Re: Like to track balloons? How about tracking radiosondes!

Barry L. Lankford

(See the last paragraph for my experience with obtaining Raspberry Pis recently)

As for chasing radiosondes: Been there, done that! And yeah, it was a lot of fun. I think I started chasing ozonesondes around 2006 with Bill Brown WB8ELK and Gary Dion N4TXI. University of Alabama-Huntsville's (UAH) Atmospheric Science department was launching Ozonesondes every Saturday at 1:00pm. Around that same time, I believe, Joe Leggio WB2HOL put up his steel tape measure & PVC pipe Yagi antenna design on a website. It was a simple 3-element Yagi for 2 meters that had a nice cardiod pattern with a deep & narrow notch on the backside, a broad forward beamwidth, and even some gain. Don't recall the year, but it was near June I think. I recall going to Sears (R.I.P.) and getting a nice discount on 1 inch tape measure refills because they were having a Father's Day sale! Nowadays, in the US, you could get 25 foot x 1 inch tapes for free from Harbor Freight!

The narrow notch was good for refining the direction. There's still a current website that has what appears to be the original WB2HOL design, although I think some of the links may be dead, particularly the ones for the YAGI-CAD41 program:
I was able to find the Zip file for Yagi-Cad on one of my old hard drives, but I recall that the program had some issues even then with the then-current version of MS-DOS (Yes, that's right, YagiCad runs in MS-DOS, NOT Windows!). I wouldn't even think about trying to run it with Win10's DOS window!

I have an Icom IC-R3 that works well at 403 MHz that I used in the "twenty-aughts" (or is it: "Twenty-naughties") with its extensible whip antenna, so I used YagiCad to re-tune WB2HOL's 2 Meter Yagi design to 403 MHz. Worked very well to replace the R3's whip -- I was able to pick up signals and direction from at least a mile away with the 'sonde laying on the ground in a tightly packed old residential area of a nearby city. No one else was able to get a signal at all, IIRC. When the balloon was a ways into the sky, I could pick it up from many miles away.

I also built a Tape Measure Yagi from WB2HOL's original 2 Meter dimensions. Never used it much, but it seemed to work well to add some extra range to 2M HT comms.

For both antennas, I didn't much like Joe's mechanical design, with its big worm-drive hose clamps and everything on the outside of the pipe, so I came up with my own design as you can see in the attached photos. I modified a spade-type 7/8th inch wood bit by grinding off equal amounts from each edge so it'd drill a 0.807" hole (I think that was the dimension - it's the outside diameter of 1/2 inch pipe). I used the modified bit to remove the shoulders inside the tee and cross fittings for the elements, so the tape would lay all the way through the fitting without kinking. The elements were clamped in place with 3/4" plugs which were longitudinally slit (band-saw kerf) and filled with RTV. I actually used Google/Trimble's "SketchUp" 3D modelling software to draw detailed plans of how to make all the PVC parts and assemble them with the tape measure elements, unfortunately I can't find the files now. The hairpin match was also moved inside the PVC parts. I had no problems at all soldering to the steel tape, but I used a single-cut mill bastard file to file off the paint AND the dull coating on the steel, until I got bright, shiny metal. It would've been easy to use RTV instead of PVC cement to assemble the antennas and make them watertight, and probably capable to being disassembled for repair if necessary.

As for the Raspberry Pis, I just ordered and received a 4GB R-Pi 4B, a 8GB R-Pi 4B, an R-Pi Zero 2 W and an R-Pi Pico (along with a lot of other goodies) from The US Raspberry Pi Shop ( almost a month ago. The parts were priced the same as the Foundation's advertised prices (but shipping was extra). I got everything I ordered, but there were a few things I wanted that were out of stock.

Barry N4MSJ

On 11/24/2021 2:00 PM, Mark Conner N9XTN wrote:
Mike KD2EAT and I did a presentation a couple of years ago about tracking NWS radiosondes.  At that time, the "price of entry" was a little steep both in terms of Raspberry Pi setup and building a 1680 MHz helical antenna with an attached LNA.
Since then, more and more of the NWS sites have migrated to 400 MHz for their sondes.  In addition, some sites use Graw and Vaisala sondes which have meteorological data that is decodeable by the Pi software.  The Lockheed Martin LMS-6 series only has lat/lon/alt data that is decodeable.  The user community reports very good 400 MHz range performance (200 mi/300 km or more if sonde is above horizon) using simple antennas (1/4 ground plane) and no preamp necessary most of the time.
If you are near a site that launches 400 MHz sondes, you can get into the tracking business with these items:
* 403 MHz ground plane antenna (maybe $5 for a SO-239 or N bulkhead
connector and some solid 12-14 ga copper wire)
* Feedline with appropriate ends ($20-ish depending on length needed)
* RTL-based SDR covering 400 MHz band (most of them, $20-30, Nooelec
is a good brand)
* Raspberry Pi 3B or 4 (Zero will probably not give good enough
For 1680 MHz tracking, you'd need these items:
* 1680 MHz helical antenna (3D-printer file available)
* 1680 MHz LNA ($50)
* Bias-T capability on the SDR to power the LNA via feedline
A note about Raspberry Pi's - they seem to be in short supply at the moment.  Pricing on Amazon is kind of high right now IMO and availability is not so great.  There appear to be plenty of 4 Gb Pi 4's available, but they're expensive and 4 Gb RAM is overkill for this application.  Pi 3's are priced well above the normal MSRP of ~$35, even allowing for typical kit parts.  More extensive searching might be worth some time.
The Linux "radiosonde_auto_rx" software is now installable within a Docker container.  You do not need in-depth knowledge of Docker to install the software, and Docker manages all the library dependencies for you.  Software updates are really simple and Mark VK5QI is very active in maintaining and upgrading this software. has all the info about how the receiver software works and how to install it.  The instructions are very clear and the user community is pretty helpful. <> is the email list. <> is a central location for tracking radiosondes.  You can see where current stations are receiving data (green circles) and where sondes are launched (gray).  When there are sonde flights in progress, you will also see their tracks on the site. Clicking on a circle brings up info about the type, timing, and frequency of sondes being launched.  If the sonde site reports the sonde type is RSxx, LMS-6 403, or DFM-XX, you can receive it on a 400 MHz antenna.  This site is global in nature, with quite a few European, US, and Australian users but only a handful of Canadians appearing.
My own station is a 1680 MHz setup that has been in operation since April 2020 - at first, just a portable setup but now a weatherproof one outside on a mast.  The local NWS office will migrate to 400 MHz next spring, so I need to get busy and build an antenna for it.
This might make a good winter project if the weather is too unfavorable for doing ARHAB launches and chases in your area.  Sorry if this seems a little random, but I'm hoping more people in our community will give this a try.
73 de Mark N9XTN

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