Message	Date	From	Subject
1161	2007-11-11 20:48:35	bdebbasch	Double-Tuned Circuits loaded with a FET
I have played with DTC (EMRF 3.14) and used RFSim99 to verify the frequency responses. Everything match. My question is related to the practical implementation of DTC in receivers (VHF as an example). In those receivers, I am seeing the output of the DTC going to the gate of a FET. The gate also has a resistor (generally a few k) to ground and CE is much higher than the calculated value. My questioni s the following: how is this circuitry presenting a 50 ohms load to the DTC? Simulation shows that the performance of the filter is dramatically impacted when the loading impedance diverges from the expected value. I am basically looking for a pointer that show me how is the filter working in these conditions.
1162	2007-11-12 18:38:47	Allison Parent	Re: Double-Tuned Circuits loaded with a FET

I have played with DTC (EMRF 3.14) and used RFSim99 to verify the
frequency responses. Everything match. My question is related to the
practical implementation of DTC in receivers (VHF as an example). In
those receivers, I am seeing the output of the DTC going to the gate
of a FET. The gate also has a resistor (generally a few k) to ground
and CE is much higher than the calculated value.

My questioni s the following: how is this circuitry presenting a 50
ohms load to the DTC? Simulation shows that the performance of the
filter is dramatically impacted when the loading impedance diverges
from the expected value. I am basically looking for a pointer that
show me how is the filter working in these conditions.