[regenfreak]

I have replaced the lossy cores by T50-6 for the 5-pole 10.7MHz Chebyshev with a bandwidth of 300kHz and 330ohms I/O impedance. The insertion loss is about -6bd including some mismatch losses with the L-pads. Tuning is very sharp and it is very difficult to make it perfectly flat and symmetrical in practice. So this is the best I can get so far. The S21, S11 and group delay are attached.

I will compare the overall responses between the following IF Amp and bandpass configurations:

1) 280kHz ceramic filter ---->CA3053 cascode IF amp--->280kHz ceramic filter

2) 280kHz ceramic filter ----> CA3053 cascode IF amp------> 5-pole 300kHz Cherbyshev

3) 280kHz ceramic filter --->LA1222 IF amp--->280kHz ceramic filter---->LA1222 IF AMP--->two 280kHz ceramic filter in cascade (total 4 ceramic filters like the Kenwood KR-9600)

4) 280kHz ceramic filter --->LA1222 IF amp--->280kHz ceramic filter---->LA1222 IF AMP--->5-pole 300kHz Cherbyshev

LA1222 is two IF amps combined in one package. I am building the TA7303P IF amp and discriminator IC using homemade discriminator coil with a blank Toko style transformer. I can add a signal strength meter for the TA7303P later. The MPX decode is TA7343AP.

Further experiment with the TAA661B chip has been futile. I swapped different 10.7MHz tank coils for the quadrature detector with different impedance and Qs. I can only get mono with some audio distortion, potentially due to the mismatch in impedance and Q. I do not bother to mess about with the value of the damping resistor which affects the loaded Q of the LC quadrature detector coil. There is plenty of gain and selectivity though. I strongly believe the TA7303P IF amp and discriminator IC will be much better.