Hello fellow BITX'ers,
Because I want do do some experiments with a ladderfilter on 9 MHz, I
studied the amplifier stage Asshar discribed and used in his BITX20.
I have some questions about it.
- I understand that the input and output impedance depends on the
resistors Rf and Re: Rf*Re=Rout*Rin. In the exemple with Rf=1000,
Re=10 and Rin=50, Rout becomes 200. But what happens if the input
is 100? There will be a mismatch but where will it be? Is the output
impedance fixed because of Rload (220 in the schema) and will be the
mismatch at the input of the amplifierstage?
- I studied the ladderfilter theory and different C's means different
input and output impedance of the filter. How to match the amplifier
to these impedances? Witch resistors do I have to change for the
exemple of 100? How to calculate them?
- The last question is about the two amplifier stages around the
ladderfilter. Left of the filter the emittor resistance is 220. Right
of the filter the emittor resistance is 470. The other resistors
around Q2 and Q3 are the same.Why is this? Does this has anything to
do with matching the impedance?
I hope someone will spend some time to answer my questions.
73
Ruud,
PE2BS
