Radio Stations below 448 kHz with BT878 ADC

Winrad is running under Wine on Ubuntu. It is playing back a WAV file which has all the radio stations below 448 kHz (that my antenna hears). I tune through a few ones that come in really good....
390 kHz:DDP non directional beacon
380 kHz:LQ non directional beacon (barely audible)
306.5 kHz:The strongest radio station except for the 60 hertz from the power lines...an FSK modulated DGPS beacon
100.0 kHz:LORAN-C, both in USB, LSB and AM mode
59.075 kHz: WWVB in USB mode
24.000 kHz:Cutler Maine Submarine FSK communications, with some other unidentified FSK signals nearby

I then try to find if the file has a 20 second pulse recorded in it, but my arm gets tired holding the camera with one hand. I would have used the scan converter to record the screen, but Winrad needs a large screen resolution which my scan converter doesn't support. If you listen closely, you can hear my baseboard heaters interfering acoustically while I'm recording with the camera's microphone.

Category:

Science & Technology

Tags:

• very
• low
• frequency
• wwvb
• ddp
• LORAN
• LORAN-C
• 896000hz
• software
• defined
• radio

[Mofo3210]

Does this contain all the frequencies below 448kHz? How is it possible to record several frequencies without tuning in on every single one?

[Amishman35]

What you hear in the video is everything that my antenna can hear below 448 kHz recorded at night. I made the video of it being played back in the morning. Winrad tunes the recording to selectively hear what you want to listen to. Since the sampling rate is 896,000 hertz, it contains all the frequencies below the Nyquist, (448kHz), this is in comparison to a Compact Disc's 44,100 hertz. I can go back in time in the recording and listen to a station that was transmitting on another frequency.

[Mofo3210]

Ok, as you may understand I don't have much knowledge in electronics, as I just recently became insteresting in this field. I'm a structural engineer so I recalled having read about the Nyquist-frequency in regards to earthquake spectrums. Very interesting btw. Are you into general electronics as well, or do you mainly focus on audio/radio?

[Amishman35]

I'm mostly into audio, radio and some simple C programming. Did you say earthquake? The ASUS Eee-PC 900's microphone can record bass quite well. It can record down to 3 hertz or so. I've sent messages through the floor of my house at the other end of the house by tapping my foot on the floor--10 taps for a dot and 30 taps for a dash. To pick it up, I record at 2,756 hertz in Audacity, export at 500 hertz, then open it up and speed the file to 10,000 hertz (20x normal speed).

[Mofo3210]

You mean the integrated mic on the laptop? 3 hertz is very low isn't it, I can't understand how the membrane in the mic is able to pick it up. It's far below the audible frequencies of the ear (20Hz?) so it's impossible to hear, right? What is the range if such low frequencies?

[Amishman35]

Yes, the eee-pc 900 has a very bass sensitive mic. I can also send inaudible QRSS morse messages using a door at a low frequency. If you use Baudline and the decimation function, you can make a log of the cycling of refrigerator compressors. Car engines are around 40 to 70 hertz.

[denelson83]

Now if only the radio signals could be sampled at 500 GHz...

But then you'd need a *hell* of a lot of hard drive space on which to store that snippet of radio spectrum.

[rzsigray1]

i was playing arround with the program i could get my own mic with it...great for evp work

[p0llenp0ny]

You're talking about radio frequency and sound frequency. It's apples and oranges.

[pdmillar]

Sorry I can read the title now

[pdmillar]

Did you modify a BT878 tuner card to use the high-speed ADC for audio? I have a few laying around and I have been meaning to do that.