K3 hardware - The Mystery Mods?

[Don Rasmussen]

There are two hardware changes that I know about. One
is for the KXV3 where very strong signals on the
external antenna might cause purity problems on the
transmitted signal on another antenna in rare cases.

The other is an RF board modification to the AGC
circuit that improves on a scenario that I noticed
early on with my K3.

I saw the AGC pumping while receiving a CW signal
using a 800hz DSP filter setting, but heard no QRM.

I found an S9 +20 db signal was about 2 khz away.

Turning on the 1.0 roofing filter made the pumping
disappear with no degradation of the signal I was
listening to whatsoever, but Elecraft seems to want to
improve this condition for those that don't have other
that the stock 2.7 filter. Something will be released
shortly.

There are five or six SMT resistors involved and at
first I chickened out on doing the mod for myself, but
after the K2's I built I also built a SoftRock 40 and
it has SMT in roughly the same scale so I think I can
do it.

After some investigation (GOOGLE), I found that there
are some "Hot Air" tools for this purpose, but they
are -expensive-. I expect that Elecraft owns one and
would perform updates using this.

But I updated my OMNI VI+ with the SSB mod (discrete
components plus SMT), and made that SoftRock work, so
it's just a matter of deciding whether to "ship and
forget", or sit down and have a small project.

All that having been said - it's very hard to find any
time away from the radio, it's a real treat and an
absolute joy to operate.
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[Brett Howard]

There is no need for a hot air rework tool unless you're working with QFP's
or BGA's or something like that.  For SMT resistors you can do it with just
an iron and a bit of a quick job with a slight flick technique or even
better you get a cheapy second iron so you can heat both sides and lift it
off the board.  If you're really into getting the right thing they sell
irons that work like chopsticks for the task but again not really needed.
I'd bet that Elecraft would replace the module if there was to be an IC
change (or they'd offer to do the mods for a nominal fee) but for a few R's
and C's being changed... I think that would be perfectly acceptable to just
be able to get a few parts from them (or just have the parts on hand) and
get a set of instructions.

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Don Rasmussen
Sent: Wednesday, February 27, 2008 11:14 AM
To: ElecraftQRXQRXQRX List
Subject: [Elecraft] K3 hardware - The Mystery Mods?

There are two hardware changes that I know about. One
is for the KXV3 where very strong signals on the
external antenna might cause purity problems on the
transmitted signal on another antenna in rare cases.

The other is an RF board modification to the AGC
circuit that improves on a scenario that I noticed
early on with my K3.

I saw the AGC pumping while receiving a CW signal
using a 800hz DSP filter setting, but heard no QRM.

I found an S9 +20 db signal was about 2 khz away.

Turning on the 1.0 roofing filter made the pumping
disappear with no degradation of the signal I was
listening to whatsoever, but Elecraft seems to want to
improve this condition for those that don't have other
that the stock 2.7 filter. Something will be released
shortly.

There are five or six SMT resistors involved and at
first I chickened out on doing the mod for myself, but
after the K2's I built I also built a SoftRock 40 and
it has SMT in roughly the same scale so I think I can
do it.

After some investigation (GOOGLE), I found that there
are some "Hot Air" tools for this purpose, but they
are -expensive-. I expect that Elecraft owns one and
would perform updates using this.

But I updated my OMNI VI+ with the SSB mod (discrete
components plus SMT), and made that SoftRock work, so
it's just a matter of deciding whether to "ship and
forget", or sit down and have a small project.

All that having been said - it's very hard to find any
time away from the radio, it's a real treat and an
absolute joy to operate.
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