Saturday, February 16, 2019

Bypass the power supply to prevent cross feed

Using the old Germanium transistors provide some RF immunity. They have 1 MHz high frequency limit. This might be another reason to build a TRF receiver. A crystal set can perform quite well. With an AF amp even more so. I think this is part of the advantage the old timers had. The limits of their components were in their favor. In the final build I may add an RF amp which will help with sensitivity AND boost noise which could have been below the detector threshold. It is give and take. We get the bad with the good. Then a band pass filter could be used to help reduce out of band noise.
Anyway I like the little amp and it could be used in my next build. I don't have any variable capacitors yet. Peebles Originals has some in route. When they arrive I will add the front end and see how it works out.
Anyway this is the final schematic for the AF amp. I added some bypass caps (in the red box).
For the input to reference AC ground I need to bypass the battery. Without the bypass the signal is passing through the battery to ground. This could produce cross feed and cause instability.

No comments:

Post a Comment