Minima Crystal filter

Started to measure all 30 pcs i have. 2 was really bad i put them in the wastebasket (nr 15, 19 ). Putt all f values in a spread sheet. Then it is simple to select the 8 X-tal with the closest frequencies. I put them on a pcb. and use 100pF as original loading capacitor, this give around 4kHz bw, try 200 pF but tis give below 2 kHz bw. Then I order 180 pF.

After testing this I try to change order of the X-tal, the effect was minimal, time to put them on the minima board. This measurement is on the minima board. Note the 3dB point and try to adjust BFO to +/- 400 Hz was not possible so i must change the circuit to succeed.

In teori the X-tal should not be mor spred then +/- 5% off BW 2.4 kHz means +/- 120 Hz the best 8 pcs i have spred -160 + 145 Hz, here is the result measured when mounting on the pcb.

After all I put murphy out of the shack and will son start the last step with the LP- filter,

stay tuned SM4HNG Leif.