Category Archives: Ham Radio

Guest Post: Indoor Noise and Ferrites, Part1

8 Replies

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

Indoor Noise and Ferrites, Part 1

by TomL

My magnet wire loop antenna on the porch reminded me to revisit aspects about my noisy Condo that I still needed to understand.  Some RF noise I could control if I could find the right kind of information that is understandable to a non-engineer like me.  There is a lot written about the general problem of noise and radio listening, for instance this ARRL article with web links to research – www.arrl.org/radio-frequency-interference-rfi, but I needed to get more specific about my particular environment.

I had tried some common clamp-on TDK ferrites I had obtained from eBay a long time ago but they only seemed to work a little bit.  I have since found out these are probably the ones which are widely used on home stereo system connections used to reduce noise on those systems.  There must be a better way.

The more I researched topics, like a portable “Loop on Ground” antenna, or, using RF chokes on the magnet wire loop, it dawned on my feeble, misguided brain that I was wrongly thinking about how to use ferrite material.  For one thing, the material used to suppress RF noise is made with a certain “mix” of elements, like Manganese-Zinc, that electrically “resists” a specified frequency range.  Fair-Rite has a useful Material Data Sheets web page which lists the Types of ferrite material.  For dealing with noise (at the Source causing the problem), I needed to use the right kind of “Suppression” materials and proper placement.  So, it (partly) made sense why the TDK snap-on ferrites might not fully work to reduce certain noise coming from my computer screens, LED lights, USB devices, and cheap Chinese-made power adapters.

A very good  paper is by Jim Brown (K9YC) of Audio Systems Group entitled, “Understanding How Ferrites Can Prevent and Eliminate RF Interference to Audio Systems [PDF]”.  There is a longer paper speaking directly to Amateur Radio folks, but the Audio version is simpler and it uses some of the same  graphs and ideas.  I was drawn to the very detailed Impedance measurements of many different “Types” of ferrite material used for different noise mitigation.  I remember the traumatic pain of my college experience trying mightily to understand the Van Vlack Materials Science text book to no avail.  But Jim’s paper reminded me of the importance of using the correct type of ferrite material and in an optimal way that reacts favorably in the target frequency range to solve a particular noise problem.  So, what are my problem areas?

Shortwave Noise

Loop antennas have been what I have experimented with the most.  They do not pick up as much man-made noise (QRM) and they have a space saving footprint.  Fortunately, there is a wooden porch where these things have been tried.  I had successfully built a broadband amplified “ferrite sleeve loop” (FSL) in the past.  It was useful for a while but it fell into disrepair and also the Condo building has steadily increased in noise output.  The amplifier was just amplifying the noise after a while.  I also tried phasing two antennas but found the ever increasing noise cloud was coming from all directions and I could not null it out.  I even tried a “mini-whip” from eBay but that just produced a wall of noise.

I recently tested AirSpy’s YouLoop written about before, and the results were good.  However, it seemed obvious to me that it was too small as a passive loop to capture shortwave signals strongly enough without resorting to another amplifier attached at the antenna and would not improve the signal/noise ratio.  My current solution is a unamplified stealth magnet wire loop about 32 feet in circumference.  In that article, I mention things like common mode RF chokes at both ends of the antenna connection, horizontal polarization, and basically accepting that only the stronger shortwave signals will be received in a predictable manner.  I think for now, this is about all I can do for shortwave and mediumwave noise, as far as my own Condo-generated noise. Neighborhood noise is a different topic.

VHF Noise

I then started to isolate which devices caused which kind of noise when listening to my outside amplified antennas for FM/VHF and UHF-TV transmissions.  Many consumer Power adapters make a lot of noise from VLF up into UHF ranges.  One thing I did right was to try a 10 pack of these little miracle “Wall Wart” toroids from Palomar Engineers.  One by one, I put one of these small toroids (19mm inside diameter) on my home AC adapters as shown in the pictures, and the noises started disappearing.  It does not explicitly say, but I believe it is Type 75 material which suppresses the noise generating AC adapter (at very low frequencies) when wrapped 8 – 12 times.

Most egregious of these was my CCrane FM2 transmitter.  A strangled warbling sound kept emanating from the monitor closest to my laptop. Installing ferrites on the laptop and back of the monitor were not working.  I moved the FM Transmitter and noticed a reduction in noise.  So, I put one of these little toroids on the power input of the device and the noise disappeared.  Apparently, it was picking up noise from the monitor (as well as its own power adapter) and rebroadcasting it to all my other radios!  The strangled warbler is no more, I choked it (HaHa, sick bird joke).

While looking for the monitor noise, I put the eBay TDK ferrites on all the USB ports and HDMI ports.  This has helped greatly on VHF and confirms my suspicion that these cheap TDK ferrites are indeed a common type of ferrite material.  Some informative graphs can be seen in Jim Brown’s Audio paper mentioned before.  One example might be Figure 22, which shows the #61 Series Resistance which peaks around 100 MHz when using a toroid with three “Turns”.  More confused, I could not find a definition of a “Turn”.  Eventually, in his longer paper to Amateur Radio operators, he defines it, “…is one more than the number of turns external to the cores”.  Somewhere else he describes using many single snap-on ferrites being electrically equal to just one toroidal ferrite with multiple Turns.  And interestingly, more Turns shifts the peak impedance substantially lower in frequency.  So, using the graphs he supplies, one can target a noisy frequency range to try to suppress.

I then put 6 of the TDK ferrites on the VHF input to the AirSpy HF+.  Some FM grunge was reduced and was thankful for that.  The rest of the background noise truly seems to be coming from the outside picked up by the amplified antenna.

Also, I juggled a couple of the amplifiers around and now have separate VHF/FM and UHF/TV amplifiers which cleaned up the FM reception a little bit more – https://www.youtube.com/watch?v=zkDsy95et2w .

UHF TV Quality

On a whim, I put the balance of the TDK ferrites on the FM/TV splitter input cable, 10 in all.  The FM reception did not improve but the Over The Air UHF TV reception Quality improved noticeably.  My weakest TV station now has a stable Signal level and the Quality is pegged at 100%.  This is a nice surprise since it means that now all local TV stations on UHF will come in cleanly without dropouts and I can view all digital subchannels.  I was even able to rescan and added two more low-power stations never seen before. ?

LED lights

I have common LED lights hanging over a number of fish tanks and some grow lights over an indoor plant box and can hear this noise on upper shortwave and higher radio bands.  In a future article, I will explore RF noise from lights as its own special topic. For instance, why do some LED lights generate RFI and how to know before buying (I am using BR30 spot bulbs from name brands)?  Also, there is a new kind of LED “filament” light out now that uses much smaller LED’s on both sides of an aluminum strip, greatly reducing electromagnetic noise output (or do they??).  More questions than answers.

I will explore creating my own customized AC power cord attached to the AC power strips of the LED lights.  I will need to test this for safety and efficacy, so I will want to take some time to do this right.  The hope is that, using Jim’s info, I will be able to create a broad spectrum RFI suppression AC power cord and cost less than $30 each cord.  We’ll see.

Finally, I will look at “stacked” toroids using different mixes of ferrite Types, creating a custom RF suppression better than using just one Type of ferrite material, using AC cords as the main examples. For instance, the best set of graphs in Jim’s paper, in my opinion, are Figures 21 and 24 compared to each other.  Something I did not know before is that one can not only use multiple turns on a single toroid to get a lower, peaked frequency response, but also stack multiple toroids of the same Type to get a smoother frequency response.  Then on top of this, combine that set with other Types to create a customized frequency response curve.

Radios are quieter now.  Those pesky grow lights are still a problem as well as the upstairs neighbor’s lights which seem to be on a timer, making FM reception noisy again after 5pm!

Spread the radio love

HF-START Web Tool: A new web-based, real-time shortwave radio propagation application

2 Replies

Many thanks to SWLing Post contributor, Tracy Wood, who shares the following journal abstract from EurekaAlert.com:

Commencement of shortwave propagation simulator (HF-START) service

Demonstrating radio wave propagation paths between any two points based on real-time space weather information

NATIONAL INSTITUTE OF INFORMATION AND COMMUNICATIONS TECHNOLOGY (NICT)

[Abstract]

The National Institute of Information and Communications Technology (NICT, President: TOKUDA Hideyuki, Ph.D.), in collaboration with Electronic Navigation Research Institute, National Institute of Maritime, Port and Aviation Technology (ENRI, Director General: FUKUDA Yutaka) and Chiba University (President: TOKUHISA Takeshi), has started the service of shortwave propagation simulator (HF-START). It provides real-time shortwave propagation that reflects real space weather information from ground-based observations and model calculations. The HF-START web system has been successfully developed and is now available at https://hfstart.nict.go.jp/.

The web calculation function of this system allows shortwave propagation between any two points in Japan based on real-time GNSS observations and between any two points on the Earth based on model-based space weather information. Real-time estimation is possible. The calculation in the past and up to about 1 day ahead in the future is also possible. In addition to amateur radio, HF-START is expected to benefit efficient frequency operation of aviation communications that relies on shortwave in the polar route.

[Background]

Communication and positioning technologies play an important role in social infrastructure in various fields today. The ionosphere has regular temporal cycles and fluctuates greatly every day associated with solar activity and space environment. Of benefit to us is the fact that ionosphere is good at refracting shortwave, which is why we can hop shortwave signals off the ionosphere to communicate with people over large distances.

Shortwave band has been used for communication and broadcasting for a long time, and are still widely used in radio broadcasting, aviation communication, amateur radio, etc. Ionospheric variation, however, has a great influence on the propagation of radio waves. Communication environment such as the communication range and usable frequency changes significantly due to the influence of the ionospheric fluctuation. Thus, fluctuations in the ionosphere affect the operation of shortwave broadcasting, aviation communications, and amateur radio.

There have been websites that provide estimated information on how radio wave propagation changes due to such ionospheric fluctuations. The problem is that it is based on a simple model and does not reflect realistic ionospheric fluctuations.

[Achievements]

We have developed a shortwave propagation simulator HF-START that estimates and provides shortwave propagation information in real-time under realistic ionospheric fluctuations based on ground-based observations and model calculations. We open real-time information estimated by HF-START, and the web application at https://hfstart.nict.go.jp/.

Figure 1 shows an example of visualization of shortwave propagation by HF-START. In this system, the user can check the radio wave propagation information that is updated in real-time. As shown in Figure 2, the user can also use the web application to estimate and visualize radio wave propagation by specifying any frequency in the range of 3-30 MHz, any two points on the Earth, and any transmission angle. The date and time can be set retroactively to the past (after 2016), to the real-time, and in the future (up to about 1 day ahead).

The system can be used to visualize the radio propagation path and clarify whether it is affected by space weather when the shortwave you are using does not reach the destination, or when you can listen shortwave broadcasted from the far source that normally you cannot hear. Furthermore, in addition to amateur radio, it is expected to benefit efficient frequency operation of the aircrafts that use shortwave in polar route.

[Future Prospects]

We are conducting research and development to extend the HF-START to estimate radio wave propagation not only in the shortwave band but also in other frequency bands. In addition, we will evaluate the simulator accuracy and improve it by comparing it with radio wave propagation observations.

NICT has been providing information related to communications, satellite positioning, and radiation exposure since November 2019 as a member of the Global Space Weather Center of the International Civil Aviation Organization (ICAO). With the HF-START service, we expect to improve the information provided to directly relate to communications, such as communication range information.

###

As the abstract mentions, you can use the tool online now via the HF-Start Web Tool.

Thanks so much for the tip, Tracy. This is fascinating!

Spread the radio love

Jack finds that chokes have a huge impact on switching power supply noise

7 Replies

These “Wall Wart” type adapters can create a lot of RFI

Many thanks to SWLing Post contributor, Jack Dully, who writes:

I was putting some things in my radio junk parts box and came across some chokes. So I tried a test with my Tecsun PL-880 on battery and the Tecsun supplied switching AC adapter, with and without chokes on the adapter.

WOW!

I tuned to a vacant station on battery power with headphones on. Then on AC power, the hash and static were incredible. Putting one large choke on the adapter power cord, wrapped about four times and it decreased considerably. So I attached a second choke and once again the static & hash decreased even more, almost to the point of sounding like I was running just on battery power.

Those chokes really do work well.

Thank you for sharing this, Jack. I almost never operate my portables while connected to a power supply, so I often forget about the importance of using a choke with inexpensive, lightweight radio power supplies. Thing is, so many things in our houses and shacks are powered by these QRM generators. In the shack, I’ve added chokes I’ve picked up at hamfests to a number of various power supplies. It does certainly help decrease the noise level. I’ve even used them on power cords for other appliances in the house that tend to spew RFI.

If you ever find a deal on chokes at a hamfest or electronics store, grab some. They can be an affordable solution for those noisy power supplies we still rely on.

Thank you for the reminder and  tip, Jack!

Spread the radio love

Radio Waves: Friedrichshafen Cancelled, Coast Guard Seeks Rare Diode, Kindred Spirits in DXing, and DRM Pitch for India’s FM Band

1 Reply

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 Dennis Dura, Ron Chester, and Mangosman for the following tips:

Ham Radio Verbindung 2021 kommt nicht zustande/Ham Radio convention 2021 has been cancelled (Messe Friedrichshafen)

[Note that the following is a Google translation of the original piece in German]

Ham Radio cannot take place this year either – other trade fair events remain on course

Due to the current corona developments, Messe Friedrichshafen cannot hold the international amateur radio exhibition Ham Radio in the planned period from June 25 to 27, 2021. Instead, the industry meeting will take place from June 24 to 26, 2022.

“The decision was not an easy one for us, but a trade fair like Ham Radio lives from its high level of internationality. Due to the current uncertainties in the travel sector, implementation is currently not feasible, ”explains Klaus Wellmann, Managing Director of Messe Friedrichshafen. All other trade fair events in the second quarter of 2021 and beyond should take place as planned at the present time. “A large percentage of our customers from these industries are still on board at the 2021 events. Together we hope that the immunization of society continues to gain momentum and that we can carry out the events with appropriate protection and hygiene concepts. “

Further information at: www.messe-friedrichshafen.de and http://www.hamradio-friedrichshafen.de/.

Rare Diode Threatens Coast Guard’s Arctic Ambitions (Hackaday)

The United States Coast Guard heavy icebreaker Polar Star is literally a one-of-a-kind ship. After its sister Polar Sea was deactivated in 2010 it became the most powerful icebreaker in the fleet, and one of only two US icebreakers capable of operating in the treacherous polar regions. The vessel is critical to protecting America’s scientific and economic interests in the Arctic, but according to a recent article in Business Insider, the ship’s age and scarcity of spare parts is making an already difficult mission even harder.

In the article, Captain William Woityra specifically mentions that the ship’s diesel-electric propulsion system is running on borrowed time as the diodes used in its AC/DC rectifier are no longer manufactured. With none remaining in the Coast Guard’s inventory, the crew has had to turn to eBay to source as many spares as possible. But once their hoard runs out, Captain Woityra fears his ship will be dead in the water[…]

A toast to the fools standing high on broadcasting’s hill (Doc Searls Weblog)

In Winter, the cap of dark on half the Earth is cocked to the north. So, as the planet spins, places farther north get more night in the winter. In McGrath, Alaska, at close to sixty-three degrees north, most of the day is dark. This would be discouraging to most people, but to Paul B. Walker it’s a blessing. Because Paul is a DXer.

In the radio world, DX stands for for distance, and DXing is listening to distant radio stations. Thanks to that darkness, Paul listens to AM stations of all sizes, from Turkey to Tennessee, Thailand to Norway. And last night, New Zealand. Specifically, NewsTalk ZB‘s main AM signal at 1035 on the AM (what used to be the) dial. According to distancecalculator.net, the signal traveled 11886.34 km, or 7385.83 miles, across the face of the earth. In fact it flew much farther, since the signal needed to bounce up and down off the E layer of the ionosphere and the surface of the ocean multiple times between Wellington and McGrath. While that distance is no big deal on shortwave (which bounces off a higher layer) and no deal at all on the Internet (where we are all zero distance apart), for a DXer that’s like hauling in a fish the size of a boat.

In this sense alone, Paul and I are kindred souls. As a boy and a young man, I was a devout DXer too. I logged thousands of AM and FM stations, from my homes in New Jersey and North Carolina. (Here is a collection of QSL cards I got from stations to which I reported reception, in 1963, when I was a sophomore in high school.) More importantly, learning about all these distant stations sparked my interest in geography, electronics, geology, weather, astronomy, history and other adjacent fields. By the time I was a teen, I could draw all the states of the country, freehand, and name their capitals too. And that was on top of knowing on sight the likely purpose of every broadcast tower and antenna I saw.[…]

DRM Makes Its Pitch for India’s FM Band (Radio World)

In India, where regulators have been working toward recommending a standard to digitize the FM band, Digital Radio Mondiale is presenting its case.

DRM has been conducting trials and demos since late February, when a digital radio transmission with three audio services and Journaline text information went live in Delhi alongside existing analog FM transmissions.

It said it is also showing the possibility of extending a shared transmitter infrastructure by broadcasting up to six individual DRM signals or blocks, carrying up to 18 audio services plus 6 multimedia services, being broadcast from one FM transmitter and antenna. It said the number of individual DRM signals is only limited by the bandwidth of the transmitter. Each signal can have its own power level, and gaps in the spectrum are possible, as are individual SFN networks per DRM signal.

“The transmission is part of an extensive trial and demonstration of DRM conducted by Prasar Bharati and its radio arm, All India Radio (AIR), with the help of the DRM Consortium and its local and international members,” DRM stated in a press release. “The test was officially launched on Feb. 24 and 25 at the headquarters of All India Radio in New Delhi.”

The test was requested by regulator TRAI and the Ministry of Information & Broadcasting.

DRM officials said a presentation to AIR’s committee showed DRM in the FM band on various car radios including line-fit, aftermarket, standalone receivers, mobile phones and tablets. A head unit from Mobis, upgraded for FM via firmware, was installed in a Hyundai Verna. DRM said, “The reception was found to be excellent for over 15 km radius with just 100 W of DRM power in digital,” including 5.1 surround sound test broadcasts on DRM.[…]

You might also check out the article HD Radio and Digital FM in India at Radio World.

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

Social DXing: Looking back at one very radio-active year

17 Replies

One year ago, I posted an article about making the most of social distancing as the world started locking down due to the rapid spread of Covid-19. Here in March 2021, the news is looking much better: vaccines are being distributed at a record pace across the globe and number of cases and deaths are mostly on the decline.

Looking back

As I look back at the Social DX Bucket List I made last year, I’m happy to see that I actually accomplished about 64% of the goals I listed. I knew some of those goals would take well over a year to achieve (the QRP EME one especially).

In particular, I’m chuffed that I braved up and started doing Parks On the Air (POTA) and Summits On The Air (SOTA) activations in CW (Morse Code). That was a huge step for me and I’ll freely admit: I was nervous about it. But in July 2020, I managed to do my first CW activation and since then it has become my choice mode of operating in the field. CW is such a simple mode and so efficient–plus it gives me a sense of connection with the roots of radio communications.

I also accomplished a few things I never set out to do:

Not a typical radio year for me

In a “normal” year, I do way more SWLing than I do ham radio activity.

Last year, I started doing caregiving for my parents in my hometown–I’m typically there 2-3 days a week. While I’ve done shortwave listening and even a little MW DXing in my hometown, I typically don’t have a lot of time, especially in the evening hours. I just want to hit the sack early. QRM is also debilitating there and while I’d like to install a permanent Loop On Ground antenna to mitigate the noise (you heard that right, Andrea!) I’m not entirely sure I’d even have the dedicated listening time to justify it. When I’m there, I like to spend quality time with my folks.

In general, I’ve had much less free time. Indeed, if you’ve written to me via email, you’ll know this based on how long it’s taken me to reply. It can take several weeks especially if the reply requires a detailed response (which many do).

En route to, and on the way back from my hometown, I’ve found that doing park and summit activations has been very rewarding. Last year, I believe I completed a total of 82 park activations.

POTA has given me an excuse to explore public lands I’ve never visited before. Plus, I love nothing more than taking radios to the field–both receivers and transceivers.

Hamming and SWLing

At the end of the day, I’m an SWL and a ham radio operator. I find the two activities complimentary.

Side note: As I mentioned in my Winter SWL Fest presentation this year, it saddens me when I receive angry emails from readers after I post items that are ham radio related. We’ve upwards of 7,000-10,000 daily readers on the SWLing Post and the number of complaints are a teeny, tiny fraction of our readership. I only receive messages like this about once a month and they typically say something akin to “I don’t like the ham radio stuff, so if you don’t stop posting it, I’m leaving!” (FYI: That’s a real quote taken from the last one I received in January). I can only assume that at some point in the past, a ham radio operator has been a jerk to this and other radio enthusiasts. It’s a shame, too. I hate seeing the negative impact of one loud troll compared with the encouragement and support of much better people. All of my ham radio friends are not only supportive of SWLing, but almost all got their start in radio via the shortwaves. I’m certainly a case in point.

I love all things radio and I believe the SWLing Post is a reflection of that. If it offends you, then it might make sense to surf somewhere else.

Now where was I? Oh yeah…

POTA and SOTA outings have helped to satisfy some of my travel cravings as well. I miss going to radio conventions, hamfests, and especially traveling internationally with my family. We are a family who love national parks, forests, and other wildlife areas. Having an excuse to explore public lands we haven’t visited before has been amazing fun.

After POTA activations, I’ll often do a little SWLing since I already have an external antenna up and it’s typically connected to a good general coverage transceiver in a spot with zero RFI or QRM. I’ve especially enjoyed my DXing sessions with the superb Icom IC-705.

Listening habits

One indicator that I did less radio listening last year was the low number of recordings I made. I checked my audio folder recently and saw that I only made a couple dozen recordings–most were staple broadcasters, not rare or special DX.

At the end of the day, I realize that when I do SWLing sessions I like to have dedicated time–at least an hour or two–with headphones on, losing myself on the radio dial.  I simply haven’t had many opportunities this past year to make that a reality.

That’s okay, though. The great thing about the shortwaves is that they’re always there, patiently waiting for us to dive back in!

Looking forward

I’m really not sure what’s in store for me this year, but I know it’ll involve a lot of radio time and that pleases me to no end. I’ve made a few fun goals, but my hope is that, by the end of the year, I may even be able to do some proper travel–maybe even take a flight!

I do know this: I have an even more profound appreciation for my radio enthusiasm as I realize it’s the perfect space to travel and explore the world no matter how “locked down” things are. Based on feedback from readers and contributors to this site, I know I’m not the only one who feels this way.

How about you?

Did your radio activity change or pivot this past year? Did you have more or less time to hit the airwaves? Please comment!

Spread the radio love

1940: When Sears Roebuck sold a wide array of radio gear

8 Replies

Many thanks to SWLing Post contributor, Charlie (W4MEC), who shares a PDF of the 1940 Sears Roebuck Co. catalog section featuring a wide array of radio gear and test equipment.

This file is hosted on the Pro Audio Design forum and can be downloaded as a PDF (15.8 MB) by clicking here.

It’s a real nostalgia trip reading through the fine Hallicrafters, Hammarlund and National HRO descriptions. Thanks so much for sharing this, Charlie!

Spread the radio love