[Elecraft] K2 AF noise level?

[Howard W. Ashcraft]

I thought of that, too.  However, I would like to see whether clean, full range audio works better on ssb.  Also, passive filtration results in some insertion loss.  Anyway, the point is to experiment, which is what I will be doing.  It would be interesting to compare the approaches.  Thanks.

Howard W. Ashcraft, Jr.
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



-----Original Message-----
From: David A. Belsley [mailto:belsley at bc.edu]
Sent: Wed 5/17/2006 3:15 PM
To: Howard W. Ashcraft
Cc: Darwin, Keith; elecraft at mailman.qth.net
Subject: Re: [Elecraft] K2 AF noise level?
 
     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






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To ensure compliance with requirements imposed by the IRS, we inform you that any tax advice contained in this communication (including any attachments) was not intended or written to be used, and cannot be used, for the purpose of (i) avoiding penalties under the Internal Revenue Code or (ii) promoting, marketing or recommending to another party any transaction or matter addressed herein.

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