Getting Started With Building The K2

I’ve been wanting to build an Elecraft K2 for several years now, but the desire has been getting stronger, until maybe a year or so ago when I started seeing it as the logical endpoint in a progression that has included the Norcal 2N2/40, the Fort Tuthill 80 and the CC-series of transceivers (which is ongoing, as we are still in beta-testing.)  At some point I realized that if I could successfully put all these kits together, there was no reason I couldn’t build a K2 as well.  If you can solder pretty well, can identify parts, and can follow written instructions, you can put a kit together.

A number of people have asked why I would consider a K2, now that the KX3 is about to be released. The answer is that I wanted to build myself a multiband full-featured HF rig from a kit at the component level, which I wouldn’t be able to do with the KX3. The K2 has been around a long time now – something like 13 years. It doesn’t have the cutting edge SDR technology that the KX3 will have, but it’s still a solid performer and very capable. If you want to build a full-featured HF rig from a kit containing individual components (as opposed to modules that you connect together), the K2 is the only choice out there. I had no problem with the fact that the K2 has no direct competition in the kit world, as from everything I’ve read, it seems to be such a great-performing transceiver – especially for the QRP CW enthusiast.

I’d been umming and aahing about ordering the K2 for a while and although the plan was to wait until the new year, the recent increased sunspot activity and excellent propagation on the upper HF bands prompted me to hurry up so that I can get in on a bit of the DX action too (as my current station consists just of 3 monoband QRP rigs on 80, 40 and 20M).

I ordered the basic version of the K2 (no options) online last Sunday evening. They shipped it on Monday, and the $12 Priority Mail option got it to my door the very next day, as I only live about 50 miles from Elecraft.

I know that the K2 has been extensively documented over the years on many blogs and websites, but allow me the obligatory “I just opened the box” shot:

I’m not going to go into great detail about the K2 kit as that has been done on so many other websites over the years, but I will offer a few of my thoughts and share a little of my experience.

Documentation is great. The manual is a lot like I imagine one of the old Heathkit manuals would have been like – very detailed with clear, step-by-step instructions. For the experienced builder, some of the descriptions and suggestions on how to install components will not be needed, but it’s definitely a good thing to have all that information there. In fact, I found that some of Elecraft’s suggested methods for mounting components differed from my preferred practices, in which case I opted for my way. More on that in the next blog-post.

There are 3 boards in the basic K2, the control board, the front panel board, and the RF board. The first board to be assembled was the control board; the brains of the transceiver:

You can see the multi-pin connectors at the bottom of the board that are used for all inter-board connections in the K2. That represents one big difference from the Heathkit days – no complex wiring to route around the inside of the enclosure. Not only does it simplify construction, but it must contribute a great deal to reliability too. On the reverse side of this board, you can see the extra caps that have been added (as recommended in the manual) to improve the keying waveform:

The control board wasn’t particularly exciting to build – just a board that needed filling with components.  However, the next stage – the assembly of the front panel board, felt a lot more engaging, as I got to slowly see the front panel of my new transceiver take shape:

To aid in making sure that all switches are mounted at the same height above the board, Elecraft include a really neat little spacer tool that you place underneath the switches before soldering them to the board. This ensures that all the switch buttons protrude an equal amount from the front panel to give a nice, uniform appearance.  A small PCB is supplied for constructing an RF probe to help with alignment. Attached to this PCB are two small strips of board that are broken off to make the switch spacers. The manual instructs the builder to snap the protrusions at 4 points as indicated in the manual, to make 4 spacers.  As well as being used to set the switch heights, the spacers are used later to set the exact height above the board of the LCD backlight. Although not mentioned in the manual, I found that it would be easier if I initially broke the PCB at only 2 points, to make 2 long spacers for setting the switch heights. This way, each spacer could fit under 2 switches at a time.  On reaching the stage where I installed the LCD backlight, I snapped each spacer in half to get the 4 spacers required for setting the height of the backlight.

I also want to talk about soldering, but first of all, another view of the front panel board just for the heck of it:

The back of the front panel board (with the front panel attached):

When installing the encoder, Elecraft recommend that the 4 wires that attach to the encoder are wrapped around the connection posts before being soldered. I didn’t do this because I figured that if the wires were wrapped around the terminal posts, it would increase the chances of a short between the posts on the encoder. The other reason was that it felt like overkill to me.  While I like to make solid electrical connections, I also like to plan for the possibility that I might need to disassemble parts of the transceiver in the future.  Here’s how I made the connections to the encoder:

If I ever need to de-solder the encoder, all I have to do is hold the iron to each post and move the wire away with a small screwdriver – or wick the solder away with de-soldering braid.  Job done – and personally, I think it looks neater than if the wires were wrapped around the posts.

While I’m on  the subject of soldering, take a look at how I soldered the IC to the left of the encoder. I’m not claiming that it’s the neatest or prettiest soldering job in the world. I’m still trying to find a pair of flush cutters that will cut a wire completely cleanly and horizontally, without leaving a bevelled edge on the wire. Does such a pair exist? If I have to spend a lot of money to get such a pair I’ll do it, as I’d like to have my PCB’s look neater if possible. Anyway, what I wanted to point out is the fact that I have filled the plated-through holes with solder but have not allowed the solder to build up on top of the board. Many people when soldering boards with plated-through holes like an accumulation of solder on top of the board, and it is just not necessary. Depending on your personal taste, I can see that it might possibly make your joints look nicer to have a little build-up of nice shiny solder around the wire on top of the board. Thing is, if you ever have to remove a part from the board in order to replace it, that’s a whole lot more solder you have to suck up or wick away with desoldering braid.

I think one of the reasons folk often put more solder than is necessary on joints is to “make sure” that it’s a good connection, and if they can’t see solder on a joint because it’s in the hole, they perhaps think that it’s not there, so they put a little more on top “just to make sure”. It’s kind of like putting one sugar in your coffee, and then adding an extra one (actually, I’m not sure that it is, but I’m feeling a bit sleepy and am in stream-of-consciousness mode). If you’re dealing with plated-through holes, all you need do to make an excellent connection is make sure both the tinned pad on the board and the component lead are hot so that the solder will melt onto them, then hold the solder close to the top of the hole and experience a wonderful moment of zen as you see the solder wick down by capillary action into the hole. If you use a nice thin solder (I use .02″) then you’ll be able to apply just the right amount to get the job done. If you’re fairly new at soldering, allow me to give you a tip. Once you’ve made sure the tip of your iron is clean (I wipe mine before every joint, unless I’m soldering several in a row one straight after the other), then a great way to ensure maximum heat transfer from the iron to the pad and component lead is to melt a very small amount of solder onto the iron. The solder melts, makes contact with the iron, pad and lead all at once, and you’ll notice the solder suddenly wicking down into the hole and making a perfect joint. Bingo. It’s a beautiful thing!

Incidentally, if you’re soldering on a board that is single-sided without plated-through holes, then you do need a little fillet of solder on top of the board.

EDIT:  I just read a short essay on soldering on the Elecraft site in which “Dr Solder” at Weller says that you should never have a solder joint in which the hole is slightly under-filled, leading to a dimple in the hole. This is what many of my joints in the above photo are like. Hmmm…..now I’m wondering if I should have put just a touch more solder on those joints.  I think I’ll leave them as they are and only resolder them if they are problematic.  I have a sneaky feeling they’ll be fine though.

Here’s what that front panel board with the front panel attached looks like from the front:

It’s really gratifying seeing the transceiver slowly take shape. The whole process of putting this together has given me even more respect for folk who put kits like this together – or who design any product like this.  So far, almost every component has fitted the corresponding holes on the board exactly – and with the rate at which these things change, it’s something of a feat to make a kit available – and have it still available for purchase 13 years later. Every single fastener, spacer, enclosure piece – they are all part of a whole, and it takes a great deal of creativity and engineering experience to fashion a product like this.

The next step was to assemble the DC and control circuits on the main board so that the transceiver case could be assembled and all the boards plugged into each other to ensure the correct operation of the control circuitry, before proceeding with the build of the receiver and transmitter circuits. I got very close to completing this step when I came across my first missing part, and kicked myself for not doing a complete inventory earlier.  I had performed an inventory of the control board and front panel board parts, as well as the bag of miscellaneous parts. On looking at the sheer number of parts in the bags for the RF (main) board, I decided to wing it and hope there was nothing missing, which there was – a 20-pin connector for mating the main RF board to the front panel board, a rather essential part.

At this point, it was late on Sunday evening, so I decided to conduct a complete inventory of all remaining parts so that when I called Elecraft in the morning, I could put in one order for all the missing parts.  As it happened, that was the only part that was missing. Only one missing thing out of many hundreds is pretty good. There was one other part which, although present, I wasn’t completely happy with, and that was the main tuning knob. I’m fine with the weight, feel and look of it, but the machining of the one I received was a little substandard; one of the holes for the set screws had a very ragged edge, and the knob looked like it had bumped up against some hard object or sharp edges, as there were a number of marks on the side. It wasn’t terrible but compared to the high quality of everything else in the kit, it looked a bit shabby. Madeleine at Elecraft was very helpful and suggested that they send me another tuning knob.  I may end up getting a different knob, but would like to start out with the stock one.  I’ve spoken to Madeleine over at Elecraft a number of times now and she’s great. It’s a real pleasure to call a company and have my phone call taken by someone who is articulate, friendly, and communicative.

So I spent part of yesterday taking pictures of the progress so far and writing this blog-post.  Later today when the 20-pin connector arrives, I’ll finish off the DC and control circuits, assemble the enclosure, plug the boards together, and run the first tests. Fingers crossed – hope there’s no blue flash or whiff of smoke 🙂