The major problem with VLF reception is interference noise, so ideally you want to situate the receiver a long way from sources of that – 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 hadn’t seen before. I found what I was looking for in the first, but am pleased I didn’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, that’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. There’s a feedback resistor change in my near future.įirst though I reckon I’ll draw up the circuit as it stands (in KiCAD). Signal is of the order of microvolts, their overall gain is x1500 – rather more than I’ve allowed for so far. It doesn’t have the schematic – I expect it’s one of their INSPIRE models.
#SIMPLE VLF RECEIVER CIRCUIT PORTABLE#
But I’d forgotten a key consideration, how much overall gain the thing should have.Ī quick google later, found this rather nice poster on NASA’s site, “ Building and Testing a Portable VLF Receiver“. I’ve already soldered up the input & filter stages, yesterday breadboarded the output stage – 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 that’s essentially required is a whip antenna and a high input impedance, high gain, audio frequency amplifier. I’m doing a little more on a simple handheld VLF receiver I’ve been working on.
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