March 2000 QST

two inductors. Don’t let this happen to you!Be careful to identify the correct locationfor every part before you install it, andrecheck before soldering.Figure 5—A closer look at the completed control board. The glass epoxy boardshave plated through holes and the component identifications and locations areclearly silk-screened on the boards.quite informative. Someone mentioned thatthey really missed not having a dimple onthe main tuning knob. Someone else noticedthat the knob on their Yaesu FT-100 wasabout the same size. Subsequent postingsindicated that the parts sales staff at Yaesuquickly learned that all these knobs werebeing ordered for Elecraft K2 radios—notYaesu FT-100s. Within two days they hadsold out their entire stock of replacements!In another posting, a European buildercirculated a question regarding degradedreceiver performance after installing thenoise blanker option. After severalquestions about measurements and hearingfrom a few others who had noticed a similareffect, Wayne and Eric went to worktracking down the problem. Their response?A change in the design of the noise blankerand an upgrade kit for the earlier version.The optional noise blanker that wereceived with our initial K2 shipmentseveral months ago was the “original”version. With it installed, our lab testsrevealed reduced intermodulation distortiondynamic range and blocking dynamic rangeand a degraded third-order interceptpoint—even with the noise blankerdeactivated. Elecraft provided us with theupgrade. Table 1 reflects the performancethat we measured with the latest version ofthe noise blanker installed.If you have Internet access, once you’veordered your kit, I highly recommend thatyou subscribe to the reflector. Send an e-mail to majordomo@qth.net withsubscribe elecraft in the body of themessage. You can also view the list archivesat http://www.elecraft.com.Back to BuildingAfter completing the first-stagealignment and testing, the boards areremoved from the partially completedenclosure and the remainder of thecomponents are installed on the RF board.Most of your efforts will be in assemblingthe receiver section. Here you will windyour first toroidal inductors andtransformers. The K2 contains a total of 14toroidal inductors and six toroidaltransformers. In addition, there is onetransformer wound on a binocular core.Because time was running short tocomplete this review for this special QRPissue, once I’d finished up the receiversection, I turned the kit over to Zack Lau,W1VT, for completion of the transmittersection and the final alignment. Zackreported no major difficulties, except thatI had installed RFC3 in L16’s spot and viceversa. This caused some problems with thereceiver on 40 and 80 meters. Once Zacklocated and corrected my error, everythingwas fine. In my defense, the label for RFC3is directly between the locations for theseHow Did It Do in the Lab?The technical performance of radios comes out during lab testing. Usually, the transmit IMDand receiver dynamic range results separate the toys from the big boys. Usually!On SSB, this radio is clean. As seen in Figure 1, the high-order intermodulation productsare quite good. The CW keying is nice, too, as shown in Figure 3. No key clicks from this baby!But where the K2 really shines is in its receiver performance. On average, transceiverspositioned in the upper tiers of the popular HF product lines (in the $2000 to $3500 price class)exhibit blocking dynamic range measurements somewhere in the vicinity of 130 dB and a twotone,third-order dynamic range near 95 dB. The K2’s receiver performance compares veryfavorably to that of the samples of the high-end radios we’ve recently examined, turning inimpressive 136/97 dB figures for these parameters.The fact that a radio in this price class—and a home-built one at that—can stand proudlyin such company is a remarkable accomplishment. This is the first-generation radio that Elecrafthas produced. I can’t wait to see the next one!—Ed Hare, W1RFI/QRP, ARRL LaboratorySupervisorAlignment and TestingThe alignment steps involve adjusting afew tuned inductors and variable capacitorsto set the voltage controlled oscillator andthe various tuned circuits. The controlsoftware performs a procedure to linearizethe VFO operation across the tuning range.You also adjust the crystal filter settings andthe BFO settings for each mode and band.The filter scheme is especially interesting.Most commercial transceivers comewith a “stock” filter for sideband and anarrower filter for CW operation. Inaddition to these there is usually room toadd one or two additional optional filters.The K2 uses a scheme of diode switchingand software control to provide four crystalfilter settings for each mode. These are adjustable,so you can tailor the bandwidthsto suit your operating style. The factorydefault settings for CW are 1.5 kHz and700, 400 and 100 Hz.You also set up four filter bandwidthsfor SSB reception. The defaults are 2.2, 2.0,1.8 and 1.6 kHz. (You can still receive SSB,RTTY and the data modes even with a basic“CW Only” K2).If you should decide to add the SSBadapter, there is yet another filter—optimized for SSB operation at about2.3 kHz. In that case, filter 1 is optimizedfor SSB transmit and filter 2 is optimizedfor SSB receive. Filter 3 can be set as anarrow bandwidth SSB filter. The defaultis 1.6 kHz. Filter 4 can even be set at anarrower bandwidth—useful for the datamodes.Some builders have reported confusionabout the procedures for aligning the filtersand BFO settings. When we followed thesteps in the Owner’s Manual we came close,but the settings were not “perfect.” Therehave been several discussions about this onthe e-mail reflector, including postingsabout programs to download that will allowyou to use your computer’s sound card asan audio spectrum analyzer. Elecraft hasindicated that they will be changing someof the procedures in the manual.The K2’s control software includesextensive diagnostics. If you turn on theradio and the display shows “LOW BATT,”the software is telling you that the batteryor power supply voltage is too low, adisplay of “HI-CUR” on transmit indicatesthat the user-programmable current levelwas exceeded, and so on. Troubleshootingcharts are provided. This could be especiallyhelpful if you run into difficultiesgetting the radio working initially.72 March 2000