[time-nuts] KD2BD WWVB receiver/decoder in QEX

[Charles Steinmetz]

Paul wrote:

>post down conversion to 10 Khz I was scratching my head as to why not
>the TL08X series.

Input voltage noise.  Unless you need the low input current of the 
FET part, there is no need to take the noise hit.  If you *do* need 
the low input current, there are 4 or 5 generations of FET-input 
opamps that are all far superior to the TL0xx parts.  Take a look at 
the OPA134/2134/4134, for example.  (I haven't used TL0xx opamps 
since the '70s.)

BTW:  I suggested using NE5532s instead of LM387s and said they were 
better in every way.  Comparing the LM387 to the NE5532, one might 
notice that the bandwidth spec of the 5532 is lower (10MHz) than that 
of the 387 (15MHz).  But what is important for most applications is 
not the small-signal BW, it is the power BW (full-output BW), which 
depends on the slew rate, not on the SSBW.  The 5532's 9v/uS slew 
rate supports a PBW of 140kHz, while the 387's PBW is only 75kHz (S/R 
is not stated).  (This tells us two things -- first, that the 387's 
slew rate must be <5v/uS; and second, that the 387 has less phase 
margin than the 5532.)

Best regards,

Charles