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Registered Member #188
Joined: Thu Feb 16 2006, 05:18PM
Location:
Posts: 67
For 20khz-noise: The ignition system of our gas burner runs at around 19Khz, on-time about 20s, as good as i could record it with a DSO, with capacitive pick-off from the ignition wires. So i guess thats it.Signal seems to be rather strong, the wires leading to the spark electrodes are not shielded at all and the ignition system outputs fast-rise pulses with high harmonic content.
Similar experiments i did some time ago stopped when i blew up my nice low-noise amplifier. That was while using a unused electric fence as antenna.I grounded the far end and used a ground electrode close to my reciever as the second connection. I started wondering what these 16Hz signals were because they were more or less periodical. I was thinking around and correlated them to the railway traffic and it seemed to match. So i went near the track and set up my stuff to confirm it. Somehow the signal was a little larger then expected and well, blew the whole amplifier including the input protection network (which can withstand a little transistent energy) and some pcb tracks. Then i saw that a weld on the railway track probably broke and the huge current flowing trough the ground generated a little much volage differential...
... not Russel! Registered Member #1
Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052
Carbon_Rod wrote ...
Well, I think perhaps filtering the sound card’s noise sources first may be logical.
1.) Laptop soundcards and built-in motherboard are notoriously noisy. Often clock ticks, fan noise, legacy dos system timer, and even the peripheral’s own circuitry can add noise.
Interestingly, I pick up very little noise from my computer at all, as long as the antenna is more than ten feet away, give or take. In order to keep RFI out, I use twisted pair right up to the mic input... using a straight wire connection seemed to allow the laptop to induce a little noise on the input; now I get no measureable signal at all from the laptop unless I really really search for it. The worst offender for RFI is definitely mains, and mains harmonics. The band is a mess of strong harmonics for the first 2-3kHz, and as you can see above, annoyingly strong harmonics persist even up to 15kHz. A few weeks ago, we had a power outage, and I got to see what the spectrum looks like without all that 60Hz noise. Pretty incredible. Very clean. When the power is out, I can make out several additional transmitters not visible above, such as Anthorn, in the UK.
Registered Member #27
Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058
After several days of seemingly random signals and bursts the Russian Alpha naviagation system is now emitting a steady train of pulses on 3 different frequencies.
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A VLF Capture
