PI4ZLB

What attracts a lot of people to amateur radio is that it gives you the ability to make your own gear. Scratch-building hams usually start by making their own antennas, but eventually, the itch to build one’s own radio must be scratched. And building this one-transistor transmitter is just about the simplest way to dive into the world of DIY radio.

Of course, limiting yourself to eight components in total entails making some sacrifices, and [Kostas (SV3ORA)]’s transmitter is clearly a study in compromise. For starters, it’s only a transmitter, so you’ll need to make other arrangements to have a meaningful conversation. You’ll also have to learn Morse code because the minimalist build only supports continuous-wave (CW) mode, although it can be modified for amplitude modulation (AM) voice work.

The circuit is flexible enough that almost any part can be substituted and the transmitter will still work. Most of the parts are junk-bin items, although the main transformer is something you’ll have to wind by hand. As described, the transformer not only provides feedback to the transistor oscillator, but also has a winding that powers an incandescent pilot lamp, and provides taps for attaching antennas of different impedances — no external tuner needed. [SV3ORA] provides detailed transformer-winding instructions and shows the final build, which looks very professional and tidy. The video below shows the rig in action with a separate receiver providing sidetone; there’s also the option of using one of the WebSDR receivers sprinkled around the globe to verify you’re getting out.

This little transmitter looks like a ton of fun to build, and we may just try it for our $50 Ham series if we can find all the parts. Honestly, the hardest to come by might be the variable capacitor, but there are ways around that too.

So far in the $50 Ham series, I’ve concentrated mainly on the VHF and UHF bands. The reason for this has to do mainly with FCC rules, which largely restrict Technician-level licensees to those bands. But there’s a financial component to it, too; high-frequency (HF) band privileges come both at the price of learning enough about radio to pass the General license test, as well as the need for gear that can be orders of magnitude more expensive than a $30 handy-talkie radio.

But while HF gear can be expensive, not everything needed to get on the air has to be so. And since it’s often the antenna that makes or breaks an amateur radio operator’s ability to make contacts, we’ll look at a simple but versatile antenna design that can be adapted to support everything from a big, powerful base station to portable QRP (low-power) activations in the field: the end-fed half-wave antenna.

Making a Match

There are plenty of hams out there for whom antenna building is the be-all and end-all of the hobby. I get that; there’s a non-zero amount of wizardry that goes into designing an antenna that will do what you want it to do electrically, and plenty of engineering involved in making sure it stands up to the elements. I think the latter aspect of antenna building is more attractive to me personally. Getting an antenna to survive wind, snow, sun, and rain is an interesting challenge, so I tend to spend more time thinking about the mechanical aspects of design that someone has already worked the RF bugs out of.

So I set out looking for an antenna that would work for my situation. Perhaps the easiest antenna to build is the classic half-wave dipole. These have two elements, each one-quarter of the design wavelength, radiating out from a central feed point, which is where the coaxial cable feedline attaches. There are elaborations and complications, of course, but the basic issue for me is the central feed point. My shack is located at the very back corner of my property, so it’s difficult to rig an antenna like that without a long feedline, which can introduce unacceptable signal losses. Plus, a dipole for the 80-meter band would be 40 meters end-to-end, and that would be hard to fit across my long, narrow suburban lot.

For my purposes, the end-fed half-wave (EFHW) antenna is a good choice. It’s exactly what it sounds like: a chunk of wire one-half of a wavelength long (in my case, 40 meters long so I can work the 80 meter band) that is fed from its end. But it’s not as simple as cutting a 40 meter long piece of wire and sticking it on your radio. The problem is that the impedance of an antenna varies as the feedpoint moves away from the center. The impedance increases all the way up to about 2,500 ohms when the feedpoint reaches the end of the wire, which would be a very bad match indeed for a transceiver expecting a 50 ohm load.

To fix this, EFHW antennas need a transformer to match impedances. When used to match impedance between a balanced antenna, like a dipole, and an unbalanced feedline, like coaxial cable, these are referred to as “baluns”. In this case, though, both the antenna and the coax feedline are unbalanced, so the transformer I built is technically an “unun”. Whatever you call it, it’s a pretty easy build.

I followed the excellent instructions provided by Steve Nichols (G0KYA) to wind my 49:1 autotransformer. It’s basically just big ferrite toroid core — I got mine from eBay, but there are plenty of options on Amazon — with a few windings of magnet wire. My core is an FT-240-61, which means its outside diameter is 2.4 inches and it’s made of type 61 material. I used 18 AWG magnet wire for the windings. While I was winding it, I noticed that the lacquer coating on the magnet wire was getting nicked by the edges of the ferrite core. I rewound it after covering the toroid with cloth friction tape to cushion the edges a bit — shorts would be no bueno in something designed to handle 100 Watts of transmitter output.

Like I said, a lot of the fussing I did with this transformer had to do with making it work mechanically. I mounted it into a sturdy plastic electrical enclosure and provided stainless steel fittings for connecting the antenna wire and the ground connection. I also installed an eye bolt to tether the antenna wire. A good-quality SO-239 socket for the feedline connection and a 100 pF high-voltage capacitor for better matching on the higher frequency bands completed the transformer. With luck, this antenna should cover 80 m to 10 m bands.

Pushing Rope

As luck would have it, my lot is just about 150 feet deep, and I’m both blessed and cursed by a lot of very tall, very sturdy Ponderosa pines. The length of my lot and the location of the trees allows for a full 40-meter wire in a sort of “inverted-L” configuration. My plan was to slope the wire from the transformer up as far as possible in the first tree, then run it horizontally to an anchor point in a second tree.

This sounds far, far easier than it actually is. While many hams have had good luck suspending antennas from lines lofted over branches, my pine trees have all been pruned of their lower branches, with the first living branches more than 40′ (12 meters) above the ground. I opted for a “work smarter” approach and came up with an idea to basically push a loop of rope up the tree using PVC pipe as a push stick. Although the roughness of the Ponderosa bark constantly snagged the nylon rope and the PVC pipe flopped around as I added sections , it actually worked well enough to get the anchor point about 25′ (7.5 m) above the ground — not much higher than I could have gotten with my 24′ ladder, but with a whole lot less risk of falling to my death.

The anchor point was set in the other tree using a similar method, which drew a lot of attention from the neighbors. One should always seize such opportunities to do a little “ham goodwill” outreach, and I assured the neighbors that I wouldn’t be sterilizing their kids or interfering with their TV reception. In an example of karma, though, the tree I was working in decided to shed a dead branch the next day, which came down and damaged my neighbor’s Durango. It clearly came from much higher in the tree than I was working, but it still caused a little bit of the old stink eye.

One of the most important parts of using trees as anchors for long-wire antennas is dealing with sway. Trees move around quite a bit, and if you anchor a wire tightly between two trees without allowing for them to move with the wind, sadness will ensue. And yet, you want your wire to stay more or less taut, since its shape affects its performance. There are a couple of ways to deal with this, and I chose to use clothesline pulleys at both my anchor points. At the midpoint, the wire runs through the pulley; at the end anchor, the wire is tied off to a length of strong nylon cord through a dogbone insulator. That cord runs through the pulley and down the trunk of the tree to an anchor point through a strong spring. When the trees sway, the antenna can extend or retract by several inches without sagging or snapping.

On the Air at Last

I have to admit that this installation isn’t actually complete yet. Antennas really should be properly grounded, and I’m keen to pound a ground rod in near the transformer. However, both the mains feeder for my house and the primary feeder for the entire neighborhood are buried directly under our back fence, making this a high-risk endeavor. As good as underground location services are, I’m not keen to test their precision with my precious self. So I’m going to wait for a decent ground.

Still, I couldn’t help but want to try this antenna out, so to keep RF out of the shack, I wound a 10-turn air-core choke on the feedline and hooked it up. I haven’t made any QSOs yet, but using WSPR, the Weak Signal Propagation Reporter system, I was able to reach four continents over a 24-hour period on the 80-, 40-, 30-, and 20-meter bands.

And speaking of WSPR, that and other digital modes are what we’ll be talking about in the next installment of the $50 Ham. Spoiler alert: despite my previous gripes, I think I’m falling in love with ham radio again.

If you are below a certain age, you’ve probably never heard of a Q multiplier. This is a device that increases the “Q” of a radio receiver’s intermediate frequency and, thus, provide a higher selectivity. If you enjoy nostalgia, you can see inside a 1960s-era Heathkit QF-1 Q multiplier in [Jeff’s] informative video, below.

The Q multiplier was a regenerative amplifier that operated at just below the oscillation point. This provided very high amplification for the frequency of interest and less amplification for other frequencies. Some radios had a stage like this built-in, but the QF-1 was made to add into an external radio. For some Heathkit receivers, there was a direct plug to tap into the IF stage for this purpose. Othe radios would require some hacking to get it to work.

The QF-1 had several modes of operation where it could act as bandpass filter or a notch filter. You could also tune the frequency using the main knob. The circuit when revealed isn’t overly complex and there is no printed circuit board. The active device was a dual triode.

If you want a deeper discussion of the circuit, the Orange County Amateur Radio Club newletter a few years back had a great article on this device by [AF6C]. It explains how each mode works. It also mentions a few of the device’s offspring such as the HD-11 and GD-125, which was sold until 1971.

If you have plans of building a circuit like this, keep in mind that the intermediate frequency for most radios in those days was 455 kHz, which is what the QF-1 expects. Most communication receivers today use significantly higher IF for a variety of reasons (10.7 MHz, for example, is common).

We always enjoy [Jeff’s] videos of old receivers and gear. Not that he’s the only one doing things like that.

The United Kingdom is somewhat unique in the world for requiring those households which view broadcast television to purchase a licence for the privilege. Initially coming into being with the Wireless Telegraphy Act in 1923, the licence was required for anyone receiving broadcast radio, before being expanded to cover television in 1946. The funds generated from this endeavour are used as the primary funding for the British Broadcasting Corporation.

Of course, it’s all well and good to require a licence, but without some manner of enforcement, the measure doesn’t have any teeth. Among other measures, the BBC have gone as far as employing special vans to hunt down illegally operating televisions and protect its precious income.

The Van Is Coming For You

To ensure a regular income, the BBC runs enforcement operations under the TV Licencing trade name, the entity which is responsible for administering the system. Records are kept of licences and their expiry dates, and investigations are made into households suspected of owning a television who have not paid the requisite fees. To encourage compliance, TV Licencing regularly sends sternly worded letters to those who have let their licence lapse or have not purchased one. In the event this fails, they may arrange a visit from enforcement officers. These officers aren’t empowered to forcibly enter homes, so in the event a homeowner declines to cooperate with an investigation, TV Licencing will apply for a search warrant. This may be on the basis of evidence such as a satellite dish or antenna spotted on the roof of a dwelling, or a remote spied on a couch cushion through a window.

Alternatively, a search warrant may be granted on the basis of evidence gleaned from a TV detector van. Outfitted with equipment to detect a TV set in use, the vans roam the streets of the United Kingdom, often dispatched to addresses with lapsed or absent TV licences. If the van detects that a set may be operating and receiving broadcast signals, TV Licencing can apply to the court for the requisite warrant to take the investigation further. The vans are almost solely used to support warrant applications; the detection van evidence is rarely if ever used in court to prosecute a licence evader. With a warrant in hand, officers will use direct evidence such as a television found plugged into an aerial to bring an evader to justice through the courts.

Detecting Television Usage

The vans were first deployed in 1952, with equipment designed to pick up the magnetic field from the horizontal deflection scanning of the picture tube, at 10.125 KHz. Loop antennas were used to detect the second harmonic of this signal at 20.25 KHz, which was mixed with a local beat frequency oscillator at 19.25 KHz to create a 1 KHz tone to indicate to the operator when a signal was picked up. Three antennas were used, one on the front of the van and two on the rear on the left and right sides. When the van was next to an operating television in a house, the signal between the front and side antenna would be roughly the same. Signal from the right and left antennas could then be compared to determine which side of the street the television was on.

Once ITV started broadcasting in 1963, this method of detection became impractical. The two television stations did not synchronise their line-scan signals, so neighbouring houses watching different channels would create confusing interference for the detector. To get around this, the vans switched to detecting the local oscillator of the TV set’s superheterodyne VHF receiver instead. With stations broadcasting on bands spanning 47 to 240 MHz, it was impractical at the time to build a tuner and antenna to cover this entire range. Instead, the equipment was designed to work from 110-250MHz tuning in the fundamental frequencies of the higher bands, or the harmonics of the lower frequency oscillators. A highly directional antenna was used to hone in on a set, and a periscope was installed to allow the operator to view the house the antenna was pointing at. If operating in the dark, the periscope could instead be used to shine a small dot of light in the direction of the antenna’s facing, to identify the relevant target. Results were cross-referenced with a list of houses with lapsed or absent licences to help hunt down evaders.

The introduction of UHF transmissions led to further redesigns. Engineers again leaned on harmonics to allow a single system to cover the full range from low VHF to higher UHF frequencies. A pair of 6′ long log-periodic spiral antennas were used, mounted on top of the van, which could be varied in spacing to effectively tune different frequencies. In practice, the antennas would be pointed towards a row of houses, while the van was slowly driven along the street. The beam pattern of the antenna pair would show seven distinct lobes on a CRT inside the van when a TV was detected. An operator would press a button to mark house boundaries on the CRT as the van moved, and when the lobe pattern centered on a particular house, the TVs location was clear. The hardware was further refined over the years, with various antenna rigs and detection equipment used as technology marched on.

Seeking Television in Modern Times

Modern efforts to detect licence evasion are shrouded in mystery. Modern flatscreen displays receiving digital television signals do not emit as much radio frequency interference as older designs, and any such signals detected are less easily correlated with broadcast television. An LCD television in the home can just as easily be displaying output from a video game console or an online streaming service, with both being usage cases that do not require the owner to pay a licence fee. Based on an alleged BBC submission for a search warrant in recent years, there may be optical methods used in which reflected light from a television in a viewer’s home is compared to a live broadcast signal. The BBC declined to answer the Freedom of Information request with any details of their methods, other than to say they have employed vehicles and handheld devices in enforcement efforts. However, given the multitude of broadcast, cable and satellite channels now available, the comparison effort would necessarily be much harder, leading some to suspect the days of the detector van are largely over.

While the TV licence may have its days numbered with the increased dominance of streaming content, it remains a quirky piece of legislation that spawned the development of a technical curiosity. If you fancy yourself a television sleuth, sound off in the comments with your chosen approach to hunting for televisions watching broadcast content illegally in this modern era. And be sure to look over your shoulder – you never know when TV Licencing might be knocking on your door!

If there’s anything about amateur radio that has more witchcraft in it than the design and implementation of antennas, we don’t know what it would be. On the face of it, hanging out a chunk of wire doesn’t seem like it should be complicated, but when you dive into the details, building effective antennas and matching them to the job at hand can be pretty complex.

That doesn’t mean antenna topics have to remain a total mystery, of course, especially once someone takes the time to explain things properly. [Charlie Morris (ZL2CTM)] recently did this with a simple antenna tuner, a device used to match impedances between a transmitter and an antenna. As he explains in the first video below, his tuner design is really just a Wheatstone bridge where the antenna forms half of one leg. A toroidal transformer with multiple taps and a variable capacitor forms an LC circuit that matches the high impedance antenna, in this case a multi-band end-fed halfwave, with the nominal 50-ohm load expected by the transceiver. A small meter and a diode detector indicate when the bridge is balanced, which means the transceiver is seeing the proper load.

The second video below shows the final implementation of the tuner; as a fan of QRP, or low-power operation, [Charlie] favors simple, lightweight homebrew gear that can be easily taken into the field, and this certainly fits the bill. A final video shows the tuner in use in the field, with a NanoVNA proving what it can do. As usual, [Charlie] protests that he not an expert and that he’s just documenting what he did, but he always does such a good job of presenting the calculations involved in component selection that any ham should be able to replicate his builds.

The modern ham radio shack can take many forms. Some are shrines the “boat anchor” radios of old, named for their considerable weight. Others are simply a small, unassuming software-defined radio (SDR) hooked up to a laptop. Nowadays, many shacks fall somewhere in the middle. It’s not uncommon to find a sleek Icom IC-7300 sitting atop an ancient Hallicrafters SX-115 (which sounds suspiciously like the author’s setup). When a ham wants to work a digital mode such as FT-8, they will undoubtedly reach for a newer radio complete with USB (Universal Serial Bus in this case, not Upper Sideband) rig control — but what if the newest piece of equipment they have is a thirty-year-old Kenwood?

If that sounds like you, then fear not because [Steve Bossert] has you covered. He took his trusty Kenwood TS-50, a classic radio from 1993 whose most advanced feature is fuzzy logic, and upgraded it with USB (again, the serial bus) control.

When Kenwood designed the TS-50, they had computer control in mind. There’s a hidden port on the bottom of the unit which reveals a connector that mates with Kenwood’s proprietary (and expensive) set of serial control cables. Thankfully, the engineers over at Kenwood decided to use UART for PC communication, so slapping a USB port in the radio’s case isn’t as daunting as it may sound. [Steve] picked up a CP2104 USB-TTL UART Serial Adapter and wired it up to the radio’s control port. After a bit of drilling, screwing, and gluing, the radio had an upgraded (and non-proprietary!) interface compatible with the ever-popular hamlib. While this doesn’t cover all radio control functions, it gets you tuning, which is pretty important. For a fully modern radio experience, [Steve] suggests using the 8-pin mic connector along with an interface such as Rigblaster or Signalink. This adds PTT and audio signal routing.

If you want to try this for yourself, be sure to check out [Steve]’s extremely well-documented writeup. You could even take this a step further and control your TS-50 from your smartphone with this HTML5 interface we saw a few months back.

Many ham radio operators now live where installing an outdoor antenna is all but impossible. It seems that homeowner’s associations are on the lookout for the non-conformity of the dreaded ham radio antenna. [Peter] can sympathize, and has a solution based on lessons of spycraft from the cold war.

[Peter] points out that spies like the [Krogers] needed to report British Navy secrets like the plans for a nuclear boomer sub to Russia but didn’t want to attract the attention of their neighbors. In this case, the transmitter itself was so well-hidden that it took MI5 nine days to find the first of them. Clearly, then, there wasn’t a giant antenna on the roof. If there had been, the authorities could simply follow the feedline to find the radio. A concealed spy antenna might be just the ticket for a deed-restricted ham radio station.

The antenna the [Kroger’s] used was a 22-meter wire in the attic of their home. Keep in mind, the old tube transmitters were less finicky about SWR and by adjusting the loading circuits, you could transmit into almost anything. Paradoxically, older houses work better with indoor antennas because they lack things like solar cell panels, radiant barriers, and metallic insulation.

Like many people, [Peter] likes loop antennas for indoor use. He also shows other types of indoor antennas. They probably won’t do as much good as a proper outdoor antenna, but you can make quite a few contacts with some skill, some luck, and good propagation. [Peter] has some period spy radios, which are always interesting to see. By today’s standards, they aren’t especially small, but for their day they are positively tiny. Video after the break.

If you think spy radios were small then, you should see what you can do now. Then again, some of the most famous cold war spy radios didn’t have any obvious antenna or even required power.

[K6ARK] likes to operate portable, so he puts together very lightweight antennas. One of his latest uses tiny toroids and SMD capacitors to form trap elements. You can see  the construction of it in the video below.

You usually think of toroid winding as something you do when building transmitters or receivers, especially small ones like these. We presume the antenna is best for QRP (low power) operation since the tiny core would saturate pretty quickly at higher power. Exactly how much power you should pass through an FT50-43 core depends on the exact application, but we’ve seen numbers around 5 watts.

The SMD capacitors mount right inside a hacked up BNC connector. That makes for a very compact construction at the expense of a little fine work with a soldering iron while building. There is more construction detail on similar traps in a second video that you can see below.

The availability of antenna analyzer equipment makes projects like this easier. The concept of end-fed halfwave has its detractors and proponents. [AA5TB] has a page that explains a bit about the theories surrounding the antenna. Regardless, [K6ARK] says he’s worked the world on this type of antenna and many people swear by them.

Not a ham yet? [Dan Malone] wants you to invest $50 and change that. We suspect, though, you’ll be happier with more wire in the air.

I suppose most of us have had the experience of going to the mailbox and seeing that telltale package in the white plastic bag, the sign that something has just arrived from China. This happened to me the other day, and like many of you it was one of those times when I puzzled to myself: “I wonder what I bought this time?”

With so many weeks or months between the time of your impulsive click on the “Buy Now” button on AliExpress or eBay and the slow boat from China actually getting the package to your door, it’s easy enough to forget what exactly each package contains. And with the price of goods so low, the tendency to click and forget is all the easier. That’s not necessarily a good thing, but I like surprises as much as the next person, so I was happy to learn that I was now the owner of a tinySA spectrum analyzer. Time for a look at what this little thing can do.

First Impressions

A caveat: I’m by no means an expert on spectrum analyzers. In fact, this is the first time I’ve ever handled one, unless you count using the FFT functions in my digital oscilloscope, which you probably shouldn’t. So there’s probably plenty of room for operator error and misconceptions about what a spectrum analyzer can do in the tests that I ran, but I still think this is valuable as an example of what a tool like this can do in the hands of an enthusiastic newbie.

Anyone familiar with the NanoVNA, a small but full-featured vector network analyzer that we’ve featured a few times on these pages, will see a strong family resemblance between it and the tinySA, both in the hardware and the software. That’s for good reason — the code behind tinySA is a fork off the NanoVNA codebase, and the main developer of NanoVNA, edy555, is a contributor to the tinySA project, which is owned by Erik Kaashoek.

The tinySA arrived in a surprisingly nice “presentation quality” box with a gold-stamped logo on the top. Erik takes pains to note that this is one way to tell you’re getting an original tinySA as opposed to one of the inevitable knock-offs that’ll flood the market soon enough. I’m not sure that alone would keep the pirates at bay, but it’s at least an attempt and it’s a nice touch to boot.

Along with the tinySA, which is about the size of a deck of playing cards, the box contains a pair of SMA jumper cables, a small telescoping whip antenna, a female-to-female SMA adapter, a wrist strap, and a USB-C cable. The case of the tinySA is injection molded ABS, and a nice upgrade in look and feel from the open board design of the NanoVNA. The front of the tinySA has no controls, just the 2.8″ 320×240 resistive touch-screen display. The top has a power switch and a jog control. The left side has two SMA jacks, labeled HIGH and LOW. It’s very lightweight but feels solid in the hand.

Of course the first thing I did was pop the case open and take a look inside. There’s not a lot to see at first — most of the interesting RF stuff is safely tucked under shielding. I figured I’d have to bust out the Hakko to take the tins off, but luckily they’re all spring-clipped to the ground plane, so removing them just took a small screwdriver. Underneath lay the expected RF wizardry, including the expected Silicon Labs chips. I found two Si4432 ISM transceiver chips, presumably one each for the high and low range of the tinySA. There’s also what appears to be a Peregrine Semiconductor PE4302 RF digital attenuator, and a bunch of other goodies. The layout is nice with plenty of via stitching, and the assembly quality is really good.

Satisfied with the insides, I moved on to the “First Steps” as listed in the video below, to get acquainted with the device. Erik has chosen to rely on the tinySA wiki and some how-to videos for most of the documentation, and while that’s understandable it also leaves a few holes that are up to the user to fill in. For those of us who prefer a real manual, Kurt Poulsen, a ham from Denmark, has written up a comprehensive how-to document that might be of help.

Anyone who has used a NanoVNA will feel at home in the tinySA interface. Calibration of the tinySA is done via the built-in signal generator, more on that below. Calibration itself is simple: hook the jumper coax between the two SMA jacks and select LEVEL CAL from the configuration menu. The calibration then proceeds automatically. The same menu offers a self-test function too, which cycles through a series of ten tests that take about 15 seconds to complete.

The Good Stuff

As for its primary purpose, the tinySA performed admirably in my limited tests. I took a look at the spectrum of signals generated by my scope’s built-in waveform generator and everything looked good — a 10-MHz sine wave appears as a single strong fundamental spike and one harmonic about 50 dBm lower. Switching the waveform to a square wave at the same frequency did what I thought it would — a big peak at the fundamental and a bunch of spurs at the odd fundamentals.

With the basics out of the way, I took a look at the tinySA’s built-in signal generator. As mentioned above, the signal generator is used for calibration, but it’s a pretty capable tool all on its own. It’s actually more of a function generator, since it can not only output a nice clean sine wave on the low output between 100 kHz and 350 MHz, but it can also modulate the signal (AM, narrow FM, and wide FM) and do sweeps both across a frequency range and over amplitude. On the high output, the signal generator does a square wave output from 240 MHz to 960 MHz with a configurable, non-sweepable amplitude, narrow FM or wide FM modulation, and a frequency sweep.

I gave the signal generator a go and took a look at its output with my Keysight DSOX1102G. The sine wave generated on the low output looked clean across the specified bandwidth, and the frequency was spot on. I tried playing with the modulation function, and it worked pretty much as I expected. It’ll be nice to have another signal generator around the shop.

With all the pleasantries dispensed, I turned to the one task pretty much every ham will want to turn a spectrum analyzer on: finding out just how bad the signal from a cheap handy talkie is. I talked about this a bit in one of my $50 Ham articles, and we’ve seen comprehensive analyses of spurious emissions from these radios that are far more in-depth than anything I could come up with using the tinySA. But still, I thought I’d give it a whirl. I grabbed my Baofeng UV-5RA, a homebrew 40 dB attenuator I built a while back, and an unwieldy collection of adapters to connect everything together.

Being under the impression that the spurious emissions on Baofeng tend to be worse on the UHF band, I tried 420 MHz first. The first thing I noticed was that the fundamenal was off a bit from the where it should be. I also noticed a small forest of spurs starting at 500 MHz and extending all the way up past 800 MHz. The strongest spur was about 43 dBm down from the fundamental. The FCC rules on spurious emissions don’t seem to cover this band, but they do say that between 30 and 225 MHz, spurs need to be at least 40 dBm below the fundamental. So within the limits of my test setup, the Baofeng seems to just barely comply.

Just for completeness, I repeated the same test on the 2-m band. The signal was much cleaner here, with only a few spurs, the big one being at around 270 MHz. Again, this was about 43 dBm down from the fundamental, meaning it was probably in compliance. Again, this was only a rough test, with a test setup leaving much to be desired. But still, the tinySA is a nice way to take a look at what you’re actually putting out into the ether, and to at least get a rough idea how clean you’re operating.

The Not-So-Good Stuff

Like the NanoVNA before it, the tinySA has the capability of PC control. The Python program, TinySASaver, is geared mostly toward saving scans from the tinySA, but also provides additional capability, like doing frequency sweeps in segments and exporting data for further analysis. It also implements time-domain reflectometry (TDR) to measure cable lengths and find faults. Sadly, try as I might I was unable to get TinySASaver running on my Ubuntu machine. Erik is pretty clear that the code is still rough, and I’m far from a Python guru so I might be having library problems that would be easy to fix for someone with more experience. Luckily, I was able to scrounge up a decrepit Windows laptop and get a compiled version of another program running, so I didn’t have to resort to cell phone pictures for my screenshots.

I have noticed a couple of other annoying issues. The biggest is that the tinySA appears to crash when you click the screen off of one of the menus. This is annoying, as I often found myself stuck in a menu with no obvious “Back” button, and clicking on the background seemed like an intuitive way to work back to another menu. But this just throws a dump of all the registers up on the screen and locks the thing up. It’s not a huge deal to recover — toggle the power and it’ll boot right back up — but it can be annoying.This bug has been removed recently so this is working as it should by now.

I also found the touchscreen a bit finicky, which was a common complaint with the NanoVNA. The screen is far too small for my meathooks, but without a proper stylus, I resorted to a plastic spudger that worked only most of the time. Of course it was only then that I looked in the box and noticed the wrist strap with the attached guitar pick-like stylus — a thoughtful accessory indeed.

Verdict

I’m not entirely sure what I paid for the tinySA — like I said, I tend to order these things and then just forget about them. But I think it was around $60, and at that price I’d say adding a tinySA to your toolkit is a no-brainer. It’ll never substitute for a larger, full-featured instrument, but if your only need for a spectrum analyzer is to design the occasional filter or check signal quality, the tinySA is a pretty good deal.