[Boatanchors] Single-Chip NBFM Detector?

[N4ch at aol.com]

Hello.....
 
What kind of receiver are you wanting to put the FM  detector circuit in ?  
 Reason I ask is the circuitry upstream (most  notably the IF crystal or 
perhaps L/C filtering) must be sufficiently wide  enough so that the FM 
"channel" you want to receive isn't badly  clipped.   If the widest available 
filter is only 5-6 KHz wide  (total), this may present problems, but if you have 
a receiver that works well  on AM and has a selectable bandwidth of at 
least 10-15 KHz or so you may be  OK when you want to demodulate an FM signal 
that's deviating +/- 4 or 5  KHz.   I've built up several FM 
amp/limiter/detector circuits using  30-35 year old ICs such as the CA-3065 and CA-3089 
(seems like I built up  something for a Gonset Communicator to use on 6 meters FM 
some 30-35 years ago),  but these of course are 14-16 pin ICs that DO 
require a handful of  parts.   Most all are simple resistors and capacitors, but 
there is an  inductor (and resonating cap) that is used to demodulate the 
incoming FM signal  in a fairly easy to build and adjust quadrature detector 
circuit.   If  there's a simpler-to-build design (requiring fewer parts, no 
inductors to tune,  etc.) I've not seen it, but then again I've not looked.   
Not knowing  what you want to put the FM back-end into, I'd say the 3089 
might be a good one  to start out with and try (and I have a handful of NOS 
ICs).........it has  sufficient limiting such that only 3 or perhaps 4 gain 
stages (such as the  receiver's RF amp, mixer, and an IF preamp) need to be 
ahead of it for good  results.   Of course good layout practices must be 
observed for  stability, as you will probably be asking the IC to provide a 
minimum of 80-90  dB of gain to do the job it needs to do.   Got a couple 
hamfests I'm  going to try to attend this week-end.........I'll try to get some 
more info  together in a couple days if the 3089 looks like something you may 
want to  try.
 
73, Herman, N4CH.