[MRCA] Radiosondes

[Tim]

Hi Ray - Yep it's true...This can become a Time Sink! I can receive them
out to 50+ miles with a simple 6" 450 mc DIY ground plane on the roof
driving my multimode receiver.  No preamp or other antenna gain necessary.
(I remember that big dish in the Fair catalogs!)
It's interesting to see their path and the predicted landing spot converge
with the actual landing spot as reported by GPS.  These RS-41's use around
9 GPS birds for very accurate X,Y, Z  spatial coordinates and speed over
the ground plus rise/fall rates. The sondes transmits all this info to
ground stations, then to the Internet.  It's crazy cold up there but then
begins to get warmer higher up....
You can go retrieve them if you like, Youtube videos on simple
reprogramming them to 450 mc ham usage...
I've not looked into decoding the data but there are methods online.  The
data seems to be NFM in bursts every second.
I can often see the ones launched from OAK as they fly over my area at
around 30,000 feet on their way up.  Binoculars help. At altitude they can
be 20' in diameter.  Sondehub.org shows their azimuth and elevation from
your home too, pretty easy to acquire.  I watched one burst awhile back.
It was over 100K feet and they are apparently lined with talcum powder -
made a very noticeable white puff but the parachutes are pretty tiny....
Fun!
Tim
N6CC

On Tue, Oct 6, 2026 at 1:13 PM Ray Fantini via MRCA <mrca at mailman.qth.net>
wrote:

> It's amazing all the ways you can waste time on the internet! Before Fair
> Radio closed shop, they had a four- or five-foot dish on a tripod with a
> receiver built onto the back. Assume most people thought it was a radar
> dish and when I went and looked at it up close saw it was an automated
> tracker for what I would think was weather ballons being it was like 403 or
> 405 MHz
> Completely unrelated but years ago I set up a system for capturing the old
> APT satellites on 137.5 MHz and just the other day had someone ask what the
> circularly polarized antenna and down converter they had picked up was for,
> along with seeing a lot of that old VHF stuff turn up but as far as I know
> that entire network is gone now with them pulling the plug on NOAA-15 last
> year.
>
> Ray F/KA3EKH
>
>
>
>
> ------------------------------
> *From:* mrca-bounces at mailman.qth.net <mrca-bounces at mailman.qth.net> on
> behalf of Al Klase via MRCA <mrca at mailman.qth.net>
> *Sent:* Monday, October 5, 2026 8:08 PM
> *To:* mrca at mailman.qth.net <mrca at mailman.qth.net>
> *Subject:* Re: [MRCA] Radiosondes
>
> Fascinating!
>
> 73.
> AL
>
> On 05/10/2026 7:28 PM, Tim via MRCA wrote:
>
> Speaking of Sondes....Here's a link to current radiosonde weather balloon
> ops worldwide.  They are at-altitude at 0000Z and 1200Z daily.  They
> actually launch about 45-60 minutes before that.  Major airports are the
> usual launch sites.
> The ones out west here are RS41's that operate at 404 MHz, around 60 mw
> and I can receive the basic telemetry from a LONG distance away. Click on
> your local balloon and it shows all the data including its GPS coord's,
> current altitude, temp etc.
> Plot shows the track and predicted future track.  They usually get up to
> around 100,000' AMSL, often higher before they burst.  Then a long ride
> down on a parachute.  (fun fact:  from 105,000' the parachute has NO
> initial effect on the fall rate...very little air up there... LOL)
> Enjoy! https://sondehub.org/
> Tim
> N6CC
>
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