DATA-log

Since googling up NASA’s online VLF receiver mp3 stream (seems to be defunct now, fortunately there are other streams available.. see http://abelian.org/vlf/) I wanted to try to receive these signals myself. So I came up with some schematics on the internet for a basic vlf receiver and built and tested a couple of these.

E-field receiver clip 1

E-field receiver clip 2

The sferics are crisp, loud and clear, the circuits work very well if the conditions are right. Small enough to fit a pocket, it’s interesting to walk aroud the area I live and listen in to the various weird signals eminating from all sorts of electronics and machinery. I’ve yet to record auroral activity, but that is next on the agenda.

Got around breadboarding a voltage controlled filter for my analog synthesizer finally. The circuit is very simple, it is based on the SSM 2045 integrated circuit I salvaged from half working Siel polysynth. The circuit consists of the filter chip together with some opamp buffering and amplifying to get the signal levels matched with the rest of the modules and with the correct polarity. I still need to breadboard the two voltage controlled amplifier blocks in the circuit.

The operation is very stable and accurate, it’s the usual integrated circuit performance you’d except. The chip has outputs for 2-pole and 4-pole points from the integrator cascade. I really like the 2-pole sound of it. I think I’m going to wire both outputs to the panel with inverted phases so you also get some sort of bandpass output if you sum those together.