Tag Archives: SDR

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UPDATE 11 May 2020: We recently learned that the MSI.SDR software defined radio dongle in the following post and tutorial is a clone of the SDRplay RSP1 SDR. We did not realize this when the post was published. Grayhat had done research prior to purchase and believed it not to be a clone, but only using the same chipset as the RSP1 (hence the compatibility with SDRuno). We have confirmed that it is indeed a clone now via SDRplay (clear here to read more via the excellent RTL-SDR blog). What follows isn’t an SDR review. Indeed, Grahat’s post has little to do with the receiver and much, much more to do with building proper antennas! We’ve removed links to the MSI.SDR and would encourage you to invest in the excellent SDRplay RSP1a instead (click here to read our RSP1a review). Thank you for understanding!

Many thanks to SWLing Post contributor, Grayhat, who shares the following guest post. He lives in Italy and has been in lock-down since the beginning of the pandemic. He pitched the idea of building an entire SDR setup from scratch–receiver and antennas–for less than 150 Euros (roughly $163 USD). I thought it was a brilliant idea and I believe he thoroughly enjoyed the challenge of sourcing the components and building a mini antenna farm on his balcony while in quarantine:

From Zero to SDR

by Grayhat

What follows doesn’t pretend to be some kind of “definitive guide” or “last word”, on the contrary, it’s aimed at people who have little or no experience with SDR but want to try putting together a decent station without paying an arm and a leg.

The idea of writing this came to me after reading a number of messages and discussions on various online groups/forums, in a lot of cases, someone bought an SDR (usually the ones coming with a telescopic whip antenna), and after connecting it was expecting it “just to work” or, better said, pretending that the SDR connected to that whip (usually placed on a table right near the computer) could receive ANY POSSIBLE signal, including transmissions coming from the “dark side of the moon.” 🙂 Those folks got scared by the fact that the SDR “didn’t work” and decided to give up; now, this short “guide” should allow anyone to setup what’s needed to have a working SDR

My self-imposed limitations for this project/experiment were the following:

The whole setup shouldn’t cost more than 150 Euros so that, if after trying the SDR one doesn’t like it, (s)he won’t have paid $$$, otherwise, if (s)he decides to keep it, the resulting station will allow for further expansion/improvement
The available space was considered to be that of an apartment, that is, no large field to put up huge wire antennas or to raise towers, the limit was the one of a balcony (in my home) that is 8 meters (max antenna length) by 3 meters (available height) by 2 meters (balcony width)
The whole setup should be simple and straightforward, no need to solder components or to build special types of antennas
Given the current Covid-19 sheltering, most components should be available online, while for others one may arrange with whatever is locally available (e.g. duct tape)

With the above limitations in mind, I took pencil, paper and rubber eraser (high-tech instruments, indeed) and started writing down a list of the needed stuff, after some writing, wiping and second thought, I came out with the following list, available on Amazon:

Bill of materials

Insulated wire (100mt x 2.5mm)
Paracord (100mt x 3mm)
Nylon cable tiers (100 pcs x 2.5mm x 100 mm)
Waterproof electrical junction box
NooElec Balun 1:9 V2
iChoose Ltd RG58+BNC coax, 15mts
BNC female to SMA male adapter (2 pcs)
Snap-on ferrite chokes for 9mm cables (10 pcs)
MSI.SDR 12 bit ADC was used for this experiment before realizing it is a clone of the SDRplay RSP1. We recommend the RSP1a as an upgrade.

The above includes all the needed stuff to put together a number of wire antennas (random wire, random dipole, loop…) the coax to connect the SDR, a balun to match the coax to the antenna and the accessory parts needed to put up the antenna. The selected SDR isn’t the common “RTL SDR” type, not that they don’t work, but their 8 bit ADC is far from being a good performer, so I decided to pick a different SDR which offers a 12 bits ADC and which also “presents itself” to the system as an SDRplay RSP1.

[Please note: we’ve since learned from SDRplay that the MSI.SDR is indeed a clone of the SDRplay RSP1. Here’s a post from the RTL-SDR blog confirming this. We recommend purchasing the RSP1a as a better alternative.]

Anyhow; all I can say is that after some tests, the MSI.SDR is a quite good unit and offers quite a lot of bangs for the buck, so I believe it may be a good unit for people willing to get their feet wet with SDRs

The above being said, here’s a pic of the MSI.SDR unit with the included stuff:

The unit is very small and the box has two connectors, an SMA for the antenna and a micro-USB (like the ones used in cellphones) for the USB cable which is used to both power and control it; the other bits are the telescopic whip antenna (around 98cm fully extended) with a magnetic base and a short run of coax, and the USB cable.

Once I got the SDR I decided to give the included whip antenna a try… well, to be clear, while it will allow you to pick up some strong local FM stations and maybe a bit else, it will only be useful to test if the SDR unit is working (before putting together our antenna), so don’t expect to receive much with that whip, yet… don’t throw it away, it may become useful (more later).

The other important piece is the BalUn. I picked a NooElec “Nine to One” v2, since I’ve used their v1 model and I’ve found it to work well, I decided to pick the newest model which has a better antenna wire connector. The BalUn, which is in effect a so-called “transformer balun” is really small and the junction box I bought is much bigger, but it isn’t a problem. All in all, the box may host a preamplifier in the future, but for the moment it’s fine for the balun. The following pic shows the balun “installed” inside the junction box:

The scissors are there to give you an idea of the sizes; to put together the whole thing, I started by preparing two pieces of wire (the 2.5mm one), made a turn with each wire and locked them with a nylon cable tier. Those turns will prevent the wire from sliding out and putting a strain on the balun connector. I did that since I didn’t have plastic washers at hand, otherwise you may just slide two plastic washers (or proper diameter) over the wires and use two nylon tiers to lock them. In either case, the idea is that the “loops” or the washers won’t slide through the box holes and will support that (little bit of) strain caused by the wire connection.

Next, I stripped some of the insulation from the ends and connected the wires to one of the balun connectors (I chose the one in the pic since I believe it’s the most suitable for this setup), at that point I continued cutting the smaller “ring” of the box insulation caps (the two at top and the bottom one). Then I placed a piece of carboard roll (from a kitchen-paper roll) at the bottom to serve as a support (you can see it below the balun). At that point, I slid the balun SMA connector through the bottom hole and used the SMA to BNC adapter to hold it, done so I slid the two wires (connected to the green wire connector) through the side hole and then inserted the connector into the balun. I then placed the other piece of paper roll above the balun and closed the box with its cap. As a note, to properly close it, start by inserting the screw into the cap holes till end, so that they’ll extrude from the bottom, then place the cap over the box and tighten the screws–you may need to use some force to properly tighten it.

Notice that the wire shown in the pic are SHORT, later on I replaced them with longer wires (outside the box) to be able to better connect the balun box to the antenna, but the remainder of the build is the same.

Now that I had my “balun box” ready, I measured the antenna wire and, using the paracord and some nylon tiers, I installed it. I also installed the “counterpoise” wire. For the latter, at first I tried just connecting the remainder of wire to the “gnd” of the balun, leaving the spool laying on the floor, but later on I decided to hang up the counterpoise and the final result was the following:

Click to enlarge

Not a work of art, but then since I was experimenting, I decided not to add PTFE and tape to allow me to quickly rearrange the antenna to run other configurations, yet, the whole setup worked quite well and stood fine to some wind and rain, the picture below shows the balun box with the antenna/counterpoise wires and the coax with the snap-on ferrite chokes.

Click to enlarge

Notice that to avoid putting strain on the balun wires, I used a wire clamp I had in my junkbox–the clamp is then tied to the paracord using a nylon tier and the paracord holds the assembly and keeps the antenna wire in position. The ferrite chokes aren’t properly seated, and I’m planning to remove and re-place them, but for the moment they’re okay. The balcony faces to south/south-west so the antenna has a free horizon of about 270 degrees ranging from the Adriatic coast to the Appennines (Mt. S.Vicino can be seen behind the paracord)–not bad. Here’s another pic showing the horizon to West, just to give you an idea:

Getting back to the antenna installation, the other end of the antenna wire is tied to the opposite side of the balcony as shown below (let aside the tent/awning, I raise them when using the SDR, also, the bowline knot isn’t correct, I’ll need to tie that again):

The counterpoise instead is supported by a lamp I’ve on the terrace, here’s it’s setup:

The “paracord” goes down to a plastic bottle filled with a water/chlorine mixture which serves to keep it in place. The remainder of the wire is just hanging down for about 1.5 meters (the counterpoise is shorter than the antenna wire, it’s about 2/3 of its length).

Ok, time to put the antenna and SDR to test, so I brought the coax inside home, connected the other SMA to BNC adapter to the SDR and connected the coax going to the antenna. Note that 15 meters of coax is enough for me, but if one wants a length of up to 25 mt, it won’t be a problem.

I already installed the SDR software, in my case since the unit identifies itself as an “SDR1” I downloaded the SDRPlay “SDRuno” software https://sdrplay.com/windl2.php and since I was at it I also downloaded the PDF manual https://www.sdrplay.com/downloads/ and the “CookBook” http://www.nn4f.com/SDRuno-cookbook.pdf and I heartly recommend reading and digesting them before starting the whole thing (while you wait for all the stuff to be delivered). An important note is that you MUST install the SDRuno software BEFORE connecting the SDR since that way, the SDRuno setup will install the proper drivers and you won’t have issues.

Anyhow, I connected the coax to the SDR and then it was time to fire up the whole thing and give it a spin; so I powered up the laptop (technically, a “transformable” laptop/tablet), started SDRuno, opened the “RX control” and “Main Spectrum” windows and then clicked the “play” button, clicked the “broadcast” band, and the “MW” one and got this:

Not exceptional maybe, but not bad, either; in particular if one considers that it’s from a quite short piece of wire which isn’t exactly placed in an ideal position.

Deutsche Welle

So I went on and explored the bands a bit. On ham bands the SDR picked up signals from the whole mediterranean basin (Cyprus, Lebanon, Spain and then some) and from north too (Russia, Germany, Denmark); then depending on time, I was able to clearly receive broadcasts from China, South America, Africa and more ham QSOs from a lot of places.

BBC Ascension Island 5/9+ and just a bit of QSB

I must admit I didn’ record the callsigns or stations identifiers (“guilty” your honor–!) but I was more focused on testing the SDR and antenna than running a “DX session” at any rate. On the BCB bands I picked up WWV, BBC, VoA, China Radio International, Radio Free Asia, Radio Romania and a bunch of others from Middle East, Asia, Africa and South America. While on the ham bands, I was able to pick up some quite interesting QSOs and then… well, I went hunting for higher frequencies signals!

I got Police, Ambulances, Air control…so even if that “piece of wire” isn’t optimized for VHF/UHF it seems to be working decently there too. By the way, when changing bands you may (and probably will) need to adjust the gain control, but that will be almost the only thing needed to pull in signals

At the end of the day, I can say that I’m quite pleased with the performance offered by this simple and cheap setup. For less than 150 euros you have everything you need, not just the SDR.

Sure, the setup may be improved, but then again you’ll have all of the basic parts, so you won’t need too much. For example, if you live in a really noisy environment, it would be a good idea to use a loop antenna. You would only need a “cross shaped” support (PVC pipes or wood will do). You could quickly put together the SRL (Small Receiving Loop) designed by Matt Roberts (KK5JY) http://www.kk5jy.net/rx-loop/ the balun will be the SAME (yes, no need to wind whatsoever!) so building it will just be a matter of assembling a cross shaped support for the wire (which we already have because it’s the same used for the wire antenna) and you’ll have it. While I already tried the SRL, I didn’t build one to test with this SDR, but I’ll probably do that as soon as SWMBO will start complaining about those “wires on the balcony.”

Also, at the beginning I wrote “more later” when writing about the telescopic whip included with the SDR. Here’s the idea–it requires soldering, so if you don’t want that, skip this: remove the adhesive sheet on the bottom of the antenna base to expose the bottom cap and then remove (extract) the bottom cap. You’ll see a magnetic ring and a “bell shaped” piece of metal (the “ground” for the whip). In the middle of the “bell” there will be the antenna connector which is soldered to the coax wire with a nut holding the connector (and the “bell”) in place. De-solder the coax, unscrew the antenna connector and extract it, at that point you’ll have the telescopic whip and its connector, now you may use them to build the active “whip” antenna described here:

http://www.techlib.com/electronics/antennas.html#Improved%20Active%20Antenna

Notice that it is NOT the “usual” active whip–the circuitry and idea behind it is totally different–yet it works fine and will serve you from VLF (not kidding) up to around 100MHz. It might be a good companion for the SDR. It won’t be as quiet as the loop, yet it may be a valid “all rounder.”

To conclude, I believe that the setup described above is something anyone can afford. You don’t need to be an engineer or to have special knowledge or abilities–it’s just a matter of putting together some bits and pieces.

Obviously, this setup doesn’t require a large space and offers good performance across the bands. Plus it’s so easy to improve since the 12bit SDR is a good starting point

All the best everyone and STAY HOME, STAY SAFE !

Thank you so much, Grayhat!

I love the fact that you invested (however modestly) in a proper antenna setup to better serve you rather than relying on the basic whip antenna that comes with the SDR. You’re right: too often, we invest a receiver, yet invest no money or time into building an appropriate antenna. The antenna is the most important component in a proper radio setup and those included telescoping whip antennas simply don’t perform well on the HF bands.

Based on our correspondence, I know you had fun piecing together this little system using a simple bill of materials and items you had on hand during the Covid-19 quarantine. Thank you for sharing it here with your SWLing Post community!

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More about hacking VGA cables to make binocular ferrite cores

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A few days ago, we posted an a short article showing how Oscar hacked a VGA cable to make a binocular ferrite core for his homebrew NCPL/Youloop antenna. Many thanks to SWLing Post contributor, Grayhat, who explored this clever hack a little further:

Hi Thomas, Having some time in my hands Sunday afternoon I decided to try pulling out the ferrite chokes from a VGA cable I had around, and while doing so, I decided to coarsely document the process with some pics.

Figure 1

The first thing to do is use a cutter to carefully cut around the “washer” shaped plastic at the connector end of the choke (fig.1, #1,#2, #3 above), then on the same side, after cutting the plastic also cut the inner conductors (fig.1, #1).

Move to the other side of the choke, gently cut around the “washer” w/o cutting the inner conductors, now pull the cable to extract it from the choke (fig.1, #3), repeat the process for the other choke.

Now look at the “cans” containing the chokes, one side of those will show a “cap” (fig.1, #4), insert a small screwdriver into the center hole and gently ply to one side to raise the cap and extract it (fig.2, #1).

Figure 2

The result will be as in fig.2, where #1 is the closing cap, #2 is the ferrite choke and #3 is the “can” containing the choke. Repeat the process and you’ll have two ferrite chokes as shown in fig.3 (the VGA connector is there to give an idea of the dimensions):

Figure 3

At this point, use some tape (duct tape will be a better idea, I used clear tape just to make an example) to tie the two ferrites together as in fig.4 and you’ll have your “binocular ferrite”:

Figure 4

Willing to use whatever you have there to wind the transformer, you may now extract the tiny insulated wires from the VGA cable (fig.1, #3, see wires) and use them for the windings.

Notice that other cables may use different choke “cans” which may need to cut a larger portion around the flat faces at the ends. But remember that in any case, those are just “snap-in” cans containing the ferrites, so with a bit of attention and patience, it shouldn’t be difficult extracting the ferrites.

Based on a little online research, it sounds like the ferrites used to choke the VGA cables (HDMI ones too) are generally type #31.

Looking at some #31 datasheets it appears that while #73 is works fine at frequencies below 50MHz, the #31 is best suited for the 1-300MHz range.

This means that #31 won’t be the best pick for mediumwave, although if one doesn’t have another choice… well, go for that! Also notice that the ferrite permeability is different:1500 for #31 and 2500 for #73. This means that we’ll need to increase the number of windings to achieve acceptable signal transfer, otherwise the transformer loss will make our antenna deaf.

One might try increasing the number of windings to say 8:8 or 16:16; as long as the winding
ratio will remain the same, there won’t be problems (although the resulting bandwidth will become narrower).

Thanks for documenting and sharing this, Grayhat! Since most of us have more time on our hands at home, I think it would be worth experimenting with the number of windings to see how it affects the antenna performance. That’s a clever thought, too, to use the VGA wires to wind the Balun. As long as the cable is long enough for the amount of turns, it’s certainly the most efficient use of resources!

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Radio Waves: Libre Space Foundation Reviews SDRs, ARRL VEC Statement, Pandemic Pastime, and Former CEO of RadioShack Now C-19 ER doctor

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Radio Waves: Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers. To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Ron, Paul, Marco Zennaro, and Richard Langley for the following tips:

The Libre Space Foundation reviews software defined radios (Hackaday)

If you want to go to the next level with software defined radio (SDR), there are a lot of choices. The RTL-SDR dongles are fine, but if you get serious you’ll probably want something else. How do you choose? Well, your friends at the European Space Agency Libre Space Foundation have published a paper comparing many common options. True, they are mostly looking at how the receivers work with CubeSats, but it is still a good comparison.

The devices they examine are:

RTS-SDR v3

Airspy Mini

SDRPlay RSPduo

LimeSDR Mini

BladeRF 2.0 Micro

Ettus USRP B210

Pluto SDR

They looked at several bands of interest, but not the HF bands — not surprising considering that some of the devices can’t even operate on HF. They did examine VHF, UHF, L band, S band, and C band performance. Some of the SDRs have transmit capabilities, and for those devices, they tested the transmit function as well as receive.

The review isn’t just subjective. They calculate noise figures and dynamic range, along with other technical parameters. They also include GNURadio flowgraphs for their test setups, which would be a great place to start if you wanted to do these kinds of measurements yourself.[…]

ARRL VEC Issues Statement on Video-Supervised Online Exam Sessions (ARRL News)

Very few ARRL Volunteer Examiner teams have successfully conducted in-person exam sessions (following social distancing guidelines) and video-supervised exam sessions using fillable PDF exams and documents. So far, we have found that both types of sessions take volunteer teams two to three times longer to conduct and accommodate fewer candidates than sessions conducted prior to the COVID-19 pandemic. So far, the video sessions have included only one examinee per session.

We ask the community to be patient with our volunteer teams as they navigate uncharted territory. Please remember with the introduction of significant new processes such as these, that there should be proof of concept, establishment of protocols and procedures, and beta testing before expanding to a larger audience. Video-supervised exam sessions require a different skillset than in-person exam administration. Not all teams will be equipped to deliver video exams right away.

The ARRL Volunteer Examiner Coordinator (VEC) has been investigating options for an online examination system.

Fillable PDFs are cumbersome within a video-supervised exam session process. We recognize that online testing would represent a large-scale solution for our thousands of VEs and would make session procedures easier for our teams, but this will not happen overnight.

The ARRL VEC will continue to adapt and respond to the evolving crisis as we search for viable and easy-to-use online examination system solutions and conduct exam sessions in innovative ways.[…]

Pandemic Pastime – Shortwave Radio (KFGO)

Ever since I was a little kid, I was fascinated that at night you could listen to radio stations from all over the country. My little Heathkit radio, which I built myself, could pick up stations in Minneapolis, Chicago, St. Louis, Denver, Little Rock, Pittsburgh to name a few. West coast stations were rare because it was tough getting a signal over the Rocky Mountains.

Then there was shortwave radio. A buddy of mine had one and he showed me a list of all the countries he was picking up. England, France, Germany, Latin American countries, numerous stations on the shortwave bands in America. Even Radio Havana coming out of Cuba. Anything from religion to hard edge rock and roll. He also noted he picked up Radio Free Europe and the Voice of America.

Well years later I would stop by my local Radio Shack and decided it was my turn to take up this hobby of monitoring shortwave radio. This particular radio also had a built in cassette player so you could record your found stations as well. It was really interesting to hear the news from other countries and get their take on what was happening in America.

One of the first frequencies I tuned in was WWV a shortwave radio station out of Fort Collins Colorado, that broadcasts the time via the atomic clock. The seconds tick off until the top of the hour when you hear a voice announce the time, followed by a tone that hits the top of the minute exactly on the nose. Great way to set the clock.

Now I know you can probably find all these shortwave stations on the internet, but what fun is that right?

With the covid-19 pandemic, this is a little something different than binge watching television, or building that 10th jigsaw puzzle or cleaning out that closet again and again.

Have a chair on the patio, a glass of your favorite beverage, extend the antenna, and start turning up and down the dial and see what you can find. I had a little notebook that I kept track of my searches. Don’t have it now though…lost it.

I’ll start a new one.

Stay safe everyone![…]

Former CEO of RadioShack now an ER doctor (National Post)

‘I am just one of those people who was very fortunate, where things worked out, and where I could do not just do one thing I really enjoyed in life, but two’

Brian Levy loved science as a kid. He had a microscope, read up on stuff in the encyclopedia and messed around with home experiment kits. During his high school years, he took every science credit possible. By his own admission, he was a “geek,” one with an equally strong passion, alongside science, for electronics.

Levy knew how to operate a shortwave radio. Weekend teenage heaven, in his mind, was hanging around the local RadioShack store, a warehouse of gizmos where he scored his first part-time job in 1974, earning US$1.40 an hour at a shop in downtown Atlanta. He was 15, which, alas, was too young to be working for the company, according to the folks at corporate headquarters in Texas, who fired him upon receiving his paperwork.

The dismissal didn’t sit well with Levy.

“I actually called the vice president of human resources in Texas,” he says. The executive was impressed by the moxie of the kid. On the day he turned 16, Levy was hired back.

[…]Levy did not foresee the premature end to his business career. When it came, rather than being crestfallen, he felt liberated, and free to pursue an “itch” that he had always felt the need to scratch. So he applied to medical school at McMaster University in Hamilton, ON. (Levy came to Canada in the first place after relocating RadioShack HQ north of the border as CEO. He is now a dual citizen, although his soft, buttery accent betrays his roots in the American south.)[…]

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Hack a broken VGA cable to make a binocular ferrite cores for your NCPL antenna

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Many thanks to Oscar (EA3IBC) who shares this simple hack.

I’ve gotten quite a few emails from Post readers telling me that the only thing holding them back from building a NCPL antenna is the BN-73-302 binocular ferrite core needed for the 1:1 Balun. While so much of the world is sheltering at home due to Covid-19, it’s less convenient to purchase one just for this purpose.

But almost everyone has an old VGA or USB cable with ferrite cores they can cannibalize for this very purpose. Oscar shared this super-simple hack on Twitter:

1. Cut the cable and remove the ferrite cores

2. Tape the two cores together

3. And wind four turns on both sides

Admittedly, this 1:1 balun might not have the same properties as the BN-73-302 from our tutorial, but it seems to be working for Oscar. Check out this screenshot he shared from SDR# while hooked up to his NCPL antenna:

Thanks again!

Readers, you can follow Oscar on Twitter by clicking here.

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Fenu posts a Malahit-DSP & Afedri LAN-IQ “Head to Head” comparison

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Many thanks to SWLing Post contributor, Dan Robinson, who shares the following video from Fernando Duarte, comparing the Malahit-DSP and the new Afedri LAN-IQ: