[Elecraft] Back to the KAF2

[Baker]

On Mon, 20 Oct 2003 18:11:31 -0400, Dale Boresz wrote:
>Wolf,
>
>I can appreciate your feelings regarding the hiss, which is
>particularly
>noticeable when using high-quality headphones. However, there's=
 a
>relatively easy way to restore the "KAF2 Sound" while retaining=
 the
>utility of the KDSP2 module. I removed the components from the=
 KAF2
>which make up the eliptical filter which is responsible for=
 taming
>the
>hiss. Those components are: R11, R12, R13, L1, L2, and C1 - C4.=
 I
>mounted the components in a 'dead bug' configuration (against=
 the
>surface of a blank pc board with the component leads up in the=
 air),
>and
>wired them together to duplicate the filter.
>
>Since I didn't care about the turn-on thump, I removed the two=
 FET's
>Q5
>and Q6 from the KDSP interface board (not the DSPx module, but=
 the
>board
>into which it plugs), and used the pads to connect the filter=
 as
>follows:
>- the (S)ources are connected to the inputs of the filter (R11,=
 and
>R12)
>- the (D)rains are connected to the outputs of the filter=
 (across
>R13)
>
>That's it. It works great, and sounds just like the KAF2 when
>neither of
>the filters are selected.
>
>Regarding the 'artifacts' of the DSP - welcome to DSP. I've=
 never
>heard
>a DSP unit without those artifacts; they're just part of the
>package. I
>also have an ICOM 746PRO and the effects of the DSP are very=
 similar
>sounding. I'll admit they're not necessarily pleasant, but the=
 DSP
>can
>make the difference between some copy and no copy at times.=
 I'll
>happily
>trade the significant reduction in noise for a bit of rhaspiness=
 on
>the
>cw note. To me, under noisy band conditions, there is much less
>listening fatigue with the KDSP on, than with it off.
>
>If you decide to try this and have any questions, I'll be happy=
 to
>help
>however I can.
>
>73,
>Dale / wa8sra
>
>Wolf-Ruediger Juergens wrote:
>
>>Hello,
>>After using the KDSP over the month i decided to remove the=
 KDSP
>>and plug
>>back the KAF2 in my K2. The always present noise (hiss) in the
>>headphone
>>makes me angry. Also the artifacts with weak signals...
>>
>>73 Wolf, DL2WRJ
>>
>>
>
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All,

I have not noticed any significant increase in hiss with the=
 KDSP2, 
however I find the nr artifacts on SSB so annoying I only use the=
 
notch filter.

I beleive that the success of nr on SSB is very dependant on the=
 
algorithm used. My findings are that the nr on my FT1000MP is=
 next to 
useless, the KDSP2 is better at nr, but the resultant audio is=
 not 
very pleasant to listen too.

The best I have found is from a small British company BHI with a=
 
product range that in practice gives good nr with minimal=
 artifacts.
They are producing an after-market PCB for the Yaesu FT817. 

It is interesting that samples of this board have been shipped to=
 
Japan, and during  a conversation with a representative of Yaesu=
 in 
the UK he agreed  that the company  might be looking at ways of 
improving their nr algorithms.

73

Stewart G3RXQ
-- The Bakers' Home
-- baker@nildram.co.uk on 21/10/2003