Re: Canadian radiosodes


I read that there was now software on the web to decode sondes, but not for the sondes used the last time I checked, but the rumor was that they would be changing to the GPS sondes in a few years and if that’s the case – great. The old sondes also used the 403 MHz band and transmitted a very wide bandwidth FM signal  (about 20 MHz I believe). You could RDF the signal using a narrow bandwidth amateur radio receiver but they were not very frequency stable so one had to keep tuning 5MHz up and down the band for the strongest signal. I actually bought a HT with a wide band FM setting to use which made tuning much less of a problem but for position information the old sondes simply rebroadcast received LORAN signals by AM modulating the sondes 403MHz carrier. This meant to decode the sondes position you would also need an AM receiver and a commercial LORAN receiver. A very complicated expensive system so RDF was our only option when James and I used to try and find them. LORAN was turned off in 2010 so I’m guessing you’re right and EC is now using GPS sondes.


Just saw Grahams message – Thanks Graham, I was just about to call EC and ask them which sond is being used now.





From: [] On Behalf Of Mark Conner N9XTN
Sent: Friday, September 04, 2020 11:46 AM
Subject: Re: [GPSL] Canadian radiosodes




It appears EC is now using GPS sondes, and the radiosonde_auto_rx software (which can be run on an RPi) should be able to decode positions if not the full telemetry stream.  If they work like the LMS-6 sondes the NWS uses, you'll have position reports at 1-sec intervals.


Here's an example of one decoded by a station near Ottawa this morning:


Frequency band used is ~403 MHz.


73 de Mark N9XTN


On Fri, Sep 4, 2020 at 8:52 AM James Ewen VE6SRV <ve6srv@...> wrote:



Carvel is the closest upper air sounding station. Before we launched our first balloon, we went for a tour of the station and saw how they filled and launched their balloons. We based our first fill device off of their design. 


We then chased and recovered a number of radiosondes. We had just moved into Sherwood Park, and my neighbors discovered they had a crazy neighbor early. 


I would be standing on the front lawn waving a UHF yogi at the sky, and then every few days, I would lay on the lawn staring at the sky with binoculars. Burst was observed visually as there was no way to decode telemetry. 


I learnt how to judge where the radiosonde would land based on where the balloon burst overhead. I was picky and only chased the ones that burst almost at my zenith. That meant they would land about 5 to 6 miles east of me. Burst west of my zenith meant a shorter drive, and deviations north or south of my zenith meant a north or south recovery. 


You needed to know where the sonde would land fairly precisely as the radio signal on the ground would only propagate about a mile or so. 


Toughest recovery was just a few miles south of us. We got to the area and could hear the sonde. Chased it down to a cow pasture behind a house, but the signal seemed to be moving on us. It ended up that the lift line got tangled around one cow’s leg,  and the sonde was going for a tour as the cow grazed. As luck would have it, cows are curious, and the herd came to see what these silly people were doing in the next field over. Serendipity helped as the tangled line came free as the transport cow decided we were not that interesting after all. 





On Fri, Sep 4, 2020 at 7:30 AM Mark Conner N9XTN <mconner1@...> wrote:

James - not sure where you're located relative to any Environment Canada upper-air sites, but you could build a radiosonde ground station and chase those!


73 de Mark N9XTN


On Thu, Sep 3, 2020 at 9:24 PM James Ewen VE6SRV <ve6srv@...> wrote:



There haven’t been any balloons to chase around here with this silly pandemic. I’m getting bored!





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