[continued from previous message]
device with two SMA connectors and a USB socket. Other than the branding,
there were no markings on the device and it came without any instructions.
It did come with a couple of SMA adaptors, which came in handy.
A little research later determined which of the two SMA adaptors connected
to an antenna and which connected to a radio.
The gadget itself is called an upconverter.
It's an interesting little device that essentially mixes two frequencies together, creating two new ones, start with say 720 kHz and mix it with 120
MHz and you end up with 120.720 MHz and 119.28 MHz. In other words, if you
mix two frequencies together, you end up with both the sum and the
difference of those frequencies.
If you have a radio that can listen to 120 MHz, but cannot listen to 720
kHz, then using an upconverter, you can, as it were, expand the frequency
range of your radio to hear different signals.
I purchased the upconverter with the intent of connecting it to my
PlutoSDR, since the lowest frequency it can do is 70 MHz. Combine the two
and I should be able to listen to all of the amateur HF frequencies at once.
Given that my PlutoSDR is currently doing something else, I had a look at
using the upconverter with my WSPR beacon monitor that uses an RTL-SDR
dongle. Technically it's not required, since my particular dongle can be
used to tune to HF frequencies, but as an experiment, it works well enough.
So, I connected the antenna to the upconverter, the upconverter to the
dongle and the dongle to a Raspberry Pi, a single board computer that runs Linux. Essentially the exact same setup I've been running for years, except that I inserted the upconverter between the dongle and the antenna.
That and some power took care of the hardware.
The software initially gave me some challenges. After discovering that the
tool I'm using, rtlsdr_wsprd, has an option for an upconverter, I was up
and running in minutes.
So, at the moment, and for the next foreseeable little while, my WSPR
monitor is using an upconverter to scan HF. Technically this should
increase the sensitivity by a significant amount, since the dongle is
better suited to tuning to higher frequencies than it is to lower ones, but only time will tell.
I updated my monitoring scripts to take into account if the frequency I was monitoring was out of range, so it currently won't report on anything above
60 MHz, but then that's fine for what I'm working on.
I've updated the script on github if you want to have a look. It's nothing fancy, it essentially checks to see if there's a file called upconverter
and if so, it calls a slightly different monitoring script.
Given that I have existing logging data associated with this monitor, I
should be able to discover if there's any significant difference between
what I've been monitoring to date and what's coming in now that an
upconverter is in the listening chain. Theoretically, I should be able to
hear weaker signals, but time will tell.
One thing that was interesting whilst I was discovering how this all works
and hangs together is that it wasn't immediately obvious how to set it all
up in software. I tried several tools to make sense of the data. In the end
the combination of gqrx, setting the local oscillator offset to a negative frequency, in my case 120 MHz, got me to the point where I could set the frequency to 720 kHz and hear my local broadcast station, whilst the
software actually, secretly behind the scenes, added 120 MHz to that and
tuned the radio to 120.720 MHz.
Once I got my head around that, things started falling into place.
The same is true for rtlsdr_wsprd, adding the upconverter flag with the
value of 120MHz, got my monitoring station up and running.
This is a pretty user friendly way of getting started with frequency
mixers. You might recall my exploration into components apparently made
from unobtainium. The intent is to use a variable frequency to achieve a similar thing, but that's a project still on the drawing board, for now, I
have a fixed frequency, 120 MHz, which is plenty to get started.
If you're curious why I'd want a stable variable frequency, consider for example, what might happen if you transmit from a HF frequency into an upconverter. Perhaps you could use your HF capable WSPR beacon to make a
signal on 2m or 70cm. 120 MHz won't cut it, but perhaps you can work out
what's needed to get from the 10m WSPR band to the 2m WSPR band, or the
70cm WSPR band.
I'm Onno VK6FLAB
This posting includes a media file:
http://podcasts.itmaze.com.au/foundations/20220123.foundations-of-amateur-radio.mp3
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When I said Parrot Repeater ... I likely had a different picture in mind.
Posted: 15 Jan 2022 08:00 AM PST
http://podcasts.itmaze.com.au/foundations/20220116.foundations-of-amateur-radio.txt
Foundations of Amateur Radio
A little while ago I mentioned in passing that I was considering
implementing a parrot repeater to help determine how your radio is
performing. Discussion afterwards revealed that not everyone had the same picture in mind, so I thought I'd share with you some of what I'm
considering and why.
Most of the modern radio landscape revolves around hooking a computer up to some type of radio frequency capable device. Commonly it's the audio and control signals that travel between computer and radio, but there are
plenty of examples where raw data makes the journey, like in the case of an RTL-SDR dongle.
That journey is increasingly made using USB, the cable, not the sideband,
and limits are based around the maximum speed that a Universal Serial Bus
has. Essentially the amount of data that you can process is limited by how
fast your computer can talk to the radio.
For my parrot repeater, I'm imagining a device that can receive RF from any radio and process that signal to determine what the centre frequency is,
the deviation, stability, the mode, what ever parameters I end up being
able to determine, a whole other discussion on its own. In response, the
idea is that the device generates a report and either presents that using
text to speech, or as a web-page, or both.
Using traditional methods, this would involve a radio, a computer, some software, connections between the radio and the computer, not to mention
power for both the computer and the radio, an antenna and perhaps an
amplifier. The picture I have in mind is not anything like that. I'm
imagining a single device that takes power and does all I've described
inside the one device. No external computer, no audio cables, no control cables, no hard drives, not anything, just a PlutoSDR and a power source connected to an antenna or two.
You might think that's fanciful. As it happens, we already have some of
that today. When I run dump1090 on my PlutoSDR, it presents itself to the
world as a website that I can visit to see which aeroplanes are within
range, where they are exactly on a map, what messages they're sending and
where they're going. All of the processing is done inside the PlutoSDR. All
I have to do is give it power and an internet connection.
This is possible because the PlutoSDR is essentially a computer with RF. It runs Linux and you can write software for it. Unlike my Yaesu FT-857d,
which also has a computer on board, rudimentary to be sure, but a computer
none the less, it cannot be altered. I cannot load my own piece of
software, launch a web browser and point it at my Yaesu, not without
connecting an external computer that in turn needs to be connected to the radio. I might add, that this is is how many repeaters work and how devices that implement AllStar and Echolink manage to make the jump between the Internet and the world of RF.
If your eyes are not lighting up right now, let me see if I can put it in different terms.
The PlutoSDR has the ability to access signals between 70 MHz and 6 GHz. It
can do so in chunks of 56 MHz. Said differently, if you were able to
consider all of the amateur HF spectrum, from zero to 54 MHz, you could fit
all of it inside one chunk of 56 MHz that the PlutoSDR is capable of. You couldn't send it anywhere, since you're limited to how fast a USB cable is,
but you could technically process that inside the PlutoSDR itself.
To get the PlutoSDR to see the amateur HF bands you could connect it to a transverter, in much the same way that today many 2m handheld radio owners
use a transverter to get to 23cm, except in this case, we're going the
other way.
In order to actually use this massive amount of information, you're going
to need to do some serious signal processing. Accessing 56 MHz of raw data
is hard work, even if you don't have to get it across a serial connection.
As it happens, the PlutoSDR also comes with an FPGA. As I've mentioned previously, it's like having a programmable circuit board, which can be programmed to do that signal processing for you. It has the capability to massage that massive chunk of data into something more reasonable. For
example, you might be able to use it to extract each of the amateur bands individually and represent them as an image that you might show to the
world as a waterfall on a web browser.
Now to be clear, I'm not saying that any of this exists just yet, or fits within the existing hardware constraints. I'm only starting on this
journey. I'll be learning much along the way. No doubt I'll be using
existing examples, tweaking them to the point that I understand what they
do and how they work. I've already been talking about some of this for
years. As you might have discovered, this adventure is long with many
different side quests and at the rate I'm going I'm confident that this represents the breadth and depth of what amateur radio means to me.
So, if you're wondering why I'm excited, it's because the amateur radio
world of opportunity is getting bigger, not smaller.
I'm Onno VK6FLAB
This posting includes a media file:
http://podcasts.itmaze.com.au/foundations/20220116.foundations-of-amateur-radio.mp3
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Products made from unobtainium
Posted: 08 Jan 2022 08:00 AM PST
http://podcasts.itmaze.com.au/foundations/20220109.foundations-of-amateur-radio.txt
Foundations of Amateur Radio
The other day I received an email from a fellow amateur, Elwood WB0OEW.
We've been exchanging email for a little while and having been in the hobby since before I learnt to ride a bicycle, he's always got some interesting insight into something I've said and an encouraging word to share.
This time he introduced me to a project he built and published a couple of years ago. It's a variable frequency standard, built from parts and, at the time, costing all of about $150, more on that shortly. Compared to the microwave oven sized HP-606A signal generator sitting on my bench in bits,
with some diligent layout, this project could fit inside one of the valves
that drives that massive hunk of equipment.
As an aside, truth be told, I'm a little afraid of the HP. It managed to
pop the RCD, a residual current device, or safety switch, in my house and
in doing so, took out the UPS that powers my main workstation, so, not unexpectedly, I'm reluctant to repeat the experience. Once I understand precisely what happened, I'll pick up the restoration efforts and based on
what I learnt today, it might get me where I want to go faster.
Elwood's frequency standard is a very interesting project that delivers a
very precise Variable Frequency Oscillator or VFO with an accuracy
approaching 1 part per billion. His project uses an Arduino to control a
touch sensitive display, read a knob and set and correct the frequency
using a GPS as an accurate external time source. It's all very compact,
easy to follow and I immediately thought that this would be an excellent project to build with a little twist.
I'm thinking that it would be really great to have this device sit on your local network and make it remote controllable.
The heart of this frequency standard project is a chip called an Si5351.
The Silicon Labs Si5351, to use its full name, was first sold by Mouser in
2010 and has been popular since. You'll find it in all manner of places, including the Linux kernel source tree, the QRPlabs QCX and BITX to name
two, the Elecraft KX2, scores of Arduino projects and countless frequency source products and projects used in amateur radio.
The Si5351 is a configurable clock generator. Think of it as a programmable crystal that can be configured on the fly, as often as you like. For configuration, it uses an I2C bus, or Inter-Integrated Circuit
communications protocol, a special serial bus intended for chip to chip communications, invented by Philips Semiconductors in 1982. That's the same Philips from the light bulbs and audio cassettes, CD, DVD and Blu-ray, also
the Philishave. To complete the picture, Philips Semiconductors became NXP
in September 2006.
Back to our frequency standard project.
I wondered if I could cut out the Arduino from the actual correction
process, since I didn't need a display or a knob and discovered that the
Si5351 comes in several flavours. Elwood's design uses the A-version, but there's also a C-version that has the ability to take in an external clock, like say that from a GPS, and correct within the chip itself.
With that information in hand, I figured that I could use a simple Wi-Fi capable system on a chip, something like say an ESP8266, to configure the
clock and take care of communications with the outside world. In the
process I'd learn how to do a bunch of new things, including my first foray into generating RF, first time writing actual firmware, first time
designing circuits and no double many more firsts.
Then I hit a snag.
It seems that the Si5351 has gone from commonplace to zero in stock. Not
just zero in stock in Australia, or the US, no, zero in stock anywhere.
There are a few A-version breakout boards, that is, the chip on a circuit board, available from one supplier. There is also a new compatible chip, an MS5351M, available from China, but that's a drop-in for the A-version, not
the C-version.
So, where it stands is that I can almost taste the design, essentially
three chips, an almost trivial circuit board, some SMA connectors, a power source and an external GPS antenna, something that would represent the very first circuit I actually designed, which is a long way from reading the
circuit diagram for my Commodore VIC-20 back in the days before I owned a soldering iron.
It did bring me face to face with an odd realisation.
There are components that we use in day-to-day use, ones that are common,
used across many different industries, that come from a single source. I
should also mention that this particular manufacturer just got sold to
another company, which doesn't help matters.
Nobody seems to know how long this shortage might last with forecasts
varying wildly, but I'm beginning to wonder how many of these kinds of components exist and how we might reduce our dependence on single supplier hardware.
I'm also starting to look at using an FPGA to do all of this in software,
but that's going to take some time, of course we could start using valves again. My 1960's era HP signal generator is starting to look much less intimidating.
I'm Onno VK6FLAB
This posting includes a media file:
http://podcasts.itmaze.com.au/foundations/20220109.foundations-of-amateur-radio.mp3
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Leaving the hobby ...
Posted: 01 Jan 2022 08:00 AM PST
http://podcasts.itmaze.com.au/foundations/20220102.foundations-of-amateur-radio.txt
Foundations of Amateur Radio
The other day I came across a how to video on becoming a radio amateur.
It's a recurring kind of publication, the kind that I've contributed to in
the past.
I wondered what it would take to leave the hobby.
First of all, I'd have to let my callsign lapse. That's easy enough, but I
paid for five years, so it's going to take a while. When it has finally
ceased being mine, have I stopped being an amateur?
For one, my qualifications would still be in the regulator's database,
likely well beyond my breathing years. I wonder if they implement the right
to be forgotten?
Another thing I'd have to do is stop knowing about how antennas work in day-to-day situations. I'd have to stop noticing the location of free to
air television antennas, mobile phone towers, Wi-Fi antennas throughout the community and even the network in my home.
I'd also have to say goodbye to all the friends I've made around the place. There's hundreds of people scattered around the globe who with a single
word might lure me back into their world, and with that the risk of being sucked back into the community once again.
At a minimum I'd have to stop using computers, or radios, or electronics really. I'd have to stop wanting gadgets and measuring equipment, not to mention having to mothball my soldering irons and give away all my heat
shrink.
I'd have to give back the space I've eked out in the house and return it to
the general living space it once was. I'd also have to sell all my radio
gear and antennas. I'd have to rip out the coax, fix up any holes, cancel pending orders for new antennas and donate my books and magazines to the
local library.
I'd have to stop looking at electronics magazines, cut up my loyalty cards
for the local electronics and hardware stores and start an online store to
sell all the connectors and adaptors I've amassed over the time I've been
part of the community.
I'd have to forget the phonetic alphabet that I use almost daily and start using crazy words to spell things over the phone like a normal person does.
Experimentation would be a thing of the past and would be frowned upon as a fringe activity, one only suited to madmen and amateurs, and I'd have to
stop investing my time in software and projects that might one day be used
in amateur radio.
One of the hardest things to give away would be my curiosity, the one thing that's innate to my wellness. I'd have to stop asking Why? and How? all the time. I'd have to plead ignorance when someone asks how coax works and
what's inside a blob of goop on a random circuit board they found on the
side of the road.
Then there's the other things like physics and general science. I'd have to disavow all knowledge of these activities. I'd have to stop looking at the stars and stop wondering which radio frequencies were being emitted from
all over the night sky.
I'd have to become ignorant of emergency services and communication, of
event management and club life. I'd have to feign interest in anything that wasn't science or technology and I'd have to keep a straight face and my
mouth shut when someone extolled the virtues of an irrational belief system.
I would likely have to give up my job as an IT consultant and start on a
more manual job. Perhaps I'd take up gardening, though I'm not sure how I'd
do in the weather at my age.
Even if I achieved all that, and kept it up for the rest of my life, I'd
still be an amateur, just one hiding from the hordes of humanity striving
to live on this ball of dirt, hurtling through the heavens on a journey
through the stars.
I'm not sure I could do that.
So, for better or worse, as I see it, once an amateur, always an amateur
and if you're curious and believe in science and technology, I'm here to
say that you're well over halfway towards being an amateur! Welcome to the club!
I'm Onno VK6FLAB
This posting includes a media file:
http://podcasts.itmaze.com.au/foundations/20220102.foundations-of-amateur-radio.mp3
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What testing equipment is essential?
Posted: 25 Dec 2021 08:00 AM PST
http://podcasts.itmaze.com.au/foundations/20211226.foundations-of-amateur-radio.txt
Foundations of Amateur Radio
After discussing the notion that it's not really possible to determine how
your gear is performing without measuring, several people commented that in
the good old days an amateur was expected to have sufficient equipment to
test performance of their gear.
I flippantly pointed out that once upon a time, computers ran on punch
cards too. That's not to dismiss the notion of testing, but rather that
times have changed. Testing equipment that was suitable in the 1980's is
still available around the place, but expect to pay for it. Some of it is
still relevant, some less so.
Even if you do acquire suitable equipment, how do you know if what you're measuring is real? How do you know if the frequency counter that you have
is accurate, how do you know if 1 Volt is 1 Volt, or 1 second is 1 second?
As I've said before, measurement is the act of comparing two things.
If you think that's ludicrous, consider the rulers and tape measures in
your home. They all indicate the same measurement, right? Just for a laugh, pull out all the ones you can find and see what you discover. If you've not done this, you're in for a surprise.
I don't want to dissuade you from getting testing equipment, far from it,
but don't expect to fork out to get the equipment and call the job done.
The point being that spending lots of money on gear isn't the end of the
story, it's just the beginning and in my opinion it's not the place you
should start.
Based on community responses, ninety recommendations in all, so hardly scientific or representative, but still a good feel for the space we're
playing in, the single most important piece of equipment you should get
after sorting out your radio, antenna, coax, power supply, computer,
software and other fun things we fill our shacks with is the Digital Multi Meter. You can spend anywhere from $10 to $500 on one, but it should be
high on your list. As with the rulers, your results will vary, so be
mindful of that when you go shopping.
While the SWR meter and the Watt or Power meter appear regularly, they're
not the next highest ranked testing gear. Mind you, most current radios
have those built-in to some extent, so perhaps the numbers are somewhat distorted here.
The next essential piece of equipment is some form of monitoring. Either active, passive, programmable, automated, manual, what ever. Hardware like
the NanoVNA, the TinySA, even using a Software Defined Radio feature high
on the list. Most of these devices either generate a signal to test
against, or they rely on your radio to do the heavy lifting, depending
entirely on what you're testing. An antenna analyser is among these kinds
of tools.
As an aside, the dummy load, either a high power one, or a more modest one, come recommended by many different people.
Together with this list of monitoring equipment comes associated
accessories, adaptors, patch leads, attenuators and filters.
After that comes equipment such as variable power supplies, Watt meters,
grid dip meters, oscilloscopes and frequency counters.
I will observe that from the responses I received there was a distinct
flavour to the recommendations.
On the one hand there was the combination of recommending something like a station monitor, or a signal generator, an oscilloscope and a frequency counter, including things like a Bird 43 RF Watt meter. On the other hand
were recommendations for spectrum analysers, NanoVNAs, SDRs and the like.
It's not quite across the analogue to digital divide, but it's close.
Note at this point that I'm a software guy in the process of restoring an analogue HP 606A Signal Generator from the early 1960's, so I'm not
pointing the finger anywhere.
There were other tools recommended too, an LCR meter, a tool that allows
you to measure Inductance, Capacitance and Resistance, something you can
buy in kit form if you want to get started, or similarly, can be purchased
for varying amounts of money online. Speaking of money, varying amounts
that is, the service monitor was on the wish list for several people.
Prices between that of a new radio or a new car with varying amounts of warranty.
I will make mention of a bi-directional coupler which was marked as
essential by one amateur. It's a tool that allows you to sample a signal in
the forward and the reflected path which comes in handy when you're trying
to test and build equipment.
As mentioned before, your transceiver has some of this equipment built in,
or can be set-up to do some of this, so there's no need to go out and spend thousands of dollars to set-up your testing bench on day one, but the day after, I'd add it to my birthday list.
No doubt that there's many and varied opinion on this. What is your
essential testing equipment?
I'm Onno VK6FLAB
This posting includes a media file:
http://podcasts.itmaze.com.au/foundations/20211226.foundations-of-amateur-radio.mp3
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How does your gear measure up?
Posted: 18 Dec 2021 08:00 AM PST
http://podcasts.itmaze.com.au/foundations/20211219.foundations-of-amateur-radio.txt
Foundations of Amateur Radio
When you spend some time in this hobby you're likely to find equipment with similar performance for vastly different pricing. At one end of the
spectrum you might compare a cheap $25 hand-held radio to a $450 one. At
the other end, a $1,500 SDR or Software Defined Radio against a $4,500 one.
Those examples are for brand name devices, which generally speaking have published specifications, come with regulatory approvals, a wide user base, reviews and a distribution network. If equipment is found to be operating
out of specification, a regulator might seek a remedy or ban the sale of
the equipment.
Those various sources and processes make it possible to compare those
devices in a structured way to discover just how deep into your pockets you need to reach in order to acquire a shiny new gadget.
If you buy any of these devices in the used market, you have no way to determine just how far from the factory specifications the device you're contemplating has deviated. Is that waterproof radio still waterproof, or
did the previous owner open up the case and put it together incorrectly?
Was it dropped and did a component get damaged? Did the static electricity
from a local thunderstorm leak through the circuit via the antenna, or did
the previous owner not use anti-static precautions when they looked inside?
If it actually failed, it's easy to know. If it's still working, absent a laboratory, you're essentially on your own.
If that's not challenging enough, consider hardware that's released as open source, that is, the original designer released their project, shared the design, a circuit board with component list and specifications. Another
person can pick up the documentation and legally build a copy of the
hardware.
How do you know how the two compare?
Aside from considering how well any design might actually match the real
world, how do you know if the original design can be improved upon or not?
Did the second builder use the same components, substitute with better
ones, or economise on parts they thought were too expensive?
What happens if the two designers argue with each other about the
performance of their respective designs? What if the second design becomes vastly more popular than the original and what if you throw in outright intellectual property theft over the top of all this?
Now consider the same physical hardware, from the same factory, but using different software. How do you know what impact the software has on the performance of the equipment? For example, one component seen more and more
is a chip called an FPGA, a Field Programmable Gate Array. Think of it as a programmable circuit board where updating the software creates a different circuit.
An FPGA might be used to filter radio signals. With just a software update,
you can program different filters and change the actual performance of the entire device. How do you know if the new version of the software has
improved or worsened performance?
What all this lacks is a standard way of describing performance. Not only
the kind of standard that's achievable in a laboratory, but one that we can test at home. There's no documentation that I've been able to find that
shows how to measure some of this objectively, or even compare your own kit against itself.
It would be great if I could measure my gear against a standard and you
could too and we could compare our respective equipment against each other.
Even using the laboratory standard measurements, for example the Sherwood Engineering Receiver Test Data, which allows you to compare other tested equipment in the same list, is hard, if not impossible to compare at home
by the likes of you and I. Not to mention that Rob NC0B has finally retired after 45 years, so having been licensed in 1961 age 14, there is a good
chance that updates are going to become a thing of the past when Rob stops volunteering his time.
I will mention that this isn't a new thing. Many years ago I spent some
time as a broadcaster. One of the very first things I was taught is that
you need to set levels to trigger the VU Meter just so. When you make a recording to tape, you're required to generate a 1 kHz tone at a specific
level so when it's played back to air, the voice levels will be correct.
When I became licensed in 2010 I almost immediately discovered that there
isn't even a standard way to test if the signal that my radio is putting
into the local repeater is the same as that of other amateurs. You'll
notice this because you're forever twiddling the volume on your radio when
you speak with others on-air because their voice levels vary widely.
One idea I've been toying with is using a parrot repeater that can measure
a signal, allowing anyone who uses the same parrot to compare their
equipment.
How would you approach this increasingly complex problem in such a way that
the amateur community can share their results in a way that makes
comparison meaningful and useful?
I'm Onno VK6FLAB
This posting includes a media file:
http://podcasts.itmaze.com.au/foundations/20211219.foundations-of-amateur-radio.mp3
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Getting Amateur Radio propagation data at home
Posted: 11 Dec 2021 08:00 AM PST
http://podcasts.itmaze.com.au/foundations/20211212.foundations-of-amateur-radio.txt
Foundations of Amateur Radio
For some time now I've been discussing the potential of weak signal
propagation and its ability to create a live map from the data that your
own station transmits. There are several systems in place that show a map
of where and when your station was heard in the past little while. Using
200 milliwatts, I've been transmitting a WSPR or Weak Signal Propagation Reporter beacon on 10m for the past few weeks.
At the moment, the furthest away my beacon has been heard is 13.612 km
away. That's an 0.2 Watt signal heard on the other side of the planet, on
10m. As distance goes, it's a third of the way around the globe. I must
point out that there's no way of knowing if this signal travelled the short path or the long path.
If you've heard those terms, short and long path but were wondering what
they mean, here's how it works. If I get on my bike at my QTH in Perth in
VK6 and peddle East until I hit Sydney, I'll have crossed Australia, taken about 184 hours and travelled about 3.746 km. That's the short path. If I
head West instead and start swimming, visit Cape Town, Buenos Aires and Auckland along the way, I'll have travelled much further, still made it to Sydney, but taken the long path.
Radio waves can do the same. Depending on propagation, a signal might take either the shortest route, or go in the opposite direction and take the
longest route along the great circle between two stations.
I'm mentioning this because WSPR doesn't tell you if it's one or the other
and if you're using a vertical, it could be either. Even directional
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