Elecraft K2

In the words of someone else, “I have a dream!” OK, mine isn’t as historically significant or socially impactive as his, but everyone’s got to start somewhere! My sponsor has made mention on a few occasions of “Can you actually talk to anyone on these radios you build?” That depends on your definition of “talk” but I know where he’s coming from. With that in mind, the ultimate challenge would be to build a multi band HF radio capable of voice and digital communication. Why on earth would you want to build something like that I hear you ask? Good question, when you could spend the same amount of money and let Mr Yaesu or Mr Icom do all the hard work for you. There’s something deeply gratifying in building something which provides you with the ability to converse with someone half a world away. It’s also a journey of discovery and deeply educational both in terms of knowledge, practical skills and determination not to louse it up! So what do you buy to achieve this? When it comes to that, there is only one option in my book, the legendary Elecraft K2.

When I was looking to buy my first radio (SoftRock) I stumbled across Elecraft’s site and drooled at the toys. Since then I’ve been back and forth adding things to the shopping basket but never checking out. When I bought the Yaesu FT857D, that was a tough mental battle between that rig and the KX3. I made the right choice at the time as my operating skills and understanding of radio has evolved. As I’m now older and wiser I’m now in the zone to do an Elecraft product the true justice it deserves.

One thing I am good at is getting my sense of timing completely wrong in this game. I regularly unearth fantastic items, kits and the like on the internet only to discover that they were discontinued however many years ago or occasionally just last week. My attempted purchase of a Microcode DSP Morse Code Reader is a case in point!

With that in mind I decided to secure an iconic piece of Ham hardware before Elecraft decided they wouldn’t make them anymore. For once I may have got this right. Knowing I would be looking at an eye watering amount of import duty if I ordered direct from Elecraft in California (I’ve since discovered a nice little excise and duty calculator online after my last mugging by Border Force and the Royal Mail) I sourced my prize from QRP Project in Germany rather than the UK, simply because there was almost a straight pound dollar translation to UK purchase prices. With the pound strong against the Euro, I was quids in. A few days after pressing the checkout button on QRP Project’s web store, someone thought it’d be a good idea to Brexit Europe, the pound slumped, triple A financial ratings were reduced to quadruple Z ratings and a few hedge fund managers no doubt went sky diving without parachutes!

Admittedly I had to wait 6-8 weeks for delivery as QRP Project were low on stock and they closed down over the summer for a well deserved holiday. That time was spent productively doing an awful lot of internet research and reading for hints, tips and tricks to aid me on my next little adventure.

As ever Dave Richard’s site, AA7EE was a mine of information and my main source of reference material. There are others out there such as CDJ’s blogM1HOG’s site and The K2 Project and when you put it all together you’ve got a huge resource pool to work from.

So after much anticipation, the big box of fun from Germany arrived. Talk about Christmas coming early, I haven’t had this much excitement in opening a cardboard box in years!

I could do death by photographic overload on this one, but I’m going to keep it simple and I’ll explain all in a moment. That said it’s nice to bask in the glory which is antistatic bags full of components inside a big box!


If nothing else, with Elecraft you get fantastic attention to detail. I’m guessing after 12 years of K2 production they’ve had every opportunity to perfect how they do this, but the fact everything is wrapped and protected so nicely and fits together beautifully inside the outer transit box makes you feel, if nothing else, that your investment was a wise idea.

The K2 is in essence a modular system. You build the basic multiband HF CW radio and can then pimp it with additional features in the form of modules including ATU’s, battery packs and power amps to ramp the 20W output up to a full 100W. I’ve plumped for the radio plus the SSB module (to give voice comms), the ATU and serial connectivity kit (to allow the radio to be hooked to my PC).

Breaking it down further, the radio is comprised of 3 boards. The control board which is the radio’s brain, front control panel with switches dials and knobs which is your user/radio interface and the RF board which handles all things RF. These all slot together in an ingenious way giving the basic format of a box enclosure which is reinforced by metal panels, building your outer shell. Hence why, the whole kit comes in a very small transit pack, all things considered.

The commentary on this project will be kept to an overview of the three boards as they’re built. As a separate resource and in a similar fashion to The K2 Project I’ve kept a photo diary, more for myself as a memory jogger on a separate page which can be found here. It may be of use to someone as there has been a degree of evolution in these kits and I’ve noticed already that things which Dave Richards noted in his build vary in my kit. If nothing else, the discontinuation of various components has caused Elecraft a few headaches and several items are now replaced by SMD type devices on daughter boards which are patched into the main PCB’s – a sign of the times. More on those later! At some point no doubt through hole components will go the way of the Dodo and I’m sure the K2 and other such inspirational pieces of kit will go the same way. With my luck it would probably happen the day before I bought one, if I hadn’t already!

Control Board

Elecraft break you in gently to the build, with the Control Board being your first task. The kit is pitched at intermediate level builders and they use this stage to get you in the zone. Part of the package with Elecraft is the support they provide and part of that comes with the caveat that they want you to build it their way, which is fair enough as no doubt when faced with someone sending a board or radio back for assistance they want to be able to have at least a fighting chance of seeing what’s wrong. By asking you to insert resistors in a certain orientation to aid readability, they get you into a mindset which is both structured and organised.

The Control Board is simply a board of components and isn’t overly challenging apart from the first encounter with an SMD on a daughter board. Wisely I had spent about a week carrying out a full kit inventory and making errata entries in the build manual (which is about an inch thick!) to ensure I knew what went were. I also discovered why I had been to Specsavers last year! The markings on some of the components were impossible to read even with the assistance of my rims, a loupe and a high powered light source. That said, easier to do at leisure rather than mid build. Now our little SMD device was a replacement for the DIL package incarnation of the NE602, which although discontinued is still out there, but I’m guessing Elecraft need to secure stock by the tonne, rather than ones or twos that your average amatuer needs. One of the first revisions in the manual is where the SMD component is no longer mounted on a header and socket arrangement and is soldered flush to the main PCB using 1″ lengths of hookup wire which are then trimmed down.


Hindsight is a very exact science! It’s tighter than the proverbial in there and it’s much easier to solder the hookup wires to the daughter board away from cramped area of the Control Board and then insert it as you would a normal IC and solder it. Also, go easy with these things. Even with considerable care, while clipping the hookup wire the pad on the daughter board detached at Pin 2, leaving me with no way of attaching the device to the PCB. Thankfully, the substitution for an SMD device throughout the kit means I could “rob Peter to pay Paul” while I waited for Elecraft to send me a replacement. Not a good start to the proceedings!


Eventually we got there!


As I’ve mentioned before, Elecraft have had 12 years to tweak and perfect the K2 and as such you need to make a few modifications as you go. To be honest there’s nothing dramatic to it, I’m guessing they’re not going to redesign a whole board just to accommodate a few components which with a little patience can be added to improve functionality.


These two capacitors are added to to the back of the Control Board to optimise the keying envelope shape to give you a completely click-free CW transmission.

The total build time for the Control Board was 12 hours spread over three days. If you were so inclined you could build it in half the time but that’s one thing I don’t have! There’s no time frame on this build but like everything, once you get started you then develop an itch to progress it as the next stage always looks a bit more interesting. Ideally I’d like to have this done before it gets to that time of year where I can only manage 40 minutes in the garage before my hands are so numb I can’t feel my fingers. Garage heating is something I really need to look at but in the meantime I’ve got a K2 to build!

Front Panel Board

Stage two is definitely more fun as very rapidly you have something evolving in front of you which is far more representative of the finished product and is easier to relate to. The Front Panel Board is the “customer service interface” where all of the buttons and dials used to control the radio live, along with the LCD display panel.

Elecraft, being the clever people they are include a very simple spacer tool, which is a length of PCB material, which you use to ensure all the buttons are at the same height from the boar, giving you a nice uniform appearance. It also doubles as the probe for the RF meter which is part of the radio and used to setup and align the radio in later stages.


A few buttons later and things are starting to take shape and you get a real feel for how the K2 will look.


As this is the visible front end I really took my time (not that I haven’t so far!) and got things just how I wanted them. OCD? No just a perfectionist.

One thing I have embraced from the outset of this build is antistatic precautions. Several points in the manual make it very very clear that what you’re about to touch will go bang very quickly if you introduce it to the enemy of electronics which is static. I routinely work on an antistatic mat and my soldering iron is ESD protected but this is the first time I’ve looped myself into the system with an ESD wrist strap. It takes a bit of getting used to and I now know what a dog on a leash feels like, but rather that than a dead radio before we even start.


It’s at this point that components for the various options make their first appearance. A basic K2 is a CW transceiver, but I’m building the full blown SSB version and the way Elecraft have you work is to add those options in after you’ve got the basic radio working. That makes sense, but is also dependant on you undoing various parts of your assembly to accommodate additional or different components. As such, there’s a degree of reliance on you being able to de-solder your boards without doing any damage to the bits you don’t need to touch during these “reworks”.

There is the option to buy a third party rework eliminator from unpcbs.com which are a clever system of headers which you substitute during the build stage and gives you a simple unplug or plug in option for all of the possible K2 mods. The only snag is that they cost money and if things went south and you had to send your build to Elecraft, it may compound the support issue in that you’re building off piste rather than following Elecraft’s script. Unpcbs.com make it quite clear that it’s not an Elecraft endorsed product but the reviews of the rework elimators on eHam.net are a resounding 5 out of 5. That said, I’m sticking to the plan and have faith in my soldering ability. It’s a voyage of discovery after all!


These are the SSB module components added to the Front Panel Board.


In a similar manner to the control board, you get to run some basic resistance tests on the board ahead of more sophisticated and extensive testing further on in the build. With those out of the way without incident you reach the stage where you get to play with pieces of the enclosure as you mount various filters and bezels for the display.


I’ve said it once and will say it again, it’s a thing of beauty and you really do get what you pay for, despite the fact its in a 1001 pieces and you’ve got to put it together!

After a bit more work where you get to play with more of the fixtures and fittings, you reach a point where the fruits of your labour are rewarded with a nearly complete module which looks like a radio and you get a real feel for what it is you’re building.


The addition of the rotary encoder, which has evolved again from my reading material of those who’ve gone before, finishes off the module.


Stick a knob on it and –


Total build time 8 hours over about a week.

RF Board Build Part I

The snag is you get this far and it becomes tantalisingly close to having something tangible and functional in front of you. Not a working radio, just the preliminary system. For this you need to start work on the main RF board which is the largest of the PCB’s and the one which will cause you the most headaches if you place one on the countless capacitors in the wrong place! Thankfully, to get to the first level of achievement the build centres around a few key components, connectors and a lot of relays. It’s not a taxing section of the build, but you could easily let the brakes off in the haste to get there and self control’s a virtue. Check twice, solder once!


The whole radio builds together like a rather sophisticated piece of Ikea furniture using 2D connectors which are used to attach the PCB, modules and chassis together to give a rigid structure.


And with the application of a few chassis screws things begin to take shape.










Word of caution here. The boards all slot together using jumper connectors which works perfectly but watch out for the alignment of the lock washers used to secure the 2D connectors. I couldn’t get the control board to sit squarely on the connectors to the RF board for love nor money until I realised the lock washers were protruding ever so slightly into the vertical plane the PCB needs to occupy. Easily resolved by application of a screw driver to the required chassis screw and move it the washer out the way but it starts getting a bit cramped in there with the boards slotted into place and it took a while to work out what the cause of the problem was! Don’t resort to brute force and ignorance. You’ll regret it!

So, judgement day has finally arrived and you get to feed your new creation with 12V and pray to the Gods of all things radio that you’re not about to release the mystical blue smoke.


Not a chance! All systems AOK!

As I said before this isn’t a radio yet and is a long way from it. What you have to play with is the basic front end and system controls. Elecraft walk you through a series of tests and calibrations to ensure you’ve got everything right, as well as building the necessary probes for the onboard voltmeter, frequency counter and RF probe. It’s very rewarding getting to play with the keyer and getting some noise out of radio. The only bummer, after spending about another 8 hours over a week to get this far with the RF board and skeleton chassis, is you’ve got to take it all apart to crack on with the second part of the RF board assembly. Forwards and onwards!

RF Board Build Part 2

As others who have gone before comment, the main build of the RF Board is a bit of a solder fest of resistors and capacitors. It could be seen as a daunting task but there’s not much to it if you take your time. Don’t get sucked into trying to rush it, the more the main PCB becomes populated the harder it becomes to spot a gaff. Remember, check at least a dozen times and solder once! Check the resistors and capacitors with the relevant meters, not that I’m saying Elecraft will throw you a curved ball but everything is made in a factory and manufacturing processes have hiccups.

There are a couple of things worth considering during this stage. There have been a few modifications to the K2 over the years as commented on previously. One of them is the Phase Locked Loop (PLL) upgrade which involves building a small PCB in place of a resistor network.


There’s not much to the PLL upgrade but when you attach it to the RF board, if you follow Elecraft’s build guide you may end up stitching yourself up. The board needs to be mounted firmly against the PCB without impinging on the nearby components, which in the build order prescribed aren’t installed yet. With everything soldered and trimmed you’re then left with the problem of trying to engineer wiggle room on very short lead lengths. My advice is to jump ahead slightly and install C87 first, then attach the PLL Upgrade.


The build guide says you may need to bend the board away from the capacitors to prevent it touching and it certainly is a tight squeeze. The tilted board certainly offends my sensitivities, but not as much as if I’d not realised the potential log jam on the horizon and stuck C87 in place first!

Another one worth considering is the area between the SSB option connector and J7. On the back of the board in a few pages time there is a need to install a pre wound toroid L3 in a rubber bumper flush against the board.


The only snag is that by then you’ve populated the area on the top side of the board with components and even with flush cutters you’re not going to achieve a flat surface. As the board becomes more populated it does become tighter to get cutters in there. Bearing in mind you need to leave some component leads unclipped and undamaged (relays and resistor networks), take a moment to consider your build technique. I’m a fan of soldering then clipping leads, it helps to keep the components in place as you flip the board over. Others favour pre clipping leads and this is well worth considering in places, especially in preparation for the later work on the rear of the board. I’ve marked out the area where I need a billiard table smoothness with a piece of tape as a memory jogger.


Also seriously consider pre trimming the leads of the capacitors which are installed between the rows of relays. A few are highlighted here.


When you come to trimming the leads you are dangerously close to the relay pins which Elecraft remind you repeatedly NOT to cut, bend or damage. Lets face it, they’ve printed it on the silk screen on the underside of the PCB, so they mean it!


So after 67 capacitors, 47 resistors, a smattering of diodes and a handful of transistors we’re really making progress as we start to install the IC’s. Again there’s a need to utilise the SMD on carrier board solution for a few devices, but once bitten twice shy and this time it all went off without a hitch.


Unfortunately, there’s a need for a few bottom of the PCB mods again. This one is a little more fiddly especially as the shipped 100uH RF chokes are all the same size despite the inventory listing one of them as subminiature. With a little patience you end up with the mod to the MC145170 IC


The next phase is to install the various crystals which have been pre tested and matched for the various parts of the circuit. Don’t mix them up, that’d be very silly and remember to note down the various numbers on the packs in the manual as you’ll need the details later.


From my homework I’d read the comments made by Dave Richards about the grounding of the five crystals X7-X11 and tried to come up with a cunning plan to prevent similar solder frustration. The best I could do was to mark the required 6mm height for the grounding wires around the body of the cans with masking tape and solder the necessary pieces of wire to the PCB first and get them in position ready.


Soldering the little line of soldiers on the right hand side was a doddle however, once again you’re foiled to a degree by the build sequence in the manual. On the left hand side access to the side of the crystal cans is limited by the SIL resistor networks and it’s fiddly and I’m afraid that’s as good as it gets. I’m with you on the aesthetics for this one Dave and I’ll be awarding myself a B- for this attempt!


The next step is to start winding toroids and transformers. I get some weird sense of satisfaction from this however not all of these are as easy as anticipated. The cores for this build are like a multicoloured selection of iron based Cherrios! Elecraft get you to sort them into separate piles to prevent any mishaps. Never a bad thing!


You’re broken in with an easy one for starters, RFC14, but it’s a tight squeeze to install it on the board. Remember the PLL modification? Guess where RFC14 lives? Yup, you guessed right!


Things start getting a bit more complicated with T5 and T7 which are toroidal transformers. With T5 make sure you follow the wording of the manual as the diagrams at 6-16 and 6-17 are representative NOT depictions of reality. It took me a while to figure that out as I was merrily building, looked at the diagram and convinced myself I’d got it wrong. The Note saying “T5’s 3-4 winding must be wound exactly as illustrated or the VFO will not function correctly” doesn’t help when the diagram shows 14 turns and the literature tells you to wind 16 turns!



Here’s my T5 and to be honest it matches the one Dave Richards wound (I could just make it out in his photos) and I’m sticking to it.




Somewhat ironically when you get to T7 you get a helpful “the drawing shows 14 turns” note when you’re winding a 20 turn element.


That said, you can only do your best with these things and keeping a mental note of any difficulties experienced during construction may be a good thing if things don’t pan out on testing. At least you know where to start looking if things are misbehaving!



At the point shown above, you’re still a long way from putting the K2 back together (its taken a cumulative 23 hours over 13 days to get this far) and seeing if the fruits of your labour work. I took a serious time out at this point and called “Miller Time!” Once my eyes could focus again from staring at toroids through a loupe not beer, I spent a good hour going over all the components on the board in a placement check. I’d rather waste an hour to discover everythings as it should be than charge headlong into the next phase only to find things had been cocked up previously.

There’s a cautionary tale with this stage of the RF board build. When you get to the point of building the underside of the board have your wits about you and working eyeballs. The lead length of some of the components isn’t the same as on the topside and there’s definitely no consistency between bottom ones. Case in point I foolishly assumed R75 was the same as something on the topside I was using as a spacer to precut the leads only to find it was way too short. All on a Friday night when everything was closed. Next day saw me off to Maplin for a new 680 ohm resistor, which I could only buy in a pack of God knows how many along with every resistor value under the sun for £7. To add insult to injury some prize idiot had decided to complicate matters by closing one of the three arterial routes in and out of Portsmouth for the entire weekend. Net result was complete and utter gridlock followed by copious amounts of road rage from others finding the situation less than funny. I just kicked back and watched the world go by on a road trip that lasted 1 1/2 hours rather than 10 minutes. With a degree of irony my £7 bucket of resistors turned into a godsend as having failed to learn from my experience with R75, I did exactly the same with R18. Muppet!

Anyway, moving on, after a grand total of 36 hours and 10 minutes work (in sporadic bursts over the course of 3 weeks) the RF board was completed up to the next point of alignment and testing. It seemed slightly strange seeing the K2 morph back into a radio like object after having peered at the inner circuit board for such a long time.






Proof of life. That was a sight for soar eyes after that amount of work!