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 on HF.

Eventually, on 10 April 2022 at 2208 UTC, propagation was good enough to grab a clean screenshot of the test signal. This was transmitted from WWV on 15 MHz.

Comparing my received signal to the what was actually transmitted shows the voice, tones, and chirps are very easy to hear when propagation is good. But interestingly enough, I ...

Read More →

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 ...

Read More →

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 ...

Read More →

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 ...

Read More →

Just after setting up a remote receiving station in the hills above Santa Cruz for tracking radiosondes launched from Monterey Bay, I started noticing some weird stuff with the station. The station would detect a LMS6-403 radiosonde, but was unable to actually decode anything. The "jamming" signal was always on the same frequency of 400.259 MHz, and occurred daily around noon and midnight UTC.

I speculated that it might be radiosondes from Vandenberg Space Force Base, approximately 300 km (~180 miles) south of the receiver along the coast of California. Although it would be cool to receive those radiosondes, the purpose of this station was to track the Monterey Bay radiosondes, so I put that frequency on the blacklist and turned my attention to the task at hand.

New LMS6-403 Radiosonde Version

A few days later, my curiosity got the better of me, and I started to investigate these signals. Over the course of four days, I did decode a single packet each from two radiosondes. Based on the location, these definitely were from Vandenberg, but the signal must ...

Read More →

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 ...

Read More →

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 ...

Read More →

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 ...

Read More →

I recently went on a work trip to Newfoundland, Canada. Checking Sondehub before I left, I saw that there were two radiosonde launching stations on the Island of Newfoundland, one on the west side in Stephenville, and the other on the far east end in St. John's. And as luck would have it, I was traveling to Lewisporte, which is on the Trans-Canada highway almost halfway between the two launching sites. I might be able to receive both sondes at the same time!

As far as I could tell, the radiosondes launched at both of these sites were Graw DFM-09P (pdf), which transmit around 403 MHz. One interesting thing about these radiosondes is that they don't transmit a serial number with every packet, so it takes a while to determine the serial number of the radiosonde you are receiving.

Receive Station

Since I was traveling, I needed a portable station with two receivers. This is very similar to my standard radiosonde receive station at home, and I didn't use a preamp or filter.

The Comet M-24M dual-band amateur radio antenna ...

Read More →

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 ...

Read More →