I haven’t posted much in the last month or so, but I have been working on a few projects. One of them involves the 20 meter band and my quick attic antenna wasn’t cutting it, so I put together a new one made from speaker wire. I wound a proper balun on an FT240-43 and connected one end to the coax running down through the wall. I used some electric fence insulators for the ends and I strung it up in the attic.

I used to play the guitar a lot when I was younger, but haven’t done much since my kids were born. I recently pulled out all of my gear and thought it might be fun to try to make my own effects pedal. I came across an article on building your own stompboxes and thought I’d give it a shot. Here is the schematic from the article. I built the circuit on a small breadboard.

A few weeks back, I ordered a Russian sbm-20 Geiger tube and it finally came in. The tube runs on 400v and will emit a pulse when it detects ionizing radiation. Due to the Townsend avalanche phenomenon the tube is able to register a significant pulse from even a single ionizing event. To test the tube, I needed to build a 400 volt power supply. The simplest and quickest way to do that (with what I had on hand) was to make a simple switching supply using an arduino to supply a pulsing dc voltage to an irf840 mosfet.

I came across an interesting site by Charles Wenzel called techlib.com. His site contains a lot of interesting projects. The first one that caught my eye was the various lightning detector circuits. There is a lot more detail on the techlib site, including the theory behind the detector and test circuits along with other cool projects, so I’d encourage you to take a look. Here is the schematic for the detector that I built.

I’m still tinkering around with my superhet receiver. The plan is to eventually turn it into a full transceiver, but I keep getting sidetracked. I did knock together a mic amp based on one of n6qw’s designs. Here is the schematic. Here is how it turned out. It seems to work okay. I connected my d104 mic to it and hooked it up to the scope and the scope pattern looks good.

I finally received a batch of 1n-14 nixie tubes that I purchased from ebay for a future clock project. The tubes need a power supply that can supply 170 volts DC, which I didn’t have, so I built one. I came across a few switching designs online and I settled on the one from here, mainly because I had most of the parts on hand. I made a few changes from the schematic which I’ll detail below.