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 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 (Pishop.us) 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.
On 11/24/2021 2:00 PM, Mark Conner N9XTN wrote: