[Elecraft] KSB2 Increased Gain Modification

[Mike Harris]

G'day,

> I'm pretty sure that you will find that the "IMD mod" *has* been
> incorporated into the KSB2... a long time ago.

I think you might be referring to the ALC time constant change to improve
IMD in PSK31 transmissions, this is just a few component changes.  These
component changes are now standard KSB2 issue.

The other mods from KI6WX are:

1.  Crystal filter bandwidth for which most reports seem to favour 2.5kHz.
2.  Increased gain of the order of 10dB by circuit changes around U5
(balanced modulator).  Improves output on 10 metres due to marginal gain in
the KSB2.
3.  Reduced IMD by adding a resistor across U5 pins 1 and 2 to reduce
clipping on its input. Note: this should only be done in conjunction with
(2.) above otherwise the resulting drop in gain of the order of 6dB will
make the overall KSB2 gain even more marginal.

It seems that most of the problems with low audio from mic's should be
overcome by (2.) above, merely adding af gain will drive you into the IMD
situation (3.)

I see a little mod kit coming on.

Regards,

Mike VP8NO (IOTA SA-002)
GQRP 10148
QRP-Canada #57
K2/100 #1400