So on Friday lunchtime last week I ran home to try and setup WXtoImg so that I could start my wx satellite attemps. However, Linux again thwarted my attempts.
Unfortunately (like so many linux radio apps) WXtoImg is designed for the old Open Sound System (OSS), but new distros (I'm using Ubuntu 10.10) have now at the very least moved to PulseAudio. I mentioned these kind of problems before, but my previous experience and the WXtoImg mailing list helped me resolve it.
Normally, if you have an OSS app you can attempt to run it from the command line with the help of padsp. So for WXtoImg you would ideally just do:
$ padsp wxtoimg -G
And all would work. WRONG.
Even with that, it has issues when it tries to access /dev/mixer (but no issues accessing) /dev/dsp. If you search the mail list you will see others are reporting issues with it failing to access /dev/dsp and /dev/mixer and so they've gone and recompiled the kernel – which IMHO is overkill. Instead, to fix the mixer issue (which I'm not sure why padsp doesn't fix) you simply add a symbolic link from /dev/mixer to /dev/null. Therefore, the full solution to get wxtoimg working on Ubuntu 10.10 is:
$ sudo ln -s /dev/null /dev/mixer
$ padsp -M wxtoimg -G
The 'padsp -M' tells padsp not to emulate /dev/mixer and that makes the app actually open the /dev/mixer symbolic link you created the step before.
SO, once you do all that everything appears to work. As a result, I spent the week-end getting a few images from all four of the satellites that currently have APT running (NOAA-15, 17, 18 and 19). But my setup is not ideal as:
* My antenna is for 2m and 70cm – not 137MHz – and it's just a vertical – not a circular polarised antenna or a beam with a Az/El rotator; and
* My radio is just a 2m/70cm FM dual band Yaesu (FT-7800) which only has a selectivity (–6dB/–60dB) of 12 kHz/30 kHz – you ideally want 50kHz.
But none the less, I still received an image with every pass. Some were pretty rubbish, but the best are probably those attached.
So I may play more (as I think I get the best images from NOAA-15 and NOAA-19), but not sure if I'll bother trying to improve my setup so as to be dedicated. Or, I may attempt to build a Lindenbald antenna – although they seem a bit involved for something that was just meant to be a bit of fun…
Actually, I'd love to attempt to receive images from the geostationary satellites or the high res images on the POES. However for that I need to get into the 1.2GHz+ gear….