amateur radio

204 Articles

Listening To The ISS On The Cheap

June 10, 2023 by 36 Comments

Like any hobby, amateur radio has no upper bounds on what you can spend getting geared up. Shacks worth tens of thousands of dollars are easy to come by, and we’ll venture a guess that there are hams out there pushing six figures with their investment in equipment. But hands down, the most expensive amateur radio station ever has to be the one aboard the  International Space Station.

So what do you need to talk to a $100 billion space station? As it turns out, about $60 worth of stuff will do, as [saveitforparts] shows us in the video below. The cross-band repeater on the ISS transmits in the 70-cm ham band, meaning all that’s needed to listen in on the proceedings is a simple “handy talkie” transceiver like the $25-ish Baofeng shown. Tuning it to the 437.800-MHz downlink frequency with even a simple whip antenna should get you some reception when the ISS passes over.

In our experience, the stock Baofeng antenna isn’t up to the job, so something better like the Nagoya shown in the video is needed. Better still is a three-element Yagi tuned down slightly with the help of a NanoVNA; coupled with data on when the ISS will be within line-of-sight, picking up the near-constant stream of retransmissions from the station as Earth-based hams work it should be a snap — even though [saveitforparts] only listened to the downlink frequency here, for just a bit more of an investment it’s also possible for licensed hams to uplink to the ISS on 145.900 MHz.

For those who want a slightly higher level of difficulty, [saveitforparts] also has some tips on automating tracking with an old motorized mount for CCTV cameras. Pitchfork notwithstanding, it’s not the best antenna tracker, but it has promise, and we’re eager to see how it pans out — sorry. But in general, the barrier to entry for getting into space communications is so low that you could easily make this a weekend project. We’ve been discussing this and other projects on the new #ham-shack channel over on the Hackaday Discord. You should pop over there and check it out — we’d be happy to see you there.

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Hackaday Links: June 4, 2023

June 4, 2023 by 9 Comments

A report released this week suggests that 50 flights into its five-flight schedule, the Mars helicopter might be starting to show its age. The report details a protracted communications outage Ingenuity’s flight controllers struggled with for six sols after flight 49 back in April. At first attributed to a “communications shadow” caused by the helicopter’s robotic buddy, Perseverance, moving behind a rocky outcrop and denying line of sight, things got a little dicey once the rover repositioned and there was still no joy. Since the helicopter has now graduated from “technology demonstration” to a full-fledged member of the team tasked with scouting locations for the rover while respecting the no-fly zone around it, it was essential to get it flying again. Several attempts to upload a flight plan failed with nothing but an acknowledgment signal from the helicopter, but a final attempt got the program uploaded and flight 50 was a complete if belated success. So that’s good, but the worrying news is that since Sol 685, the helicopter has been switching in and out of nighttime survival mode. What that portends is unclear, but no matter how amazing the engineering is, there’s only so much that can be asked on Ingenuity before something finally gives.

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Hackaday Links: May 21, 2023

May 21, 2023 by 14 Comments

The reports of the death of automotive AM radio may have been greatly exaggerated. Regular readers will recall us harping on the issue of automakers planning to exclude AM from the infotainment systems in their latest offerings, which doesn’t seem to make a lot of sense given the reach of AM radio and its importance in public emergencies. US lawmakers apparently agree with that position, having now introduced a bipartisan bill to require AM radios in cars. The “AM for Every Vehicle Act” will direct the National Highway Transportation Safety Administration to draw up regulations requiring every vehicle operating on US highways to be able to receive AM broadcasts without additional fees or subscriptions. That last bit is clever, since it prevents automakers from charging monthly fees as they do for heated seats and other niceties. It’s just a bill now, of course, and stands about as much chance of becoming law as anything else that makes sense does, so we’re not holding our breath on this one. But at least someone recognizes that AM radio still has a valid use case.

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Building A Receiver With The ProgRock2 Programmable Crystal

April 28, 2023 by 11 Comments

Crystals are key to a lot of radio designs. They act as a stable frequency source and ensure you’re listening to (or transmitting on) exactly the right bit of the radio spectrum. [Q26] decided to use the ProgRock2 “programmable crystal” to build a receiver that could tune multiple frequencies without the usual traditional tuning circuitry. 

 The ProgRock2 is designed as a tiny PCB that can be dropped into a circuit to replace a traditional crystal. The oscillators onboard are programmable from 3.5KHz to 200 MHz, and can be GPS discliplined for accuracy. It’s programmable over a micro USB pot, and can be set to output 24 different frequencies, in eight banks of three. When a bank is selected, the three frequencies will be output on the Clock0, Clock1, and Clock2 pins.There was some confusion regarding the bank selection on the ProgRock2. It’s done by binary, with eight banks selected by grounding the BANK0, BANK1, and BANK2 pins. For example, grounding BANK2 and BANK0 would activate bank 5 (as 101 in binary equals 5). Once this was figured out, [Q26] was on top of things.

In his design, [Q26] hooked up the ProgRock2 into his receiver in place of the regular crystal. Frequency selection is performed by flipping three switches to select banks 0 to 7. It’s an easy way to flip between different frequencies accurately, and is of particular use for situations where you might only listen on a limited selection of amateur channels.

For precision use, we can definitely see the value of a “programmable crystal” oscillator like this. We’ve looked at the fate of some major crystal manufacturers before, too. Video after the break.

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Low-Cost RF Power Sensor Gets All The Details Right

April 25, 2023 by 25 Comments

Dirty little secret time: although amateur radio operators talk a good game about relishing the technical challenge of building their own radio equipment, what’s really behind all the DIY gear is the fact that the really good stuff is just too expensive to buy.

A case in point is this super-low-cost RF power sensor that [Tech Minds (M0DQW)] recently built. It’s based on a design by [DL5NEG] that uses a single Schottky diode and a handful of passive components. The design is simple, but as with all things RF, details count. Chief among these details is the physical layout of the PCB, which features a stripline of precise dimensions to keep the input impedance at the expected 50 ohms. Also important are the number and locations of the vias that stitch the ground planes together on the double-sided PCB.

While [Tech Minds]’ first pass at the sensor hewed closely to the original design and used a homebrew PCB, the sensor seemed like a great candidate for translating to a commercial PCB. This version proved to be just as effective as the original, with the voltage output lining up nicely with the original calibration curves generated by [DL5NEG]. The addition of a nice extruded aluminum case and an N-type RF input made for a very professional-looking tool, not to mention a useful one.

[Tech Minds] is lucky enough to live within view of QO-100, ham radio’s first geosynchronous satellite, so this sensor will be teamed up with an ADC and a Raspberry Pi to create a wattmeter with a graphical display for his 2.4-GHz satellite operations.

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Tiny Three-Tube Receiver Completes Spy Radio Suite

April 22, 2023 by 6 Comments

In our surface-mount age, it’s easy to be jaded about miniaturization. We pretty much expect every circuit to be dimensionally optimized, something that’s easy to do when SMDs that rival grains of sand are available. But dial the calendar back half a century or so and miniaturization was a much more challenging proposition.

Challenging, perhaps, but by no means unachievable, as [Helge Fyske (LA6NCA)] demonstrates with this ultra-compact regenerative vacuum tube receiver. It’s a companion to his recent “spy transmitter,” a two-tube radio built in — or on, really — an Altoids tin. The transmitter was actually a pretty simple circuit, just a crystal-controlled oscillator and an RF amplifier really, but still managed about 1.5 Watts output on the 80-meter ham band.

The receiver circuit ended up being much more complicated, as receivers do, and therefore harder to cram into the allotted space. [Helge]’s used a three-tube regenerative design, with one tube each devoted to the RF amp, detector/mixer, and audio amplifier stages. As in the transmitter, the receiver tubes are mounted on the outside of the box, with the inside crammed full of components. [Helge] had to be quite careful about component positioning, to prevent interstage coupling and other undesirable side effects of building in such close quarters.

Was it worth it? Judging by the video below, absolutely! We’ve rarely heard performance like that from even a modern receiver with all the bells and whistles, let alone from a homebrew design under such constraints. It sounds fantastic, and hats off to [Helge] for completing his spy radio suite in style.

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Your Multimeter Might Be Lying To You

April 10, 2023 by 33 Comments

Multimeters are indispensable tools when working on electronics. It’s almost impossible to build any but the most basic of circuits without one to test and troubleshoot potential issues, and they make possible a large array of measurement capabilities that are not easily performed otherwise. But when things start getting a little more complex it’s important to know their limitations, specifically around what they will tell you about circuits designed for high frequency. [watersstanton] explains in this video while troubleshooting an antenna circuit for ham radio.

The issue that often confuses people new to radio or other high-frequency projects revolves around the continuity testing function found on most multimeters. While useful for testing wiring and making sure connections are solid, they typically only test using DC. When applying AC to the same circuits, inductors start to offer higher impedance and capacitors lower impedance, up to the point that they become open and short circuits respectively. The same happens to transformers, but can also most antennas which often look like short circuits to ground at DC but can offer just enough impedance at their designed frequency to efficiently resonate and send out radio waves.

This can give some confusing readings, such as when testing to make sure that a RF connector isn’t shorted out after soldering it to a coaxial cable for example. If an antenna is connected to the other side, it’s possible a meter will show a short at DC which might indicate a flaw in the soldering of the connector if the user isn’t mindful of this high-frequency impedance. We actually featured a unique antenna design recently that’s built entirely on a PCB that would show this DC short but behaves surprisingly well when sending out WiFi signals.

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