Tag Archives: QRM

Radio Waves: AM Buzzkill, AM FEMA Push, AM Devitalization, and RFI-Blocking Chips

Radio Waves:  Stories Making Waves in the World of Radio

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 Rich Dalton and Dennis Dura for the following tips:


The JacoBLOG Junk Drawer – The AM Radio Edition (Jacobs Media Strategies)

Is there a bigger buzzkill blog topic than AM radio?

In a an era where digital has transformed radio broadcasting’s content and revenue focus, the last thing anyone wants to talk about in 2023 is lowly AM radio. But like that old drunk uncle who shows up at the reunion, AM is still part of the radio family.

In its heyday, AM ruled the radio roost. It wasn’t until the late 70’s when FM surpassed AM in total listening, and later profitability. Before then, AM was the behemoth. And the biggest and best in class could be magically heard in dozens of states each night. Weather, atmospherics, and bodies of water all factored into AM reception.

Many Baby Boomers vividly recall laying in bed at night, precariously tuning in a faraway AM station carrying a ballgame or even broadcasting progressive music. Or grabbing a portable transistor radio – like the one sitting in our junk drawer – taking it to a sporting event and having a great audio soundtrack from legends like Vin Scully, Ernie Harwell, or Jack Buck. [Continue reading…]

Former FEMA Leaders Continue Push for AM Preservation (Radio World)

Say the removal of AM radios from cars is “a grave threat to future local, state and federal disaster response and relief efforts”

The laundry list of current and former government officials advocating for the safeguarding of AM radio in electric vehicles continues to grow.

On Feb. 26, seven former leaders of the Federal Emergency Management Agency penned a letter to Secretary Pete Buttigieg of the Department of Transportation advocating for the preservation of the senior band and urging regulators to take action to protect the nation’s public safety.

“Because of the great distances that its signal carries, and due to its resiliency during even the worst natural disasters, the success of the National Public Warning System hinges on the use of AM radio,” the collective of former FEMA leaders wrote. “However, should EV makers continue removing AM radios from their vehicles, this vital public safety system will no longer function as intended.”

The dialogue between automakers and AM advocates has grown signficiantly in recent weeks. As we reported earlier, the Alliance for Automotive Innovation sent a reply to Sen. Ed Markey after he asked individual car companies about their commitment to broadcast AM radio in electric and other future vehicles. In the days following, Markey, the alliance, the National Association of Broadcasters and, now, FEMA officials and and an FCC commissioner have continued a public discourse.[Continue reading…]

AM Devitalization (All Access)

Been to a shopping mall lately?

It’s not pretty. Vacancies dot even the most successful malls. The lesser malls feel abandoned, like modern ruins, isolated and scary. One mall near us is so barren, they’ve marked off part of one end and use it for pickleball. Even the mall walkers are gone. If a mall can’t draw mall walkers in South Florida, that’s a harbinger of doom.

The reasons that big indoor malls aren’t thriving anymore aren’t a secret. Habits changed. Tastes changed. People shop online now, or go to discounters like Walmart or Target. Department stores have fallen out of favor. Teens don’t hang out in the food court anymore; they’re congregating on TikTok. What’s left are traditionalist shoppers who want to try stuff on or handle it before buying, or people who want to see stuff in person before firing up the Amazon app and buying it there. Other than Apple stores and a few other chains with loyal customers, there’s not a lot to draw people to the mall anymore, and what’s left is kinda creepy. Some malls are now mostly occupied by local businesses trying to make a go of it, and things like gyms and churches and DMV offices. I got my Florida driver’s license in a half-repurposed mall. It was strange. [Continue reading…]

Boffins concoct interference-busting radios (The Register)

Radio interference can be a pain to deal with, regardless of whether it’s a rogue baby monitor interrupting your Wi-Fi or a stadium full of smartphone signals drowning each other out.

However, brainiacs at MIT say they’ve developed a radio chip that can see through the noisiest RF hellscape by actively blocking unwanted frequencies before they can scramble messages.

The chip was developed to address the growing challenges associated with 5G and other wireless communications standards. It takes inspiration from several adjacent domains – including digital signal processing and applied electronics – explained Negar Reiskarimian, assistant professor of electrical engineering and computer science at MIT.

The work, presented at the International Solid-State Circuits Conference (ISSCC) last week and detailed in a recent blog post, combines a number of existing technologies into a novel radio chip, which researchers say can contend with RF interference 40 times higher than existing wideband receivers. What’s more, they say the method doesn’t require large, bulky filtering equipment.

Even in its current development stage, the chip is small enough – just 0.65mm square – for use in mobile devices, according to Reiskarimian and Soroush Araei, an MIT grad student working on the project. And while 5G is highlighted as a potential application for radios based on the design, they note there’s no reason it can’t be used for other wireless signals like Wi-Fi. [Continue reading…]


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Resource for tracking down sources of PV system RFI

Photo by Vivint Solar

Many thanks to SWLing Post contributor, Jerome van der Linden, who writes:

Hello Thomas,

In asking the manufacturer of the inverter for the solar array on our house what I might be able to do to reduce the EMI coming out of it, he gave me some Googling ideas, which led me to the following article which I think is worth passing on to others:

https://www.solar-electric.com/learning-center/reducing-electromagnetic-interference-pv-systems.html/

I was particularly interested in the sentence: Conversely, inverters connect to AC circuits in the home, turning every inch of the house wiring into an antenna that radiates the interference.

The guy who wrote the article has a lot of experience in chasing down this problem.

Cheers

Jerome van der Linden

Thanks for sharing this, Jerome. As more and more homes install solar solutions, tracking down sources RFI has certainly become an art form. When we installed our rather simple PV system over a decade ago, our installer stuck with telephony approved gear–charge controllers, etc. that are often used in communication central offices. 

Thank you for sharing!

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Radio Waves: AU2JCB Special Event, 1 Million Watt FM Tower, 3ZZZ Breaches Rules, Australia Calling, WWII KGEI, and EV Charger QRM

Icom IC-756 Pro Transceiver Dial

Radio Waves:  Stories Making Waves in the World of Radio

Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!


AU2JCB Special Event Station (Nov 25 – Dec 13, 2022)

Many thanks to SWLing Post contributor, Datta, who shares the following announcement:

AU2JCB is a special event call-sign to commemorate the birth date (30 NOV) & to pay homage & to tell about the great INDIAN scientist Acharya JAGADISH CHANDRA BOSE who is recognized as the “Father of Wireless Communication” by the scientific community of our world &IEEE.

I, VU2DSI, have been operating with this call sign for the last 17 years since 2005 & operate AU2JCB from 25 NOV 2022 to 13 DEC 2022.

The Details of operation —-

Period: 25 NOV 2022 to 13 DEC 2022

Frequencies:

  • 10 M: 28545, 28510,28490
  • 21 M: 21235, 21310, 21350
  • 20M: 4210, 14250, 14310
  • 40 M: 7040, 7150
  • 80 M: 3710
  • 6M in FM mode 50800, 51500
  • 10 M: 29700

Preferably the operation will be on higher bands according to propagation conditions.

QSL— Direct to VU2DSI, “SURABHI” MEHERABAD. AHMEDNAGAR.414006. INDIA.

FOR DX STATIONS PLEASE SEND 2IRC’s—–IF POSSIBLE— as many many DX stations are requesting QSL’s.

I will appreciate the GOOD number of used postal stamps instead of IRC as I love collecting stamps.

About

Aacharya J.C.Bose is well known as the “Father of Wireless Communication”.

Acharya Bose’s demonstration in 1895 & 1897 predates all.

Bose transmitted wireless signals to a distance of a mile. Popova in Russia was still trying remote signaling at this time & the first wireless experiment by Marconi was not successful until May 1897.

Bose is a pioneer in microwave optics technology.

Bose’s invention of 1-centimeter to 5 millimeters radio waves is being used in radars, satellite communication& remote sensing.

Bose’s concepts from his original 1897 papers are now incorporated into a new 1.3 mm multi-beam receiver on the NRAO (National Radio Observatory) 12 Meter Telescope.

Bose anticipated the use of P-type& N-type semiconductors & hence 60 years ahead of his time. Bose developed the use of GALENA crystals for making receivers.

In Bose’s presentation to the Royal Institution in London in January 1897, he speculated on the existence of electromagnetic radiation from the sun. This radiation from the sun was not detected until 1942.

Video: Exploring a 1 MILLION Watt FM Tower (YouTube)

My Dad and I took a road trip to tour the 1 MW FM community tower in Crestwood, MO, serving the entire St. Louis metro area combining 10 FM radio signals into two antenna systems.

Special thanks to the Audacy engineers who allowed us to take a peek at their (very clean!) transmitter rooms and equipment!

Click here to view on YouTube.

3ZZZ breaches community radio broadcast rules in its coverage on Ukraine (ACMA)

The Australian Communications and Media Authority (ACMA) has found Melbourne-based community broadcaster 3ZZZ in breach of community broadcasting rules in its coverage of the invasion of Ukraine by Russia. Continue reading

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Small Unidirectional Loop Antenna (SULA) Part 3: Questions & Answers

Many thanks to SWLing Post contributor extraordinaire, 13dka, who brings us Part Two of a three part series about the new SULA homebrew antenna project. This first article describes this affordable antenna and demonstrates its unique reception properties. The second article focuses on construction notes. This third and final article will essentially be a Q&A about the SULA antenna. 

This wideband unidirectional antenna is an outstanding and innovative development for the portable DXer. I love the fact that it came to fruition via a collaboration between Grayhat and 13dka: two amazing gents and radio ambassadors on our SWLing.net discussion board and here on the SWLing Post. So many thanks to both of them!

Please enjoy and share Part 3:


Part 3: SULA Q&A

by 13dka

Q: Where can I ask questions, discuss all aspects of the the SULA or collaborate in its further development?

A: There is a thread dedicated to the SULA in the new SWLing.com message board: https://swling.net/viewtopic.php?t=55

Q: Since the antenna is “lossy”, what’s the point of having a “beam”?

A: The answer is once again “SNR”: First off, remember that the LNA is there to make up for most of the losses. Secondly, this is all about the noise pickup, 20dB less gain/more losses outside the main lobe means also a reduction of atmospheric/cosmic/whatnot QRN and of course everything manmade from all these sides. The wide horizontal lobe is more or less one hemisphere horizontally, but the flat-ish vertical pattern makes that only a slice of it. In other words, there will be less QRN and QRM pickup from the back and the top. The idea is that the SNR will ideally increase more than the preamp’s noise figure will cost and it often sounds like this is what actually happens. Of course it’s also nice that you can turn an unwanted signal down using the more or less pronounced notch in the backside pattern up to 21 MHz – also very helpful for direction finding.

Q: Do I need a rotor?

A: It depends. If you are one of the lucky few still having a low-QRM-environment at home and you want to put it in the backyard, you really may want to be able to turn it remotely. If you’re using it portable you can simply rotate the mast manually. If you have local QRM or can’t mount it very far away from your or other houses, you may want to rotate the back of the antenna towards that source, leave it at that position forever and enjoy what’s coming in on the pretty wide main lobe of the antenna. The horizontal lobe covers more or less half of the horizon, depending on your stations of interest and location you could get away with never turning the antenna at all.

Q: Is it better than the XYZ loop?

A: Hey, that’s exactly what I wanted to ask you! 🙂 Even though the SULA is very similar in appearance and performance to a good SML working in ideal (ground conductivity) conditions, the SULA is a pretty different animal with a different behavior: Regular small loops, besides being bidirectional, can lose quite a bit of their low angle sensitivity over “poor” ground while the SULA is supposed to be retaining its properties better over any type of ground. Also, while many SMLs are tuned for VLF through the lower portion of the shortwave, the SULA complements those with quite uniform (good) properties up to 30 MHz and beyond.

Q: I have an end-fed random wire or dipole strung up from the house to a tree etc. – can the SULA beat that?

A: That’s quite possible. To get low takeoff angles from horizontal wire antennas you need to string them up at least 1/2 wavelength high, that’s 20m/66ft on 40/41m, 10m/33ft on 20m and so on. If you can’t do that, the SULA may be your ticket to listen farther beyond the horizon. Also, wire antennas are often strung up to match space restrictions or avoid QRM vectors and that way you may end up with some directionality in directions you don’t want, or no directionality at all when the wire is too low. Another noteworthy point is the ground: For most horizontal antennas, better ground means a considerable higher takeoff angle so the dipole needs even more height for low angles. The SULA’s takeoff angle benefits a little from the better ground and only gets a little worse over poor ground.

Q: Do I really need an LNA?

A: I hope so? Of course it depends… if you are going to try this antenna in a very noisy environment, the LNA may have little to no benefit. The noise is limiting your “radio horizon” to very loud signals anyway and for those you may not need an LNA, ever. On the other hand, the antenna is very lossy and in a quiet environment where noise is not an issue at all, weak signals may drop below the sensitivity threshold of your receiver without the LNA. The less noise you have, the more you’ll be able to benefit from an LNA. You will also need one when your radio isn’t all that sensitive, similar to the requirements to run a YouLoop. Andrew kept the loop impedance as constant as possible in order to allow any low impedance coax preamp to work behind the Balun. Any LNA with 20dB of gain should do, as per usual, better stuff may bring better results.

Among the sparse offers for decent shortwave LNAs, the NooElec LANA HF seems to be the only decent LNA sold via Amazon. It’s comparatively low-cost and unlike the other offers on Amazon, ready to be powered via Bias-T or even via Micro-USB and therefore happy with 5V. Since I also had the balun from the same company I could simply connect that all with a couple of these cute little SMA plumbing bits and it worked. The downside is its unknown but perceivably low resilience against intermodulation (low 3rd-order intercept point), this is usually not a problem with such a small loop but it can be in the presence of nearby transmitters.

If you do have nearby transmitters and don’t mind sourcing an LNA from Europe, Andrew recently pointed me to preamps from here. They offer a moderately priced preamp with a 2N5109 transistor (based on the W7IUV design) for a high IP3 value and low noise, which is also available in PCB-only and fully assembled versions including a compartment. They also offer Bias-T boxes.

Q: What is special/different about this antenna? There are already very similar designs!

A: It’s supposed to be simpler and more compact/portable, and it seems to deliver more consistent results over the entire coverage range in different usage environments than similar designs. The SULA was designed to be made with things that are particularly easy to obtain, or which were already obtained — many of us SWLs have some of that Nooelec stuff in our drawer anyway, even when (or because) we’re not habitual antenna builders and balun winders. Now making a better balun and buying a better preamp is not hard and could even bring better results but the point is that you don’t have to. In summary, this is not meant to be a miracle antenna, just number of compromises re-arranged to create a particularly uncomplicated, small, unidirectional loop antenna that aims for DX, for apartment dwellers and DX nomads like me.

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Small Unidirectional Loop Antenna (SULA) Part 2: Construction Notes

Many thanks to SWLing Post contributor extraordinaire, 13dka, who brings us Part Two of a three part series about the new SULA homebrew antenna project. This first article describes this affordable antenna and demonstrates its unique reception properties. This second article focuses on construction notes. The third and final article will essentially be a Q&A about the SULA antenna. All articles will eventually link to each other once published.

This wideband unidirectional antenna is an outstanding and innovative development for the portable DXer. I love the fact that it came to fruition via a collaboration between Grayhat and 13dka: two amazing gents and radio ambassadors on our SWLing.net discussion board and here on the SWLing Post. So many thanks to both of them!

Please enjoy and share Part 2:


Part 2: SULA Construction notes

by 13dka

The drawing [above] has all you need to know. You basically need to put up a symmetrical wire diamond starting with a balun at the one end and terminating in a resistor at the other end of the horizontal boom, the sides are supposed to be 76cm/29.92″ long so you need to make yourself some…

Support structure:

I used 0.63″/1.6cm square plastic square tubing/cable duct profiles from the home improvement market to make the support structure. You can use anything non-conductive for that of course, broom sticks, lathes… The plastic profiles I used had the advantage of being in the house and easy to work on with a Dremel-style tool and everything can be assembled using the same self-tapping screws without even drilling. The profiles are held together with 2 screws, for transport I unscrew one of them and put that into an extra “parking” screw hole on the side, then I can collapse the cross for easy fit into the trunk, a rucksack etc.

These profiles are available in different diameters that fit into each other like a telescoping whip. This is useful to make the support structure variable for experiments and to control the loop shape and tension on the wire. The booms end up at 1.075m each, the profiles come in 1m length, so that’s 4 short pieces of the smaller size tube to extend the main booms by 37mm on each side

On the resistor end of the loop that smaller tube isn’t mounted in the “boom” tube but to the side of it in order to keep the wire running straight from the balun box on the other side.

Mast/mounting:

You can use anything non-conductive to bring it up to height. On second thought that is indeed bad news if you were planning on putting that up on your metal mast…and we have no data on what happens when you do it anyway. I don’t know if the smallest (4m) telescoping fiberglass poles would suffice for portable operation, but I’m a fan of just using the big lower segments of my 10m “HD” mast for the stiffness they give me (3 segments for the height, the 4th collapsed into in the base segment for easy rotation). Telescoping masts also give you easy control over…

Height:

The published patterns are for 3m/10′ feedpoint height over “average” ground. Increasing height further has no expectable advantage, instead it will deteriorate the favorable directional pattern of the loop. Flying it lower, or even a lot lower in windy weather on the other hand is causing a surprisingly moderate hit on performance.

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Introducing the amazing SULA: An affordable unidirectional DX-grade loop antenna that you can build!

Many thanks to SWLing Post contributor extraordinaire, 13dka, who brings us a three part series about the new SULA homebrew antenna project. This first article describes this affordable antenna and demonstrates its unique reception properties. The second article will focus on construction notes. The third and final article will essentially be a Q&A about the SULA antenna. All articles will eventually link to each other once published.

This wideband unidirectional antenna is an outstanding and innovative development for the portable DXer. I love the fact that it came to fruition via a collaboration between Grayhat and 13dka: two amazing gents and radio ambassadors on our SWLing.net discussion board and here on the SWLing Post. So many thanks to both of them!

Please enjoy and share SULA Part 1:


Introducing the Small Unidirectional Loop Antenna (SULA) 1-30MHz

A small and simple, unidirectional and DX-capable loop “beam” for SWLs!

by 13dka

In early June, Andrew (grayhat), SWLing Post‘s resident antenna wizard suggested a variation of the “cardioid loop” on the SWLing Post message board: The original “cardioid loop” is a small loop receiving antenna deriving its name from a cardioid shaped (unidirectional) radiation footprint. The design is strikingly simple but it has a few downsides: It relies on a custom preamp, it needs a ground rod to work and it is unidirectional only up to 8 MHz.

Andrew’s version had the components all shuffled around and it did not only lose the ground rod, it also promised a nice cardioid pattern over the entire shortwave, from a small, diamond shaped loop. Wait…what? It can be made using parts available on Amazon and your DIY store:

You need some 3m wire and PVC tubes to create a support structure to hold the wire, a 530 Ohm resistor and a 9:1 balun like the popular “NooElec One Nine”. Since it’s a “lossy” design, adding a generic LNA like the NooElec “LANA HF” would help getting most out of it. When you put that all together you have what sounds like an old shortwave listener’s dream: a small, portable, tangible, and completely practical allband shortwave reception beam antenna with some more convenient properties on top, for example, it is a bit afraid of heights.

That sounded both interesting and plain crazy, but the .nec files Andrew posted were clearly saying that this antenna is a thing now. Unfortunately Andrew suffered a little injury that kept him from making one of those right away, I on the other hand had almost all the needed parts in a drawer so I ended up making a prototype and putting it through some of its paces, with Andrew changing the design and me changing the actual antenna accordingly, then mounting it upside down. Let me show you around:

  •  Small, diamond shaped wire loop (with 76cm/29.92″ sides), needing as little space as most other small loops.
  • Unidirectional with a ~160° wide “beam” and one pronounced minimum with a front/back-ratio of typically 20dB over the entire reception range 1-30MHz.
  • Moderate height requirements: It works best up to 3m/10′ above ground, where it gives you…
  • …a main lobe with a convenient flat takeoff angle for DX
  • Antenna is comparatively insensitive to ground quality/conductivity.
  • Wideband design, works best on shortwave and is pretty good up to 70cm.

A functional small beam antenna for shortwave reception that’s just as small and possibly even more lightweight (prototype:~250g/9oz) than your regular SML, that can be easily made out of easy to obtain parts and easily carried around for mobile/portable DXing and due to its cardioid shaped directional pattern also for direction finding, a “tactical” antenna that’s also doing DX? Unlike conventional, Yagi-Uda or wire beams it can achieve a low takeoff angle at only 3m/10ft height or less, the front/back ratio is typically better than that of a 3-element Yagi, with a particularly useful horizontal pattern shape. That it’s rather indifferent to soil quality could mean that more people get to reproduce the good results and being a real wideband antenna is making the SULA an interesting companion for multiband radios and SDRs. Really? A miracle antenna? Is it that time of year again? If I had a dollar for every….

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A little off-line, off-grid camping

You might have noticed a lack of posts this weekend and that would be because I was completely off-grid and off-line, camping with two good friends in Pisgah National Forest.

It was brilliant, actually. I got to hang with friends I’ve known for over 30 years, test my new one person backpack tent (a.k.a. the “Bear Burrito”–the one on the right above), and of course I played a bit of radio.

Black bears are a fact of life here in the mountains of western North Carolina and we spotted three hanging out within 25 meters of our campsite.

By the way: the trick when camping with bears? Don’t put food in your tent, else that whole “bear burrito” thing becomes a reality.

I had a fabulous time putting my Elecraft KX1 “Ruby” on the air. I made perhaps 15 contacts in CW (Morse Code) with 3 watts of power.

One of the cool things about the KX1 is you can change the mode to SSB and actually tune through several shortwave broadcast bands (if you have the three or four band version of the KX1). Of course, I had to do a little SWLing.

As I mentioned in my previous post, I’m also a proper coffee snob and I firmly believe coffee tastes better when brewed outdoors. Yesterday morning, I brewed a pot of Rock Creek French Roast.

Off-grid, off-line camping recharges my internal batteries and it’s for this reason, I’ll be doing a lot more this year with my family.

It’s is also a brilliant way to experience an environment without any forms of radio interference (QRM or RFI). If you want to do some proper DXing, take your radio on some primitive camping experiences. It’ll remind you what life was like before switching power supplies ruled the world!

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