Sensitivity of a colpitts oscilator...

if you haven't look at this book all ready

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its a good way to get started

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Very cool!
A funny coincidence, I live in “Lafayette” Va.

My Dad built the beachcomber from popular electronics July 1967 back in the late 60’s. That was the first detector I ever new. I built one using the same circuit in college. I have always had ideas for improving the depth but never had the time until recently. Now I’m tinkering again. My Brother and I metal detect around some old homesteads once in a while and we like to dig everything anyway so the BFO is ok for that. Using a homade detector from the 60’s makes it more fun somehow.

That old beachcomber operated at higher frequency though, around 500kHz I think. That’s higher than most BFO’s that came later. About the best we ever did on coins was 6 inches from a 6” coil. And of course you only have ferrous vs non-ferrous discrimination.

Looking forward to seeing the material you are looking for.

Thanks.

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Sorry for the loss.

I am not an engineer by schooling but I worked as a technician at a mobile robotics company for about 6 years and have been a tinkerer since childhood. I’m still learning though. I’m playing with oscillators and looking to improve on the old BFO design as a learning experience. I’m interested in determining what makes the colpitts oscillator the most susceptible to inductance change. From circuit design to types of capacitors (low resistance and temp stability) to the type and size of coil wire (Litz?). The old BFO from the 60’s used 50+ year old technology. I’m thinking that using modern tech it can be made better. Granted it will still be a BFO but I’d like to think it can be made to detect deeper be more stable and I plan to add a meter.
I am interested in learning more about EM fields with focus on detectors. I recently researched field shaping and found some interesting articles but nothing that I can apply to detectors as of yet. Anything that can increase the effectiveness of the EM field is interesting to say the least. For 50 some odd years we have been working under all the known limitations. I’m trying to think outside the box.
I’d even like at some point to add an onboard micro controller and get into some signal processing.
So that maybe shows you where I’m going. I have also done some pic32 project work communicating with I2c sensors, rs232, designed and built motor controllers, amplifiers, pic32 motherboards, used xbee radios, circuit board layout, use meters, scopes etc. I am also a software developer.
Having said all that I think I have more desire and interest in things than I have skills to back up but that’s the curse of being a jack of all trades.

Any help and discussion is welcome and appreciated.


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