Where is W6MRR-19?

Robert K6RGG and I launched a pico balloon from the Berkeley Marina at noon, Monday September 20. It didn’t start sending so I gave up. I was alerted to beacons received on September 22 over the Pacific in grid square CL20. It was received by the amazing KFS receiver. It was and continues to report 2 W (<36,000′). It is has been received with with very low SNR so I figured there was something wrong with the antenna. The new spool of wire was different from the last batch. The good news was the driven element only weighed 2 grams. The bad was it had over 200 ohms DC resistance.

New Toy!

Miniware MHP Mini Hot Plate – I bought a cheap reflow oven but it was broken when received and never replaced. I mostly hand solder or use a hot air rework tool. This seems like a great tool for hand assembling and rework. There are three preset temps that are preprogrammed but can be changed (200/250/300C). Because I’m using 0.8 mm PCB, boards heats up quickly. Just starting with it but I’m impressed.

How High Is The Balloon?

The WSPR power field is used to convey altitude. (I’m using a 10 mW output into a dipole). The latest data can be found in the WSPRnet database.

Note – this is out of date, we’re now using more precise 6 character grid square and more precise altitude using Type 1 andf Type 3 WSPR messages.

The WSPR data is transferred to APRS.fi with this format: RX_UTC_day  RX_UTC_time  Callsign  Frequency_MHz  RX_SNR_dB  RX_drift  TX_gridsquare  TX_power_dBm  RX_callsign  RX_gridsquare  RX_miles

New Solar Power Design

Going with cheap Chinese polysilicon solar cells over Powerfilm. The difference between the two in weight is: polysilicon – 3.75 g, Powerfilm is 6.7 g. The cost difference is enormous. The polysilicon is incredibly fragile. The flat connecting wire is called “tabbing” wire and comes pre soldered. I tried using a soldering iron and found it like working on potato chips. I moved on to solder paste with a hot air tool and am getting great results. The problem is once I get everything put together, I inevitably break a cell. I need to figure out how to get from workbench to launch without breaking it.

High Altitude Balloon Launch 2021-09-04


11:28am PDT 2021-09-04

The image below from the HYSPLIT forecast shows the projected paths, provided courtesy of Bryan KF6ZEO.

HYSPLIT balloon launch predictions.
HYSPLIT Projections


We launched the balloon at approximately 9:50am PDT.

There was a fair amount of fog, so we decided to wait until it would clear some. After waiting about 40 minutes, we launched the balloon with fog still present. The balloon ascended at a promising rate and went mostly straight-up.

The WSPR callsign for the payload is W6MRR, the callsign for APRS tracking is W6MRR-18.

Folks present at the launch in person included Martin W6MRR, Rob NZ6J, and Robert K6RGG.

Prelaunch Notice

SF-HAB will be launching a high altitude pico balloon on the morning of Saturday, September 4, 2021 at 9:00am PDT, at the Berkeley Marina in Berkeley, California. It will be carrying a custom-built Amateur Radio payload that reports position and altitude using the popular WSPR mode on 20m. We look forward to the launch and welcome folks to join in person.

See the map below for the precise launch site location: