Antenna Magus 3.0 released

April 20th, 2011

We are proud to announce the third major release of Antenna Magus, version 3.0!

Here’s a quote by Sam Clarke, our Managing Director:
“Soon after the first release of Antenna Magus we received numerous requests from customers who wanted to add their own antennas and designs to the Antenna Magus database. Having a tried and tested system that was already regularly used by our own engineers in developing content for our product, and having received valuable feedback from a group of selected users, we developed a way to store antenna information which makes sense to antenna engineers. We are confident that this feature will not only improve the way antenna information is managed but will become the norm for any organisation who wants to capture, reuse and share valuable knowledge efficiently.”

This calls for a celebration! Read more about Version 3.0 in Newsletter 3.0.

Here are two movies which highlight the “Add your own antenna” and new “Chart tracing tool” features:

Add your own antenna movie.

78 Second Chart tracing tool demo.

Author: Robert Kellerman

Have we reached the tip of the ice berg?

February 14th, 2011

iceberg

With almost 160 antennas in the Antenna Magus database we have heard people saying, ?Are you still planning on adding more antennas to Magus or do you think you?ve almost reached the tip of the ice berg?? and our response has always been, “we’re not even close”.

Recently one of our blog readers was looking for an antenna with about 10 dB gain in two opposite directions, for use in a tunnel (Narrow band). Even though there are so many antennas in Antenna Magus, the only bi-directional ones are the spirals. The spirals don?t have the gain, and require baluns, which add to manufacturing costs. Of course he could use an array, but this is going to be too big, and the feed network adds a lot of manufacturing complexity. This just proves that there are still more antennas that need to be included in our database!

I thought this is actually a nice opportunity for a challenge. Lets see if anyone can come up with a better (but simpler) type of antenna to achieve this (pattern below). Actually one of our antenna engineers came up with a great idea which I will share with you in an upcoming blog.

More or less the pattern he is looking for.

More or less the pattern he is looking for.

Author: Robert Kellerman

Antenna Magus Evaluation version corner reflector improves home internet reception by 12 dBi.

January 17th, 2011

900 MHz corner reflector designed in Antenna Magus

900 MHz corner reflector designed in Antenna Magus

I was quite chuffed when I saw this post on mybroadband about a corner reflector that was designed using the free Antenna Magus Evaluation version.

He explains how he designed and built a corner reflector from an old printer box and aluminium foil. It is used to boost the 900 MHz UMTS link between his home 3G modem and internet base station which increased the signal by 12.5 dB!

Obviously this will save a lot of money compared to commercial options which will cost over 150 US$ for a > 10 dB gain antenna and coupler which still has to be mounted on the roof (see http://www.poyntingdirect.co.za/c22/Antennas.aspx). I just don?t know how I will convince my wife that we have to place this beautiful foil covered box in the living room (coincidently the position of best reception).

Wife: ?Under no circumstances! Our internet works fine.?
Me: ?I know it is not an oil painting honey but this will greatly improve our internet speed?and we save 150 dollars!?

Author: Robert Kellerman

Antenna Magus version 2.4 released!

December 15th, 2010

We recently launched Antenna Magus 2.4.0. This update features 8 new antennas – 6 of which are dielectric-supported helical antenna variations. The other two antennas are the Sierpinski gasket antenna and a blade antenna. The Sierpinski gasket was a very popular antenna in the late 1990’s when fractal antennas were being widely researched, while the blade antenna family is one of the most frequently requested antennas in our communications with Antenna Magus users.

You can read more about this release in the latest Newsletter 2.4

Preview of newsletter 2.4

Preview of newsletter 2.4

Author: Robert Kellerman

Antenna Magus coffee art

December 6th, 2010

If you’ve been following my blog, then would have probably realised that we at Magus are very passionate about our coffee. We’re also passionate about antennas so we thought of a way to combine these two passions. I present to you…antenna coffee art! One of our engineers (who also earned his reputation as our local barista) taught himself how to make pictures pouring frothed milk onto an espresso. Here’s a 90 second movie of some beautiful antenna patterns he created.

Author: Robert Kellerman

Antenna made from salt water!

November 26th, 2010
Sea water antenna

Sea water antenna

I love it when engineers think outside the box. When asked to design an antenna that can be mechanically adjusted for different frequencies most engineers would think of metal structures with some sort of adjustable length (like that ancient TV antenna which I blogged about some months ago). But who would think of making an antenna from salt water? When someone told me about it my first reaction was, no ways, this is probably some joke or something, but it’s not. Follow this link or watch the video clip below for a detailed explanation. The principle is quite simple – a salt water fountain with variable height acts as the resonant structure and a magnetic current probe picks up the induced fields from the water stream positioned in the center of the probe which is connected to a receiver.

I’m sure we’re going to see more of these salt water fountain antennas in the future. Can I have one for my iphone please!

Author: Robert Kellerman

The isotropic radiator

November 18th, 2010

head

I wonder how many engineers fully understand the term “isotropic radiator”. We recently had an interesting discussion about this. What is really interesting is the fact that although an isotropic radiator cannot exist in practice, it is used in so many antenna synthesis and theoretical applications that one commonly finds the term used as if such a device does in fact exist in reality!

In order to clear up any confusion around isotropic radiators, we need to first make sure about the definition of the term “isotropic radiator” (some people – even university lecturers and highly regarded academia – confuse this term with “omnidirectional radiator”). The IEEE standard defines these two terms quite clearly as:

Isotropic radiator, A hypothetical, lossless antenna having equal radiation intensity in all directions.
Note: An isotropic radiator represents a convenient reference for expressing the directive properties of actual antennas.

Omnidirectional antenna, An antenna having an essentially non-directional pattern in a given plane of the antenna and a directional pattern in any orthogonal plane.

Few if not none, antenna textbooks explain why an isotropic antenna is theoretically impossible. However Silver gave a simple proof more than six decades ago (S. Silver (Ed), Microwave antenna theory and design, MIT Rad Lab Series, McGraw-Hill, 1949, pp 78-79). Subsequently, in 1954, Mathis offers a more complicated proof after invoking an obscure mathematical theorem of Brouwer, 1909.

Isotropic radiators are commonly used in array synthesis to determine the antenna factor which is then multiplied by the vector field of the single element in an array to synthesise the array pattern.

I remember how I once spent quite a lot of time struggling to analyze an array of radiators in a full-3D EM simulation tool to determine the array factor of a base station antenna. The array patterns in my simulations all showed a ?glitch? (extremely high field value) in a specific direction and only after lots of investigation and ?debugging? I realized that the field vector orientation in the isotropic element patterns that I was trying to use as array elements was undefined (or rather ambiguous) at the poles (theta = 0 and theta = 180).

The analogy used by an antenna engineer I know describes the problem quite well: ?The direction of field vectors at the poles of an isotropic radiator are undefined, just like the direction of the hairs at the crown of your head ? it?s just something one has to make a peace with!?.

Author: Robert Kellerman

Why 50 ohm?

November 10th, 2010

A couple of our engineers recently had a long discussion while trying to decide what range of impedances to include for the design of a coaxial feed for one of our antennas. The question that quickly arose was: ??why are most coaxial cables that are commonly available 50 ohm or 75 ohm??. I?m sure you must have asked yourself the same question before.

While looking into this, we discovered a 1955 IEE paper, titled ?THE CHOICE OF IMPEDANCE FOR COAXIAL RADIO-FREQUENCY CABLES? by WT Blackband. It is an excellent study considering various factors like attenuation, voltage, cable thickness and thermal characteristics of coaxial cables of various impedances and made with various materials. Though each performance measure for coaxial cables suggests a different optimal impedance, the general conclusion is basically: ??The best choice of impedance is 75 ohms for low-loss air-spaced cables, and 50 ohms for general-purpose thermoplastic cables.?

A definite must read if you ever wondered what the best coaxial cable impedance might be for a specific application ? and why 50 Ohms and 75 Ohms seem to be so popular!

Author: Robert Kellerman

NASA radio telescope photography at Goldstone, Mojave Desert

November 5th, 2010
230 ft NASA radio telescope.

230 ft NASA radio telescope.

One of my friends recently sent me a link that he thought I would like and he was right. Dave Bullock, a programmer, photographer and frequent contributor to Wired.com took some beautiful photos of the NASA radio telescopes at Goldstone in the Mojave Desert. There are some nice pictures with descriptions of the 230 feet dish, control center, horn feed, cooling and amplification components. Visit http://eecue.com/a/1581/Goldstone-NASA-Deep-Space-Network.html to view Dave?s photos.

Author: Robert Kellerman

Birds eye view of Magus offices taken by 2 cameras mounted on an L-39 Albatros model aircraft

October 26th, 2010

One of my colleagues spend most of his spare time building gadgets from components that he imports directly from Hong Kong. He recently bought an L-39 Albatros 50mm EDF remote controlled aircraft and mounted two imported mini video cameras on the front and back of the aircraft to capture the front and rear facing views. He made a short movie (see below) of a bird?s eye video taken of our offices and surrounding area in Stellenbosch, South Africa.

I was very impressed by the quality so I asked him about the cameras. Apparently these mini cameras aren?t very expensive as they are basically reconfigured cell phones without the keypad and RF components and are mass produced in +- one million batches. The only drawback is that due to the nature of the cell phone industry the components change all the time so in 6 months one wouldn?t be able to get hold of those specific cameras any more.

Here’s the view taken from the ground, http://www.youtube.com/user/megatesla#p/a/u/2/pyGd3DKDlD0. Note how fast the aircraft is moving!

Author: Robert Kellerman