The K2 modules (KSB2, KNB2, K160RX, KAT2) add useful capabilities to the
K2. However, there are times when you might want to remove one or more modules
from your K2. Installing many of the modules requires that you remove jumpers
and/or components from the RF board of the K2, so you can't remove the modules
by simply unplugging them. I do not yet have the KIO2 or the KAF2, so I have
not yet designed Un-Modules for those modules.
removing modules without rework
Mark J. Dulcey, KE1L (
The usual procedure for removing a module is to unplug the module, and then
put back the removed components and jumpers. If you are permanentely removing
the module, that's fine, but you might want to take it out temporarily, for
any of the following reasons:
Enter the Un-Modules! By building these simple circuits on header connectors,
you can remove one or more modules from your K2 without any need to modify
your RF board. The Un-Modules are simple and inexpensive to build, too!
- Troubleshooting a problem
- Comparative performance testing (how does a module affect sensitivity,
dynamic range, or ultimate filter rejection?)
- Minimizing weight and/or power consumption for field use
Using Un-Modules isn't quite equivalent to removing a module by the other
procedure. The leads to the jumpers and components are longer than if they
were soldered to the RF board, so signal leakage and stray inductance and
capacitance will be higher. They should be good enough for most purposes,
By the way, you don't need to build an Un-Module for the KAT2. But I cover
removal of it anyway.
Please let me know if you build the Un-Modules, and if you find them useful.
If you have any comments or suggestions, I'd love to hear from you.
What you'll need
First, you'll need appropriate header connectors. You want headers with a
single row of pins, spaced at .100 inch intervals. (There are now also metric
headers with pins at 5mm spacing, you don't want those.) The ones used by
Elecraft in the K2 are made by Samtec
; they can be bought directly from them, or from a number of distributors,
. Unfortunately, the distributors that are most friendly to small orders
from hams, Digi-Key
, do not carry them. Fortunately, alternatives are readily available. You
can either buy headers of the exact lengths needed, or buy a single large
header strip which you can cut to length. Gold-plated headers are preferred,
as the K2 uses gold-plated sockets. The Un-Modules in the pictures were built
using a Mill-Max 800-10-064-10-001 pin header strip (Digi-Key ED7264-ND);
this strip has 64 pins, which is enough to build all the Un-Modules with
some left over for possible future KIO2 and KAF2 Un-Modules.
You will also need the components that you removed from the K2 RF board when
you installed the modules, or equivalent components. (I used new parts from
my collection.) Finally, you will need short lengths of bare wire, such as
To build the Un-Modules, you'll need a good soldering iron (the one you used
to build the K2 will be fine), diagonal cutters, needle-nose pliers (to bend
the component leads and to hold the components while you solder), solder,
paint or nail polish, and a small vise to hold the connectors while you build.
To prepare for installation, remove the top cover of your K2. You will not
need to remove any other covers unless you're installing the Un-K160RX; that
one requires removal of the heat sink. (But read the directions first!!)
To replace the KSB2, you'll need to build three Un-Module parts. You will
need the following:
1 12-pin header
2 3-pin headers
1 .001uf ceramic capacitor (C167)
2 bare wires
The .001uf capacitor is soldered between pins 7 and 12 of the large header.
Each of the small headers gets a jumper wire soldered between pins 1 and
3. Mark the pin 1 end of the long header (I used orange nail polish, left
over from Halloween); it goes toward the left side of the K2 when plugged
in. The small headers can go in either way, so I didn't bother to mark pin
1 of those.
To install the Un-KSB2, first remove the KSB2 (carefully). Plug one of the
small headers into J9, and the other into J10; both are near the right of
the space the KSB2 occupied. Plug the large header into J11, with pin 1 toward
the left side (viewed from the front) of the radio.
If your K2 has any filter settings configured to OP1, they will not work
with the KSB2 removed. (The receiver will be very insensitive if you choose
any such filter.) If you're planning to keep the KSB2 out of your radio,
you may want to use the filter calibration procedure to change those settings
back to using the standard variable filter.
Replacing the KNB2 requires just one Un-Module, but you do need to solder
three components to it. (The pictures above show front and rear views of
the same Un-Module.) The parts list:
1 8-pin header
2 470-ohm 1/4 watt resistors (R88 and R90)
1 100-ohm 1/4 watt resistor (R89)
Solder 470 ohm resistors between pins 1 and 2, and between pins 5 and 6.
Position the resistors toward the back of the header. (This is important;
if they point toward the front, the Un-Module will bump into the KSB2.) Then
solder the 100-ohm resistor between pins 1 and 6, going over the top
of the header. (Again, you're avoiding the front.) Mark pin 1.
To install, remove the KNB2, then plug the Un-Module with pin 1 toward the
left side (viewed from the front) of the K2.
This is the simplest of the Un-Modules to build. The parts list:
1 16-pin header
1 bare wire
Solder the bare wire between pins 1 and 7. Mark pin 1. You're done!
The installation of the Un-160RX, on the other hand, is the most involved
of the Un-Modules, mostly because the K160RX is physically inconvenient to
take out. Basically, to get the K160RX out, you have to reverse the process
that you used to install it. (See the K160RX manual.) And after you're done,
you will need to redo the 80-meter transmit alignment if you plan to use
that band. Because this one is such a pain to install, I haven't actually
tested it, but I am confident it will work.
Removing the KAT2
Since you didn't have to make any changes to the RF board (other than installing
the Aux RF connector) when you installed the KAT2, you don't need an Un-Module.
If you just want the KAT2 out of the circuit for testing, all you have to
do is unplug the AUX RF connector from the RF board, and the control connector
from the control board. Then take the cover off the main antenna input, and
you're set. On the other hand, if you actually want the KAT2 out of your
radio (it is the heaviest of the modules), you'll have to reverse the procedure
you used to put it in. (See the KAT2 manual.)