Group, I believe there is an error in the schematic of the daylight again radio. The RX first mixer has the PTO going to the gate with the high impedance input, while the RF input is going to the gate with the 1K resistor.?
I think they need to be reversed.?
The band pass filter should be terminated into a high impedance and not low impedance. A low impedance termination will degrade the filter and the sensitivity becomes poor. This is what I have experienced in this build after many hours of tinkering.
Plots of the filter show about 10db loss when terminated into 50 ohms. I have not done plots with a higher termination impedance. In my build, flipping the two signals improved the performance dramatically. I have not increased the PTO gate termination resistor from 1K to a higher value. The PTO signal measured 3.4Vp-p with the 1K.
All in all, the receiver sounds pretty darn good!!
73
Barry
