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: [EMAIL PROTECTED]
________________________________
From: Darwin, Keith [mailto:[EMAIL PROTECTED]
Sent: Tue 5/16/2006 6:45 AM
To: [email protected]
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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