Sunday, August 30, 2020

YAAC is not Yak


YAAC is not Yak but Gnu, you really ought to k-now wa-who's wa-who. YAAC is - Yet Another APRS Client written in Java under GNU license. YAAC, I'm quoting here - "can be used as a stand-alone APRS client, an APRS RF-Internet gateway (I-Gate), or as a AX.25 digipeater". It doesn't matter what does this even mean but this app can actually be used to display multiple weather sondes at the same time on a map.

Monday, August 10, 2020

How to receive and decode multiple weather sondes with only one RTL-SDR receiver (Part 2)

As I finished the first article I got a tip from Zilog80 that he has finished a preliminary version of his iq_server concept. iq_server is a kind of a channelizer that allows clients to connect over TCP and request decimated baseband IQ stream of floats for a specific frequency offset. I was really excited to learn about his work because it would allow to allocate/dispose decoding processes upon request dynamically!

Thursday, August 6, 2020

How to receive and decode multiple weather sondes with only one RTL-SDR receiver

Note: there's part 2 to this article with the script updated for performance

It could sound strange but I haven't seen a simple solution that would allow me to receive and decode multiple weather sondes at the same time with only one receiver. dxlAPRS software has a channelizer if I'm not mistaken but the software itself is too complex and is designed for things I'm not even interested in. auto-rx on the other hand would require a receiver per frequency. But is it a problem to get me more RTL-SDR dongles to receive as many sondes as I like at the same time? No, getting an RTL-SDR dongle is not a problem, the problem is the antenna - each dongle would require one. So either I would have to install as many antennas as dongles or I would have to use an antenna splitter. And without an amplifier (LNA) a splitter would reduce signal power by a number of its outputs. So both solutions would require additional hardware and investments. But then I had an idea that it should be possible to build a very simple (and very inefficient of course) channelizer even in bash by multiplexing IQ samples baseband stream into multiple decoding processes.