[TenTec] Switched audio filters

[Jim Allen]

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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