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See Also related topic KSB2_IMD_ModDate: Wed, 05 Sep 2001 18:48:50 -0500

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Date: Tue, 04 Sep 2001 22:26:39 -0700
From: "John Grebenkemper, KI6WX" <KI6WX at pacbell.net>
Subject: Re: [Elecraft] KSB2 modifications for PSK

Eduardo;
My understanding is that the resistor value changes and capacitor value
change will be incorporated in the next revision of the KSB2 kit.  I don't
believe that Wayne is planning any other changes.  Putting a 5.6K resistor
across R1 is my idea to avoid clipping in the NE602 if you have plenty of
mike output, or you use PSK31 and want to leave compression enabled.  Don't
do it if you have a low output mike because you might not have enough drive
to get full output on the higher frequency bands.  Except for PSK31, doing
this change is not very critical because any out of band audio
intermodulation distortion will be removed by the SSB filter.
- -John
 KI6WX

- ----- Original Message -----
From: "Eduardo Jacob" <edu at tass.kender.es>
To: <elecraft at qth.net>
Sent: Tuesday, September 04, 2001 6:12 AM
Subject: [Elecraft] KSB2 modifications for PSK


> I will begin mounting soon the KSB2 module. I have read the modifications
> proposed by KI6WX, they seem to be fully approved by Elecraft, I also read
> some days ago that somebody stated that these mods will be included in new
> versions of the board, so the question is: should I directly make the mods
> to my board? I also understand that in the general case the addition of a
> 5.6K resistor across R1 is not recomended.
>
> Regards
>
> Eduardo/EA2BAJ #2061

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Date: Wed, 05 Sep 2001 18:48:50 -0500
From: Dave Gingrich <gingrich2 at dcg.org>
Subject: Re: [Elecraft] KSB2 modifications for PSK

At 22:26 9/4/2001 -0700, you wrote:
>Eduardo;
>My understanding is that the resistor value changes and capacitor value
>change will be incorporated in the next revision of the KSB2 kit.  I don't
>believe that Wayne is planning any other changes.  Putting a 5.6K resistor
>across R1 is my idea to avoid clipping in the NE602 if you have plenty of
>mike output, or you use PSK31 and want to leave compression enabled. 

It should be pointed out that the version 2 of the firmware adds an RTTY mode which separately saves
compression settings for RTTY, and four more filter/BFO setups each for RTTY normal and reverse.  I doubt
the mod is needed for rigs with ver 2 firmware (see the release notes).

- -Dave

=====================
Dave Gingrich, K9DC
Indianapolis, Indiana
Dave at dcg.org

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Date: Thu, 6 Sep 2001 05:06:01 EDT
From: JohnK1JD at aol.com
Subject: Re: [Elecraft] KSB2 modifications for PSK

  Having operated both PSK31 (and MFSK ) in RTTY-inverse mode using the new 
Rev 2 firmware, there is no question that an unmodified KSB2 board works well 
as is (compression off). I set the K2 for 5 watts output but only drive it to 
2-3 watts by adjusting the sound card output. IMD reports have been 
excellent. The additional benefit of running the K2 at lower power is 
improved frequency stability since internal temperature change is minimized. 

73,
John  K1JD
Jamestown,  RI
IOTA NA31
K2's #139 & #583

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Date: Thu, 6 Sep 2001 06:48:53 -0400
From: "Bob Lewis \(AA4PB\)" <rlewis at staffnet.com>
Subject: Re: [Elecraft] KSB2 modifications for PSK

> there is no question that an unmodified KSB2 board works well
> as is (compression off).

It does, but adjustment is a bit more critical without the
modification. One of the things you have to watch is that the required
sound card level changes from band to band; the lower bands require
more audio drive for the same power output. If you are not careful you
can end up driving the K2 into ALC action and generating IMD on the
higher bands if you leave the sound card levels set for one of the
lower bands.

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Date: Thu, 06 Sep 2001 10:29:17 EDT
From: JohnK1JD at aol.com
Subject: Re: [Elecraft] KSB2 modifications for PSK

<<It does, but adjustment is a bit more critical without the
modification. One of the things you have to watch is that the required
sound card level changes from band to band; the lower bands require
more audio drive for the same power output. If you are not careful you
can end up driving the K2 into ALC action and generating IMD on the
higher bands if you leave the sound card levels set for one of the
lower bands.>>

It is prudent to ALWAYS check the sound card level, not only band to band but when changing frequency
(clicking on another waterfall signal) within a band. The level needs to be fine tuned from one part of
the filter passband to another. 

73,  John

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