[TenTec] Switched audio filters

[rick@dj0ip.de]

Jim,

Indeed it looks good and the youtube demo is impressive, but it is HUGE.
It's as big as the YouKit radio (HB-1B).

I found another, certainly not as good, but tiny and half the price.
It's called "Hi-Per Mite" from Four States QRP Goup (designed by NM0S).
I think this would be a better fit for the HB-1B.
The AF-1 would be a nice option for the Scout when used at home or portable,
other than backpacking.

Obviously buying a kit like this is much easier than starting from scratch
and building your own.
Back in my building days, I was working in the HF lab of Rhode und Schwarz
and had every thinkable instrument available for measuring and optimizing my
AF and RF filters.

Today?  I have my ears.  Nothing else to measure with.  

73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)



-----Original Message-----
From: TenTec [mailto:tentec-bounces at contesting.com] On Behalf Of Jim Allen
Sent: Thursday, March 24, 2016 4:51 AM
To: wb5jnc at centurytel.net; Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Switched audio filters

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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