[Boatanchors] Boatanchors Digest, Vol 131, Issue 22

[Rob Atkinson]

I don't recall exactly but when you look at the specifications for the
filters from Murata, they are expressed in some way so that you have
to double the figure to get the IF bandwidth.  I have no idea why.  I
am not an engineer so a lot of modern component specifications are
mysterious to me.

I put together a lot of information about all this--how to construct
the filter board, schematic diagram, filter assembly pinout, the
Murata part numbers, but no one was all that interested and I found
articles on building 75A-3 filters in ER and figured it was all rather
trivial and I was re-inventing the wheel.  I don't know what happened
to my information.

I think one of the ER articles is in issue number 64.  It may
reference the others.

here is the result of a mouser search:
http://www.mouser.com/Murata/Passive-Components/Signal-Conditioning/_/N-8bzui?P=1yyzvevZ1z0wkwmZ1z0ycabZ1z0zlftZ1z0z7l5
The five pin packages is what worked for me.  You have to click on the
data sheet to see the bandwidth.  it is the 6 dB fn +- X kc
specification so the bandwidth is 2X.  They are not extremely
expensive.

You don't wind up with this perfectly flat filter--it has some ripple
but it is better than having the two stages coupled with a capacitor
and nothing else, and I found that for casual AM ragchewing the
ceramics are fine.

I hope the link works.

73

Rob
K5UJ

>    Did you mean this?  I think you must halve the passband for the audio
> response for AM (unless you tune only one sideband) and I think its what you
> meant to say.
>