[TenTec] Switched audio filters

[Al Gulseth]

AH-1 or AF1?

73, Al

On Wed March 23 2016 10:51:18 pm Jim Allen wrote:
> I just built an audio filter from Elecraft, AH-1.  It went together on a
> Sunday afternoon, so easy even a lawyer could do it, and if I had known how
> well it worked, how much it helps digging out weak signals, I would have
> built it before now.
>
> 73 de W6OGC Jim Allen
>
> Sent from my iPad
>
> > On Mar 23, 2016, at 22:15, Al Gulseth <wb5jnc at centurytel.net> wrote:
> >
> > From what I've seen (these are all duals, there are also quad versions of
> > most?) the NE5532 is noted for a good price/performance (low noise) ratio
> > for an AF active filter. The LM833, TL072/82, and NJM2068 might also
> > possibly be good candidates. Even the lowly LM358 might be usable with
> > the caveat of adding a pull down resistor (drawing about 1 ma) to
> > eliminate crossover distortion. (Info per ARRL's EMRFD p. 3.25.)
> >
> > Disclaimer: as they say, YMMV....
> >
> > 73, Al
> >
> >> On Wed March 23 2016 12:03:01 pm Tim wrote:
> >>
> >> I copied the 208 filter as well, even etched the pc board. I wired it
> >> for the 515 and gave it to my Dad for Christmas one year. I have that
> >> filter, but I know the chip isn't made anymore. I would guess that an
> >> ordinary audio op amp would work. So yeah we can see what someone else
> >> might suggest.
> >
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