Satellite Snoopers Pick Up Surprising TV Broadcast

March 22, 2022 by Jenny List 25 Comments

While Internet based streaming services appear to be the future of television, there are still plenty of places where it comes into the home via a cable, satellite, or antenna connection. For most satellite transmissions this now means a digital multiplex carrying a host of channels from a geostationary satellite, for which a set-top box or other decoder is required. Imagine the surprise of satellite-watchers than when the Russian polar communications satellite Meridian 9 which has a highly elliptical orbit was seen transmitting old-style terrestrial analogue TV (ThreadReader Link). What on earth was happening?

How a Russian polar comms satellite picked up a TV station.

The TV signal in question comes from Turkmenistan, so were some homesick Turkmenistanis in an Antarctic base being treated to a taste of their country? The truth is far more interesting than that, because the signal in question comes from a terrestrial transmitter serving domestic TV viewers in Turkmenistan.

We’ve all heard of the idea that somehow every TV show ever transmitted is somewhere out there still traveling as radio waves across space, and while perhaps we can’t fly far enough out to check for 1960s Doctor Who episodes it’s true that the horizontal transmissions from a TV tower pass out into space as the earth curves away from them.

Thus Meridian 9 passed through the beam from the Turkmenistan transmitter which happened to be on a UHF frequency that matched one of its transponders, and the result was an unexpected bit of satellite TV. We’re indebted to the work of [@dereksgc] and [Scott Tilley] for bringing us this fascinating observation. We’ve featured [Scott]’s work before, most notably when he relocated a lost NASA craft.

Owning A ShortWave Radio Is Once Again A Subversive Activity

March 17, 2022 by Jenny List 149 Comments

An abiding memory for a teen fascinated by electronics and radio in the 1970s and 1980s is the proliferation of propaganda stations that covered the shortwave spectrum. Some of them were slightly surreal such as Albania’s Radio Tirana which would proudly inform 1980s Western Europe that every village in the country now possessed a telephone, but most stations were the more mainstream ideological gladiating of Voice of America and Radio Moscow.

It’s a long-gone era as the Cold War is a distant memory and citizens East and West get their info from the Internet, but perhaps there’s an echo of those times following the invasion of the Ukraine. With most external news agencies thrown out of Russia and their websites blocked, international broadcasters are launching new shortwave services to get the news through. Owning a shortwave radio in Russia may once again be a subversive activity. Let’s build one!

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ice fishing tent and antenna in a snowy field

Ice Fishing Tent Makes Winter Ham Radio Comfy

March 12, 2022 by Donald Papp 29 Comments

Cross-pollination between different activities and industries can yield some pretty useful techniques or product combinations, and [Steve] shares some details on using ice fishing gear to make winter ham radio activities more comfortable and portable.

With the help of a folding tent shelter, [Steve] was able to create a minimal and self-contained field station that hosted all his needed equipment, and with the help of a small propane heater, stayed quite comfortable during a 24 hour winter event.

For those interested in the radio end of what [Steve] was doing, he goes into detail about the radio equipment and antenna he used, which itself stows easily into a bag and withstood high winds with success. The goal of the event after all was emergency preparedness, and while radio can operate without a wider infrastructure to support it, antenna design is crucial for best results.

As for keeping the operator safe and sound during all this, it turns out that the problem of a pop-up winter shelter that is both light and compact has already been solved by ice fishers; and while it can be fun to roll one’s own solutions, there’s not always a need to re-invent the wheel.

Boat Anchor Twins Get A Little Digital Help Staying On Frequency

March 11, 2022 by Dan Maloney 9 Comments

In the ham radio trade, gear such as the old Drake units [Dr. Scott M. Baker] has in his radio shack are often referred to as “boat anchors.” It refers to big, heavy radios that were perhaps a bit overengineered compared to the state of the art at the time they were designed, and it’s actually a shame that the name has taken on something of a pejorative connotation, since some of this gear is rock solid half a century or more after it was built.

But older gear is often harder to use, at least compared to the newer radios with microcontrollers and more stable oscillators inside. To make his 1970s-era Drake “Twins” setup of separate but linked receiver and transmitter a little more fun to use, [Scott] came up with this neat Raspberry Pi-based DDS-VFO project to keep his boat anchors afloat. Compared to the original mechanically tuned variable frequency oscillator in the Drake receiver, the direct-digital synthesis method promises more stability, meaning less knob-nudging to stay on frequency.

The hardware used for the DDS-VFO is actually pretty simple — just a Raspberry Pi Zero W driving an AD9850-based signal-generator module. Sending the signal to the Twins was another matter. That was done by tapping into the injection cable linking both units, which meant a few circuit complications to deal with signal attenuation. [Scott] also added amenities like a digital frequency display, optical encoder with crank-style knob to change frequency, and a host of Cherry MX keyswitches for quick access to different features.

From the look of the video below, the Twins are now rock-solid and a lot easier to use. This project is loosely based on a recent panadapter project [Scott] undertook for the receiver side of the Twins.

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A Variable Capacitor For Not A Lot

March 7, 2022 by Jenny List 38 Comments

There’s one component which used to be ubiquitous in every experimenter’s junk box, but nowadays unless you happen to be a radio amateur the chances are you may not have seen one in a long time, if ever. We’re talking of course about the air-dielectric variable capacitor, the tuning element for millions of radio receivers back in the day but now long ago replaced by much flimsier polymer-dielectric parts. There’s still a need for variable capacitors though, in particular a high-voltage variant for use in magnetic loop antennas. It’s something that [Ben] had a need for, which he solved with a clever combination of PCB material and 3D printing.

While the variable capacitors of yore invariably used intersecting vanes on a rotor, this one has two large parallel plates that intersect as one is moved over the other with a lead screw. It’s cheap and effective, and best of all, the files to make it can be downloaded from Thingiverse. He claims a 34pF-164pF capacitance range, which, looking at the size of the plates we find to be believable (and which is a useful range for most HF applications). We like this solution, and believe it makes more sense than being scalped for an older example at a radio rally.

This isn’t the first variable capacitor we’ve shown you, though some previous examples have been more conventional.

The Battlefield That’s 5 KHz Wide

March 4, 2022 by Jenny List 36 Comments

The airwaves are full of news from the battle in Ukraine, with TV and radio journalists providing coverage at all hours. But for those with a bit of patience there’s something else from the conflict that can be found with a radio receiver, the battle over 5 kHz of spectrum starting at 4625 kHz. This has for many years been the location on the dial for “the Buzzer“, a Russian military transmitter whose nickname describes its monotonous on/off buzzing transmission perfectly. As the current Ukrainian situation has taken shape it has become a minor battleground, and the Buzzer now shares its frequency with a variety of other stations broadcasting music, spectrograms, and other radio junk intended to disrupt it.

A spectrogram showing the wavy line of an air raid siren — The air raid siren produces a particularly distinctive spectrogram.

For the curious this can be watched unfolding on a spectrogram or through headphones by anyone within range who has an HF receiver, or for everyone else, with a WebSDR. In Western Europe it’s best listened to in hours of darkness, we suggest you consult the webSDR.org list to see which has the best signal. We’ve heard it on receivers in Poland, Russia, and the ever-reliable uTwente WebSDR in the Netherlands. Over the time we’ve been monitoring it we’ve heard overlaying speech, and music varying from the Soviet and American anthems through dance music and K-pop to 1960s British rock and of course Boney M’s Rasputin, with a few slightly macabre choices such as Final Countdown and an air raid siren. We’ve even heard TV intros from the Benny Hill Show, the A-Team and Mission Impossible, so whoever is doing this has a wide taste.

Alongside the music at about 4628kHz meanwhile we’ve watched a series of spectrogram messages scroll past in Ukrainian, Russian, and English, ranging from “Stop war” to lewd suggestions about the Russian President. It’s fair to say that none of these transmissions have obscured the Buzzer, but they have had the effect of significantly increasing the noise on the channel.

To have a listen yourself, point a receiver within range at the appropriate time of day towards 4625 kHz and select USB demodulation and a 5 kHz bandwidth. Meanwhile, for some background on the Cold War HF relics, have a read about numbers stations.

Retro And New Tech Combine In This Hybrid Ham Transmitter

February 27, 2022 by Dan Maloney 9 Comments

We’ve said it before and we’ll say it again: the best part about holding an amateur radio license is that it lets you build and use your own transmitting equipment. Hams have been doing this for more than a century — indeed, it was once the only way to get on the air — using whatever technology was available. But the mix of technologies in this low-power transmitter for the 80-meter band is something you don’t see every day.

As ham [Helge Fykse (LA6NCA)] describes in the video below, the project began when he came into possession of a bonanza of vacuum tubes — 12A6 tetrodes, specifically. The new-old-stock tubes were perfect for an RF power amplifier, but that left the problem of what to use for an oscillator. [Helge] chose to meld the old with the new and used oscillator board that he designed. The board has an ATmega88 microcontroller and an Si5351 oscillator, along with a 3V3 regulator to let the module run on 12 volts. And for a nice retro touch, [Helge] put the board in a 3D printed case that looks like an old-fashioned quartz crystal.

There are some other nice design touches here too. A low-pass filter cleans up the harmonics of the oscillator’s 3.5-MHz square wave output before feeding it to the amplifier, in a nod to proper spectrum hygiene. The primary for the amp’s air-core output transformer is hand-wound, with 3D printed spacers to keep the winding neat and even. The tuning process shown below is interesting, and the transmitter was used to make a solid contact with another ham about 100 km away. And we really liked the look of [Helge]’s shack, stuffed as it is with gear both old and new.

We’ve personally tried the Si5351 for QRP transmitters before, but this blend of the old and new really makes us want to find some tubes and get to playing.

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