Vlf receiver portable portable#
Vlf receiver portable plus#

The Arduino+ESP8266 offer 7 channels, so I propose having the first being relatively broadband, pretty much just a buffer for everything coming from the receiver (post notches). These filters are shown as the yellow block in the diagram. Given what will follow in the circuit, I donвЂ™t think these need to be very high Q/narrow, just enough to prevent these parts of the input swamping everything else, saturating what comes next. So I propose using notch filters at these frequencies (also in that earlier post). It seems that as well as the 50Hz fundamental, thereвЂ™s also a significant amount of the 3rd harmonic at 150Hz. ItвЂ™s a relatively simple 2-transistor design, with a high impedance FET input followed by a bit of further amplification provided by a regular BJT.ДЄ major problem, as mentioned here before is mains humВ interference. A good starting point for this seems to be the BBB-4 VLF Receiver. This will be some kind of antenna, picking up the electric field with a frequency range from somewhere probably in the 100s of mHz up to around say 200kHz. Starting at top left, the blue circle represents the actual ELF/VLF radio receiver. But I have all the components for an attempt at a useful radio subsystem, provisional design as followsвЂ¦ IвЂ™ll come back to this is a while вЂ“ I need to research & buy the gyro & accelerometers.

Vlf receiver portable plus#

On the seismic side, I think a first pass worth trying is a home-hacked sensitive, one axis sensor, plus a 3 axis gyro and a 3 axis accelerometer. As such, while they should be ok for picking up seismic data, they fall far short for the ELF/VLF radio capture which should really go up to the region of 20kHz. These are quite limited вЂ“ 10 bit ADCs with bandwidth that at best may go up into a few kHz. An Arduino Uno has 6 analog inputs, and the ESP8266 WiFi card which I plan to use has one.

So, as mentioned in previous posts, I reckon itвЂ™s worth trying to use Arduinos as front-end microcontrollers for this project, as shown in the block diagramВ here. Looks like thereвЂ™s some good material.ДЄuthor Danny Ayers Posted on AugCategories Analog, Electronics, Hardware, Radio Leave a comment on VLF Receiver Oddments Arduino front endВ ideas

I must admit, it does have a bomb-like appearance! It spent the rest of the night under an overturned flower pot with the VLF antenna sticking out the little drain hole in the bottom.вЂњ.ДЄnother very promising site I ran across, have still to read, is LarryвЂ™s Very Low Frequency Site. That turned out to be a questionable location, by the way! Not only did several neighbors become alarmed by it, but a couple of police officers also spotted the thing. вЂњ The antenna was horizontal and near the ground under my truck for this recording. Here the author bends a baby monitor transmitter, replacing the mic with a VLF preamp. houses, computersвЂ¦ Which is a pain if you want to record/analyze the signal. The major problem with VLF reception is interference noise, so ideally you want to situate the receiver a long way from sources of that вЂ“ eg. One piece of utter genius jumped out at me. It features a variety of simple receiver designs. This page is notable : VLF Natural Radio Reception at. While vlf.it is the site for all things Radio Nature, I did stumble on some material I hadnвЂ™t seen before. I found what I was looking for in the first, but am pleased I didnвЂ™t close the others. When I was looking for the gain requirements yesterday, I opened a bunch of the results in browser tabs. Hmm, gain of 1500, thatвЂ™ll be tempting to stability problems. I also need to check roll-off at the frequency extremes (call it 20Hz & 20kHz). I can figure out the gain bits from there, and simulate. ThereвЂ™s a feedback resistor change in my near future.ДЇirst though I reckon IвЂ™ll draw up the circuit as it stands (in KiCAD). Signal is of the order of microvolts, their overall gain is x1500 вЂ“ rather more than IвЂ™ve allowed for so far. It doesnвЂ™t have the schematic вЂ“ I expect itвЂ™s one of their INSPIRE models.

Vlf receiver portable portable#

But IвЂ™d forgotten a key consideration, how much overall gain the thing should have.ДЄ quick google later, found this rather nice poster on NASAвЂ™s site, вЂњ Building and Testing a Portable VLF ReceiverвЂњ. IвЂ™ve already soldered up the input & filter stages, yesterday breadboarded the output stage вЂ“ an amplifier to drive a little speaker/headphones. Some filtering is desirable to limit the bandwidth and cut the noise of mains hum. For an electric field receiver all thatвЂ™s essentially required is a whip antenna and a high input impedance, high gain, audio frequency amplifier. IвЂ™m doing a little more on a simple handheld VLF receiver IвЂ™ve been working on.