K2? Easy peasy

[David Perrin]

Hi-

I need to get as much Mic. gain as I can with the current Mic. I have had no need to adjust it for 15 years until now as I use CW.

My manual is not available.

Can someone give me a lesson in Mic. gain adjustment??

Thanks, Dave  K1OPQ
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[Jim Brown-10]

On 1/27/2018 8:32 PM, David Perrin wrote:
> I need to get as much Mic. gain as I can with the current Mic. I have had no need to adjust it for 15 years until now as I use CW.

I developed a simple mod that adds about 6 dB and adds some low
frequency rolloff. I don't recall details (that was 15 years ago), but I
think W3FPR has notes on it somewhere. It involves changing a few
resistors and one or two caps in the audio chain. I recall that there
other mods farther up the chain.

73, Jim K9YC

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[Don Wilhelm]

All,

I do indeed have that mod, but I thought it was mainly for Low Frequency
rolloff.  I do know that it works quite well for that purpose, but I
don't know about the 6 dB gain.

Change C34 to 0.47uF, and change C32 to something in the range of
0.003uF to 0.005uF.

If you want additional gain, I would recommend the KI6WX KSB2 increased
KSB2 RF Gain mod.  It adds gain without the possibility of overloading
the Speech Compressor.  If you do that mod, change R9 to 15k and add a
1k resistor between P1 pin 5 and the base of Q3.

73,
Don W3FPR
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[Don Wilhelm]

All,

On the KI6WX mod, the value of R9 should be 1.5k instead of 15k as
stated. Please excuse my "late night fingers".

Those two resistor changes are only necessary if the KI6WX KSB2 mod is
added to a K2 with the KPA100 installed.

73,
Don W3FPR

------------------------------------------------------------------------

All,

I do indeed have that mod, but I thought it was mainly for Low Frequency
rolloff.  I do know that it works quite well for that purpose, but I
don't know about the 6 dB gain.

Change C34 to 0.47uF, and change C32 to something in the range of
0.003uF to 0.005uF.

If you want additional gain, I would recommend the KI6WX KSB2 increased
KSB2 RF Gain mod.  It adds gain without the possibility of overloading
the Speech Compressor.  If you do that mod, change R9 to 15k and add a
1k resistor between P1 pin 5 and the base of Q3.

73,
Don W3FPR
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[Jim Brown-10]

I'll poke around and try to find my notes.

73, Jim

On 1/27/2018 10:48 PM, Don Wilhelm wrote:
> I do indeed have that mod, but I thought it was mainly for Low
> Frequency rolloff.  I do know that it works quite well for that
> purpose, but I don't know about the 6 dB gain.
>
> Change C34 to 0.47uF, and change C32 to something in the range of
> 0.003uF to 0.005uF.


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