With the release of WSJT-X 2.3.0 in September 2020, Steve Franke K9AN, Bill Somerville G4WJS, and Joe Taylor K1JT included a two new digital protocols called FST4 and FST4W. These two digital modes are the next evolution in low-power and long distance digital communications. These modes use four-level Gaussian frequency-shift keying (4-GFSK) modulation, which has smooth transitions between the four tones. This modulation is a bit easier to decode than regular WSPR, which uses 4-FSK modulation that has abrupt tone changes.

FST4 is designed for keyboard-to-keyboard QSOs (similar to FT8), and FST4W is designed for beacon transmissions like the regular WSPR protocol that we use for picoballoons. The time periods for a single transmission are 120, 300, 900, and 1800 seconds, with longer periods requiring less SNR for decoding.

In Spring 2022, Rob Robinett AI6VN included FST4W decoding in Version 3.0 of the wsprdaemon software, which is what I run for WSPR decoding at my home in San Francisco and in Inuvik, NWT. That's cool, I thought. I can just "check the box" in the configuration file ...

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The San Francisco Radio Club organized another Summits on the Air event on 23 April 2022. For this "Simul-SOTA" event, there was 11 amateur radio operators activating 9 summits around the Bay Area. Steve W1EGG made a handy map with who was activating each peak:

I activated Vollmer Peak, which is at the southern end of Tilden Park in the hills above Berkeley. Parking at the trailhead was easy in the morning, but by the time I left parking was nonexistent.

The hike up was short, and the views were excellent. I could clearly see Mt. Tamalpais across the bay, which was activated by Vlad K6VVP.

A lot of the other peaks that were activated that morning were visible from from the top, including my previous activated San Pedro Mountain.

HF Radio

This was my first HF activation. I borrowed a Xiegu G1M radio, which is a small QRP SDR. I also borrowed a lithium power pack, and a 49:1 balun for an End-Fed Half Wave antenna. I cut a piece of two conductor zip-cord 33 feet long, which ...

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I've been interested in receiving Weak Signal Propagation Reporting (WSPR) signals recently, for two reasons. The first is that the picoballoons that we launch use WSPR for position information. Not only do I directly receive the picoballoons after we launch them, but I also use the WSPR network to check on their location around the world. I don't have a receiver in Europe, so I rely on other amateur radio operators to receive the balloon and post its location online, and I want to give back to the network.

The second reason is that I'm curious about how far I can receive signals with my somewhat compromised city antenna. While my fan/parallel dipole antenna will never perform as well as the huge antenna farms other amateurs operate, I can work on making my station a bit better by reducing local noise or improving my antenna. Incremental changes is what I'm going for.

Hardware Radio

Soon after we launched the first few picoballoons, I started receiving WSPR packets with my Kenwood TS-2000 using WSJT-X. This radio is a good basic ...

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Now that Solar Cycle 25 is upon us, I wanted to get active on the HF bands. My primary bands of interest are 40 and 20 meters, so I wanted to build a multi-band antenna for these frequencies. After some research, and wanting only one antenna connection for my Kenwood TS-2000 radio, I settled on a fan/parallel dipole antenna. It's very simple to build, and really hard to beat the performance of resonant dipoles.

Choke Balun

A balun is required when you are interfacing a BALanced device, such as a dipole antenna, to an UNbalanced device, such as a coaxial cable. Coaxial cables are unbalanced because from an RF perspective, there are actually 3 conductors in a coax cable: the center conductor, the inside of the shield, and the outside of the shield. The outside of the shield acts like another ground wire, and can bring RF energy and noise down into the shack.

This antenna and balun/choke design came from the 2008 ARRL Handbook for Radio Amateurs. I always encourage amateur radio operators to have ...

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After my talk at Pacificon a few months ago, several people reached out to me about setting up a radiosonde receiving station at their house. They specifically had questions about the antenna and LNA, and after answering the same question a few times I decided to do a post about this topic.

Building a 1/4 wave ground plane antenna is very easy to do. The overall design is simple, with a vertical element surrounded by a ground plane consisting of two or four wires bent down. Here are the dimensions for the VHF/UHF amateur radio bands (from the ARRL Handbook), but these dimensions can be scaled to any frequency.

There are many online calculators that will give you the approximate dimensions for the elements, but I usually use M0KUD's calculator. Whenever you are making antennas, always cut your elements a bit longer (maybe 20%) than the calculation says, then trim them during tuning.

Use any type of wire for the elements. I use standard 14-gauge solid copper wire because it's easy to get from the hardware store, it's ...

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The SF-HAB group launched another picoballoon on December 11th, 2021, from the Berkeley Marina. The launch party was Martin W6MRR, Robert K6RGG, and Kazu AG6NS. This picoballoon used two clear Chinese party balloons with hydrogen gas for lift. Martin's custom electronics was used, with a WSPR transmitter that alternated 14 MHz (20 meters) and 10 MHz (30 meters).

The aprs.fi callsign was W6MRR-22 using the WSPR to APRS bridge, and the WSPR callsign was W6MRR.

This picoballoon floated between 9,900 and 11,100 meters (32.5k to 36.5k feet) for the duration of the flight, which is the perfect altitude for picoballoons. This is above most bad weather (rain and thunderstorms), but still low enough to be in the fast part of the jetstream.

From Oakland, this picoballoon headed east at a pretty fast clip. In total, it traveled about 23,000 km (~17,000 miles) in 12 days, for an average speed of about 80 km/hr (~50 MPH).

One interesting thing was that this balloon was not received on Dec 20th and 21st, when it ...

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While the previous Lodi picoballoon was floating over Mexico City, we launched another picoballoon from the southeast corner of the Berkeley Marina on November 13th, 2021. The launch party was Martin W6MRR, Robert K6RGG, Kazu AG6NS, and myself KF6ZEO.

The forecast for the morning was no wind, and when we arrived at 10am the winds felt pretty calm. But after assembling the picoballoon train, it was apparent that even the very light breeze was too strong. The two clear Chinese party balloons were bent over, threatening to scrape against the ground.

We waited almost 30 minutes for the winds to die down enough to release the picoballoon. During a bit of a lull in the wind, we walked across the parking lot while slowly releasing the balloon, kind of an in-motion release. This worked pretty well, and liftoff was at 10:30am local time (1830 UTC).

The tracker electronics were built by Martin W6MRR, and we used two clear Chinese party balloons with hydrogen for lift. The WSPR callsign was W6MRR, and the APRS callsign was W6MRR-21.

W6MRR-21 Flight Results ...

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SF-HAB's Central Valley Division launched a picoballoon from Lodi, California, on Thursday November 11th, 2021. The launch party was David WB6TOU and Skip N6NFB. The tracker electronics used this time was a ZachTek WSPR Pico transmitter. Two Chinese party balloons were used for lift.

The WSPR callsign for the balloon was N6NFB, and the APRS callsign was N6NFB-1.

N6NFB-1 Flight Results

Unfortunately, the tracker electronics did not power up on launch day, November 11th. We thought all was lost, but it awoke the next day in Maidenhead grid square DL58, which is ~1640 km (~885 mi) southeast of the launch location. The balloon was at an altitude between 9,900 and 11,100 meters (~32.4k to ~36.4k feet). Only 11 WSPR packets were received by the network on the second day.

In total, only 29 packets from this picoballoon were received by the WSPR network, indicating that something was wrong with the transmitter or antenna. This balloon transmitted for 3 days total.

The last packet received from this picoballoon on November 14th was in EL77, which is about ...

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David WB6TOU, Martin W6MRR, and myself gave a presentation at the Pacificon, which is the annual ARRL Pacific Division ham radio conference held in San Ramon in the fall. Our presentation was titled "Picoballooning in the Bay Area: High Altitude Balloons, Picoballoons, and Radiosondes." Download the slides here.

We also used this opportunity to launch the new SF-HAB website, which is a collection of how-tos, resources, and blog posts about our ballooning activities.

The first third of the presentation was David talking about balloon mechanics, including how to prestrech, fill, measure, and release SBS-13 and cheap Aliexpress picoballoons. David launched two SBS-13 picoballoons from the Central Valley in winter 2021, one of which went 2.5 times around the world.

The second third was Martin talking about picoballoon electronics. He discussed using APRS and WSPR for publishing telemetryon the internet. Martin designed and built a custom tracker for all of the picoballoon launches we have done from the Berkeley Marina.

The last third of the presentation was yours truly talking about radiosondes. I gave a brief overview of their purpose ...

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In the beginning of October 2021, we had a flurry of launches from the Berkeley Marina. In the span of two weeks, we launched five balloons. All of the picoballoons woke up after launch, which means that we are getting better at building, testing, and launching picoballoons. But unfortunately, only one of them survived the first night and woke up the next day. We can't achieve our goal of going around the world if the picoballoons only last for one day!

All of these picoballoons used the same custom electronics designed and built by Martin W6MRR. Two cheap Aliexpress 36-inch clear plastic balloons were used, with around 6 grams of free lift.

Picoballoon Launch 12: K6RGG-11

On Thursday, Sept 30th, we launched just after noon local time (1900 UTC). The launch party was Martin W6MRR and Robert K6RGG. The tracker turned on about an hour later at 2022 UTC.

This picoballoon was interesting because the tracker alternated transmitting WSPR beacons on 20 meters (14 MHz) and 30 meters (10 MHz). The antenna was the standard 20m dipole, not tuned for ...

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