KSB2 Mod for Increased Mike Gain

[Unifiedtx]

Does anyone remember a mod where a 5.6K resistor replaces the 1K resistor at
R14 on the KSB2 board for increased mike gain?  I cannot find my notes on this
mod.  I thought it was a KI6WX mod, but I can't find it in John
Grebenkemper's write-ups.  Thanks.  Roy Morris  W4WFB
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[Ron D'Eau Claire-2]

Yes. The original suggestion was to swap R14 and R2 on the SSB board. That
raised the input resistance and improved the mic sensitivity a great deal.

After some testing, it was decided that reducing R2 was a bad idea. Doing so
could allow the Speech IC, U3, to over-drive balanced modulator U5.

So leave R2 at 5.6 k. You can use any value handy from 5 to 10k for R14 to
improve the mic audio level.

Note that if you do that and select to attenuate the mic input level with
the MENU commands (set SSBA = 1), the amount of attenuation you get won't be
10 dB any longer. Few ops seem to use the mic input attenuator anyway or, if
they do, care if the attenuation is actually 10 dB.

Ron AC7AC

-----Original Message-----
Does anyone remember a mod where a 5.6K resistor replaces the 1K resistor at

R14 on the KSB2 board for increased mike gain?  I cannot find my notes on
this
mod.  I thought it was a KI6WX mod, but I can't find it in John
Grebenkemper's write-ups.  Thanks.  Roy Morris  W4WFB


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[Earl W Cunningham]

Roy, W4WFB wrote:

"Does anyone remember a mod where a 5.6K resistor replaces the 1K
resistor at R14 on the KSB2 board for increased mike gain?  I cannot find
my notes on this mod.  I thought it was a KI6WX mod, but I can't find it
in John Grebenkemper's write-ups."
==========
Although this is a popular mod for those using low-output dynamic mikes,
I don't believe it was ever included in the "official" mod list on the
Elecraft Web site.

I replaced R14 with a 6.8K resistor on my KSB2 to get adequate mike gain.
 Before that, I had to holler into the mike to get the VOX to trip.

73, de Earl, K6SE
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