I have volunteered to teach a (very) simple electronics course for a few interested teenagers in a summer program. I remember as a little kid that my aunt gave me a crystal radio kit. I was amazed that such a simple thing could actually receive radio stations, so I figured out why it worked, and that turned me on to electronics for the rest of my life (now 70).
But although elecronics is my hobby, I've never played with RF before. What I want to add to the crystal radios that my students build is a little solar powered (5 v.) antenna amplifier. I'll put the antenna input though an RC high pass filter, then use an opamp to multiply the signal by about a factor of 10. Then I'll feed that to an RC low pass filter to chop the amplified signal range to AM plus some amount. I like this idea because it represents relatively simple technology that I can explain to the kids, without burdening them with a huge amount of theory.
But being a complete novice at RF design, I have two questions.
1. Can someone suggest an opamp is reasonably cheap (like $1.00), will operate single-sided and include ground in the input range, will operate on 5 v., and has adequate BW product ?
2. In order to get good response over the AM band, where should I set my 3 db cutoff frequencies?
Being naive about RF, I may have missed some other important aspects of this scheme, so feel free to critique my approach.
Thanks in advance for any suggestions.
But although elecronics is my hobby, I've never played with RF before. What I want to add to the crystal radios that my students build is a little solar powered (5 v.) antenna amplifier. I'll put the antenna input though an RC high pass filter, then use an opamp to multiply the signal by about a factor of 10. Then I'll feed that to an RC low pass filter to chop the amplified signal range to AM plus some amount. I like this idea because it represents relatively simple technology that I can explain to the kids, without burdening them with a huge amount of theory.
But being a complete novice at RF design, I have two questions.
1. Can someone suggest an opamp is reasonably cheap (like $1.00), will operate single-sided and include ground in the input range, will operate on 5 v., and has adequate BW product ?
2. In order to get good response over the AM band, where should I set my 3 db cutoff frequencies?
Being naive about RF, I may have missed some other important aspects of this scheme, so feel free to critique my approach.
Thanks in advance for any suggestions.