Friday, February 26, 2010

Just a Minor Detail

On his second day sick at home, the younger member of the family remembered his crystal radio set and wanted to listen to it again. I got it down from the shelf in the office and we took it to the dining room and connected it to the ground and antenna wires that were still in place, and he gave it a good listen for a while on his headphones, then said he'd like to hook it up to speakers. I allowed as how the crystal radio set probably didn't have enough power to drive a speaker, so we'd need an amplifier of some kind for that. He asked if we could build an amplifier, and I thought that we could. I went downstairs and got out the old 300-in-one Advanced Electronics set I got in a nostalgic moment at a Radio Shack at least a decade ago, and started thumbing through the index for a suitable amplifier circuit.

Considering that my poor eyes could barely distinguish some of the resistor color code stripes, it took longer to build than the impatient one thought necessary. He also thought I was hogging all the cool assembly parts and he didn't get to help with enough of it either, but then it was finally done and we hooked it up to the outputs of the crystal set and switched it on.


Not that any longtime engineer would expect any different. Of course, one of the wires in the breadboard was in the wrong spot and that took another minute or two to find, but once found, the circuit worked just fine, and we were dancing along to KIXI AM 880 from our amplified speaker.
I think the discrimination in the crystal set is virtually non-existant; we're probably listening to a smear of the AM band about 200KHz wide, so tuning the variable capacitor (the soda can with the paper bit around it) we can often hear two or even three stations at once. Once the amplifier was working, naturally the boy had more requests.

"Can we pause it?"

Hmm. How to explain this to somebody who was born after the advent of the DVR? That's a little beyond the capabilities of the 300-in-one set, I'm afraid, though it would be cool for sure. "We'd need more parts. Lots more." Like a computer, I'm thinking, with a hard-drive recording system, just like in the DVR. For a boy who thinks his dad can build anything, that's just a minor detail.

"We can spend the weekend on it!"


1 comment:

Lucy van Pelt said...

Enjoy the feeling of your son believing you can do anything while it lasts. :)