Recently I explored the use of a radio device aptly described by a fellow Aussie Electronics Engineer, "ozeng", as "Absolute witchcraft." .. I'm talking about an "RF circulator", one of which is sitting quietly on my desk, roughly 60 mm square, 30 mm thick, weighing in at just under half a kilogram, unexpectedly with a 200 year history.

Let the spelunking commence ..

The moment you start reading the "Circulator" Wikipedia page, you'll see this sentence: "Microwave circulators rely on the anisotropic and non-reciprocal properties of magnetised microwave ferrite material.", with a helpful reference to "Modern Ferrites, Volume 2: Emerging Technologies and Applications", a 416 page reference that promises to dig into the nitty-gritty, showing 55 hits for the word "circulator".

Anisotropic you ask? It's the property that describes velvet, rub it one way, it's smooth, rub it the other way and the hair stands up on the back of your neck. Wood is another example, easier to split along the grain than across it.

While we're at it, reciprocity in physics is the principle that you can swap the input and output of a linear system and get the same result.

If you know me at all, it should come as no surprise that I went looking for an inventor. There's over twelve-thousand patents referring to a "circulator", including more than a handful relating to Nuclear reactors. In 1960, a prolific Jessie L Butler came up with patent US3255450A, "Multiple beam antenna system employing multiple directional couplers in the leadin", which states: "This circulator has the characteristic that energy into one port will leave another port to the exclusion of a third."

If you recall, that's the exact phenomenon I used to describe the "RF circulator" on my desk.

So, job done, we have our inventor. Not so fast. The patent goes on to say: "Circulators of this type are discussed in an article 'The Elements of Nonreciprocal Microwave Devices' by C.Lester Hogan in Volume 44, October 1956, issue of Proceedings of the IRE, pages 1345 to 1368." The IRE is the Institute of Radio Engineers.

I found a copy of that tome, thank you worldradiohistory.com, which includes the following sentence: "Until a few years ago, all known linear passive electrical networks obeyed the theorem of reciprocity. Today several different types of passive nonreciprocal microwave networks are in practical use".

A footnote refers to an article by Lord Rayleigh, "On the magnetic rotation of light and the second law of thermodynamics" and includes images of an optical one-way transmission system from 1901.

In that 1901 article, Lord Rayleigh in turn refers to a paper published sixteen years earlier in which he observed that light polarisation can be made to violate the general optical law of reciprocity, using a system that consists of two so-called Nicol prisms, a crystal that can convert ordinary light into plane polarised light, invented by William Nicol in 1828. Using two prisms, arranged at a 45 degree angle, you can make light go through it in one way, but not the other.

Lord Rayleigh, also known as John William Strutt, in a very sparse footnote, states: "That magnetic rotation may interfere with the law of reciprocity had already been suggested by Helmholtz."

Further digging gets me to an 1856 publication of the "Handbuch der physiologischen Optik", or the handbook of the study of how the eye and brain work together, where Helmholtz says that, translated from German, "according to Faraday's discovery, magnetism affects the position of the plane of polarization."

This gets us to 1845, where Michael Faraday experimentally discovered that light and electromagnetism are related. His notebook has the following sentence, paragraph 7718 written on the 30th of September 1845: "Still, I have at last succeeded in illuminating a magnetic curve or line of force and in magnetising a ray of light."

Today we call that the "Faraday effect"

The best part?

You can read Michael Faraday's diary, right now, and see the whole thing.

So, who then invented the RF circulator?

From Mastodon to Circulators, to Modern Ferrites, to Nonreciprocal Microwave Devices, to Multiple beam antennas, to Magnetic Rotation, to Optical Reciprocity, to Nicol prisms, to the Faraday effect, this is the perfect example of standing on the shoulders of giants, and the result sits as a little box on my desk.

Just so you don't feel left out, your mobile phone likely has one of these devices on board.

I'm Onno VK6FLAB

Recently my local power company notified me of a planned network outage, that's code for, we're turning off the power and your choice is to deal with it. If you've been paying attention, you'll note that this is not the first time this has happened in recent times.

On this occasion I want to make a difference and actually use the day wisely. Coincidentally, the 750th instalment of F-troop is coming up and traditionally we try to find an excuse to get outside and set-up a station in a local park somewhere. If you recall, I recently went outside and came across a new park, one with picnic tables, gazebos, toilets and all the mod cons required for a party.

Combine these unrelated events and you end up with testing the idea of running F-troop, a weekly net for new and returning amateurs, from this park, which also neatly turns that into a POTA or Parks On The Air activity, which raises several logistical questions.

The first one being, what is the radio noise like in this park, followed shortly by the question, can I hit my local 2m repeater, any 2m repeater, or the local 10m repeater? If the answer to those questions is unsatisfactory, I might be required to rethink my plans.

Combining those questions with a power outage at home seems like the perfect excuse to go out into the bright day to get on air and make some noise.

One challenge. Having removed my radio from my car several years ago to accommodate the replacement of the transmission, I never did replace it and never used my radio in the car again, which truth be told is not a situation I ever imagined when I first installed it many years ago.

This leads me to creating a list, which should come as no surprise, a list with what I need to bring as a minimum requirement to test the questions I need answers to. I will confess that the "making a radio packing list" skill-set has atrophied in recent times, so I started small.

I'll need a radio, and a suitable antenna, in my case, at least two, one for 2m and one for 10m. Then there's the question of power, at which point I discovered that my trusty portable sealed lead acid batteries have finally died, not bad after 15 years, well, 12 years of regular use. Likely they would have continued to be of service if I'd used them in the past three years, mainly hampered by the death of my 12 volt battery charger.

If you feel like I'm going off track, you'd be right. That was the exact experience I had when I started building my list. I added a digital multimeter, an antenna analyser, an antenna tuner and coax, then realised that I needed to check if the coax adaptors were the right ones and so it continued.

The upshot is a preliminary list with 15 items on it, in various stages of fully populated, for example, I know I have a 2m and 70cm antenna in the garage, but I haven't touched it in years, so I need to go find it, and the battery in my digital multimeter needs checking, you get the idea.

It's a good thing I started this caper well over a week before the planned outage, so at least I have half a fighting chance to get it to the point of usefulness before my screen turns black due to the threatened lack of electricity.

It occurred to me whilst I was in the middle of this extended list creation process, that I was essentially replicating what I might have experienced the very first time I went outside with my station in 2011. In coming to that realisation, the stress levels that were building steadily at that point, pretty much dissipated with the understanding that I'd already done this and survived the experience. In other words, there was nothing worth stressing about.

So, this leaves me with a question for you. What does this process look like for you, how do you prepare to get on-air and make noise, what steps do you take and what do you avoid, are there things you might share with a new amateur and if so, how will you do that?

I contemplated sharing the list in a public place, but realised that the power of the list isn't the items on it, but in the process of making it, so, no list, but the notion that you too can do this, and if it transpires that you forgot something, there's always the next adventure.

I'm Onno VK6FLAB

The pursuit of amateur radio is a glorious thing. On the face of it you're forgiven if you think of it as a purely technical endeavour. Far be it for me to dissuade you from that notion, but permit me to expand into other areas that rarely get a mention when we discuss this amazing hobby.

It's the place where you go to communicate with other people, who live a different life, doing the things that they enjoy.

It's also the place for finding an excuse to go outside and set-up your station on the side of a mountain, or a park, a museum or a lighthouse.

Then there's the joy of finding new friends who introduce you to other aspects of life, super computing, the medical field, tow truck driving, radio astronomy and electronics, to name a few.

While I was the first person in my school to save up their summer job earnings to buy their own computer, a Commodore VIC-20, I never did come across this.

"It is pitch black. You are likely to be eaten by a grue." is a phrase that might mean something to you, or not. To set the stage, it's the 1960's, you're a science fiction author and you need a ravenous predator. With origins in Danish and Norwegian, "grue", from gruesome, seemed to fit the bill for Jack Vance while was writing his Dying Earth series, mind you, Robert Louis Stevenson used it in 1916 in a short story called "The Waif Woman", writing "and a grue took hold upon her flesh", which is more gruesome than predator.

Flash forward to 1977, you're writing an adventure game for a PDP-10 mainframe computer whilst, let's call it studying, at MIT, and you need a way to stop people wandering off the map, and so the text adventure game "Zork" got its famous phrase.

I'm mentioning this because I wondered if anyone had used their love for Zork as an excuse to set-up a server on HF radio that you could play with.

I'll confess that I spent way too many hours looking at this and it appears that you can use the software "direwolf" as a way to get packet radio to work across amateur radio without needing anything more than a radio and a computer with a sound-card.

There's even an article by Rick Osgood titled: "How to Setup a Raspberry Pi Packet Radio Node with Zork", though I will mention that it relies on hardware to connect to a radio, rather than use "direwolf". There's a few moving parts, but it looks like this is totally doable, there's already Docker containers for both Zork and direwolf, even a container called "packet-zork", and a multi-user version called "MultiZork", so how hard can it be? I jest.

As an aside, because I'm a geek and I can, there's a common misconception that a Docker container is equivalent to a virtual machine. For lots of reasons, that's not true. A better way is to think of it as a security wrapper around an untrusted application.

Speaking of untrusted, while we're all essentially bipedal lifeforms with a similar set of attributes, on a daily basis we seem to discover more and more reasons to find fault or demonise differences. Contrast this within the global community of radio amateurs, where we have this "weird" activity that we all seem to share.

I think that the most under-reported, perhaps even undervalued aspect of our hobby is that it's an excuse to talk to someone else. It's like a force of attraction, the glue, the one starting point that you know another amateur has in common with you.

So, next time you venture outside, either in real life, or virtually, consider, at least for a moment, that there are other radio amateurs among us, also having fun.

I'm Onno VK6FLAB

The other day I came across an article written by programmer, artist, and game designer "blinry" with the intriguing title: "Fifty Things you can do with a Software Defined Radio". Documenting a weeks' worth of joyous wandering through the radio spectrum it explains in readily accessible terms how they used an RTL-SDR dongle to explore the myriad radio transmissions that surround us all day and every day.

As you might know, I've been a radio amateur since 2010 and I must confess, even with all the things I've done and documented here, there's plenty in this adventure guide that I've yet to attempt.

For example, when was the last time you decoded the various sub-carriers in an FM broadcast signal, including the pilot tone, the stereo signal, station meta and road traffic information?

Have you ever decoded the 433 MHz sensor signals that your neighbours might have installed, weather, security and other gadgets?

Or decoded shipping data, transmitted using AIS, or Automatic Identification System, and for context, we're only up to item 12 on the list.

One of the biggest takeaways for me was that this is something that is accessible to anyone, and is a family friendly introduction to the world of radio that amateurs already know and love.

The article touches on various applications that you might use to explore the highways and byways of the radio spectrum, including SDR++, SDRangel, WSJT-X, QSSTV, and even mentions GNU Radio.

With enough detail to whet the appetite, I learned that SDRangel, developed by Edouard F4EXB and 70 other contributors, has all manner of interesting decoders built-in, like ADS-B, Stereo FM, RDS, DAB, AIS, weather balloon telemetry, APRS, even VOR.

As it happens, you don't even need to install SDRangel to get going. Head on over to sdrangel.org and click on "websdr" and it'll launch right in your browser. Once you're up and running, you can use your RTL-SDR dongle to start your own small step into the wide world of radio, amateur or not.

Sadly the PlutoSDR does not work on the experimental web version, so I had to install SDRangel locally. That said, I did get it to run and connect to my PlutoSDR which worked out of the box.

The user tutorial is online and the Quick-Start walks you through the process of getting the software installed and running. One thing that eluded me for way too long is the notion of channel decoders.

Essentially you configure the receiver, in my case a PlutoSDR, and start it running. You'll be able to change frequency and see the waterfall display, but nothing else happens, and there's no obvious AM, FM or other mode buttons you'd find on a traditional radio.

Instead, you'll need to add a channel decoder, cunningly disguised as a triangle with circles at the corners with a little plus symbol at the top. You'll find it immediately to the left of your device name. When you click it, you're presented with a list of channel decoders, which you can add to the work space. This will do the work of actually decoding the signal that's coming into the software.

SDRangel also supports M17, FreeDV, RTTY, FT8 and plenty of other amateur modes, and includes the ability to transmit. Oh, did I mention, it can also connect to remote kiwisdr receivers?

I have to say, it's a joy to see software that I've previously looked at and admittedly shied away from, actually doing something with the radio spectrum around me. I will confess that SDRangel has a lot of moving parts and it's like sendmail, user friendly, just picky whom it makes friends with.

So, time to dig in, play around and bring it to the next amateur radio field day "Show and Tell" and share with the general public just how interesting the radio spectrum around us can be.

I'm going to work my way through the 50 items, just for giggles.

What are you waiting for?

I'm Onno VK6FLAB

The other day I went for a walk, I know, shock-horror, outside, daylight, nature, the whole thing, in a local national park, for the first time in too many years. Almost immediately I noticed that this would be an excellent location for an activation. If you're not familiar, it's an amateur radio excuse to set-up a portable station in a new location, in this case, potentially something called POTA, or Parks On The Air, but you don't need to find a formal activity with rules to get on air and make noise.

I commented on how easily accessible it was, that it had picnic tables, gazebos for shelter, nearby toilets, free BBQs, ample parking, lots of open space, and no overhead power lines. I saw one solar panel on a pole and no evidence of any other electrical noise sources.

It wasn't until later that I realised the act of noticing this, in that way, with those details, is not something I would have done before becoming a radio amateur. I'd have looked at the same location, considered its beauty and serenity and perhaps in passing considered that we could have a family gathering, or a place to come back to when I wanted some peace and quiet, or a place where I might have a BBQ with friends. Not that those things went away, just that I noticed other things, now that I'm an amateur.

It made me consider just how much this hobby has irrevocably changed me.

I know I've mentioned this before, since becoming an amateur I cannot walk down the street without noticing TV antennas pointing in the wrong direction, but this change in me is not limited to that. Now I cannot help discussing the best place to put a Wi-Fi base station in a building, or thinking about and checking on solar activity, wondering about battery capacity, RF interference, trees to potentially use as sky-hooks for wire antennas, power company substations, pole-top transformers, random weird and wonderful antennas and probably more.

The point being that this hobby opens the door to a whole new way of looking at the world and I don't think I've overstated, if I say that amateur radio has literally changed my world view.

In considering this, I suspect that it's related to a cognitive bias known as the Frequency Illusion, where you notice a specific concept, word or product more often after becoming aware of it.

You might for example have experienced this with the brand or model of radio you use and suddenly discovered that there's lots of other amateurs talking about that particular piece of equipment.

I've seen this with recurring topics during the past fourteen years of the weekly F-troop net. For example, every couple of years someone discovers magnetic loop antennas and starts talking about how they've built or bought one. The conversation inevitably goes past variable capacitors, through air variable capacitors, on to vacuum variable capacitors and then the conversation generally stops. While it's happening, multiple people come on the same journey, only to follow the exact same path. Several years later, the cycle repeats.

Don't misunderstand, I welcome the discussion, point people at relevant resources and help them on this journey.

I'm commenting on the recurrence of the journey, not the nature of it because it's easy to take this example and hold it up as "there's nothing new in this hobby", but nothing could be further from the truth.

In my opinion, the level of complexity associated with radio communications is infinite and anyone, including you and I, can contribute to the discovery associated with it.

So .. what things have you noticed that were caused by this somewhat eccentric hobby and perhaps the phenomenon of Frequency Illusion?

I'm Onno VK6FLAB