Monday activities…

February 17, 2009 | Amateur Radio | By: Mark VandeWettering

I took Monday off, and mostly sat around the house with my wife. Still, I managed to get a couple of ham radio related activities done. I worked on removing all the compiled in constants from my program for doing unattended audio recording. Basically, my program uses “portaudio” to record audio with the rate, depth and channels you specify. I use it to record 8khz audio of WSPR and MEPT beacon activity for later analysis, but you could also use it to recording I/Q audio from a softrock at 48khz (or even 96khz) and later playback. The way it is currently setup is to dump 15 minutes of audio at a time into separate files, but that is reconfigurable as well. I’m satisfied with the general logic of the program now, but it needs a bit of work in the option handling and in signal handling to make it robust. It takes less than 2 percent of the CPU of my laptop to record my audio, and I bet that I could lower that even further with a little “impedence matching” between the portaudio and sndfile libraries. Right now, I read floats from portaudio, and send floats to sndfile. If we agreed that 16 bit was good from both, presumably that would avoid a couple of recasting operations.

Anyway, in between all this hacking I managed my first voice QSO on 40m with WY7USA using 5w on my FT-817. I’ve had problems working local stations, but apparently this 600-700 mile skip zone works pretty well.

Overnight, I also see a new New Zealand spot from ZL2FT on WSPR. That’s neat…

But the niftiest overnight thing seemed to be my reception of both VK6DI and VK2ZAK VK2ZAY (thanks David, VK6DI for the correction) on the 30m MEPT band. You can also see NM5DV sandwiched in there with regular Morse. VK6DI is running a signal of 500mw into a dipole, and reports that VK2ZAY is running 1.5 watts into a short loaded vertical antenna.


This recording started about 1:13 AM Pacific time, and I had pretty good reception for over an hour.

Addendum: Eldon, WA0UWH up in Seattle (CN97) caught my SMT beacon, and sent me this screengrab:


He’s setting up his own grabber, which is completely awesome! I’m working toward my own dedicated grabber too.