Category Archives: Guest Posts

W9IMS: A delayed start for the Indianapolis Motor Speedway special event station 

Many thanks to SWLing Post contributor, Brian D. Smith (W9IND), who shares the following announcement:


W9IMS: A delayed start for the Indianapolis Motor Speedway special event station

by Brian D. Smith, W9IND

It’s a late start for auto racing at the Indianapolis Motor Speedway, as well as the amateur radio station that honors this century-old tradition … but the show must go on!

And this week it will, as special event station W9IMS returns to the airwaves from now through Sunday to offer radio hobbyists a fresh opportunity to collect more “wallpaper”: Two vivid racing-themed QSL cards and the popular certificate known as the Checkered Flag Award.

The 2020 certificate will be easier than ever to earn. Normally the Speedway’s three major races take place on three different weekends, but this year, because of Covid-19 concerns, they’ll be consolidated into two. Accordingly, hams and SWLs will be required to contact or tune in W9IMS during only two race weeks – the current one, which continues through Sunday, July 5; and Aug. 17-23, which ends on the day of the venerable Indianapolis 500.

Even if you succeed in snaring W9IMS only once, you can still send off for the corresponding QSL card. All certificate and QSL designs are new each year.

The coming Independence Day weekend will feature an unprecedented racing doubleheader, with the IndyCar Grand Prix and the NASCAR Brickyard 400 slated for Saturday and Sunday, respectively. Consequently, the first W9IMS QSL of 2020 will be a full-color, four-sided card portraying images from both races.

So where do you find W9IMS? The station will stick to three bands, 20, 40 and 80 meters, and may appear at any time of day or night from now through Sunday.

However, the best bet is to catch the station during prime time – 2200 through 0200 UTC on weeknights (6 to 10 p.m. Indy time). W9IMS operators also plan to activate 20 meters during daytime hours, often between 8 a.m. and 2 p.m. (1200-1800 UTC); and will cover the various bands all weekend starting at 10 a.m. (1400 UTC) daily.

If you still haven’t caught W9IMS by the time Sunday evening arrives in Indianapolis, operators commonly conduct their own happy hour – working stations in rapid contesting style – right up to midnight (0400 UTC Monday).

Here are a couple of hints for tracking down the station during special event weeks:

  1. Go to the W9IMS web page (www.w9ims.org), find the “2020 Operating Schedule” heading, and click on the link to “Grand Prix & Brickyard” or “Indianapolis 500.” Although some W9IMS operators get on the air at unscheduled times, you’ll have your best luck looking for the station during the hours and bands reserved with a name and a callsign.
  2. Check DX Summit (www.dxsummit.fi) for spots that identify the current frequency (or frequencies) of W9IMS, if any. And if you type “W9IMS” in the search box, you can customize it to show reports for only that station.

For additional details, consult the W9IMS web page. Feel free to submit both of your 2020 QSL card and certificate requests in the same envelope, and if you don’t have your own QSL card, a printout of your W9IMS contacts or reception reports will suffice.

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Building the EA3GCY DB4020 Dual-band 40 and 20M QRP SSB Transceiver Kit

Many thanks to SWLing Post contributor, Frank (ON6UU), who shares the following guest post:


Building EA3GCY’s DB4020 QRP Transceiver kit

by Frank Lagaet (ON6UU)

In May, I discovered via a newsletter that a new kit was available from Javier EA3GCY in Spain.  I was immediately sold as this was a kit from my favourite kit producer and it has 2 bands–it will also be able to do CW and there also will be a CW filter.

After building 2 MFT’s from Javier which work without problems, I needed to have the DB4020.  The MFT’s are for 20 and 40 mtrs and do DSB (double side band).  I did put them in a not-so-graceful box but they do what they are intended for which is QRP phone (SSB).   They came together without problems so I expected the same for the DB4020–I knew for sure when I saw the board:  all through-hole components (except for some capacitors which are factory soldered) and a lot of space on the board.   The board has been silk-screened with clear indications on where all components have to come and the manual has very clear instructions where each component has to be soldered with referral to a quadrant.  The manual provides a 252 quadrant page so it is a piece of cake to find where each piece goes.

What do you get?

Javier provides you with all components which need to be installed on the board and, of course, the kit board.  The components come in small marked plastic bags and all is well-wrapped up in bubble wrap.  The board is wrapped separately and that is put together with the component wrap which is then again wrapped up in bubble plastic.  All goes into an envelope.  Very well packed I must say.

Here’s a picture of the bags with components:

The silk-screened board:

I started with the resistors since that’s the easiest way. After that, I did the capacitors.  I like to solder in all flat components first, so next were the diodes and IC sockets followed by the elco’s.  The transistors were next together with all relays.  As you solder in the transistors one also has to mount the cooling heatsinks,  these cooling sinks are high and are ideal to protect the coils one has to make,  they also protect the polystyrene caps (which I always find vulnerable) when the board is upside down.

Many kit builders are afraid of winding the toroids in kits–don’t be!  It is easy.  Just take your time and follow the instructions given by Javier in the construction manual.  In this kit the builder has to wind 8 toroids:  6 are a single wire which goes through the toroid body,  1 is a toroid with 2 different windings, and 1 has a twisted pair which goes through the final toroid.  Be sure to measure the wire you need per toroid as instructed in the manual.  Javier gives some spare, so you can be sure.  You will also see that on next picture where the legs of the toroids have not been trimmed yet.  Once done I still had some centimetres of wire leftover.

Picture of the toroids ready to be soldered in:

Finally all other parts and pin headers went in,  jumpers were immediately put on where needed.

As I’m using a military-grade plastic box, I have to break-out some components like the display,  tuning encoder,  volume and rx control from the board.  I also have put an on/off switch on the box and already have the CW KEY connector ready installed. I also installed a loudspeaker in the box.  The SI5351 board and the Ardiuno Nano are the final components which go into the board after installing all wires.

Picture of the board:

I intend to attach a CW paddle to the box made out of a relay.  A HWEF tuner (from EA3GCY) which I was planning to incorporate in the box is I think a bit overkill. That HWEF tuner is already in a nice little box and would be a pity to dismantle,  also I’m running out of space in the box…  Maybe I can fit in a 9-1unun which would then give me good results on both bands…?

Maybe I will install a battery pack in the same box.

The box with board installed:

The box completed front side:

Mind you,  it still needs some additional switches for the CW part of the transceiver.

73
Frank (ON6UU)

Video


Brilliant, Frank! I really appreciate the video as well–sounds like the kit produces smooth audio and should serve you well. No doubt, that military box enclosure will survive even the roughest field conditions!

Click here to check out the DB4020 kit at EA3GCY’s store.

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Reunited with an old friend…

Many thanks to SWLing Post contributor, Marwan Baayoun, who writes in response to our recent post about radio regrets:

For me, my biggest regret was when in November 2018 I sold my well-protected Sony ICF-SW77.

I bought it brand new over the phone from Universal Radio. My ICF-SW77 was my side kick and went with me everywhere. I remember working the second shift at a publishing company, I would always eat my lunch outside while listening to any international broadcasters I could catch like the BBC, Radio Havana Cuba, Deutsche Welle, or the VOA.

I remember how my co-workers reworded the saying “Life Without A Wife, Is Like A Kitchen Without A Knife” to “Life Without A Wife, Is Like Marwan Without His Shortwave Radio.”

When I got married, my best friend invited us to visit with his wife and children at their house in Upstate New York. He even bought one of the tickets as his way in helping me paying for the fares. I remember the night we arrived at his house me pulling my ICF-SW77 and tuning it to the BBC World Service because we all wanted to get the latest on a sad piece of news that was just breaking that made us, and almost everyone in North America and around the world, stare at TV sets hoping for the best. Then Tom Brokaw came on to announced something that we, and others who were listening to the BBC World Service, had already knew 15 minutes earlier: the sad news the Lady Dianna did not survive the car crash.

My friend was impressed with what shortwave radios could bring to the table.

In the last month I went on a binge and bought a used Realistic DX-440 (love this radio BTW, very nice), and all new XHDATA D-808, Tecsun PL-880, and Tecsun PL-680. I also bought but then returned a Sangean ATS-909X.

To close on a happy note, today I received an almost brand new Sony ICF-SW77 that I bought from a very kind gentleman on eBay–he was willing to accept my fifty dollars less than his asking price offer.

My happiness is beyond expression. I would have never thought I would be able to re-unite again with one of these radios in a condition that is identical to the one I sold. He kept it very well. I tried to find a scratch or a piece of dust on this radio but couldn’t. Not only that, it also came with it the original box, very well kept manual and “Catch the Waves” booklet, (I gave mine to the gentleman who bought my radio, so it was sweet that they were replaced with this purchase). My new ICF-SW77 seller just did not have the power adapter that came with this radio, which is fine with me. I can always find a third party power adapter to buy.

I feel so lucky I am once again an owner of one of these awesome radios.

What an amazing story, Marwan, and I’m so glad you’ve been reunited with an IC-SW77!

Radio love is a funny thing and hard to compare with any fondness one might have of other consumer electronics. For example, I’ve never lamented over the loss of a laptop, iPhone, or iPod–but, like you, I have indeed regretted parting with radios. I know many of you feel the same way.

To me, radios feel much more like companions who share the world with you–through travels and over the air.

I’m happy to hear you’ve got your companion back, Marwan!

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Guest Post: KK5JY’s Porch Loop Receiving Antenna

Can you spot the antenna in this photo?

Many thanks to Matt Roberts (KK5JY) who has kindly given me permission to re-post the following article he recently published on his website KK5JY.net. Many thanks to SWLing Post contributor, Grayhat, for the tip!

 Note: The Porch Loop project below is a re-configured Small Receiving Loop (SRL) antenna. For SRL construction details, check out Matt’s primer.


The Porch Loop

by Matt Roberts (KK5JY)

The small receiving loop, or SRL, is a versatile, effective, and very space-efficient receive-optimized antenna for the HF bands.  They are easy to build, and can be made very inexpensively.  Most typical designs use symmetric shapes, like circles, diamonds, octagons, etc., and are mounted on some kind of mast.  This makes it easy(-ier) to install the antenna clear of nearby metal and electronics.  It also makes the antenna rotatable, so that the nulls can be pointed at RFI sources.

These aren’t the only options for the SRL, however.  These little loops can be made to fit in just about any available space.  In fact:

  • They are effective at any reasonable installation height, including very close to the ground.  The installation height doesn’t change the pattern shape, only the pattern strength.
  • They can be made nearly any shape.  The shape does not have to be symmetric about any axis or combination of axes.
  • They can be fed at just about any point on the loop.  A typical feed location is bottom-center, but off-center feeding has negligible effect on the pattern shape.
  • The wire can be bent out-of-plane; in other words, the loop doesn’t have to be “flat.”

There are a couple of requirements for obtaining predictable performance, however.  First, the antenna does need to be an electrical loop.  That is, it is a single wire connected between the conductors of the feedline, forming a complete circuit.  Also, the circumference of the loop wire should be electrically small (i.e., significantly less than ? / 4) on the bands where it is to be used.

Figure 1. The antenna location (click to enlarge)

As a personal challenge, I recently installed such a loop on my front porch.  Everything about this installation defies conventional wisdom — it was installed very close to the ground, it was an irregular shape, it was fed off-center, and the wire was wound in and around an irregular support structure, rather having all the wire in a single plane.

And the resulting antenna still performed very well.

Figure 2: Antenna Location Outlined in Red (click to enlarge)

The loop is essentially the same device as the one in the original SRL article.  See that article for more construction details.  This version is simply stretched and twisted to make it fit the space and supports available.  The wire was woven around the boards in the porch’s deck rail, and fed off to one side, so that the transformer housing could be “hidden” behind the trash cans.

Figure 3: Feedpoint Transformer (click to enlarge)

The wire was insulated with an off-white THHN, which made it blend in with the color of the trim of the house.

Figure 4: 40m Reception 10h Overnight (click to enlarge)

Even with its suboptimal installation details, the overnight 40m DX spots were numerous and well-distributed, as seen in Figure 4.  There were DX spots at nearly 10,000 miles, there were NVIS spots, and there were countless at all distances in between.  So the antenna was just as effective as its more ideally shaped brethren, despite it’s unconventional installation details.

Other ideas for possible locations of such a device could include:

  • In an attic.  The antenna could be nailed to a vertical panel, or strung like a spider’s web inside the frame of a truss or other open area.
  • Under a tree.  Taking another idea from the spiders, the antenna could be hung and pulled into shape using light guys or tree branches.
  • On a wooden fence.  If you have a wooden fence, the antenna could be installed against the fence panels.  This option could allow a wide range of circumference lengths.
  • Attached to an interior wall of an apartment.  The shape could be chosen to keep the loop clear of in-wall wiring, to help preserve its performance.

The original mast-mounted SRL antennas still have some advantages.  Perhaps the biggest advantage is that they can be easily rotated to null out a nearby strong noise source.  That said, if you are looking for an antenna with better receive performance than a large resonant vertical, the SRL can be stretched and squeezed into service just about anywhere.


Many thanks for sharing this project, Matt!  So many of our readers live in situations where they are forced to use stealthy and compromised antennas. What I love about your porch loop is that even though it breaks several loop antennas “rules,” it’s still amazingly effective. 

I encourage SWLing Post readers to check out Matt’s website as he has written articles covering a number of interesting radio and antenna projects.

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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! 

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Example of a manual wavechange at BBC Skelton A Transmitter

By Michael Whitfield, CC BY-SA 2.0

Many thanks to SWLing Post contributor, Dave Porter (G4OYX), who shares the following:

Here’s Steve Gale in the late 80’s or early 90’s starting a wavechange on a Marconi BD272 250 kW sender at SKA.

There were eventually 11 of these senders at the BBC Skelton A site.

The first pic is the Final RF amplifier output stage with the 15/17 MHz coil being in situ. It sits between the two anodes of the output tubes.

Below the anode coil sits the coupling coil and it is on a motorised deck, that can be moved backwards and forwards on power to couple up to the required power output.

Steve is just starting the band change as he is wearing the leather gauntlets because after a transmission the coils are very hot.

Both the anode and coupling coils will be removed and replaced by those for the next required frequency.

A fifteen minute period was allocated by the BBC WS Schedule Department to accomplish a band change though two of us could do them in about eight minutes if pushed!

The picture below shows Steve starting to remove one of the pair of the 3-turn 40 kW Penultimate stage to Final stage coupling coils, again he is wearing the gauntlets. A different coil will be used for the next band.

The three turn coil covered 9, 11 and 15 MHz.

All those senders have gone now at Skelton.

Two are still in use at Woofferton and some in Singapore.

Thanks so much for sharing this glimpse into a working shortwave radio transmitting station, Dave! There’s nothing QRP about those transmitters and I bet those coils got incredibly hot!

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Patrizio’s simple homebrew NCPL antenna

Many thanks to SWLing Post contributor, Patrizio Cardelli, who writes:

I’m Patrizio (SWL I – 5184 /AN) from Riva del Garda, Italy.

A few days ago, I built a Noise-Cancelling Passive Loop (NCPL) antenna. I built the 1:1 balun with a couple of ferrite 175 – 285.

I got a good result on medium wave on my ICOM IC R 71 E with the antenna inside my house installed behind the desk just to avoid any problems with my wife.

On shortwave, the signal was low in comparison with the Bonito mini whip but in my QTH I have a lot of QRM and with this antenna I solved my problem.

Yesterday I tried the balun with my random wire (15,2 meter long) also with good results.

About my NCPL antenna: I made mine with RG-58 coaxial cable just to have easy portability in SOTA (please see photo) and also the feed line is made by the same coaxial cable. OK, you are right…it’s ugly:

Electrical connections are not soldered, still I don’t see any mechanical issues and this antenna since it is made for SWL / BCL purposes (meaning, RX only, no TX).

Concerning the binocular ferrite core, I didn’t have one, so I used two ferrite core type 175 – 285 (28,5 mm length, external diameter 17,5 mm and internal diameter 9,5 mm) normally used to reduce HF interference:

For the winding I used PVC insulated cable cat no: 7/0,2 type 2 (def61 – 12) conductor 7/0,2mm TSCu X 0,3mm R/T type single (4 turns primary and 4 turns secondary). It’s the same cable with which I built my random wire antenna (also portable for SOTA but now installed on my balcony until the COVID – 19 emergency is over).

The attached videos show the situation in comparison with my BONITO MINI WHIP active antenna (also installed inside my house). Recently I changed my QTH and unfortunately here I have a lot of interference both on MW and SW. The better results that you can hear are achieved with my NCPL antenna.

I have made this test with my ICOM IC R 71 E + BHI noise cancellation speaker…..you can assess yourself, the better results that you can hear are achieved with the NCPL antenna and in the case of Tecsun PL-660 without any noise cancelling filter (BHI speaker off).

Thanks for sharing this, Patrizio! As you say, the NCPL loop seems to do a fine job helping to eliminate local RFI/QRM. The Bonito Mini Whip is a fine antenna, but not optimal for environments with a lot of radio noise–that’s where the NCPL antenna really shines.

You also make a good point that if you’re simply experimenting and only using an antenna for receiving, you can be more relaxed about the build because you’re not sending RF through it. In the end, however, properly soldered and protected connections will last much longer and provide better, more reliable performance.

Thank you, again, for sharing your build, Patriio! Those reception results speak for themselves!

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