In 1992 the BBC science documentary series Horizon, ran an episode entitled “Molecules with Sunglasses”. It was a pretty hardcore theoretical science episode detailing the discovery by scientists of a third form of solid carbon eventually named as ‘buckminsterfullerene’.
One line in the episode, detailing how the 60 atoms of carbon were arranged in space, will stick with me forever. The commentator is telling how they were wrestling to understand the mathematics and physical form of the structure. In a discussion with a colleague, where some pretty high powered terms were being used, one turns to the other and says “basically Chuck, what you’ve got there is a soccer ball”.
It epitomises how, if you keep it simple, you can explain anything to anyone.
A follower of this blog has said “great pictures, but the theoretical stuff is way past me.” The fact he’s actually taking the time to read this warms the cockles greatly, so just before the reveal, let’s put what this is about in “soccer ball” terms.
WSPR (Weak Signal Propagation Reporting) is a form of data communication/transmission which sends 160 characters in slow audio tone bursts lasting exactly 2 minutes. The sending and receiving of these transmissions is time critical and is reliant on the transmitter and receiver both having a very accurate clock, otherwise they would be out of sync. The receiver would be sat there aimlessly waiting for transmissions that would be being broadcast when his/her receiver wasn’t listening. The computer I use to decode received WSPR signals, with the receiver I built a few months ago, synchronises it’s clock very regularly to a series of atomic clocks which form part of the internet NTP service.
The beacon I’ve just built utilises the time signals transmitted by the GPS satellites which orbit the earth to accurately set its clock, so the transmissions are in sync with those receiving WSPR transmissions regardless of where they live on the planet.
WSPR is neither a cypher nor an encryption as amateur radio can’t be used to send transmissions that are encrypted. Morse code, although a “code” can be viewed as a shorthand, where everyone has the ability to listen to what is being exchanged if they have the wherewithal to learn or decode the the series of dots and dashes. WSPR is the same in that anyone can listen and interpret the transmission.
Once the transmission has been received and interpreted the spot is sent to the WSPR community at WSPRnet.org and appears within the database so people can track the propagation paths of their transmissions.
The data within the WSPR transmission contains information so that the receiver knows who sent it and from where, allowing the “spot” to be identied. The microprocessor inside the beacon packages that data up into the prerequisite format and then passes it to the transmitter side so it can be sent off into the ether, in my case via 7.5m of wire strung out of a bedroom window and down the garden to a fence post.
The transmission power output from this beacon, which is just a fraction bigger than a Swan Vesta match box, is 200mW (milli Watts).
A 60W domestic light bulb is 60,000 milli Watts; the beacon is transmitting with 0.33% of that power. Putting it another way, that’s 1/25th of the power which illuminates the number plate bulb on your car.
So with that in mind, I was quite impressed that within 20 minutes of attaching the beacon to my antenna, I got this.
That 200mW of power, which wouldn’t even make your number plate bulb glow faintly, is pushing that signal over 487 miles to Scotland, 498 miles to Switzerland and 506 miles to Germany!
There’s definite fine tuning needed, but I may well strut in a Bee Gee’s “Stayin’ Alive” fashion for a few minutes!