Now that the seismometer has been delivered, I can get back to work on my Multi-Frequency Monitor project. The basic idea is to monitor radio activity in several parts of the the spectrum, from VLF up to Microwaves. I was inspired to do this because of the long, deep, solar minimum we just experienced. I want to see what happens as the sunspot numbers go up through this next solar cycle.

My plan is to have several antennas covering the bands of interest, backed up by receivers for each. The receiver outputs will be conditioned, displayed on bar graphs (I LOVE blinky lights!) and then digitized with a MAX187 A/D converter. Radio SkyPipe will handle the data acquisition and display.

First up will be 111MHz (modified aircraft receiver kit), 20MHz (RadioJove), and 24.8KHz (HP3586C SLM).

I designed and built the bar graph cards last year. Here's a photo of one of the prototypes:



I searched all over the net trying to find a kit or module that would do a bargraph. When I couldn't find one, I resorted to building my own.

These will be mounted vertically in a 3U (5.25") card cage, with the LEDs poking out through a panel for each board. This prototype has the wrong Red and Yellow LEDs: they will all be T1 size. In the lower right are the input and output jacks. Next to them are the gain/offset/filter amplifiers. The pots allow me to adjust offset and gain for both the display and the signal going to the A/D. In the middle is the LM391x bar graph driver. They have three variants with either linear, log, or VU scaling. The upper right has the power input and voltage regulators.

These work great. I had only a couple of minor problems with the protos, but otherwise they work great.

Next up, the A/D board.

Cheers,

Keith

Well, here's the finished seismometer ready for delivery. It was picking up the heavy surf off the Sonoma County coast for the last week, and also recorded a 3.0 at The Geysers.
To get here, I changed the upper suspension to be mostly rigid. It's hard to tell in the photo, but the angled part is 1/2" x 1/16" aluminum angle. I only have a couple of inches of exposed wire. This really killed a rotational movement about the boom axis that was cluttering up the results.

You can also see the cast lead masses at the end of the boom. I did these with a simple wooden form, and melted the lead on my Weber barbecue over some charcoal briquettes. I ordered the lead, a ladle, and some casting putty from Rotometals. The putty was very nice to smooth out the inside corners of the mold. Rotometals has a bunch of great stuff for low-melting temperature metal casting work.

The electronics for this setup all came from Larry Cochrane at the Redwood City Public Seismic Network. I bought a sensing coil, amp/filter board, and 16 bit A/D board all in a nice box. They are working great.

In my book, Charles Darwin was one of the great original thinkers. I put him right up there with Galileo in his willingness to question conventional wisdom and make the leap from creation to evolution. He agonized over his theory, knowing that everyone, including his family, would have a very difficult time dealing with it. Check out the Make: blog link to learn more.

Cheers,

Keith

This is a side view of a Lehman style Seismometer I am building for a friend. I found some great base material at Bataeff Salvage here in Santa Rosa. It's 1/2" plate aluminum, about 6" x 18". The vertical section is 3/4" galvanized pipe and fittings. Here I'm just starting to figure out where the sense coil and magnet will go. I wrapped some plumbing solder around the end of the boom as a temporary mass. The pivot is made from two pieces of 1/4" round carbide. They are epoxied in place, one on the end of the boom and the other on the bottom of the vertical mast. The angled aluminum piece is there to hold the boom if it slips off the pivot. Only friction holds it in place.

One aside. Normally, as a good scientist, I prefer to work in Metric. But, scavenging for parts in the US generally results in inch based parts. Now, if a piece of pipe was manufactured as 3/4", I'm not going to convert it to metric. Use your brain if you need to find a metric size somewhat near the inch size I said I used. Besides, none of this stuff is that critical - use what you can find like I did!

Cheers,

Keith

This is the first entry in my new blog dedicated to Amateur Science of all kinds. I use the word "Amateur" in the original sense: One who pursues an interest just for the love of it. My focus lately is Radio Astronomy, but I am also interested in Seismology and darn near anything else about the natural world.

I'm a big fan of MAKE: Magazine and the whole "Maker" ethic. Too many people think that being prepared for an emergency means carrying a credit card and a cell phone. I believe in a high level of personal responsibility and I believe everyone should be able to survive a night in the wilderness with just the stuff in their pockets.

I'll try not to rant too much, unless something comes up that is really over the top.

Let's have some fun with this.

Cheers,

Keith