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Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Hi all
As I'm sure you already know, tomorrow is Alexanderson Day:
This means that the historic Grimeton Radio Station in Sweden will be fired up. It was built in 1920 and is now a World Heritage monument, on account of being the last usable electro-mechanical radio transmitter in the world.
It transmits with 100kW on 17.2kHz into a huge antenna system, and you should be able to receive it most places in Europe, using nothing more than a big coil of wire plugged into your computer soundcard, and FFT analysis software such as Spectrum Lab. You need good equipment and a lot of luck to receive it in the USA, however.
I've bodged a receiver together using a Tesla coil retuned to 17.2kHz, a big loop of wire and a low-noise microphone preamp, and I'm hoping to catch the first transmission tomorrow at 0800 UTC. There is a second chance at 1300.
Even if you don't pick it up, you can ponder the engineering challenges involved in generating 100kW of RF by spinning an iron disc punched full of holes really fast.
... not Russel! Registered Member #1
Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052
Hello,
I tuned in, but without any success. Alas, the old sound card + loop trick doesn't seem to be good enough for those across the Atlantic. How did you make out, Steve?
Registered Member #30
Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706
Hi Chris,
It was a success! The Tesla coil turned out to do more harm than good though, it picked up masses of EMI from my computer. In the end, I used a 5 turn square loop, 6ft x 3ft, that I connected straight to a balanced microphone preamp with 60dB of gain. I fed the output from that into a M-Audio Delta 1010 running at 48kHz and 24 bit. I put this together the night before, and managed to see some Russian Alpha beacons and the French navy station at Le Blanc, but even so I wasn't sure it would work.
I needn't have worried though. From about 0830 on I got a huge signal as they were tuning up, and I was able to watch them messing with the alternator to get it onto the right frequency. Once the transmission proper started, the frequency stability and signal quality was very good.
... not Russel! Registered Member #1
Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052
I wrote a very nice post for the occasion, but it sort of got lost in the bustle (working too damn much lately). If it's any consolation, I was using a huge 6'6" loop, and there's wasn't even a peep. Even the highly sensitive WWLN receiver in Boston barely registered a signal. Propagation across the Atlantic was very very poor this time around.
Before the next big SAQ transmission, I hope to have a super-sensitive VLF/LF antenna ready. If it works out, I'll post construction details here.
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Alexanderson Day
The Tesla coil turned out to do more harm than good though, it picked up masses of EMI from my computer. In the end, I used a 5 turn square loop, 6ft x 3ft, that I connected straight to a balanced microphone preamp with 60dB of gain. I fed the output from that into a M-Audio Delta 1010 running at 48kHz and 24 bit. I put this together the night before, and managed to see some Russian Alpha beacons and the French navy station at Le Blanc, but even so I wasn't sure it would work.
