K2 FAQ and tips

Q: I just purchased your K2 kit and some accessory modules. Do you have any advice on how to develop the soldering skills required to build this kit?

A: A good temperature controlled soldering iron is an absolute must for building a kit such as the K2. Tom Hammond, N0SS (SK) has an excellent soldering tutorial for those just getting into kit building or have limited experience with soldering.

If you have no or very limited soldering experience, you may want to get started on something smaller to gain a good feel for how to build your K2 kit. We recommend that every ham have a good dummy load for performing various tests with your K2 during and after your build. The Elecraft DL-1 Dummy Load is not only excellent for this purpose, but an excellent small kit to get your feet wet in not only soldering, but a great way to become familiar with the Elecraft kit building experience. Elecraft sells a number of Mini-Module kits to perform various functions in and around the shack.

Q: I am building the Front Panel Board and ready to install the LCD. I am a little confused about the install and do not want to damage the LCD. No matter what I do, I cannot get the pins of the LCD to extend all the way through the PCB. It just touches the top pads. Also, I am not sure about peeling the plastic film off of the LCD. Any guidance there?

A: When properly seated on the backlighting and diffuser, the LCD pins may very well not extend through the PCB. This is normal and you will want to solder those pins from the top if they do not extend through. Make sure that all pins are adequately connected to their respective pins. Follow the steps as outlined on page 28 of the current manual and you should be all set.

There is a fine document by Brian, W6FVI and Don, W3FPR that explains exactly what to do with the films on the LCD prior to installation. 

Q: I just bought a used K2 on/from (insert auction site/seller here), how can I tell if it has been upgraded to the latest hardware and firmware revisions?

A: First determine the level of your K2

The K2 was designed by Elecraft to be very modular. Adding various option boards can be accomplished at any time after the initial build of the basic K2 kit. In the same mind set, hardware improvements and firmware upgrades over the lifetime of the K2 product may also be applied at any time (some may be dependent on others). Therefore, determining what options are installed and what hardware and firmware upgrades have been performed may only be known to the current owner and would require opening up the unit for a precise determination. 

You can check the K2's main microcontroller and I/O controller firmware revisions by holding in any switch on power-up. Two numbers will then be displayed briefly. For example, you might see 2.04r 1.09. The first number is the main microcontroller's firmware revision and letter suffix. The second number is the I/O controller's firmware revision.

With this said, some assumptions based on the serial number of the K2 can be used to know what upgrades and mods were already included in the kit when it was sold. Below is a list of serial number ranges and what was included as part of the kit prior to building the K2.

K2 Serial Number 4660 and above

These K2’s have all of the current hardware upgrades included.

The MCU firmware level may be either 2.04P or 2.04r. The only difference between the two is that 2.04P (and earlier) allowed a toggle of the sidetone source between Control Board U6-25 and U8-4 (to support older K2’s) which caused some users to lose the sidetone if they entered the menu to change the sidetone level and inadvertently tapped DISPLAY without exiting the menu system. MCU 2.04r locked the sidetone source at U8-4 (and requires rewiring on the Control Board if the serial number is less than SN 3000).

Serial Numbers between 3000 and 4660

The only change between these serial numbers is the addition of the K2 Keying Waveshape Modification.

Serial numbers below 3000

SN 3000 is the point where the K2 boards were changed to include all the modifications that had been added up to that time. The complete set of A to B upgrade kits may be needed.

Which upgrades have already been installed can only be determined by physical inspection. First download the A to B instructions from the Elecraft website. The first page of those

instructions contain a list of associated upgrades. Download all of those instructions and use that documentation to compare the components which were added/changed by each of those upgrades with your K2 boards. That process will tell you which upgrades (if any) are present on your K2.

Serial numbers below 2560

The IF crystals were changed at SN 2560 to crystals that specified the crystal motional inductance parameter. You can examine the markings on the IF crystals (X5 through X11) to

determine whether they are the old or the new crystals. New crystals have a suffix of “-S”. All other designations are the previous level crystals. Changing the crystals to the newer ones will provide better filters for the K2.

The crystals on the base K2 RF board and the KSB2 option should be examined separately. If the KSB2 was added later in the life of the K2, it may be that the KSB2 has the new crystals while the base K2 has older crystals.

If only the base K2 crystals need updating, you can purchase those here. If both the base K2 and KSB2 crystals need updating, you can purchase those here.

KSB2 option filter width

The KSB2 option originally used a 2.1kHz filter width. With the advent of the IF crystals with the motional inductance parameter specified, a filter width of 2.4kHz (or in some cases 2.6kHz) could be used. Elecraft has a kit (SSBCAPKT) which will allow a change in the filter width. You must have the updated crystals in the KSB2 option to use the 2.4kHz width, and the BFO range must be checked before adding either of those two filter widths. See the SSBCAPKT instructions for the range required.

If you look at the KSB2 option board and find capacitors in the CB and CN positions, you have the original 2.1kHz filter width. If the CB and CN positions are empty, the KSB2 filter width is either 2.4kHz (most common) or the 2.6kHz width. To determine which width, you will have to examine the SSBCAPKT instructions and examine the values of the capacitors installed.

Q: I have a basic K2 without the KPA100 100W amplifier and would like to drive and external amp with my K2. Does the K2 have an amplifier keying signal I can use to key my amp?

A: While our KPA100 amplifier does have a PA Key Out connection to key an external amp, the basic K2 does not have this connection. But, the signals to produce this connection exist in the K2 and there are a couple of circuit designs out there that will provide this functionality. Here is one documented by our Eric, WA6HHQ. And another by Tom Hammond, N0SS (SK). 

I also sell a K2 T-R Relay Driver Board kit based on the design by Tom Hammond, N0SS (SK).

Q: I love operating my K2 and think that it still holds up great to the more modern rigs out there today. One thing I miss though is the capability to connect a panadapter. Are there any solutions for bringing the IF out of the K2 to a connector for this use? Can I connect an Elecraft P3 Panadapter to my K2? 

A: Although not an Elecraft solution, there are a few circuits out there that can buffer the IF and provide an output that can be used to feed a panadapter setup. DX Engineering sells an IF Buffer Amplifier board designed by Jack, K8ZOA (SK), for just such a purpose. Dave, W8FGU has a detailed description of how to install this board in your K2 and feed the IF output to a SDRPlay RSP2 SDR radio and display the IF spectrum on a PC running HDSDR. With rig control, HDSDR can use the RSP2 fed by the IF of the K2 and control the K2 and vice versa, for point and click frequency tuning. 

The Elecraft P3 could be used with an IF output as described above. The P3 would be configured to receive an IF input frequency of 4.915 MHz (the K2 IF) and display the spectrum around the IF. Unfortunately, rig control, band frequency info or point and click frequency tuning cannot be accomplished with this configuration. 

Q: I am building the KPA100 amplifier kit and I am confused as to which trimmer capacitors to use for C1 and C27. They are not marked and one is brown in color and the other red. Can you sort this out for me please? 

A: Unfortunately, some of these trimmer caps are becoming difficult to source and continually change with regard to color. The brown trimmer is for C27 (E540002) and a red one for C1 (E540012).