Tag Archives: Grayhat

Radio Waves: Dirty Transmitters, World Amateur Radio Day, Electronic Echoes, DRM via Android, and 10 More BBC AM Services Close

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 Grayhat, David Iurescia, Bill Hemphill, Harald Kuhl, and Troy Riedel for the following tips:


Transmitter Noise / Dirty Transmitters: Receiver Performance has hit a Brick Wall (DJ0IP)

For the past 15 years, Ham Radio’s Mega-Focus on Receiver Dynamic Range (DR3) has resulted in the community ignoring other factors that are just as important to receiver performance.

Even though our receivers have made a quantum leap in performance in important parameters such as DR3, RMDR, etc., On-The-Air Reception has gotten worse.

Unless used at a multi-transmitter site, today’s typical user won’t detect a difference in the receiver performance between a radio with 90 dB DR3 and a radio with 110 dB DR3. That’s because Receiver Performance is not the limiting factor.[]

World Amateur Radio Day 18 April 2021 (IARU REGION 2 Newsletter)

World Amateur Radio Day (WARD) is an opportunity to celebrate the many accomplishments and contributions of amateur radio to the communications technology revolution which has dramatically impacted the daily life of virtually everyone on the planet. Many of these technologies and techniques started as experiments, not by governments or commercial enterprises, but by radio amateurs.

WARD 2021 commemorates the 96th anniversary of the International Amateur Radio Union’s founding in 1925, where amateurs first met in Paris to band together to give voice to these early experimenters to national governments and international bodies representing all radio amateurs.

The almost universal adoption of mobile technology created ever increasing demand on a finite resource, the radio spectrum. Access to useable spectrum is the fundamental base on which amateur radio was built and continues to be developed. As a result, amateur radio is very different than decades ago. Embracing new technologies and techniques has greatly expanded what amateur radio is and opened further possibilities as to what it could be. The proliferation of technology also means that the ongoing experimentation and innovation in electronics, radio frequency technique and radio wave propagation is no longer only the traditional realm of the radio amateur but also includes university research satellites, the “maker” community, and other non-commercial experimenters: citizen scientists.

Looking ahead, this ongoing evolution of the telecommunications ecosystem makes it clear that the national Member Societies of the IARU and IARU itself must also continuously change and adapt. A century later, the future possibilities are as exciting as ever.

Celebrate World Amateur Radio Day. The pandemic and more localized natural disasters continue to demonstrate the value of ordinary citizens as technically skilled contributors to society. The original social network is robust. Expose someone new to amateur radio (properly distanced), get on the air and contact the many special event stations, on HF, VHF, or satellite.

Electronic Echoes (KPC Radio)

From SWLing Post contributor Bill Hemphill:

“I have run across an interesting set of audio interviews that were done by Aaron Castillo of kpcradio.com. This is an internet based radio station of Pierce College in California.

Aaron did a series of audio interviews in the fall of 2020 called Electronic Echoes. See following link:

https://kpcradio.com/author/aaron-castillo/

 

STARWAVES DRM SoftRadio App upgrades mobile devices to receive undistorted DRM Digital Radio anytime and anywhere (Fraunhofer Press Release)

Horgen/Switzerland, Erlangen/Germany: Starwaves, a developer and distributor of receiver technologies centered around the digital broadcast standard DRM (Digital Radio Mondiale), joined forces with Fraunhofer IIS, a leading supplier in the field of broadcast encoder and receiver components for DRM, to develop an Android app that allows DRM reception on mobile devices. Starwaves enables Android phones and tablets to receive entertainment, text information, and emergency warnings via DRM Digital Radio – without costly data plans, independent from cell phone network availability, and based on innovative Fraunhofer technology.

Digital Radio Mondiale (DRM) is the digital successor standard to the classic AM and FM radio services. In many parts of the world, terrestrial digital radio broadcasts are already an important and trusted source of entertainment and information. They do not require monthly payments and work reliably even if there are no cell networks available. Radio reception with mobile phones and tablets combines the mobility and flexibility of these devices with the benefits of free-to-air radio services.

Starwaves has been active in the field of DRM radio receivers for many years. The “STARWAVES DRM SoftRadio” app was developed in close cooperation with Fraunhofer IIS. Its goal is to ensure easy access to innovative DRM radio services for everybody. It is available from now in the Google and Amazon Android app stores. The app provides listeners with access to all the essential features of the DRM digital radio standard, across all transmission bands from DRM on long wave to FM band and VHF band-III.

Fraunhofer IIS is a significant co-developer of core digital radio technologies. This includes the innovative xHE-AAC audio codec, which provides high audio quality at lowest data rates, as well as the Journaline application, which gives radio listeners access to news, the latest sports updates, local weather forecasts, travel tips, and even radio schooling services without requiring internet access.

The app also supports many more DRM features such as the Emergency Warning Functionality (EWF), image slideshows, station logos, and service descriptions including Unicode support for worldwide application. To provide all these services, the app only requires a standard off-the-shelf SDR RF dongle that is attached to the device’s USB port.

“We are proud to launch the world’s first low-cost full-featured DRM digital radio reception solution for mobile devices, developed in close partnership with Fraunhofer IIS. Now everybody can easily upgrade their existing mobile phone and tablet to enjoy DRM digital radio with its undistorted audio quality and advanced features including Journaline,” says Johannes von Weyssenhoff, founder of Starwaves.

I order to meet the needs of everyday radio listeners and to clearly separate this app from the engineering-driven approaches of the past, usability was a primary development objective from day one. With only a few clicks on the clutter-free interface, users select their preferred radio service, navigate through the clearly structured menus, and gain instant access to the various advanced information services that DRM provides. By supporting multiple user interface languages, the app ensures optimized usability in many countries around the globe.

About STARWAVES

Found in 2005 in Bad Münder, Lower Saxony/Germany, Starwaves had set its focus on the development and distribution of receiver technologies around the digital broadcast standard DRM (Digital Radio Mondiale). As far back as 2003 after both organizations, the DRM Consortium and the WorldDAB Forum, had expressed their appeal to the industry at IFA in Berlin to develop and produce multi-standard receivers compatible with both their systems, Starwaves developed its model ”STARWAVES Prelude”, the world’s first DRM-DAB receiver and presented it at CeBIT 2004 in Hanover. In 2006 Starwaves was again in the headlines with the ”Carbox”: It was the world’s first automotive DRM-DAB receiver which then was produced in volumes and enjoyed by lots of listeners worldwide – including many DXers thanks to its excellent analogue Short-Wave capabilities as well.

Since 2008 Starwaves moved its focus to Africa where it developed and tested an innovative approach of broadcasting community television in the L-Band with DVB-T2 in cooperation with ICASA – another world premiere. After DRM was chosen the national standard in India in 2012 Starwaves relocated its headquarters to Switzerland and started developing a new generation of DRM receivers.

Starwaves also initiated Africa’s first DRM trial in the FM Band in Johannesburg/South Africa and completed it with local and international partners. The trial report contains valuable discoveries regarding the feasibility of DRM for community radio which guided the South African government to adopt DRM in the FM Band for community radio and secured the report becoming an internationally recognized piece of standard literature, recently endorsed by ITU. Today, Starwaves offers various DRM receivers and broadcast solutions for consumers and the professional broadcasting industry.

For more information, contact sales@starwaves.com or visit www.starwaves.com/de/starwaves-drm-softradio

Ten more stations turn off Medium Wave services (Radio Today)

Ten more local BBC radio stations are turning off their Medium Wave transmitters for good this year.

BBC Essex, BBC Radio Cambridgeshire, BBC Radio Devon, BBC Radio Leeds, BBC Radio Sheffield, BBC Hereford & Worcester, BBC Radio Stoke, BBC Radio Lancashire, BBC Radio Ulster and BBC Radio Foyle will be FM and digital only in May and June 2021.

In addition, BBC Radio Wales and BBC Radio Gloucestershire will reduce AM coverage.

The BBC’s intention to close MW transmitters was first announced ten years ago in 2011.[]


Do you enjoy the SWLing Post?

Please consider supporting us via Patreon or our Coffee Fund!

Your support makes articles like this one possible. Thank you!

Spread the radio love

How to Build a Simple Linear-Loaded Dipole for Low-Noise Shortwave Radio Listening

Many thanks to SWLing Post contributor and RX antenna guru, Grayhat, for another excellent guest post focusing on compact, low-profile urban antennas:


A linear loaded dipole for the SWL

by Grayhat

What follows is the description of an antenna which may allow to obtain good performances even in limited space, the antenna which I’m about to describe is a “linearl loaded dipole”(LLD) which some call the “cobra” antenna due to the “snaking” of its wires
The arms of the antenna are built using 3-conductors wire (which may be flat or round) and the 3 conductors are connected this way:

That is, connected “in series”, this means that, the electrical length of the antenna will be three times its physical one; this does NOT mean that the antenna will perform like a single wire of the same (total) length, yet it allows to “virtually” make it longer, which in turn gives it good performance even with relatively short sizes. Plus, the distributed inductance/capacitance between the wires not only gives it a number of “sub” resonance points, but also helps keeping the noise down (in my experience below the noise you’d expect from a regular dipole).  At the same time it offers better performances than what one may expect from a “coil loaded” dipole. Plus, building it is easy and cheap and the antenna will fit into even (relatively) limited spaces (a balcony, a small yard and so on…).

Interested–? If so, read on and let me start by showing my (short – 9mt total) LLD installed on a balcony:

Here it is in all its “glory”–well, not exactly–I fiddled with it lately since I’m considering some mods so the tape isn’t correctly stuck and it has been raised and lowered quite some times, but in any case that’s it.

Bill of Materials

Here’s what you’ll need to build it (the links are just indicative, you may pick different stuff or buy it locally or elsewhere).

  • Some length of 3-conductors electrical wire which will fit your available space (pick it a bit longer to stay on the safe side), it may be flat or round, in my case I used the round type since it was easily available and cheap: https://amzn.to/3g2eZX3
  • A NooElec V2 9:1 BalUn–or, if you prefer you may try winding your own and trying other ratios. I tested some homebuilt 1:1, 1:4 and 1:6 and found that the tiny and cheap NooElec was the best fitting one): https://amzn.to/3fNnvce
  • A small weatherproof box to host the BalUn: https://amzn.to/33vjZy3
  • A center support which may be bought or built. In the latter case, a piece of PCV pipe with some holes to hold the wires should suffice. In my case I picked this one (can’t find it on amazon.com outside of Italy): https://www.amazon.it/gp/product/B07NKCYT5Z
  • A pair of SMA to BNC adapters: https://amzn.to/37krHwj
  • A run of RG-58 coax with BNC connectors: https://amzn.to/2JckHcR

Plus some additional bits and pieces like some rope to hang the antenna, some nylon cable ties, a bit of insulated wire, duct tape and some tools. Notice that the above list can be shortened if you already have some of the needed stuff and this, in turn will lower (the already low) cost of the antenna.

Putting the pieces together

Ok, let’s move on to the build phase. The first thing to do will be measuring your available space to find out how much wire we’ll be able to put on the air; in doing so, consider that (as in my case), the antenna could be mounted in “inverted Vee” configuration which will allow to fit the antenna even in limited space.

In any case, after measuring the available space, let’s subtract at least 1m (50cm at each end) to avoid placing the antenna ends too near to the supports. Also, if in “inverted Vee” config, we’ll need to subtract another 50cm to keep the feedpoint (center/box) away from the central support.

Once we’ve measured, we may start by cutting two equal lengths of 3-conductor wire. Next, we’ll remove a bit of the external sleeve to expose the three conductors and then we’ll remove the insulator from the ends of the three exposed wire (and repeat this at the other end of the cable and for both arms).

The resulting ends of each arm should look somewhat like in the example image below

Now we’ll need to connect the wires in series. We’ll pick one of the cables which will be the two arms of our antenna and, assuming we have the same colors as in the above image, we’ll connect the green and white together at one end and the black and green together at the other end. Repeat the same operation for the second arm and the cables will be ready.

Now, to have a reference, let’s assume that the ends of each arm with the black “free” (not connected) wire will go to the center of our dipole.

Leave the two arms alone for a moment, and let’s install the balun inside the waterproof box. To do so, we’ll start by cutting a (small) hole through the single rubber cap found at one side of the box, then insert the cap reversed, so that it will protrude to the inside of the box and not to the outside. Slide the balun SMA connector through the hole so that it will protrude outside the box.

Now use a marker to mark the balun position and remove the balun from the box. Pick a piece of wood/plastic or other insulating material, cut it to size (refer to marking and to balun size) and drill four holes matching the one found on the balun board. Slide four screws through the holes and lock them with nuts, the screws should be long enough to extrude for some mm. Now insert the balun in the screws using the holes present on the balun board and lock it with nuts (be gentle to avoid damaging the balun). At this point, add some “superglue” to the bottom of the support we just built, slide the balun SMA connector through the rubber cap hole we already practiced, and glue the support to the bottom of the waterproof box.  Wait for the glue to dry.

Just to give you a better idea, see the photo above. That’s a photo of the early assembly of my balun. Later on, I rebuilt it as described above (but took no pics!), the image should help you understanding how it’s seated inside the box–by the way in our case it will be locked by the screws to the plastic support we glued to the box.

While waiting for the glue to dry, we may work on the dipole centerpiece.

If you bought one like I did, connecting the arm “black” (see above) wires should be pretty straightforward. If instead you choose to use a PVC pipe you’ll have to drill some holes to pass and lock the wire so that the strain will be supported by the pipe and not by the wire going to the balun box. In either case, connect a pair of short runs of insulated wire to the end (black) wire coming from each end. Those wires should be long enough to reach the balun wire terminal block inside the box.

Assuming the glue dried, it’s time to complete the feedpoint connection.

Bring the two wires coming from the centerpoint inside the waterproof box. Pick one of the wire terminal blocks which came with the balun (the “L” shaped one should be a good choice) and connect the wires to it. Then, slide the block in place until it locks firmly. After doing so, close the box and screw the SMA-BNC adapter onto the SMA connector coming from the balun. Our centerpiece and arms will now be ready, and will be time to put our antenna up!

I’ll skip the instructions about holding the arm ends and the centerpiece up, since I believe it should be pretty straightforward. Just ensure to put the antenna as high as possible and, if you have room make the arms as long as possible. In my case, due to my (self-imposed) limitations, the antenna was installed on a balcony. The arms have a length of about 3.5m each and the feedpoint (in the image above) sits at about 9m off the ground.

The more acute readers probably noticed those “blobs” on the coax, they are snap-on ferrite chokes I added to the coax (there are more of them at the rx end) to help tame common mode noise. I omitted them from the “BoM” since they may be added later on.

Anyhow, now that you have your LLD up it will be time to give it a test! In my case, I decided to start by running an FT8 session to see what the antenna could pick up during 8 hours, and the result, on the 20 meters band, is shown on the following map (click to enlarge):

Later, that same antenna allowed me to pick up signals from the Neumayer station in Antarctica–not bad, I think!

Some final notes

While running my “balcony experiment”, I built and tested several antennas, including a vanilla “randomwire”, a dipole, and a T2FD.

Compared to those, the LLD offers much less noise and better reception on a wide frequency range. By the way, it won’t perform miracles, but it’s serving me well on the LW band, on most ham bands, and even up to the Aircraft bands–indeed, was able to pick up several conversations between aircraft and ground air traffic control.

All I can suggest is that given a linear-loaded dipole is so simple, quite cheap, and may fit many locations, why don’t you give it a spin–?  🙂

Spread the radio love

How to properly install a Mini Whip antenna in an noisy urban environment

Many thanks to SWLing Post contributor, Grayhat, who shares the following guest post:


Setting up a Mini Whip antenna

by Grayhat

I’ve been fiddling with my “balcony antenna” experiment for quite a while now, and I settled with a Linear Loaded Dipole (LLD, also known as “Cobra”) which, in my case, due to self-imposed limitations was a short one (about 9m total).

Since I mentioned it, here is a pic of the antenna showing its installation:

Click images to enlarge.

In the above image you can see the overall setup of the LLD, the modification I did, by adding additional wires to the end of the arms and also the Mini Whip location

The LLD served me well, from LW up to around 200MHz allowing me to listen to broadcasters, hams, aircraft communications, time signals and then more, and it’s definitely a keeper, but I wanted to give a try to the “Mini Whip” antenna, even if a lot of people discard it saying it’s a noisy antenna and not worth it; keep in mind the Utwente SDR uses it and it seems to work fine, so I had to give it a try !

Anyhow, after searching the internet for a suitable whip, I finally found this one:

I bought the antenna on Amazon, but it’s also available on eBay and while the price isn’t the lowest one, I chose it since it uses BNC connectors only (some models use a mix of UHF/BNC or the like). This one had a top wing nut allowing to connect an additional (optional) external whip (may be useful on lower bands) and, last but not least, its color; being gray, it is quite stealth, which may be useful for some people (not my case, luckily). So I went on and ordered the antenna, the delivery took about 10 days and the package contents were exactly as shown above. The supplied coax is thin (RG-174 I believe) and it would be a good idea replacing it with some runs of RG-58, but for the sake of the experiment, I used the original wire.

So, having the antenna, I looked around for informations about the correct installation for the “Mini Whip” and found that in most cases, the reported poor performances of the Mini Whip are due to people installing it the wrong way. For reference and information about how the whip works and about how to properly install it, please refer to the information from PA3FWM found here and here.

Now, if you can place the whip in a garden or yard, using a pole, the correct installation of the whip is the one shown in this pic:

If you carefully look at the image you will notice that the whip sits above the supporting (metallic) pole and that the ground of the connector is electrically connected to the pole (through the clamp). Plus, the pole is then grounded (at the bottom) and the coax (which has chokes) runs away from the metallic pole.

What does the above mean ? Well, the Mini Whip antenna needs a “counterpoise” (ground) to work, and installing it as above, instead of using the coax braid as its counterpoise, the Mini Whip will use the supporting pole, this helps a lot minimizing the noise and it’s one of the tricks for a proper setup, the other one is placing the whip as far away from the “noise cloud” of your home as possible. In my case, I choose the far end of the balcony–also since I had a nice support there, the image below shows the whip installation using a piece of PVC pipe I bought at a nearby home improvement store:

At first, I just installed the antenna without the ground wire and with the coax coming down vertically from the connector. When I compared the whip to my LLD, the results were discouraging: the noise floor was much higher and a lot of signals, which the LLD received without problems, totally disappeared inside the noise floor.

Being the kind of hard-headed guy I am (and having read the documentation about proper setup) I went on and made further modifications.

Let me detail the installation a bit better with this first image (click to enlarge):

As you can see in the above image, the whip is supported by a piece of PVC pipe which keeps it above the metal fencing of the balcony (or a support pole if you’ll use it) and I also connected a short run of insulated wire to the ground of BNC plug at the bottom of the whip. This short run goes to a wire clamp which allows it to connect to the “counterpoise” (ground) wire.

In my case, since the balcony was at 2nd floor, I didn’t have a way to give to the antenna a real ground, so I decided to run a length of wire (AWG #11) down the pipe and then along my balcony fencing (10m total). An alternative, which will also work for roof installations, would be using chicken wire (fencing). In such a case, you may lay as much chicken wire as you can on the floor/roof and connect the wire coming down from the whip ground to it. I haven’t that that (yet!) but I think it may further lower the noise and improve performances.

Notice that in the case of the Utwente Mini Whip, the antenna support pole is connected to metallic roofing so it has plenty of (virtual) ground.

Later on, I improved the setup by raising the antenna a bit more and routing the wire (almost) horizontally from the feedpoint to reduce coupling with the vertical “counterpoise” wire.

The image below shows the final setup:

While not visible in the above image, I also wrapped the coax wire in a loop at the point where it’s held by the fencing and added some snap-on chokes to the coax at the point where it enters the building.

With all the modifications in place, the antenna started performing as it was designed to. The noise floor is still a bit higher than the one of the LLD, but given that it’s an active antenna, that’s to be expected

To give you an idea of the signals and noise floor, here are a couple of images taken from the screen of my laptop while running SDRuno. The first one shows the waterfall for the 40m band

While the second one, below, shows the one for the 80m band:

At any rate, my usual way of testing antenna performance (and modifications effects), aside from some band scanning/listening, is to run an FT8 session for some hours (and optionally repeat it over some days) and then check the received spots.

In the case of the Mini Whip, after all the modification to the setup, I ran an FT8 session using JTDX for some hours and the images below show the received spots. The first image shows the whole map of the received stations:

While the second one below is a zoom into the European region to show the various spots picked up there; the different colors indicate the 20m (yellow), 40m (blue/violet) and 80m (violet) bands:

As you can see, the Mini Whip performed quite well despite the “not exactly good” propagation.

While some time ago I’d have discarded the Mini Whip as a “noise magnet”, as of today, with a proper installation, I think it’s a keeper. While it can’t be compared to bigger antennas, I believe it may be a viable antenna for space-constrained situations. The only thing it needs is a bit of care when setting it up to allow it to work as it has been designed to.


Brilliant job, Grayhat! Thank you so much for sharing your experience setting up the Mini Whip antenna. As you stated, so many SWLs dismiss the Mini Whip as “noisy”–but with a proper ground, it seems to perform rather well. The benchmark example of a Mini Whip’s performance must be the U Twente Web SDR

Thank you again, Grayhat! 

Spread the radio love

The Allocchio Bacchini RF4D: That mystery radio from “The Last Man on Earth”

Many thanks to SWLing Post contributor, Andrew, who correctly identified the radio Ed spotted in The Last Man On Earth as the Allocchio Bacchini RF4D. Andrew shared the following notes and links:

That radio is an Allocchio Bacchini RF4D (see photo below from this site):

Here’s a snippet from an Italian movie showing the same rig:

Another pic and notes can be seen scrolling down this page:

Year : 1940
TX Frequency Range : 1,270 – 4,300 kHz in 3 bands
RX Frequency range : 220 – 4,400 kHz in 5 bands
Facilities : CW and RT
Receiver Circuit (Valves) : Superhet. 7 tubes type 6RV (same as RF 4)
Transmitter Circuit (Valves): MO(P C05), PA (2x P CO5) Mod.(3x 6RV)
RF Output : 25 W
Aerial : Dipole
Power supply : 12 V storage batteries. Mains for battery charger.

And here you’ll find the shack of an Italian ham which shows an RF4D:

Photo: I5HGM

Further info and schematics can be found here.

Wow! Thank you so much, Andrew! I would love someday to operate an original RF4D.  What a fascinating WWII era radio. Thank you again for all of the details!

Post readers: I’m very curious if anyone here owns or has owned an RF4D.  Please comment!

Spread the radio love

Build an SDR station and balcony antenna farm for less than 150 Euros

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:

  1. 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
  2. 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)
  3. The whole setup should be simple and straightforward, no need to solder components or to build special types of antennas
  4. 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

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! 

Spread the radio love

More about hacking VGA cables to make binocular ferrite cores

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!

Spread the radio love

Any experience using the T2FD antenna–?

The T2FD Antenna (Source: Wikimedia Commons)

Many thanks to SWLing Post contributor, Grayhat, who has recently been on a mission to create a low-cost SDR setup while sheltering at home due to Covid-19 restrictions. While exploring antennas he sent the following inquiry:

I recently found some information about the so-called Tilted Terminated Folded Dipole (T2FD) antenna which was apparently developed for military use as a wideband, general purpose one (which can mean if it isn’t efficient, simply throw some more KW at it).   But for receiving, the antenna didn’t seem bad to me, at least based on the info I found.

In most (if not all) ham installations of the antenna, the T2FD is used in a “vertical” setup–that is, one wire above the other. When looking at military docs, the antenna is in “horizontal” setup, that is, wires parallel to ground. Looking at a 3D lobes simulation of the antenna, the pattern for a “vertical” one seems to be a “cloud warmer” with the most radiating lobe going down toward the feedline. If that’s true, this would mean that an “horizontal” T2FD should have its most pronounced lobe at the feedline side. Perhaps “vertical” installations of the T2FD could go from “works well” to “WOW” just flipping the wires–?

Do you think and SWLing Post readers may have info or experience with the T2FD antenna they could share?

If you have any experience using or building the T2FD antenna, please feel free to comment! 

Spread the radio love