January 16, 2011 – Elecraft K3 – Final Building Tips and Suggestions

K3 Utility Software – KSUB Adaptor – A Small Glitch
First, kudos to Elecraft for supplying software for the Mac, so little ham software is written for the Apple side of things that it was a pleasant surprise to see that both a PC and Mac version of the K3 Utility software on the Elecraft website. The K3 Utility is used to set up and test various rig parameters on the K3 transceiver, and while not required, is very handy to use. With that said, I did have a bit of a challenge with the software. Like most new computers, my Apple Macbook Air does not have a serial post, just two USB ports. The K3 uses a serial port, necessitating the use of a USB to 9 Pin Serial cable, Elecraft sells such a cable, known as a KUSB. Despite repeated efforts, I could not get the K3 software to find the adaptor cable on the Macbook. I tried various software drivers, searched the internet and Elecraft email archives with no success.

Finally, I made a quick post to the Elecraft reflector, and within 10 minutes of my post Bill K1GQ nailed it. Turns out that the drivers from the Elecraft site are NOT correct for the FTDI chip set which is used on the newer KUSB cable. I downloaded the correct driver from the site Bill suggested, and things just worked! Just 100% delighted how quickly and well the K3 Utility works. The site for the FTDI chip is located at http://www.ftdichip.com/Drivers/VCP.htm Even more delighted with the prompt and accurate help provided by K1GQ on the problem, hope this saves someone else from this challenge. So, if you’ve having an issue with the KUSB on the Mac, use the Mac System Profiler to determine which chipset your USB to Serial Adaptor is using, then make sure you download the right driver.

Crystal Filters – Double Check/Double Take
I found the otherwise excellent Elecraft assembly manual a tad confusing, at least to me, on the arrangement of the xtal filters. I had chosen the 8 pole xtal Inrad filters for the K3, the layout is as follows: 250 KC, 450 KC, 2.8 KC, 6.0 KC. Those with a sharp eye will note that I initially had the filters installed in the incorrect order in K3 because I misunderstood the manual. A reading of the operations manual made things much clearer to me, and I quickly reinstalled all of the filters from the widest bandwidth to the most narrow. The new order is: Filter 1 is blank for future installation of the FM filter, then I set it up the following filters from widest to most narrow, 6 KC in slot 2 for AM, then the 2.8 KC filter for general use, followed by the 450 and 250 KC filters for CW use in slots 4 and 5 respectively.

Using A Icom Microphone on the K3 – General Info
I have a number of Icom rigs here, and more than a few spare mics laying about. I decided to use a Icom SM-8 with the K3. The SM-8 has a bit of retro look about it, nice contrast to the K3, and the electret condenser type mic element gives clear tone over a wide variety of voice levels. On the bottom of the mic base there is one control for tone. Designed to be used on two different rigs, there are separate level adjustments for input A and input B. The mic cables terminate to a standard ICOM 8 pin mic plug.

The use of a Icom mic requires a few simple changes as Elecraft has wired the microphone jack on the K3 to match the Kenwood wiring scheme. Unlike the K2, the user can not readily change this scheme, so the changes have to occur inside the microphone or cable plug. The pin out information on both the Icom and Elecraft is below, again, hope this helps someone else. You have two settings on the K3 which need to be enabled to use with the Icom microphone, the Bias voltage, and the Mic Gain. For my station I used the high mic gain setting, and also used the bias voltage, seems to work just fine. The Icom memory channel or freq changing is implemented differently that Kenwood, Icom does this by pulling down a control voltage with a 470 ohm resistor. Adding the functionality of the UP and Down buttons will require some additional work, I have not implemented that, but may do so at a later date.

How To Wire The Icom SM-8 Microphone To The K3
To implement the simple microphone cable mod, use the table below.
For simplicity sake here is a simple list of how I switched the cable leads:

1) Remove the two screws on the female mic cable clamp, then remove the one small screw holding the mic
connector into the shell.

2) Now twist and remove the mic connector from the shell, slide back the clear plastic sleeve to access the small pins on the back of the connector.

3) Using a fine tipped soldering iron, carefully unsolder Pins 2, 5 and 6 on the Icom mic plug, be sure to note which color wire went to each pin, see chart below if in question – note, your cable colors may not match mine, so best to make notes.

4) Solder the wire removed from Pin 2 to Pin 6 (bias voltage).

5) Solder the wire removed from 5 to Pin 2 (PTT)

6) Solder the wire removed from Pin 6 to Pin 7 (ground to ground).

7) For the VFO or memory channel up functions, skip this step now, I’ll have more data in a future post.

8) Reassemble the mic connector back into the shell.

9) Using the K3 Config menu set up the Mic Gain and turn on the Bias voltage, see the K3 manual for info.

10) Set the mic gain pot to a setting which sounds good in your on-air test and you should be all set.