Tag Archives: Antennas

Radio Waves: Cellular Scale Antennas, Space Comms, New Proposed Ham License in Australia, and Mid Century Television

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Apollo 11 (Photo: NASA)

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!

New miniature antenna can operate wirelessly inside of a living cell (Tech Explorist)

An intracellular antenna that’s compatible with 3D biological systems and can operate wirelessly inside a living cell.

A new study could allow scientists to create cyborgs at a cellular scale, thanks to MIT Media Lab for designing a miniature antenna that can operate wirelessly inside a living cell. This could have applications in medical diagnostics, treatment, and other scientific processes because of the antenna’s potential for real-time monitoring and directing cellular activity.

Scientists named this technology Cell Rover. It represents the first demonstration of an antenna that can operate inside a cell and is compatible with 3D biological systems.

Deblina Sarkar, assistant professor and AT&T Career Development Chair at the MIT Media Lab and head of the Nano-Cybernetic Biotrek Lab, said, “Typical bioelectronic interfaces are millimeters or even centimeters in size and are not only highly invasive but also fail to provide the resolution needed to interact with single cells wirelessly — especially considering that changes to even one cell can affect a whole organism.”

The size of the newly developed antenna is much smaller than a cell. The antenna represented less than .05 percent of the cell volume in research with oocyte cells. It converts electromagnetic waves into acoustic waves, whose wavelengths are five orders of magnitude smaller, representing the velocity of sound divided by the wave frequency — than those of the electromagnetic waves. [Continue reading…]

Space Audity (20,000 Hertz Podcast)

This episode was written and produced by Jack Higgins.

We’ve all heard the iconic recordings from the Apollo missions. But how exactly does NASA manage to run live audio between Earth and the moon? And how might we chat with astronauts on Mars and beyond? Featuring Astronaut Peggy Whitson, NASA Audio Engineer Alexandria Perryman, and Astrophysicist Paul Sutter.

Click here to listen on the 20,000 Hertz webite.

Australia: Proposed new ham radio licence (Southgate ARC)

Australia’s communications regulator ACMA has asked radio amateurs to comment on their proposed amateur class licence and considerations for higher power 1 kW operation

The ACMA say:

Following the extensive 2021 public consultation and associated response to submissions, we have released a consultation paper on the proposed amateur class licence and supporting operational arrangements, along with considerations for higher power operation. This is the next step in our review of regulatory arrangements for the operation of non-assigned amateur stations.

The draft class licence for amateur radio has been amended to incorporate changes suggested by representative bodies, amateur radio clubs and individual amateurs during the 2021 consultation.

The consultation paper, proposed class licence and details about how to make a submission are available on the ACMA website
https://www.acma.gov.au/consultations/2022-09/proposed-amateur-class-licensing-arrangements-and-higher-power-operation-consultation-312022

Submissions close COB, Tuesday 29 November 2022.

Questions about the consultation
If you have an important question about this consultation, please send it directly to [email protected]. Please note, we may use the Amateur radio update e-bulletin to answer frequently asked questions.

Subscribe to the ACMA Amateur Radio newsletter at
https://www.acma.gov.au/subscribe-our-newsletters

Mid Century Television – live, local and unpredictable late 1950s television (Southgate ARC)

In the late 1950s television networks ruled the airwaves from 7 to 11 PM, but outside of that timeslot television was live, local and unpredictable.

Jim Hanlon, W8KGI,  worked as a summer relief engineer at Cincinnati’s WCPO-TV from 1956 to 1958. At that time WCPO-TV did not have any video recording technology, so all local TV was live TV and provided a refreshing dose of live programming, equipment failures and production creativity that been lost in today’s pasteurized, homogenized TV ecosystem.

Join Jim as he recalls what it like producing live TV programming in the early days of television broadcasting.

Click here to view on YouTube.

Help keep communications history alive by becoming a member of the Antique Wireless Association at: https://www.antiquewireless.org/homepage/

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IARPA challenged to give small antennas higher gain

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(Source: IEEE Spectrum via Dennis Dura)

A Four-Year Program to Tackle a Fundamental Antenna Challenge — IARPA hopes to break past an 80-year-old limit on making small radio antennas more effective

For 80 years, a class of antenna called electrically small antennas has been stymied by a seemingly insurmountable barrier. These antennas, which can receive signals with wavelengths that are much longer than the antennas themselves, are seemingly stuck with designs in which there is a trade-off between high bandwidth and efficiency.

Now, a new program by the U.S. Intelligence Advanced Research Projects Activity (IARPA) agency seeks ways to finally circumvent or overcome these historical limitations for electrically small antennas. Over the next four years, the research teams participating in the Effective Quantitative Antenna Limits for Performance (EQuAL-P) program will work through three phases of progressively more ambitious benchmarks in order to prove their ideas can work.

The simplest form of antenna is a dipole antenna, which is essentially just two pieces of wire placed end to end with a feed point in the middle. The length of this antenna is typically half the wavelength of the signal that is being received or transmitted, so a shortwave radio dipole working in the 20-meter band would be 10 meters long. An “electrically small” antenna is one that is significantly shorter than the wavelength of the signals it is designed for. These antennas typically take the form of small loops or patches.

The benefit of electrically small antennas is clear—as the name implies, they confer an advantage when space is at a premium. Satellites, for example, can use them to reduce mass and free up more space for other components.

But the trade-off with electrically small antennas is that as they get shorter, their bandwidth and radiation efficiency also shrink, eventually hitting something named the Chu-Harrington limit. This has meant that although such antennas have been in use for decades, they remain difficult to design and limited in their applicability. Historically, any attempts to widen the usable bandwidth have decreased these antennas’ radiation efficiency even more, and vice versa. This is the problem the EQuAL-P program is aimed at.

“Because it’s an 80-year problem, we want to give them a little more time to come up with solutions,” says Paul Kolb, the program manager for EQuAL-P. The eight teams participating will work through three increasingly ambitious phases during the next four years to prove their ideas can pass muster.

At the end of 18 months, Kolb says, he hopes to see that the teams have made meaningful progress toward the ultimate goal of a 10-decibel gain in antenna performance in the HF and ultrahigh frequency (UHF) bands. But because of the difficulty of the challenge, teams won’t be required to produce a working demonstration of their technology at that point. [Continue reading full article at the IEEE spectrum…]

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

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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.

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

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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.

Continue reading →

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

43 Replies

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….

Continue reading →

Frans compares the BH5HDE QRP, GRAHN SE3, and his home made loop antenna

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Many thanks to SWLing Post contributor, Frans Goddijn, who shares the following article and video originally posted on his blog:

I got the little BH5HDE QRP portable QRP loop, assembled it and could not wait to try it out even though it was during that day and signals were sparse and weak.

This new loop performs well, in part thanks to the tuning & impedance knobs. I compare it with the GRAHN SE3 and a big home made loop that I bought second hand. The latter has no tuning but is as directionally sensitive as the others and it delivers an amplified signal to the receiver.

Click here to view on YouTube.

I found a manual for the QRP, not included in the package:

Instructions for use of BH5HDE QRP portable small loop antenna

Welcome to use the BH5HDE QRP portable small loop antenna. This product can easily and quickly set up a short-wave transceiver antenna, allowing you to enjoy the joy of multi-band reception and communication indoors, windows, balconies and outdoors.

Installation:
(BNC mount equipment needs to bring a pair of photography tripods)
Use the right-angle adapter and double male docking to connect the antenna to the m seat at the rear of the radio station or erect the ring body to the connector on both sides of the controller and tighten, then install the tripod to the fastening seat on the back of the tuner Open the tripod, place the antenna body firmly on the tripod, and finally connect the feeder (the feeder is attached with a choke, one end of the choke is placed near the small loop antenna).

use:
Now that the small loop antenna has been connected to your radio station, you can now tune in.
First introduce the function of the tuner panel. The toggle switch on the left is the band selection switch (up: 7MHz, down: 14-30MHz).
The main control knob, the upper knob is the frequency tuning knob, the frequency tuning value does not change due to environmental changes; the lower knob is the impedance matching knob, the impedance matching value will change due to environmental changes. (The tuning range of the two knobs is 180 degrees, and the panel value is 0-60).
When you start using the radio, select the desired frequency, and then turn the band switch to the desired band position, then adjust the impedance matching value of the lower knob to 30, and then adjust the upper knob to tune. At this time, pay attention to listening to the noise floor of the radio station. The more resonance, the louder the noise floor of the radio station (in the environment with extremely low noise floor, the antenna resonance noise floor is almost inaudible. It is recommended to let the radio station observe the standing wave). At this time, let the radio transmit (cw, fm, and am modes are available), pay attention to the standing wave indication, and fine-tune the frequency tuning knob while transmitting. Since the knob of the portable version does not have a deceleration function, the method of fine adjustment must be more delicate, and the smaller the rotation angle, the better.

At this time, you can observe a significant change in the standing wave, but generally the minimum standing wave ratio will not be below 1.5. At this time, you need to adjust the impedance matching knob. It is recommended to adjust the positive and negative 5 scale values randomly, and then repeat the frequency tuning steps and observe The standing wave ratio. Due to the change in the matching value, there are two possibilities before the comparison: 1: the minimum value of the standing wave ratio decreases; 2 the minimum value of the standing wave ratio becomes larger. If the minimum value of the standing wave ratio becomes lower, it means that the impedance matching adjustment approaches the correct value and can be further adjusted. If the minimum value of the standing wave ratio becomes larger, it means that the impedance matching is far from the correct value and must be adjusted in the opposite direction.

Repeat the above steps to adjust the VSWR of the antenna to 1.0.

The VHF and UHF bands are fixed with the upper knob hitting 60 to the end, and the lower knob can adjust the impedance to resonate.

Note: The best effect for outdoor use is to use antennas indoors as close as possible to windows, fully enclosed reinforced concrete, against walls and other environments where the standing wave ratio is not ideal.

Advanced technique: when the signal is weak, you can rotate the antenna direction to improve the signal-to-noise ratio, which is conducive to reception. The unique gain lobe of the loop antenna makes the horizontal gain directivity when it is erected, and its characteristics can be used to select multiple signals in the horizontal direction. It can also reduce the co-frequency interference in the horizontal direction. Of course, If the interference signal is extremely strong, much larger than the useful signal that needs to be accepted, the attenuation effect will not be too significant, compared to the whip antenna can still have the attenuation effect.

Radio Waves: DRM Part of BBC Story, Antennas and Smith Charts, Shortwave “Hot Debate,” Carrington Event, and “Deep Freeze”

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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!

DRM Is Part of the BBC World Service Story (Radio World)

The iconic broadcaster has been supportive of the standard for over 20 years

The author is chairman of the DRM Consortium. Her commentaries appear regularly at radioworld.com.

Our old friend James Careless studiously ignores DRM once more in his well-researched, but to our minds incomplete article “BBC World Service Turns 90” in the March 30 issue.

As an ex-BBC senior manager, I would like to complete the story now that the hectic NAB Show is over.

Having lived through and experienced at close quarters the decision to reduce the BBC shortwave about 20 years ago, I can confirm that the BBC World Service decision to cut back on its shortwave footprint — especially in North America, where reliable, easy-to-receive daily broadcasts ceased — has generated much listener unhappiness over the years.

In hindsight, the decision was probably right, especially in view of the many rebroadcasting deals with public FM and medium-wave stations in the U.S. (and later other parts of the world like Africa and Europe) that would carry news and programs of interest to the wide public.

But BBC World Service in its long history never underestimated the great advantages of shortwave: wide coverage, excellent audio in some important and populous key BBC markets (like Nigeria) and the anonymity of shortwave, an essential attribute in countries with undemocratic regimes.

BBC World Service still enjoys today about 40 million listeners worldwide nowadays. [Continue reading…]

The Magic of Antennas (Nuts & Volts)

If you really want to know what makes any wireless application work, it is the antenna. Most people working with wireless — radio to those of you who prefer that term — tend to take antennas for granted. It is just something you have to add on to a wireless application at the last minute. Well, boy, do I have news for you. Without a good antenna, radio just doesn’t work too well. In this age of store/online-bought shortwave receivers, scanners, and amateur radio transceivers, your main job in getting your money’s worth out of these high-ticket purchases is to invest a little bit more and put up a really good antenna. In this article, I want to summarize some of the most common types and make you aware of what an antenna really is and how it works.

TRANSDUCER TO THE ETHER
In every wireless application, there is a transmitter and a receiver. They communicate via free space or what is often called the ether. At the transmitter, a radio signal is developed and then amplified to a specific power level. Then it is connected to an antenna. The antenna is the physical “thing” that converts the voltage from the transmitter into a radio signal. The radio signal is launched from the antenna toward the receiver.

A radio signal is the combination of a magnetic field and an electric field. Recall that a magnetic field is generated any time a current flows in a conductor. It is that invisible force field that can attract metal objects and cause compass needles to move. An electric field is another type of invisible force field that appears between conductors across which a voltage is applied. You have experienced an electric field if you have ever built up a charge by shuffling your feet across a carpet then touching something metal … zaaapp. A charged capacitor encloses an electric field between its plates.

Anyway, a radio wave is just a combination of the electric and magnetic fields at a right angle to one another. We call this an electromagnetic wave. This is what the antenna produces. It translates the voltage of the signal to be transmitted into these fields. The pair of fields are launched into space by the antenna, at which time they propagate at the speed of light through space (300,000,000 meters per second or about 186,000 miles per second). The two fields hang together and in effect, support and regenerate one another along the way. [Continue reading…]

Smith Chart Fundamentals (Nuts & Volts)

The Smith Chart is one of the most useful tools in radio communications, but it is often misunderstood. The purpose of this article is to introduce you to the basics of the Smith Chart. After reading this, you will have a better understanding of impedance matching and VSWR — common parameters in a radio station.

THE INVENTOR
The Smith Chart was invented by Phillip Smith, who was born in Lexington, MA on April 29, 1905. Smith attended Tufts College and was an active amateur radio operator with the callsign 1ANB. In 1928, he joined Bell Labs, where he became involved in the design of antennas for commercial AM broadcasting. Although Smith did a great deal of work with antennas, his expertise and passion focused on transmission lines. He relished the problem of matching the transmission line to the antenna; a component he considered matched the line to space. Continue reading →