Tag Archives: QRM

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.

Another alternative would be https://www.sv1afn.com/en/product-category-5/-6.html – the design (using a GALI-84 MMIC) is promising more headroom than the LANA HF (which seems to use the lower voltage GALI-39), but needs 12V power like the W7UV preamp above. This LNA is available in a ready-to-use box as well.

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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Radio Waves: BBC License Fee Frozen, Battling RFI, Warning to RTL-SDR Users in Ukraine, and WRD Special Broadcast

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!


BBC’s funding system under fire (Marketplace)

In the United Kingdom, you need a license to drive a car, fly a plane, practice medicine and watch TV.

The “TV license” is what Brits call their system for funding their world-famous broadcaster, the BBC. Currently, it costs the equivalent of $216 a year and is compulsory. Anyone in the U.K. caught watching or recording programs broadcast on any television channel or livestreamed on an online platform without a license is likely to be prosecuted.

The BBC — the Beeb, as it’s known — derives around $5 billion a year from this source. That’s 75% of the total revenue it needs to run a vast media empire, comprising 10 national TV channels and 10 national and 40 local radio stations as well as its World Service broadcasts and a global news website.

Full disclosure: The Beeb is a content partner for Marketplace.

But the license fee is under attack. The government just announced that it’s freezing the fee at the current level for two years and not increasing it in line with inflation — a decision that could cost the corporation nearly $400 million. The government has also hinted that it would like to eventually scrap the license fee altogether. [Continue reading at Marketplace…]

RF Interference (Nuts and Volts)

It’s everywhere! It’s everywhere! Fortunately, you can take a bite out of RFI.

RF interference — is it interference to you? Is it interference by you? Possibly both! What does this interference consist of? And how can you tell what type is present? A topic that starts off with so many questions is bound to cover a lot of ground, so let’s get started. Continue reading

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Radio Waves: Broadcast v Ham Radio, Marjorie Stetson’s Secret Wartime Work, Czech Republic MW Switch-Off, and PV RFI

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!


Alike, but Not Alike: Broadcast vs. Ham Radio (Radio World)

Experience in amateur radio can be a boon to the radio engineer

Starting in the 1920s and through the ’60s, almost every broadcast engineer was a licensed amateur radio operator. That has changed a bit, but the importance of being a ham has not.

Both environments involve getting an RF signal from Point A to Point B. But it is interesting to note that radio broadcast and amateur radio are similar and yet so different.

For those who don’t know much about ham radio, I’ll tell you that communicating locally or internationally, via licensed amateur radio, can be a fascinating and challenging hobby. There are about 700,000 hams in the U.S. and an equal number worldwide.

Physics

Broadcast and amateur radio operate under the same laws of science. Transmitters, transmission lines, antennas and receivers make up an RF path to convey a message.

Broadcast engineers know that signal propagation on AM and FM bands is dramatically different. It is because our FM band is roughly 100 times the frequency and 1/100th the RF wavelength of that on the AM band. Engineers also know that 950 MHz STL signals are line-of-sight and roughly a 10-times jump in frequency from FM broadcast frequencies. Each band has its own challenges in getting a useable signal through. [Continue reading…]

A Canadian opens up about her secret wartime work — eavesdropping on Japan (CBC)

Retired sergeant remembers what it was like on the ‘front line of the radio war’

At age 97, Marjorie Stetson has never told anyone her secret code number — until now.

That’s the identity code — 225 — that she typed on every page of her highly classified work for the Canadian Armed Forces during the Second World War.

The retired sergeant’s wartime work was so covert, she said, she had to sign 15 separate copies of Canada’s Official Secrets Act.

“Nobody knew where I worked,” Stetson told CBC News from her home in Massachusetts ahead of Remembrance Day. “Nobody knew what we did. Even my parents never knew what I did in the service.”

Her husband, an American sailor she met at a celebration marking the end of the war, passed away a decade ago. She never told him what she really did during the war.

Today, Stetson herself is only now learning about the true scope of her role and the significance of all those sheets of white paper she filled with encrypted messages from Japan. [Continue reading…]

Czech Republic: MW Switch-Off by 2021 (Radio Reporter)

Czech public radio ‘?eský Rozhlas‘ is stepping up its information campaign for listeners receiving mediumwave programmes, ahead of the planned switch-off of transmitters by the end of 2021. Since 1 November, more announcements have been broadcast to warn users and a call centre has been set up to explain the possible listening alternatives (from FM to DAB). In the run-up to Christmas, public radio will launch an intensive advertising campaign in the print media and online magazines on 22 November to promote the purchase of digital DAB receivers to replace analogue radio. [Continue reading…]

The impact of photovoltaics (Southgate ARC)

Seamus Ei8EP reports on the IARU Region 1 website that the 358 page Final Report on the Study on the evaluation of the Electromagnetic Compatibility Directive has now been published.

It is publicly available, free of charge, from the Publications Office of the European Union. The Political Relations Committee of the IARU Region 1 responded recently to a European Commission Roadmap on the environmental impact of photovoltaics.

The radio spectrum is an important finite natural resource which must be protected. While PV technology of itself is to be welcomed, the IARU submission pointed out the inherent problems of non-compliant installations, particularly the installation or retro-fitting of optimisers which can produce significant spectrum pollution for very limited efficiency increase.


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Radio Waves: Extreme 2001 Geo Storm, Media Ownership Rules Loosened, Germany Bans RFI-Spewing Device, Blue Jays Radio, and L-Band Patch Antenna Review

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 Troy Riedel, Dave Zantow, NT, Wilbur Forcier, and Rob for the following tips:


20 Years Ago, An Extreme Geomagnetic Storm (Spaceweather.com)

Unlike today’s blank sun, the solar disk 20 years ago was peppered with sunspots, including a monster named “AR9393.” The biggest sunspot of Solar Cycle 23, AR9393 was a truly impressive sight, visible to the naked eye at sunset and crackling with X-class solar flares.

On March 29, 2001, AR9393 hurled a pair of CMEs directly toward Earth. The first one struck during the early hours of March 31, 2001. The leading edge of the shock front was dense (~150 protons/cc) and strongly magnetized — traits that give rise to powerful geomagnetic disturbances. Within hours, an extreme geomagnetic storm was underway, registering the maximum value of G5 on NOAA storm scales.

“I was fortunate to witness and photograph the event when I was just a teenager,” recalls Lukasz Gornisiewicz, who watched the show from Medicine Hat, Alberta:

In the hours that followed, Northern Lights spread as far south as Mexico. In 20 year old notes, Dr. Tony Phillips of Spaceweather.com describes “red and green auroras dancing for hours” over the Sierra Nevada mountains of California at latitude +37 degrees. Similar displays were seen in Houston, Texas; Denver Colorado; and San Diego, California.

“Here in Payson, Arizona, red curtains and green streamers were pulsating all across the sky,” wrote Dawn Schur when she submitted this picture to Spaceweather.com 20 years ago:

“We have seen some auroras here before, but this display was really special,” she wrote.

A second CME struck at ~2200 UT on March 31th. Instead of firing up the storm, however, the impact quenched it. When the CME passed Earth the interplanetary magnetic field surrounding our planet suddenly turned north — an unfavorable direction for geomagnetic activity.

Indeed, the quenching action of the second CME may have saved power grids and other technological systems from damage. The storm’s intensity (-Dst=367 nT) stopped just short of the famous March 14, 1989, event that caused the Quebec Blackout (-Dst=565 nT) and it was only a fraction of the powerful Carrington Event of 1859 (-Dst=~900 nT).

The whole episode lasted barely 24 hours, brief but intense. Visit Spaceweather.com archives for March 30, 31st and April 1, 2001, to re-live the event. Our photo gallery from 20 years ago is a must-see; almost all the pictures were taken on film! [Read more at Spaceweather.com…]

U.S. Supreme Court permits FCC to loosen media ownership rules (Reuters.com)

WASHINGTON (Reuters) -The U.S. Supreme Court on Thursday allowed the Federal Communication Commission to loosen local media ownership restrictions, handing a victory to broadcasters in a ruling that could facilitate industry consolidation as consumers increasingly move online.

In a 9-0 ruling authored by Justice Brett Kavanaugh, the justices overturned a lower court decision that had blocked the FCC’s repeal of some media ownership regulations in 2017 for failing to consider the effects on ownership by racial minorities and women. Critics of the industry have said further consolidation could limit media choices for consumers.

The justices acted in appeals by the FCC, companies including News Corp, Fox Corp and Sinclair Broadcast Group Inc and the National Association of Broadcasters.

The associations for other broadcast networks’ local affiliates, including ABC, NBC and CBS, backed the appeals, arguing that consolidation would help ensure the economic survival of local television amid heavy competition from internet companies that provide video content. Broadcast television stations have said they are increasingly losing advertising dollars to digital platforms.[]

Germany bans ‘water vitalizer’ over radio interference (AP News)

BERLIN (AP) — German authorities on Friday banned the sale and use of a New Age ‘water vitalizer’ device amid concerns that it is interfering with amateur radio signals.

The Federal Network Agency said it had received numerous reports that the device, sold by Swiss company Wassermatrix AG as a way to “activate” the body’s self-healing powers, was transmitting on the frequencies allocated for ham radio users.

The agency said owners of the 8,000-euro ($9,540) device, which has been sold more than 2,400 times in Germany, are allowed to keep but not use it.

Wassermatrix AG didn’t immediately respond to a request for comment.[]

Rush’s Geddy Lee is unhappy about lack of Blue Jays radio for 2021 (Yahoo Sports Canada)

Canadian rock star Geddy Lee is less than thrilled with Sportsnet’s decision to cut their dedicated radio broadcast of the Toronto Blue Jays for the 2021 season.

Sportsnet won’t directly broadcast a separate radio feed and will instead simulcast their television broadcast over the airwaves for the 2021 season, becoming the first MLB team to do so. The decision was made to minimize travel and closely adhere to team, league, and government protocols related to the pandemic, Sportsnet said in a press release.

Lee, the lead singer for Rush, spoke about the importance of preserving a radio feed during an interview earlier in March.

Lee has been avid Blue Jays fan for years, throwing out the first pitch during the 2013 Blue Jays opener, and was a regular attendee at home games for decades.

It would be easy enough to spin this into “old man yells at cloud” in defence of a slightly outdated medium, but the sports media business is tough enough as it is, and the radio broadcast does indeed have charms that television simply can’t replicate, which is especially important for the visually impaired.[]

L-Band Patch Antenna review (Frugal Radio via YouTube)


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