ELECRAFT K3 HIGH-PERFORMANCE 160 – 6 METER TRANSCEIVER K3EXREF FREQUENCY LOCK OPTION INSTALLATION AND OPERATION Revision A2, October 31, 2012 Copyright © 2012, Elecraft, Inc.
Contents Introduction............................................................................................................................................. 3 Customer Service and Support ............................................................................................................................ 3 Using the K3EXREF............................................................................................................................... 4 Installing the K3EXREF ....................
Introduction The K3EXREF option locks the K3's reference oscillator frequency to an external 10 MHz source by automatically controlling the REF CAL function. While locked to the external source, the K3’s reference oscillator frequency is maintained within 2 Hz. Since the K3EXREF does not phase lock the K3’s reference oscillator, the external 10 MHz source has no impact on the K3’s phase noise performance. For best performance we recommend your K3 be equipped with the KTCXO3-1 high stability (0.5 ppm typ.
Using the K3EXREF If you are installing the K3EXREF yourself, go directly to Installing the K3EXREF below. The operation of the K3EXREF is automatic, once a suitable signal is applied to the K3’s rear-panel REF. connector. To confirm the external reference controls the K3 reference oscillator: Turn the K3 on. Confirm that TECH mode is on (CONFIG:TECH MD On). Monitor the K3’s reference oscillator frequency (CONFIG:REF CAL) Connect the external 10 MHz signal source to the K3 rear panel REF. connector.
Preparing for Installation Tools Required 1. #0 and #1 size Phillips screwdrivers. To avoid damaging screws and nuts, a power screwdriver is not recommended. Use the screwdriver that best fits the screw in each step. 2. Soft cloth or clean, soft static dissipating pad to lay cabinet panels on to avoid scratching. 3. Long (needle) nose pliers. 4. Second pair of pliers or a 5/16” nut driver to tighten the SMA connector nut. The following tools are strongly recommended: 1. ESD wrist strap. 2.
Installation Procedure Removing the K3Top Cover and Chassis Stiffener Disconnect power and all cables from your K3. Remove the nine screws to free the top cover as shown in Figure 1. After the cover is open, lift it gently to reach the speaker wire connector. Unplug the speaker then set the top cover aside in a safe place. Whenever you remove screws from a panel, if one screw seems too tight to loosen without damaging it, first loosen the other screws then try again.
Figure 2. Freeing the K144XV Module. 3. Unplug the coaxial cables leading to the K144XV module and set the module aside. The coaxial cables have friction-fit TMP connectors that simply pull out of the sockets (see Figure 6 on pg 9). Pull on the metal connector grips. Do not pull on the coaxial cable. If needed use your needle-nose pliers to grasp the metal grips on the connectors. Remove the K3 left side panel (the side with the handle). Remove the plug from the REF.
Route the cable under the RF board and toward the front of the K3 as shown in Figure 4. Keep the cable near the edge of the board as shown. Figure 4. Routing the SMA Cable Under the RF Board. Route the cable through the notch near the front of the RF board and up between the front panel shield and the front panel board assembly. Bring the end of the cable up above the front panel shield behind the KREF3 board as shown in Figure 5. Figure 5. Routing the SMA Cable Behind the Front Panel.
Installing the K3EXREF Board Temporarily remove the coaxial cables at J2 and (if present) J1 on the KREF3 board. Handle the connectors by the grip (see Figure 6). Do not pull on the black coaxial cable. Figure 6. TMP Cable Connectors. Carefully remove the mounting screw and washers holding the KREF3 board (see Figure 7). As you loosen the screw tilt the top of the KREF3 board away from the front panel shield and look for a split lock washer between the front panel shield and the KREF3 board.
Install the K3EXREF board on the KREF3 board as follows (see Figure 9): 1. Place a #4 inside tooth lock washer on the 4-40, 5/8” (15.9 mm) pan head screw. 2. Slip the screw through the hole in the K3EXREF board with the head on the non-component side of the board. 3. Place the 1/4” (6.4 mm) spacer over the screw on the component side of the K3EXREF board. 4. Mate P4 on the K3EXREF board with J4 on the KREF3 Board while passing the screw through the hole in the KREF3 board.
If your K3 is equipped with the K144XV 2-meter option, reconnect the coaxial TMP cables to the K144XV module and mount the module on the side panel using the three 6-32 black flat head screws you removed earlier. Replace the chassis stiffener bar using two 4-40 3/16” (4.8 mm) black flat head screws at the ends. If the KPA3 is installed, attach the stiffener to the shield using two 4-40 1/4” (6.4 mm) screws with lock washers under the screws. (Some stiffener bars do not have threaded PEM nuts attached.
Appendix A - KREF3 TMP Cable Connections These illustrations show the TMP cable connections to the KREF3 board for reference during reassembly. Refer to Installing the K3EXREF on pg 4 for installation details. Note that the K3EXREF SMA cable that connects to the KREF3 board through the hole in the front panel shield is not shown.
