Category Archives: Guest Posts

Post-storm power outage leads Emilio to find the RFI-spewing source of his problems

Storm with lighteningMany thanks to SWling Post contributor, Emilio Ruiz, who shares the following guest post:

Apprehending an RFI-generating monster!

At the beginning of the year, I was sad because, at home, an awful RFI noise appeared. The next few months the noise increase until S9!!. Day and night my receivers and my feelings were so dampened with this terrific RFI–only the lower Broadcast Band (900 to 540 Khz) was relatively immune to it.

Yesterday, we had a storm and the mains electricity service went off, so I connect a 12 volt battery to my RT-749b military surplus transceiver and the received signals were very clean like the “good old days”.

(Above: Listen W1AW loong distant from my QTH in Chiapas Mexico).

When the power electricity come back on, so did the RFI too!!

(Above: W1AW gone)

Remembering the recently publish post in SWLing Post about RFI, I did some testing by
cutting the electricity to my home (the main switch) and the RFI was gone!! So I discovered the RFI lives in my house–not in the outside wires!!

I put batteries in my old shortwave portable radio and searched (like Ghostbusters) all outlets contacts, one by one, connect and disconnected each device.

And I found the guilty party!

Exhibit A: The Mitzu laptop power supply

On December 2019, the power supply of my son’s laptop broke, so I bought a cheap substitute.

The RFI produced by this little monster could be heard at a distance of about 200 meters from my QTH!!! (Much like an old transmitter spark gap–!)

Even this cheap power supply apparently featured ferrite toroids on the wire but turns out it is fake!! It was only a plastic ball!

Exhibit B: Fake toroids!

The wires were also not shielded. No doubt one of the worst switched-mode power supplies I could have purchased.

Exhibit C: The Mitzu RFI generator wire without shield, only pair wires!

I found a old Acer power supply with same specs and I replaced out the RFI monster one.

And now? The shortwave bands are clean again.

(Video: Testing my Kenwood R-600 rx with Radio Exterior de España… plugging and unplug the Mitzu monster RFI generator).

So I wanted to share what happened to me, so perhaps it can be useful for other SWLing Post blog friends.

Watch these little switched mode power supplies from all devices in your home. Replace them if you detect RFI levels that harms SWLing. Consider disconnect all devices (vampire consumption–or phantom loads) if not in use; the radio waves and electric bill will be grateful to you!

WOW! What a difference! Emilio, that was great investigative work on your part. It’s as if that switching power supply was specifically designed to create RFI! No shield and fake toroids? That’s just criminal in my world! 

Thank you so much for sharing your story. Hopefully, this might encourage others to investigate and apprehend their own local RFI monsters!

(And by the way, Emilio, I love that RT-749b military transceiver!)

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Andy builds a genius companion control display for the Yaesu FT-817 transceiver

Many thanks to SWLing Post contributor, Andy Webster (G7UHN), who kindly shares the following guest post:

Yaesu FT-817 companion display

by Andy Webster (G7UHN)


Like so many I love getting out portable with my FT-817 but I do seem to spend so much of my operating time fiddling through the soft-keys because my most used functions (CW narrow filter, power and keyer settings to tune an ATU, A/B, A=B, etc.) are spread across different “pages” of the A,B,C assignments. Compared to the sublime experience of using my Elecraft K2 the FT-817 can be a little frustrating!

Last month, inspiration struck and I thought I could cobble together a small microcontroller and a little OLED display with some buttons to provide some extra soft-keys for the radio using the CAT serial port. Nothing particularly original here (I’ve seen articles of people using PICs for this purpose) but it seemed like a nice sized project for me to play with and build some experience doing PCBs (I’ve only done this once before at home). A little bit of discussion with Michael G0POT (FT-817 and SOTA guru), some Google searching and we were looking over KA7OEI’s excellent reference page ( and thinking about our favourite FT-817 commands…


As it happened I was lucky to have the right bits (Arduino Nano, small OLED display, buttons, prototype board and an 8-pin mini DIN cable) lying around the house to see “first light” from my FT-817’s serial port that evening. The Arduino Nano is a good place to start because it works at 5V so can work directly with the FT-817 levels on the ACC port. What followed next was some late nights of hacking on Arduino code to send and receive the data for my favourite commands and more experimentation on prototype board.

I tried a couple of cheap OLED displays and they look great indoors but weren’t quite up to the job in full sunlight which is fairly typical in my portable operations.

Daytime readability issues with an OLED display

By this point I had also realised the utility of having an auxiliary display on top of the radio as a much easier thing to view than the 817’s own display on the front panel. I’d also experienced some interference from the unshielded prototype board coming through as clicking sounds on the radio’s receiver so it looked as though some isolation between radio and my circuit might be necessary. Guided by many Internet tutorials, I switched to using a Nokia 5110-style LCD for better daylight readability and lower power consumption. Adding an ADUM1201 digital isolator and a B0505S-1W isolated DC-DC converter to the prototype board (modules acquired very quickly from eBay suppliers) gave me some isolation and lowered the interference which I guessed would disappear when I made the design on PCB with good ground planes around the signal lines.

Screen capture showing the schematic (click to enlarge)

With a (mostly) working prototype it was time to hammer the Internet tutorials again, this time to learn how to use KiCad, a free open-source PCB design tool available on Linux, Windows and Mac. I’ve done one PCB for home projects before using Autodesk EAGLE and I found learning Eagle pretty hard going, it seems like it carries 20 years worth of baggage and dogma in the user interface. In fact I started using EAGLE on this project but spent 3 hours on the first evening just trying to change the labels on the ADUM1201 chip that I couldn’t find in an EAGLE library… so I gave up and thought I’d try KiCad which I’d seen some recent good reports on. I’m happy to say after finding an excellent tutorial on KiCad I had drawn the schematic and my PCB layout in about 15 hours working time spread over a few evenings.

I should add that the 15 hours of KiCad time did include several hours of agonising over the choice of slide switch so a PCB can be done much quicker than that once you’ve got your favourite parts sorted!

That’s pretty impressive for my first go with KiCad as a near-beginner to PCBs, I heartily recommend it, it was so much easier than EAGLE and quite an enjoyable tool. Right, PCB design done and uploaded to JLCPCB for manufacture. 5 PCBs with DHL shipping cost me less than £20 and arrived from China within 5 calendar days. Other PCB fabs are available… 🙂

Click to enlarge

So that brings us to today, pretty much. The PCB was assembled very quickly (!) and there is no sign of noise from the serial data lines creeping into the 817’s receiver now it’s on PCB. Some lessons have been learned through the construction (e.g. brown 6mm push buttons are less “clicky” than the black ones and that’s a good thing!) and I now have my companion FT-817 display/buttons in field trials. I’ve no plans to sell this, it’s a trivially simple design, but it does make a great home project to polish your skills in microcontrollers, PCBs and construction. I’ll post a write-up on my website in due course.

In use, the device works just as I’d hoped, I can do everything I want to on my FT-817 without having to fiddle through the awkward button presses. The frequency display is also in a much better position for me now (as most FT-817 owners will know as they jealously eye the KX2, KX3, etc…!) and I think I used it for the whole session when I took it to the field on Saturday. If only my CW had been so slick!

Next steps are to work on the Arduino code. My code is pretty rubbish (my coding style involves a lot of Stack Overflow and copy/paste!) and not safe for public consumption. There are also some health warnings to be noted in manipulating the FT-817’s EEPROM (required for some of the functions I wanted), explained on KA7OEI’s page but there have been a few volunteers on Twitter to help with the software which is great. Also I may do a “Rev 2” board with an Arduino Pro Mini to lower the drain on the FT-817 battery before sharing the PCB files. Other than that it’s now time to get back outdoors and enjoy the new improved interface to my smallest radio! 😀

Andy G7UHN

Andy, I absolutely love this project! A wonderful addition to the FT-817/818 and I’d hardly call it a “trivial” design–!

I purchased the original FT-817 shortly after it was introduced. At the time, I was living in the UK and travelled extensively throughout Europe. I loved the ability to simply throw this little rig into my carryon and play radio pretty much anywhere my work travels took me. In the end, I did less ham radio work with the FT-817 and more SWLing.

Still, I eventually sold my FT-817 for the very same reason that motivated you to build a companion display: the front panel is too small and my most used functions require too much menu digging. 

Your companion board is an elegant homebrew solution. I love the Nokia LCD screen–superb readability in the field. 

Thank you again and once you do a write-up on for your website, we’ll be sure to link to it on the SWLing Post!

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George reviews the new Tecsun PL-990

Many thanks to SWLing Post contributor, George Joachim, who shares the following review of the Tecsun PL-990.

AS George points out, the PL-990 in the following review is not the “export” model Anon-Co will eventually offer for sale later this year. It might be nearly identical in every respect, but at time of posting Tecsun is addressing some final firmware updates the the “export” version prior to starting a full first production run. As we learn more about the various versions of the PL-990 in the wild–compare serial numbers, etc.– we will eventually sort out any nuances between versions.

George purchased this PL-990 on AliExpress and I am incredibly grateful to read his review of this model:

Review of the Tecsun PL-990

by George Joachim


The Tecsun PL 990 is one of the three new radios offered by Tecsun and according to the news from the company these may be the last developed.

The other two radios are the Tecsun H-501 and the PL-330. The H-501 is the largest with dual speakers and the PL-990 is of a similar size to the PL-880, PL-680, PL-660 and PL-600. The PL-330 is the smallest and is similar to the PL-310ET and PL-380.

The Tecsun PL-990 is a medium sized portable multi-function radio. It has the following features:

  • Shortwave (SW)
  • Medium Wave (AM)
  • Frequency Modulation (FM)
  • SSB (LSB and USB)
  • Bluetooth connectivity (BT)
  • MP3 playback from a microSD port
  • Clock and two Timers with Alarms
  • Auto Sleep
  • powered by a single 18650 rechargeable 3.7V Lithium Ion Battery, unbranded and supplied.

The radio is a refinement of the PL-880 with styling similar to the PL-680. It is matte black with a hint of grey, finished in a quality plastic case and it is ergonomic with a good weight and feel, just like the PL-880.


This is my fourth portable radio of this size. I had owned the analogue Sony ICF-7601 back in the day and then the PL-660 and PL-880. The Sony was destroyed by me doing naughty electronic experiments and both the PL-660 and PL-880 were gifted to my family members.

Having no such radio, I considered the purchase of a new PL-880. I had contacted Ms Anna from the Anon Co. in HK and she was very helpful and also mentioned that Tecsun is developing a couple of new radios, but these are not yet available. This got me interested in the PL-990 and the H-501. I had also considered the H-501, because I liked the fact that it has two speaker sets, however the radio did seem a big bulky for my needs. I have a few desktop radios, but I needed something to be on my lap or by the bedside. Usually I fiddle with these portable radios lying on my chest until I find something nice to listen to then let it play on auto sleep until it puts me to sleep. I am sure some of you guys do this too. I imagine the H-501 would be a bit big for this.

After reading articles on the SWLing Post and despite the warnings about Pilot run versions and Chinese versions, I decided to risk a purchase from AliExpress. This has been my one and only purchase on AliExpress so far.


My radio was supplied by a company called Li Jia Shops in AliExpress. It cost a steep US$400 and US$157 DHL shipping. Totally expensive and risky in my opinion, but I am known to be reckless with my online purchases.? Besides, I wanted a new toy!

As this was my first purchase from AliExpress, I was a bit apprehensive, as I mainly use eBay. Also buying electronic items from China is a bit risky. One may end up not getting the item, or getting it after some significant delay. As you all know, electronic items exported from China is the largest electronics export operation in the world, so there is congestion in logistics and Covid-19 also adds to that. Selecting DHL to ship the item was very expensive, but I believe necessary. Waiting for an expensive electronic device for two months is a painful experience, at least from my perspective. Using DHL took a mere 12 days. The main delay originated from the shippers. They give the shipment information to DHL well in advance, but they do not actually take the item to DHL unless it suits their facilitators who they assign. The shipment shows as shipped and DHL status is ‘shipment information received’, but in reality the item is still with the shippers. Once it does actually get to DHL, then it is quite fast. Usually the shippers are located in the Shenzhen area and DHL is in Hong Kong. AliExpress will not release the payment unless the buyer confirms receipt of the item as described, so there is some safety for the buyer.

Overall, I was satisfied with the purchase and shipping process. But it was expensive and it was risky. It would be better to approach Anon Co in HK for your purchases rather than AliExpress and Bangood, but ultimately it is the buyer’s decision. For the English Export Version you must wait a bit I think.

The Export Version, the Chinese Version and the Pilot Run Version

This aspect is a bit confusing. From what I understood, and I could well be wrong, the versions are as follows:

Pilot run: this has the buttons as TIME DISPLAY and ALARM (this is also slightly cheaper on AliExpress and Banggood)
Chinese version: TIME TIMER A and TIMER B, but with Chinese manuals (what I have acquired)
Export Version: TIME TIMER A and TIMER B but with English manuals. (there may be further changes / improvements, as these units are still not available)

I am not sure about the firmware. My unit is presumably a later Chinese Version. And everything works properly as per the Firmware. The serial number of my unit indicates a possible manufacture date of July 2020, although this could be wrong.


The review will be based on the different functions of the radio.

FM reception

In the UAE we are blessed with several English language FM radio stations with good music and limited advertisements. Each station caters to particular tastes, such as 90s music, modern and classic hits. Reproduction was crisp and in full bodied stereo. The speaker is powerful and not unlike the speaker of the PL-880.

MW reception

I do not usually listen to AM or MW. However, the radio does a good job receiving these stations with a deep sound and minimal crackling.

SW reception

Shortwave is still out there folks, although its variety and abundance is greatly reduced. I do receive quite a few broadcasts using the telescopic antenna. Activity is concentrated around the 16m band, the 31m band and the 49m band, although occasional broadcasts can also be found in the 22m, 19m and 41m bands. The SYNC function holds on to weak broadcasts and makes them intelligible. I am sure that the Radio would do a commendable job if one could use a time machine to take it back to the SW hay-days of the 80s and 90s. I wonder if they have any time machines up for sale in AliExpress? 🙂

SSB Reception

Right out of the box I was able to fine tune into 14,182.10 kHz on the USB and hear HAMS ‘doing their thang’. It was excellent and far better than what similar attempts resulted in my previous Tecsun radios. I do think that Tecsun has improved the SSB reception with this receiver. I am not a very capable SSB chaser, but if there is something SSB out there, the PL-990 should able to pull it in. One needs to know where and when to tune and luck also plays a role.

LW Reception

Yes it is there, but no, I have never heard anything in there using the PL-990 and all my previous radios. I do wonder if submarines transmit in the LW band? I don’t know.

MP3 Playback

A lot of listeners are not interested in MP3 listening, but I am. Especially with SW being so sparse nowadays. MP3 was a feature missed from previous Tecsun radios. I enjoy compiling a list of favourite tracks and listening to them, while engaged in a barbecue or in car maintenance or cleaning. I am also a train modeler and like to listen to MP3s while running my trains. Tecsun has even supplied a Sandisk micro SD card of 16GB with various Chinese and international tracks, which I think was nice of them.


There is no Bluetooth button, but by pressing the RADIO/MP3 button an indication will come on the display as BT. The radio can then be conveniently paired with a mobile phone to transfer the audio from a you tube clip or similar to the radio, although I wouldn’t see the need for that. I am not sure if files can be transferred to the radio this way, I believe the function is only for audio playback.

Presentation and packaging

Much like the PL-880, the radio comes superbly packaged. The cardboard box functions as a glossy display of the radio and its features. Inside there are foam holders and there is a sturdy grey plastic toolbox case. In the toolbox case there is the radio, within a nylon bag inside its light brown faux leather pouch. The radio as well as the pouch have a carrying strap. In the toolbox there is a black foam case that contains:

  • A blue 18650 3.7 V Lithium Ion Battery
  • A long wire antenna in its real
  • A short(ish) charging cable
  • A UK style plug adaptor
  • A Chinese style charger with 2 USB outputs
  • A Chinese language operation manual
  • A Poster containing the map of the world and country Radio codes
  • On the other side of the Poster is a detailed view of the PL-990 with illustrations in Chinese


The radio uses one Li-Ion type 18650 3.7V battery. The included type is a blue generic unbranded type, I would have preferred a Tecsun-branded battery. I have a couple of vape equipment batteries –Golisi S30, which I believe are superior to the unbranded battery. (No, I am not a Vaper).

Concluding Remarks

The latest Tecsun offering is a great conclusion to their series of multi-function portable radios. It offers some advantages over the PL-880, such as:

  • Styling
  • MP3
  • Much improved SSB reception
  • Superb FM reproduction
  • Bluetooth

Apart from the above I don’t see a compelling reason to acquire the radio unless, SSB or MP3 is important for you. Or like me, you just must have the latest.


Style: 90%
FM: 100%
SW: 90% SYNC available
SSB: 95%
MW: 85%
LW: 80%
Battery Life: 70% for the provided battery 8/10 for externally sourced batteries
Display: 70% (the display is good, but it hasn’t really changed from previous displays)
Buttons: 85% Sturdy and precise, no wobbly buttons here.
Dials: 90% hard and precise with excellent indentations
Ports: 90% strong a tight female ports with protection plugs
Packaging: 95% anything you could wish for.
Documentation: 100% for Chinese speakers
Antenna: 60% normal telescopic antenna, should be a bit more shiny IMO.
Stability: 70% Stands well and has the rear bracket as the PL-880, however, would be easy to snap if pushed.
Sensitivity: 95% if it is there it will receive it and improve the signal over listening time.

Overall Review Score:

Final thoughts:
Go get one, if you must, but better wait for the full export version.

George Joachim
11 AUG 2020

Many thanks, George, for sharing your review of the PL-990!

So far, the PL-990 sounds like it has iterative improvements over the PL-880 which is, I suppose, what I would expect. The PL-880 is a great portable, so I believe even minor performance upgrades–especially in terms of synchronous detection–could be very beneficial to some SWLs.  And thanks for taking the deep-dive and grabbing one of the models on AliExpress! It’ll be interesting to compare notes once the “export” PL-990 is released.

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Jorge’s Portable YouLoop Antenna Frame

Many thanks to SWLing Post contributor, Jorge Garzón (EB7EFA · EA1036 SWL), who shares the following guest post which was originally published on his @IberiaDX blog:

BricoDX: A YouLoop portable frame

by Jorge Garzón (EB7EFA · EA1036 SWL)

Youloop ‘in the forest’

One of the aerials I wanted to test was the Youssef Loop (YouLoop). I own a good passive loop antenna made by Tecsun (AN-200) but this is a mini one to use with portable receivers. A video showing the test of this ‘mini-loop’ can be seen in my YouTube channel.

My main loop for serious DXing is the Wellbrook 1530LN, but this is an active loop that easily beats any other passive ones. It’s close to be the perfect loop for me as I live in a rural valley with low noise level in the bands so I enjoy every minute of my listening sessions. However I wanted to test this newcomer passive loop, but wasn’t satisfied just hanging it from a pine tree branch, so I decided to bring about my DIY YouLoop portable frame project.

So I had to find something to get a rigid (but light) support for the loop itself allowing an easy rotation to achieve deep nulls. So… what could I built?

Fiberglass tubes, hooks and crossed arms.

I am professionally involved in the heritage and communication sector, so was easy for me to refit some dismissed display rolls where I found a 1,5 m thin supporting tube made in fiberglass that suited my needs. I cut a piece of 120 cm and then split it into 2x60cm, tightening both in the middle with a fine bolt. I placed two plastic hooks up and down of the vertical tube to hold both Youloop modules. The horizontal arm was lengthened with two bamboo meat skewers firmly inserted into the tube, allowing to slide onto it. Two small holes in the bamboo pieces were good enough to secure the cable with a short wire. All this was well fixed with clamps and vulcanized tape to an extra piece of vertical tube.

Bamboo meat skewer and tied cable.

Finally all this was inserted into a thicker aluminium tube and then into a wider one in order to fit everything into the tripod hole and then get a smooth and efficient rotation of the antenna. As a base I re-fitted an old heavy metallic tripod manufactured by Manfrotto (Italy) that I used it often for birdwatching day trips. I gave back an unexpected new life for this piece of metal, always in the field close to Nature!

The whole assembly can be easily transported in the car. Aluminium tubes slide one into the other, being rapidly detachable from the loop itself. This is a cheap and DIY project to get the maximum of this surprising and low noise passive loop.

This aerial gives its best performance when used in the field. There, QRM levels are low or non existent at all. It is a must to rotate it easily and then get sharp nulls. SMA connector nuts must be well tightened as they tend to loosen easily, but beware to force them as an extra twisting could damage inner connections.

This is the first post of a series called «BricoDX» where I will show how to refit or build accessories to get inexpensive and practical DIY projects for our listening sessions.

Many thanks for sharing your article with us, Jorge! That’s a brilliant loop support.

Readers: check out more of Jorge’s articles on his blog, @IberiaDX. Also check out his YouTube channel where he posts videos.

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K9ZDK: Return of a Silent Key

Many thanks to SWLing Post contributor, Dan Van Hoy (VR2HF), who writes:

It was one of the most sublime moments in my 55+ years in radio. Almost every night I listen to shortwave station, KNLS in Anchor Point, Alaska, from my home in Hong Kong. KNLS broadcasts to Asia and the Pacific in English, Russian and Mandarin. The English broadcast is an amazing mix of secular and Christian music and topics, science, current affairs and more. It has something for both the seeker and the saint and is one of the most informative and entertaining shows on radio.

On this particular Monday evening, August 3, 2020, I tuned in late to the English broadcast from KNLS at 1000 UTC, but went on to listen to the remainder of the show. To my complete surprise as the show closed I heard “73 de K9ZDK” in Morse code and quickly wrote down that callsign. I assumed it was the engineer on duty, obviously a ham, having a little on-air fun with a big transmitter and antenna.

A few minutes later, I also heard “CQ de K9ZDK” at the beginning of the Russian program at 1100 UTC. So, I looked up K9ZDK on and found it was Zavier, a young ham who had become a silent key in June of 2019.

Zavier Klingensmith (K9ZDK) Silent Key

A little more online sleuthing and a phone call later revealed that his father, Thomas, KL0K, was at the controls of KNLS that night sending Zavier’s final CQ and 73 on this planet with at least 1 million watts of power (ERP: 100KW TX + 10dBd TCI curtain array) all around Asia and the Pacific. His call on CW was heard on every English, Russian and Mandarin show that evening over 16 hours of broadcasts (two Continental 100 KW transmitters). Wow!

In Zavier’s memory, Thomas has created a DIY kit for an Iambic Keyer and is offering it for FREE (though you might want to send some $$ for his production and mailing costs…my suggestion) to anyone who asks. Details can be found at Thomas’, KL0K, QRZ page. Maybe one of the first things you can send when your keyer is completed is,”K9ZDK de YOUR CALL, 73 OM!”

Thomas, our thoughts and prayers go out to you and your family. Thanks for the amazing on-air tribute to Zavier. I suspect he was listening with a big, big smile!

Dan VR2HF, Hong Kong

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Guest Post: What is FM Lightning Scatter DX?

Photo by Olivier Lance on Unsplash

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

What is Lightning Scatter DX?

by Bruce Atchison (VE6XTC)

Believe it or not, it’s possible to receive distant FM stations during a thunder storm. While lightning makes it difficult to hear AM and shortwave broadcasts, its crackles aren’t as evident on the 88 MHz to 108 MHz band.

When lightning strikes, it temporarily ionizes the air around it. Radio signals are reflected by the charged gasses and come back down to earth.

From my experience with this kind of DX, the signal became noticeably stronger during lightning strikes. This effect lasted for a second, then the signal level dropped to its former strength.

While a thunder storm raged overhead on July 7th, I used my CC Skywave SSB radio to check out the FM band. Instead of hearing E-skip as I had hoped, I found that tropo-like conditions reflected stations down to my home. I heard signals from a hundred miles away or further.

As just one example, I found a low-power station with the call letters CKSS on 88.1MHZ. They call themselves 88.1 The One. Find out more about this station at the link. It’s located in the town of Stony Plain, Alberta. This station plays country music and airs local news events.

At a guess, I’d say the transmitter is about 120 miles from my QTH in Radway. It normally doesn’t come in at all. The signal strength varied too, showing that it wasn’t a local.

In my instance of catching CKSS’s signal, a form of tropo ducting was also present. Rain can produce reflections of signals but it’s much more pronounced in the UHF and microwave bands.

When a thunder storm is ruining AM and shortwave reception, try DXing the FM band. You’ll be surprised at what occasionally comes in.

For further information on weather-related DX, check William R. Hepburn’s article.

To see a demonstration of lightning scatter on amateur TV, watch the
following video:

To hear what FM lightning scatter sounds like, watch this video:

Thank you for sharing this guest post Bruce. I’ll be the first to admit that I’ve never tried to hear lightening scatter DX, but I will certainly give it a go.  This time of year, we’ve numerous thunderstorms in the afternoon and evening, so I’ll certainly have the opportunity!

Post readers: Have you ever caught FM DX off of Lightening Scatter? Please comment!

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Adding CW mode to the EA3GCY DB4020 Dual-band 40 and 20M QRP Transceiver Kit (Part 2)

Many thanks to SWLing Post contributor, Frank (ON6UU), who shares the following guest post which expands upon his previous DB4020 article:

The EA3GCY DB4020 transceiver now has CW mode

by Frank Lagaet (ON6UU)

After telling you all about the DB4020 SSB build I’m here with the CW part of the kit,  let’s say this is part 2.  At a certain moment Javier let me know the CW interface kit was ready for shipment and some week later it was delivered to my QTH.

Again, a well packed kit arrived in a brown envelope, components and boards well packed in bubblewrap.  I found even a board I did not expect which can hold a push button,  a switch and the connector for your morse key.  Javier thinks of everything it seems!

Unpacking the bubblewrap gave me this result,  all components in 2 bags.  In the bigger bag another 2 bags with 2 printboards,  one for the CW interface,  one for the CW filter.  Great !!  Checking the material bill resulted in all components there,  another thumbs up.

I started, of course, immediately building it because I wanted CW in the transceiver as soon as possible.  I don’t do much in SSB mode anymore and I already started missing CW on the DB4020,  so I started my KX3 to listen to while I was populating the boards.  I never thought CW was going to have this impact on me! …. ..

I started building the CW interface,  again starting with all small items.  I soon saw that the 2 relays which need to be soldered in were ideal to protect all components when the board is upside down, so I soldered them in very quickly.  I then soldered in all other components ending with the elco’s.

Next phase was the CW filter.  This board is small and came together in a blink of an eye, no problems there, the long legs of the 3 and 4 pin headers went in last.

The following day, I made all wire connections and soldered a 13pin connector,  leaving one pin out since I want to have the option to choose the width of the CW signal I’m listening to.  By cutting the FL CW + pin and adding an additional switch, I have now 500Hz or 2400Hz.  Great option, for very little effort and simple.  Another thumbs up here.

Now it was simply a matter of inserting the sub boards in the main board and all should be working.  And it did!  Hurray!  The 500Hz filter works perfectly,  filtering away all above or below stations nearby my operating frequency.

This is the result of the soldering work,  2 small boards which need to be inserted in the main board:

The CW interface still needs the 13pin header of which I cut one pin and mounted a switch to have the 2400Hz width.

The IC you see in the middle of the CW interface is the KB2 keyer which gives you several functions like 4 memories and beacon mode.  The 4 potmeters are used to set the level on 40 and 20 meters,  to set the delay between TX and RX switchover and to set side tone monitor level.   The keyer also provides functions as keyer mode A or B,  straight key function and can be set for speeds between 1 and 50WPM.   WPM speed can be set in 2 different ways.  Handy!

Here a picture of the CW filter inserted on the main DB4020 board.

The CW interface is inserted at the side of the main board,  notice the 2 wires which go to the switch to allow switch-over between 500 and 2400Hz.

(Wiring still needs to be cleaned up in this picture.)

Finally, the result:  a good working multimode QRP transceiver with 2 bands.  It should be possible to make close to medium range with it as well as DX,  even with QRP power.

And while I was building I also made a new key for this radio,  it is made out of a relay and cost nearly nothing,  looks good doesn’t it ?  hihi.

Homebrew key

The key, when in practiced hands (fingers hi), can do 50 WPM without a problem. My friend HA3HK does without blinking an eye at 40WPM with this kind of key and tells me that he can go faster if needed.  Me? I’m going it a bit slower.

Battery pack

As this radio is only using little power (0.4A in RX,  1 to 2A in TX depending the power you set it) I thought,  let’s make a battery pack for the radio.

The first plan was installing it in the box.  I did not do that because the batterypack is also powerful enough to feed my KX2 and other QRP transceivers. Since I can use it with all of them, a loose battery works out better for me.

I started with an old laptop which had a broken screen and some other malfunctions,  but still had a good battery,  although I needed the battery connector of course.  A piece of wood to mount the connector on was my next goal.  And since I still have another laptop using the same batteries, I can charge the battery without problems.  Simple, but good and it weighs much less than a gel cell battery.

The battery provides me with 12.5V and some 5Ah.  Enough to last for hours on RX and for sure good enough to activate 2 SOTA sites in one day.   It doesn’t look great but works great– that is what matters and to test it was more then good.  Next will be getting the battery pack in a nice box.  Better to re-use stuff than throwing it away I’m thinking.

I need to do something about the cover of the OLED display,  there is still some work there to make it look nicer.

Some video can be seen on YouTube :

Finallym I’d like to thank you all for reading my articles about the DB4020. I had big fun soldering, tinkering with the box, making the key, and batteryholder/batterypack.  My Hungarian friend HA3HK told me it looks a bit like a spy radio. …. ..

I also include one more time the link where you’ll find this kit :

73 TU ee



Thank you so much, Frank. No doubt, you had a lot of fun putting this excellent little kit together.

Implementing a filter switch was a fantastic idea and, obviously, not terribly difficult to do.

Based on the videos, the DB4020 has a low noise floor and very good receiver characteristics. I’m impressed that the CW portion of the radios has so many features as well, such as a memory keyer and beacon mode.

I also love how you reused that 5Ah laptop battery! I think that could almost give you a full day of SOTA activations at those consumption levels!

Thanks again for sharing this with us, Frank! We look forward to your future articles!

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