Greetings,
While out using the home made PI detector that I posted a series of posts on I met Ken, another treasure hunter. He is also an engineer and we spent some time talking detectors. During the conversation he said now that you and built the one you have, if you built another one, would you do anything different. I told him, yes; I would add another gain stage and lower the gain in the other stages. He asked me why? I told him that even though the detector works great as it is and I have not experienced any instability, it has very high gain in the last two stages. The higher the gain is in any given stage the higher the probability is for that stage to become unstable under certain conditions. It is possible to build stable super high gain stages with proper compensation but they almost always require a PC board.
For any of you experimenters out there that are interested, I have attached the schematic of what I would do if I did it again. The total gain is the same as the one I am using now but the gain in the individual stages is reduced and there is less chance for things to become unstable.
God Bless and HH!!
Smitty II
While out using the home made PI detector that I posted a series of posts on I met Ken, another treasure hunter. He is also an engineer and we spent some time talking detectors. During the conversation he said now that you and built the one you have, if you built another one, would you do anything different. I told him, yes; I would add another gain stage and lower the gain in the other stages. He asked me why? I told him that even though the detector works great as it is and I have not experienced any instability, it has very high gain in the last two stages. The higher the gain is in any given stage the higher the probability is for that stage to become unstable under certain conditions. It is possible to build stable super high gain stages with proper compensation but they almost always require a PC board.
For any of you experimenters out there that are interested, I have attached the schematic of what I would do if I did it again. The total gain is the same as the one I am using now but the gain in the individual stages is reduced and there is less chance for things to become unstable.
God Bless and HH!!
Smitty II