Assembling and Using the KPA100/KAT100 EC2 Combo

Maximizing K2/10 Utility

Revision A

Ken Talbott – KE4RG

3/26/2015

This document describes how to retain all of the QRP and portable operating convenience of the Elecraft K2/10 transceiver while allowing QRO operation with the KPA100 and KAT100 assembled in an EC2 chassis.

The Elecraft EC2 Enclosure

Elecraft offers the EC2 enclosure which matches the K2 transceiver size, finish, and construction.  You may use this matching enclosure to house homebrew accessories for the K2.

The KAT100 ATU is available in two versions.  The KAT100-1 includes the complete low profile enclosure for the external tuner.  The KAT100-2 does not include a complete enclosure.   It does include the front and rear panels that allow you to mount the KAT100 in the taller EC2 enclosure.  The optional KAT100PNL allows you to convert your existing KAT100-1 into a KAT100-2.  The KAT100PNL provides the front and rear panels and three connectors (10-pin P4, 2-pin P3, and 2-pin P6).  These were not included with the KAT100-1. Be sure to remove pin 4 from KAT100 P4 or to clip it after installation!

The KPA100 Usage in the K2/100

When used to convert a K2/10 to K2/100, the KPA100 integral amplifier receives +13.8 VDC from an Anderson PowerPole connector on the rear panel.  A short cable from the KPA100 terminates in a 2-pin, 0.156" spacing, polarized jack (J4) and provides +13.8VDC to the host K2.  This jack plugs into the K2 RF board at P3 (AUX 12V).  If this J4 to P3 connection is not used, DC power must be provided to the K2 either via the coaxial DC connector on the rear panel of the K2 or the optional KBT2 internal battery.

Additionally, in this K2/100 configuration the RF input from the K2 to the KPA100 is obtained via a short coaxial cable terminated in a 0.156" spacing polarized 2-pin jack (J1) which mates with plug P6 (AUX RF) on the K2 RF board.

The K2/100 uses the KPA100 mounted speaker.  Audio from the K2 RF board at P5 (0.1" spacing 2-pin polarized plug) labeled SPKR is connected via jack J5 of the KPA100.

In the K2/100 configuration the KPA100 receives power and all control information for its microcontroller via the 10-pin dual row header plug (P1). This is mated by a short 10-pin ribbon cable to plug P4 on the K2.

The 9-pin rear panel connector of the KIO2 interface (included with the KPA100) is not used in this configuration.  It is available for communicating with a computer.  DO NOT USE A STANDARD 9-PIN RS‑232 CABLE.  DAMAGE TO K2 AND/OR THE COMPUTER WILL RESULT.  You may construct your own cable using the diagram in Figure 17 on Page 25 of the Elecraft KAT100 Automatic Antenna Tuner Manual.

The KPA100/KAT100 EC2 Combo

The primary impetuses for the KPA100/KAT100 EC2 Combo are the ability to retain very portable (one chassis) self-contained QRP operation (K2/10, KBT2 battery, and KAT2 tuner) as well as QRO operation when portability is not an issue.  Without the combo you may operate QRO or QRP with two appropriately connected chassis (K2/100 and KAT100).  The combo allows QRO, QRP, and portable operation with two appropriately connected chassis (K2/10 and EC2 with KPA100 and KAT100).  The combo allows you to disconnect the K2/10 transceiver from the EC2 and operate the completely self-contained (KBT2 battery and KAT2 auto tuner) QRP rig in a single chassis.

You will require the KPA100, the KAT100-2, and the EC2.  If you plan to use a KAT100-1 you will need to purchase the KAT100PNL.  In addition to the KIO2 included with the KPA100 you will need a KIO2 interface installed in the K2/10.  For maximum operating flexibility, you will want the KAT2.

NOTE: In order to ensure that the KIO2 in the K2/10 can provide adequate current to support the digital control subsystem, it is recommended that L1 (15-mH inductor) on the AUX2 board be replaced with a toroid consisting of 12 turns of #26 or #28 enameled wire on a FT25-43 or FT37-43 core.

As described above, the KPA100 amplifier requires RF input, DC power and control information. The KPA100 mounted speaker is not used and its cable may be removed or tied securely out of the way.  The K2/10 KIO2 interface is required to provide communications with the KPA100/KAT100 EC2 Combo.

The KPA100 receives +13.8 VDC from the Anderson PowerPole connector on the rear panel.  A short internal cable from the KPA100 terminates in a 2-pin, 0.156" spacing, polarized jack (J4) and provides +13.8VDC to the KAT100 AUX 12V (P3).

You must provide DC power to the K2/10 either via the coaxial DC connector on the K2 rear panel or the optional KBT2 internal battery.

In the combo configuration the rear panel RF output of the K2/10 (if KAT2 is installed use ANT1, otherwise use ANTENNA) is connected to the KAT100 rear panel AUX RF using a short 50-ohm BNC-to-BNC cable. 

The KAT100 AUX RF is connected internally to plug P6 (also labeled AUX RF).  The RF cable from the KPA100 (J1 or AUX RF) plugs into this P6.

Power and control information is shared between the KPA100 and KAT100 via the 10-pin ribbon cable (KPA100 P1 to KAT100 P4 Aux Control).

Using a short 50-ohm coaxial cable connect KPA100 ANT to KAT100 RF IN.

Connect an Elecraft 9-pin interface cable between the K2/10 KIO2 and the 9-pin connector of EITHER the KPA100 or the KAT100.  You may construct your own cable using the diagram in Figure 17 on Page 25 of the Elecraft KAT100 Automatic Antenna Tuner Manual.  This diagram illustrates how to include a third 9-pin connector for connecting to a computer.  If you construct the hydra cable ensure that the end with the shared computer connector is attached to the K2/10.  Neither the KPA100 nor the KAT100 provide the signals for computer interfacing.

When assembling the combo be very care to avoid pinching the power or RF cables connecting the KPA100 to the KAT100!  The ribbon cable is less of a problem.

Operation of the KPA100/KAT100 EC2 Combo

Connect your antenna of choice to ANT1 or ANT2 of the KAT100.  Connect the K2/10 ground, the EC2 ground (either one), and the chassis ground of all other station equipment to a common earth (do not daisy chain grounds).  Connect the Anderson PowerPole terminated cable to the KPA100 and the coaxial power plug to the K2/10.  Then turn on the power switch of the K2/10.  Operation is now equivalent to that of a K2/100.

When connected to the KPA100/KAT100 EC2 Combo the KAT2 is bypassed AS LONG AS THE KPA100 IS CONNECTED.  The menu entry PA has no effect. 

If the Tx power level is reduced to 10 watts the KPA100 is bypassed and KAT100 continues to function.

Additions and/or corrections are appreciated!

Ken - ke4rg@arrl.net