. Many repeater controllers were setup to send these. Hams caring around the popular Minitor pagers on their belts could be summoned via a touch-tone invoked setup on the repeater. You don't see much of that anymore for whatever reason. The only people you noticed still being voice paged are usually volunteer fire / EMS guys.
The idea of digital paging always interested me, but it never seem to have gotten much attention in the ham radio world. Perhaps now that digital voice formats are emerging it's time to touch briefly on the idea again.
Back in the 90's Clive Cooper, G8UNK wrote a software POCSAG digital paging encoder. Kantronic's also came out with the KPC-9612 TNC cable of encoding POCSAG. (If you are wondering what POCSAG is, it's a well known standard for radiopaging)
Paging is kind of a one way deal, much like those beaconing the APRS locations. If this sounds interesting, here is a link for more information:
Tuesday, June 12, 2007
This hobby was founded by people tinkering, if you stop and think about it.
So in that same spirit, I'm going to share/promote a few related open source software packages that I have recently stumbled into.
gEDA is a project towards a full suite of Electronic Design Automation tools. Tools for electrical circuit design, schematic capture, simulation, prototyping, and production. It also features; analog and digital simulation, and printed circuit board (PCB) layout.
For you HF PSK enthusiasts, LinPSK supports BPSK, QPSK and RTTY.
PUFF is the name of a computer aided design program for microwave circuits, developed at the California Institute of Technology. It allows one to easily edit a circuit and calculate and plot the circuit's scattering parameters.
And here is a personal favorite. SPLAT is an RF Signal Propagation, Loss, And Terrain analysis tool for the spectrum between 20 MHz and 20 GHz.
SPLAT provides site engineering data such as the great circle distances and bearings between sites, antenna elevation angles (uptilt), depression angles (downtilt), antenna height above mean sea level, antenna height above average terrain, bearings and distances to known obstructions, path loss and field strength based on the Longley-Rice Irregular Terrain Model, and minimum antenna height requirements needed to establish line-of-sight communication paths and Fresnel Zone clearances absent of obstructions due to terrain.
As a side note: All of the online interactive Wireless / RF design potting utilities on the GBPPR website are based around a slightly modified version of this program. So you if care to see splat in action without installing it you can check those utilities out.
And a really good collection of Linux Hamradio Applications called Hamsoft
http://hamshack-hack.sourceforge.net/- The Hamshack Hack is a "Live CD". As a "Live CD" system, no installation to your machines hard drive is necessary. The whole package will run off the CD by building a "ram disk" in your machine's memory. As soon as you re-boot your machine, the LINUX system vaporizes and you'll be back with whatever system is installed on your hard drive.