Picture of the Test Setup used for my earlier BPF Measurements

I have added the picture above to show the test setup used for obtaining the measurements detailed in my previous blog. The picture was taken whilst testing the response of the BPF at 7.1 MHz. A crocodile clip supplying 5 volts to the 40 Meter BPF PCB Band Select Pin can be seen temporarily connected to activate the appropriate switching diodes for this purpose. Two terminating resistors (I cheated and used 47 ohm rather than ideally 50 ohm !) can be seen temporarily soldered to the input and output ports of the BPF on the underside of the PCB. The oscilloscope probes set at x10 are shown connected to and monitoring the voltage across these resistors on the two channels of the oscilloscope which are both set to display at 10mV / cm. The larger trace on the oscilloscope therefore represents an actual input signal voltage of 710 mV peak to peak and the smaller trace an output signal voltage of 320 mV peak to peak going to and coming from the BPF when connected to the DDS which is shown set to deliver a CW output of  7.100000 MHz. The insertion loss of the filter when measured under these conditions thus appears to be approx 6.9 dB. Also note the 180 degree phase reversal which has occured to the signal during its passage through the BPF.