Thursday, July 1, 2021

Converting the Andy Osc to a GE transistor

 My young advisor looked the previous post over and gave me two points to consider. The transistor I used was an audio transistor which is not capable of operating at RF frequencies and we should consider using GE diodes with the GE transistor.

Both points are well taken. I do have some transistors to try but am woo-ful-ly lacking in data and the SPICE models. I did find I have a model for the P416 RF amp.

The original circuit.

The AC128 appears to work well. Sadly it has a very low Ft.

Still functions with one 1N34.

Second 1N34 'breaks' the circuit. Why?
Consider the voltage drop across the 220k resistor.

The current is to high and the 220k resistor is dropping to much. Let us try a smaller resistor.

OK. the 10k resistor restores our circuit operation. 
Next step is to find a suitable core.
I have a green core (43) that should work in the short wave range. The coupling being tight we will have to observe the loading effect. That will be the next post.

No comments:

Post a Comment