“Those who hear not the music, think the dancer mad”
Elecraft K2 Box
#4039, 28th Jan 2004

Elecraft K2 - Transceiver Kit Construction


Time to progress further with HF. Once again there were many options to chose from. But for me, there was really only ever one, perhaps the R500 of the Ham world. The legendary Elecraft K2..

23rd Jan - The Specification

K160RX K2 160M / 2nd RX Antenna Option
K2 HF Transceiver
KAT2 K2 20W Internal Auto Tuner
KBT2 K2 Internal 2.9AH Battery Kit
KSB2 K2 SSB Option
Proset-K2 Heil Boom Headset for the K2

3rd May - Finally started building the kit. Completed inventory check, sorted through the superbly packaged kit. The first task is the Control Board. Great instructions. The first reminder is the recommended orientation of the components, horizontal components to be read left to right (Doing this already), then turn the board counter clockwise through 90 degrees to read the vertically orientated components. 21 parts (1:30)

8th May - Visited Maplins yesterday to try and find some new, smaller chisel bits for the Weller iron, Hope less.. But, upon closer (much) inspection of the current tips, they are in fact chisel shaped, just very small! Sean explained the numbers on the back of the bit indicates it's temperature! nothing to do with size. The control, ease of bit change, temperature.. There is no other way to solder.

The PCB holder works very well but needs a foam faced board to retain the components, something to look out for at the Dunstable Rally tomorrow.

Managing to avoid the temptation of an SSB I returned to the soldering iron; placed and soldered 35 capacitors (1:30) So my rate has improved slightly.

10th -12th May - Continued work, despite a sore throat and cold, as I found the soldering quite therapeutic! My concentration was not 100% though and unfortunately the LM833 Op Amp was the victim of a U7 / U2 mix up. Completed the rest of the Control Board. 44 parts (2:30). Control Board Approx 100 parts in total.

“En oino aletheia..”

13th May - Front Panel Board. 16 switches to install, the novel spacing tool supplied works well to ensure they are soldered level with the board. The vertical components on this board get aligned to read correctly when the board is turned clockwise.. The next board will be counter clockwise again!! Making use of Blu Tack to hold the components in place while soldering them and enjoying a large glass of wine. 47 parts (4:30)

14th May - Front Panel Board. Installed the audio pot, but all 4 of the linear pots appear to be missing from the bag ... Ah.. I emailed Elecraft. Supper and a Cobra Beer (I do prefer the "Classic" bottle). Then various buttons etc are installed! 18 parts (1:30)

17th - 18th May - Front Panel Board. Back light and LCD panel. Perhaps the hardest parts to install so far, requiring careful positioning and soldering to ensure the panel was level. Installed the front panel components required from the SSB kit. 15 parts (1:00)

Elecraft K2 Testing
Testing (?)

19th May - Finishing the Front Panel and Control Board. Missing / replacement parts arrived today, service indeed! Installed the switches and chip for the control board. Ran through the basic resistance checks for both boards, the resistance's that gave a reading were correct, but most showed as infinite resistance, retested with a simple moving coil meter, only to be presented with a different set of results. Again reminded of the amusements inherent in measuring resistance (particularly in a circuit), using a DVM...

Upon checking the manual again, it states that most "greater than x tests" may show as infinite resistance on some DVM's and may show low on a moving coil meter.. Great.. Perhaps a more concrete set of tests / method could be used? 5 parts (1:30)

20th May - Finishing the Front Panel. Installed the encoder and front knobs, some of which required careful working on to their splines and a bit of "pressure". Also noticed the soldering iron had warmed one of the buttons ! Doh! it functions OK but is slightly melted on one side.. (Something for the next Elecraft order!). I console myself with a Kronenbourg 1664 Premier Cru 13 parts (1:30)

Elecraft K2
          RF Board
K2 RF Board

21st May - Finishing the Front Panel. Installed the tuning knob and noticed a notch in the RIT, this pot may need to be replaced.

Main Board - Installed all the relays (17) board stand offs and a few other bits. 24 parts (2:00)

22nd May - Main Board. Lovely bright day today! The Micra has been advertised in the local paper, so while I wait for callers, I might as well develop my soldering skills further. 21 parts (2:30)

The weather is now to good to solder. We visit the local nursery for some Geraniums and Tomatoes Returning, I cycle off to Weston, not quite ready for a pint at the Cricketers I pedal on to Walkern, then Bennington and settle down for a splendid pint of Palmers IPA at The Lordship Arms I listen on 2 and 70, a number of stations are operating but I can't get back to them. The PHOTA activation will have to wait.

Back for some more soldering! 8 parts (1:00) Then break for a curry and a glass or two of Michel Laroche Chablis. Returning to fit the side panels and bail arm stand, which proves a real challenge, requiring way to much pushing and cajoling to get into place. So tight is the fit of the bail arm that it bends the case panel slightly! Elecraft please fix this? 9 parts (1:00)

23rd May - First Power Up Tests. Installed the front panel and control board, then side panels and bail arm panel. Now ready for the first live test.. While checking and triple checking the power connections prior to power up I read Elecraft's helpful advice.

Elecraft K2
          First Test
K2 First Test
“If you see or smell smoke when you turn the K2 on for the first time, turn off power and disconnect the power supply..”

One more check.. then I press the button for main engine start..

The relays chatter briefly and the Info 201 message appears, a few moments later the display appears! Next the band switch, tuning etc tests, all A OK Houston. That will deserve a beer later, but for now I am off for a swim and lunch!

I build and test the frequency probe, then run through the remaining Front Panel tests and alignments. Already getting familiar with the menu! 6 parts (2:30)

24th May - Back to the Main Board. Removed front panel and control board. I revise my previous soldering technique, by trimming the components legs close to the board prior to soldering them, if you get this exactly right, you end up with a neat dome of solder over the end of the resistor. Looks very neat. But, it requires the components to be held perfectly flat against the board, awkward cutting near the board, and precisely the right amount of solder. As the component leg is so short it heats very quickly so the solder is apt to run straight through, the plate through hole!!

After installing 47 resistors I returned to my previous technique, trimming the component leads after soldering!! Finally reinstalled the side panels to show club members progress so far. 47 parts (2:00).. Phew, that is to long for just 47 resistors.

26th May - Main Board. Removed front panel and control board. The belated celebratory Hoegaarden was certainly on form.

Elecraft K2 Thermistor Board
Thermistor Board

30th May - Thermistor Upgrade. A fiddle job, the Blu Tack certainly came in handy. Very nearly soldered it in the wrong way round! Check this one carefully!!!! Also seems very close to a toroid's position, this will be tight.. 14 parts (00:45)

Main Board. Various varactor diodes and transistors installed. 26 parts (1:00)

The Thermistor board is very close to the holes for a toroid and capacitor. The soldered joints for the board are reworked, re bent, and re trimmed to provide some more space. Dozens of capacitors for the main board are sorted! (2:00)

31st May - Main Board. Installed 67 capacitors in several sessions during the day, many happy moments spent scouring the board for Cxx.. 67 parts (3:00)

1st June - Main Board. Installed, chips, test points and more capacitors. 20 parts (1:30)

2nd June - Main Board. Installed the BFO crystals, Filter crystals and all their earth wires, which required some careful work..

The manual says to prepare 14 short lengths of bare wire wire, but after fiddling with 8 short wires for the Thermistor upgrade (Sometimes I can take the manual a little to literally!!) I found it much easier to strip one long length, solder the end into the board, cut roughly to length then repeat..

Once that was complete I carefully bent and trimmed the wires against each crystal and to the exact length, and quickly soldered them into place. Including all the wires(!) 25 parts (1:30)

Elecraft RF
Elecraft K2 Mainboard

3rd June - Main Board. The first two Toroids! As usual Elecraft start you on the easy ones! The instructions are very clear, sure it requires care, but proceeds well, if rather slowly!

The target is to get the wire around 80 odd percent of the core, fine for the first toroid, but due to the mounting of the second it proves difficult. Never mind, lets see how well it works first, before any rewinds!! 2 parts (1:30)

4th June - Main Board. Another day another toroid! 1 part (00:15)

5th June - Main Board. Continued toroid installation, aided by a bottle of Fiddlers Elbow (A survivor of the 6 by 6!!)

18th June - Main Board Toroids. To many other destractions over the last week; but tonight, back to construction! Soldered in RFC11 Toroid and prepared the T5 Toroid transformer noting the warning that "T5 winding must be wound exactly as illustrated or the VFO will not function correctly" the diagram shows the Toroid with 14 turns (count em') not the 16 on the T5...

Despite a bottle of Leffe Blonde, Figure 6-16 still shows 14 turns. Made a start on the next T7. 2 parts (2:00)

20th June - Main Board toroids. Completed winding and installation of T7, spent way to long getting the wiring to sit "correctly" and the leads not to cross, this attention to detail may be fine for the space shuttle.. Then enjoyed some bifilar fun, impossible to do by just twisting in your hand! Clamping two ends of the wire together, and keeping them taut, while steadily twisting from the other end. The 12 inches of wire required more than the predicted 24 turns(!) But it worked out well.

Soldered in a couple of slug inductors by way of a change. Circle Master and 300s old Ale accompanied these proceedings. 3 parts (2:00)

21st June - Main Board toroids. Installed the Bifilar T6, once installed it seemed to short in all directions, but upon closer inspection I think this is correct, as the red and green wires are effectively linked by the tracks! 26 parts (1:30)

Elecraft K2 RF Board Closeup
K2 RF Board Closeup

25th June - Main Board. Posted a message to the Elecraft email list..

Mounting toroids(!) - As I did not want the wire running parallel to or crossing, the windings back to the mounting holes. I have a bare part of the toroid (i.e no wire). Not sure of the percentage, about 20%.

I know the manual says 85% coverage is the target. Am I worrying too much? Is it ok / desirable to have the wire running parallel or crossing the windings back to the mounting holes, in order to get fuller spacing around the core? If so, are the toroids secure with the extra "loose" wire? I have read the toroid page and looked at photos but I have missed this mounting detail!

They told me not to worry(!) and that T5 was the only critical one and it could easily be adjusted if the target VCO voltage was not reached.

Installed three Toroids, and sundry other components. A few more parts to go, then hopefully 40m RX tommorow! 38 parts (3:00)

26th June - Main Board. Installed more components on the bottom of the board, most of them requiring very careful soldering on the top of the board! (Sean's component "leg bender" tool works particularly well on the resistors, ensuring they "snap" into the board). The BFO toroid with it's fine wires and awkward mounting also required some careful work, certainly the most fiddly part so far.

The soldering across the entire board is carefully checked and the case panels refitted, all ready for the first proper radio tests!

With some trepidation, 4039 is powered up, the reassuring 7100 CW display appears. Clicking through the band changes, everything seems to be working OK. Back to the manual for the tests..

4Mhz Oscillator Calibration - OK

PLL Reference Oscillator Range Test - Indicates a range of 20khz (15khz is the suggested maximum). This is noted but hopefully not an issue.

VCO Test - OK.

VCO Alignment - Slugging around, until the magic 6 volts is measured. Then the VCO ranges are checked, all fine.

BFO Test - Range is 5.29Khz, OK.

BFO Alignment - Referred to page 85, it is time to read and understand more about the BFO and Filter settings. Takes a while to get the hang of the buttons, and to set the default crystal filter widths and BFO frequencies.

VFO Linearization - OK.

“Charlie Xray Two Delta Delta Papa, rings through the headphones..”

IF AMP Alignment - A little more slugging to peak the 7000khz internally generated signal.

40 Meter Band Bass Filter Alignment - Enough testing! On to the only test that counts.. The trusty high performance test antenna (10 feet of wire) is "connected" and I start tuning down through 40m, noises but nothing distinct, still in CW mode, so LSB is selected.. "Charlie Xray Two Delta Delta Papa" rings through the headphones, shortly followed by a cacophony of European stations calling him. It is 12:15 AM. 15 parts (3:45)

27th June - Main Board - Switched on at 10:00 to be greeted by GB2RS, the RSGB news broadcast. An ideal opportunity for some slugging of the 40m bandpass! Built and tested a noise source.

2nd July - Band Pass - Removed the panels again, fitted resistors and capacitors (C22 3.3pf is currently AWOL! and C201 220pf) 61 parts (2:00)

3rd July - Main Board - Ruddles County and Tiger Beer aid installation 31 parts (1:15)

4th July - Low Pass - Installed various resistors etc, slug inductors, and prepared the remaining 13(!) toroids 12 parts (3:30)

7th July - Main Board - Installed 4 toroids 4 parts (00:30)

9th July - Main Board - Install 2 remaining toroids, PA transistors case etc. Powered on for first transmitter tests.. almost no power. Time for some investigation and a post to the email list! 4 parts (2:00)

“Clearly, this problem required a hot iron and a cold beer..”

10th July - Main Board - I investigate further; after a good few hours of wandering through various tests and a few trial and errors, I find the PA Bias is grounded, instead of showing 2.7k resistance! Which is not helping matters.. The Pre Driver Bias is OK though. I read through the emails, and chat with Sean. Further digging and checking, but no real progress. Then off for a swim, and a chance to properly consider the various email suggestions; DC voltage checking, PA shorts, removing components, failed components..

Clearly, this problem required a hot iron and a cold beer. Looking again at the circuit diagram clearly something is dragging the PA bases to ground, now there aren't that many components that are, or could be connected to ground, I start removing them and checking the PA base ground as I proceed. After various capacitors and the 2 PA transistors(!) have been removed, the ground still remains.. I look across to the LPF connection and remove Z1 (Effectively a link to part of T4). The ground to the PA base disappears.. Progress..

Taking another breather, I consider T4 (As well you might), something from the LPF side of T4 is grounding across T4? Puzzled, I remove one of the T4 output wires(3), and replace Z1, the base ground again disappears. After some wonderment I resolder the wire and the short does not reappear. I fail to quite see the logic here, but clearly there was something odd happening with T4.

A considerable time is spent cleaning up and resoldering all the removed parts, checking everything along the way. K2 4039 is once again connected to its dummy load and tested, this time we have RF!!

Looking again at the PA circuit diagram, also reveals that T4 should have 3 turns on the output not 2, this could explain the slightly high current (2 turns are recommended for optimum 5 watt operation. The next task is then to take the heatsink apart again, and rewind T4!!

No parts (7:00!)

11th July - Main Board - Rewound T4 and reassembled, then did a basic rx and tx alignment. Perhaps uses a tiny bit more current than I would expect, although I expect this is down to alignment. Once the basics are all working I will use Spectrogram for a full tune up. The components for the SSB Board are sorted and the first few soldered in. 4 parts (2:00)

Elecraft K2
          SSB Kit
K2 SSB Kit

12th July - SSB Board - Various components 104 parts (3:00)

14th July - SSB Board - Installation required the removal of 2 links and a capacitor. This was done by unsoldering the top pad, using a fine iron tip and a steady hand, while gently pulling the component out. This was alot easier than unsoldering on one side while pulling the component from the other! Next an Info 230 message, Hastly looked it up in the manual, Frequency counter probe not connected to BFO test point! everything checked out then.

16th July - Assembly of topboard and speaker. Awkward soldering the speaker wire on to external speaker jack, as the wire insulation melts instantly, the plug connectors gallantly refuse to take solder, but when they finally do, the solder does not forget to run across the plug neatly shorting it.. 2 parts (1:00)

17th July - Refitted the rest of the case. When operating, 4039 seems to have developed a bit of an anoying "rock" from front left to back right. I post a message to the Elecraft group. Two helpful replys.. 1. Check the position of the two rear feet as they can be moved backwards and forwards slightly. 2. Loosen the side cabinet screws gently, press down on the top panel then retighten. These procedures get 4039 sitting correctly!!!

Next another re alignment. But the bandpass filters fail to peak properly, this is discussed with Tom (Who asked if the AGC was off) and Sean.

18th July - Tried some initial testing on 40m from the car, but despite antenna tuning efforts, RF did not want to radiate, High Current warnings on the display.. Later made another attempt on 20m, and after an hour plus of listening and calling successfully answered a CQ call from YZ80AA, and made a brief contact.

19th July - Still curious about the band pass filters, I post a message to the Elecraft List. Later N0SS emails a reply, and gives a vital clue. The clue, is of course the AGC... Once switched off, the easy peaking of the band pass filters returns! Reasembled and started the Auto ATU.

K2 Auto ATU
Completed Auto ATU

21th July - Auto ATU - 3:00

22th July - Auto ATU - 1:30

23rd July - Auto ATU - 00:45

“R6 is installed AFTER testing! Out with the solder sucker..”

24th July - Auto ATU - Control and RF cables plus a few final components. R6 does not seem to be mentioned in the manual, But after a little consideration it is installed. The manual conflicts with it's earlier requirements for the position of the lock washers on the control board. Never mind! Having read on, R6 is only installed AFTER most of the testing. Out with the solder sucker.

Removed R5 in error! The setting of C10 is very very fine, this will be revisited with the aid of an analog meter.(1:00)

Elecraft K2 Testing Power Output
Testing Power Output

24th July - Completed the final install, wiring and test. Built the RF probe and tested the power output and calibration of the ATU. (1:00)

28th July - Built and installed the 160m module. (1:00)

29th July - Built and installed the Internal Battery option. The K2 is complete! (2:00)


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