By Timothy Raneyâ€¦Bald Engineer Guy with Glasses Â
Editor's Note: Are you part of a local science club? We'd love to hear about you and profile your group! -sg
Our High Energy Amateur Science (HEAS) group held its February 2013 meeting on a chilly Sunday. Many interesting topics were discussed from meteorites to magnets and microwaves.
This meeting started with breakfast at our favorite restaurant - Anthony and Georgeâ€™s Steak House. Nothing like a hot breakfast on a winter day. We had a good time as usual. You know the deal â€“ talk and eat; eat and talk. I suppose it was not too surprising the conversation focused on meteorites at one point since we met just after the meteorite exploded over the Russian city of Chelyabinsk. So, we talked about the Chelyabinsk meteorite â€“ we were all especially interested in the meteorite type, e.g., chondrite, stony iron or iron-nickel. Given the blast effects and minimal data at the time, we settled on a chondrite (stony) type vs. others. The chondrites (as a whole) are the most common anyway. Well, it was our guess at the time and it appears we were correct. No, weâ€™re not meteorite scientists, but we could play them on TV.
After breakfast, we rolled out the door to Richardâ€™s lab for the meeting. The meeting did not have a theme this time. Though youâ€™d think it was the letter â€œMâ€ given all the talk about meteorites, magnets and microwaves. We began our festivities with an impromptu demonstration were I showed how someone could â€œrechargeâ€ (remagnetize) a steel horseshoe magnet using rare earth magnets. We first calibrated a gaussmeter, then marked the horseshoe magnet poles (#1 and #2) and measured the flux.
Pole #1 was 20 gauss and pole #2 was 34 gauss. Very weak magnets for sure. Itâ€™s not unusual for these old magnets to have a slight magnetic flux asymmetry. After all, they were used in telephone magnetos datING back to 80 or 90 years ago. After finding a piece of scrap steel and two rare earth magnets, the horseshoe magnet completed the magnetic circuit. I removed the magnets and we measured them. This time, both poles were 230 gauss. This is a good result for these old telephone magnets â€“ they were produced before the miracle Alnico alloys were developed circa 1936.
Next, I gave a short talk about Gunn diodes and the basic theory of operation â€“ something I still do not understand clearly. I explained the set-up, where I found the components and showed how the 10GHz microwave emissions were attenuated by my hand and a sheet of aluminum. We then passed 0.5â€ thick piece of acrylic between the transmitter-receiver â€“ it did not attenuate the emission.
The power supply was a 9VDC battery. I just used it intermittently since the Gunn diode draws ~380mA at 9V. The receiver was a vintage 1N23 point contact crystal diode mounted within a waveguide flange attached to a gain horn antenna as shown in the photo above. Connected to a digital multimeter, the receiver can detect the signal and its amplitude is ~160mV at 18-inches. The demonstration went very well.
We had a â€œshow and tellâ€ session too. For example, Richard Hull showed a few vintage clocks he picked up at an antique mall recently â€“ all showed some level of radioactivity since the clock hands/numerals were painted with radium-bearing paint years ago. Larry A. showed an electron charge-to-mass ratio apparatus. Missing the electron beam tube, I took a couple of vintage scientific supply catalogs off the bookshelf and showed the group similar versions on the market in 1960 and 1975. This particular piece of apparatus was discarded by a university in Maryland. I saw a tube for it in October 2011 â€“ it was only $150. Gee, if I could only have foreseen the future.
We had seven regular attendees at this meeting - Richard Hull, Larry A., Ron B., John L., Alex T. and Dave S. A few more members were not present, but that wasnâ€™t surprising given the weather. Another interesting and enjoyable meeting. I always learn something new. I expect more of the same at our March meeting where weâ€™ll discuss the 117th anniversary of Becquerelâ€™s discovery of uraniumâ€™s radioactivity. Golly gee, was that a scientifically significant event or what?