Older articles:

1. Adding a Bodnar GPS Disciplined Oscillator to a KiwiSDR

   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 ...

   Read More →

2. Installing a WSPR Receiver in Inuvik, NWT

   I recently set up a Weak Signal Propogation Reporter receiver in the town of Inuvik, NWT. I was there in the beginning of June 2022, just as the world was opening back up from the COVID-19 travel restrictions.

   

   I thought Inuvik would be an interesting place, as it's at 68 degrees North latitude, which is above the Arctic Circle. During the summer, the sun never sets from May 25th to July 19th. In the winter, the sun doesn't rise from Dec 6th to Jan 5th. But the sun does get close enough to the horizon to have civil twilight, where the sun is less than 6 degrees below the horizon, so it's not completely dark all the time in the ...

   Read More →

3. SOTA Activation of Vollmer Peak, W6/NC-298

   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 ...

   Read More →

4. Automated Recording of the HamSCI WWV/WWVH Science Signal for Sunrise Festival

   I'm planning on participating in the Sunrise Festival, which is a citizen science campaign run by the HamSCI group. Over the 30 April 2022 weekend, hams from all over North America are encouraged to record the WWV and WWVH Scientific Test Signal, transmitting at 8 and 48 minutes past the hour.

   I previously used my KiwiSDR to receive these signals, and luckily there is an easy API for the KiwiSDR that will allow us to save recordings from the SDR.

   kiwirecorder.py

   kiwirecorder.py, written by John Seamons ZL/KF6VO, is a simple python program that remotely connects to a KiwiSDR and saves spectrum locally. The output file can be demodulated audio (SSB or AM) like you get from a ...

   Read More →

5. Receiving the HamSci WWV Scientific Test Signal

   I was perusing the latest edition of QST and noticed a short article on some scientific experiments that hams were doing with WWV and WWVH. I tune in to WWV occasionally to check propogation, and also for frequency calibration of my Kenwood TS-2000.

   

   Wow, this seems cool! The HamSCI WWV webpage has a bunch of information, including a great presentation by Kristina Collins KD8OXT.

   Receiving the Signal

   I recently added a KiwiSDR at my home station, so I twisted the dial over to WWV (in software, pretty anticlimactic), and started listening. I barely heard the test signal from Hawaii because propagation that evening was very poor. There was several solar flares over the next few days, causing lots of interference ...

   Read More →

6. Simultaneous Multi-Band WSPR Decoding with KiwiSDR and WsprDaemon

   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 ...

   Read More →

7. Building a Multi-band Fan/Parallel Dipole Antenna

   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 ...

   Read More →

8. Building a Quarter-Wave Ground Plane Antenna

   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 ...

   Read More →

9. Pacificon 2021 Picoballoon and Radiosonde Presentation

   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 ...

   Read More →

Page 1 / 2 » ⇉