[Elecraft] K2 AF noise level?

[David A. Belsley]

     Why not build yourself a simple low-pass audio filter?  Even a  
simple capacitor across the earbud leads will do quite a bit.  Try  
10mf or 20mf or even 50mf.  If that isn't satisfactory, a slightly  
more sophisticated single-section LC filter would sure do what you  
want.  Check the Handbook for needed values.

best wishes,

dave belsley, w1euy


On May 17, 2006, at 4:43 PM, Howard W. Ashcraft wrote:

> One source of noise is in the K2 audio amplifier.  It isn't much of  
> a problem with the standard speaker since there is a built-in high  
> frequency roll off.  However, if you use very good quality earbuds  
> that were designed for music, the hiss comes through loud and  
> clear.  I like to use the buds because they block out virtually all  
> ambient noise and let me concentrate on CW.  (I need all the help I  
> can get).
>
> I have ordered some sample chips from National Semiconductor to see  
> if a low noise headphone amp will improve the situation.  I  
> probably won't get the chips for another two weeks and will have to  
> spend some time experimenting, so I probably won't be able to  
> report for a while, but will report back when I do.
>
> Howard W. Ashcraft, Jr.  W1WF
> Hanson, Bridgett, Marcus, Vlahos & Rudy
> 425 Market Street, 26th Fl.
> San Francisco, CA 94105
>
> ph:     415.995.5073
> fax:    415.541.9366
> e:       hashcraft at hansonbridgett.com
>
> ________________________________
>
> From: Darwin, Keith [mailto:Keith.Darwin at goodrich.com]
> Sent: Tue 5/16/2006 6:45 AM
> To: elecraft at mailman.qth.net
> Subject: [Elecraft] K2 AF noise level?
>
>
>
> Hey 'Crafters,
>
> I'm debating between the KAF2 or an outboard audio filter for my K2.
> Possible choices are the SCAF-1 and an Autek QF1A.
>
> My goal is to greatly reduce the hiss that is there in the headphones
> when the narrow CW filters are engaged.  I'd also like to add some CW
> selectivity.  A notch would be great too.
>
> KAF2 has the benefit of being integrated into the rig but doesn't  
> offer
> lots of flexibility.  The others are external but give you more  
> control
> over the filtering.
>
> How well does the KAF2 kill the hiss?  I assume it does great for  
> that.
> Does it add any noise back in?
>
> - Keith KD1E -
> - K2 5411 -
>
>
>
>
>
>
>
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-------------------------------------
david a. belsley
professor of economics