+++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Fri, 08 Dec 2000 12:36:55 -0800 From: Eric Swartz WA6HHQ - Elecraft Subject: [Elecraft] ARS Sojourner K1 Review - Comments This month the Adventure Radio Society published a technical review of the K1 in their web magazine, ARS Sojourner. I commend Russ for pushing all of us to design high performance receivers. He voices some strong general opinions regarding receiver front end designs with NE602 Gilbert mixers, audio derived AGC etc. I'd like to post some comments on the review below. As usual, Russ did an excellent job of doing the lab tests. His data is well presented and we really like the comparison charts. Russ accurately states that: "The K1 is a NorCal 40 / Sierra / SST on steroids." This is exactly what we intended and our RX specs bear this out. What I'd like to point out is that there are really two legitimate categories of RX performance: 1) The 'crunch-less' front end used by higher end, more complicated and expensive rigs (K2, FT-1000 etc.), and 2) The 'reasonable' RX performance offered by rigs like the K1, DSW-20, Sierra, NorCal 40, SST, IC706, FT-100 etc. Russ appears to have a strong bias against -any- RX based upon a '602' Gilbert Cell type mixer. (We do too, as you can see in our K2 design - but only for higher end designs - not those intended for simple construction and portable use..) I feel Russ misses the point in the case of the K1 and rigs like it. We DID design it for low current drain portable use and that basically limited us to a low power mixer like the '602. That's how we achieve its 55 ma RX drain. We optimized the RX chain so it performs significantly better than other '602 designs and we also made the front end band pass filters extremely narrow to reject out of band signals. Our K1 users in Europe (with its harsh RF environment) have been very happy with its performance, even on home antennas. Its not meant to be a K2, but it performs at the top of its class of simple, portable, low cost rigs. The '602' also allow us as designers to significantly reduce the component count in the rig. What is really interesting about the review is that the K1 RX performs exactly where we expected it to: More or less at the top end of the 'Gilbert Cell' mixer rigs, and surprisingly better in several RX specs than a couple of the 'diode ring' mixer rigs like the QRP+ and NC20. (Readings within 3-5 dbm on the charts are essentially equal since the measurements can vary by that much from rig to rig and lab session to lab session.) A third order iP in the -5 dBm to 0 dBm range is not bad for this class of rig. The ARRL numbers for the IC706 are -1.3 to -11 dBm and the TS-50 comes in between +3 and -7 dBm. Certainly the higher end RX rigs like the K2, FT-1000 etc. have much better numbers, but this comes at additional expense, size, complexity and current drain. The negative comments on the variable crystal filter are odd since he provides no supporting detail except for the raw data on the filter. The filter graph is where we expected it to be and as you have noted it works quite well. (Yes, the wider response setting has a broad roll off, but this width is only intended for use while tuning the band. I always use the narrower K1 filter settings for the final QSO.) Any of the many NC40 / Sierra / SST / DSW20 users out there will be more than happy using the K1. Russ also made a negative comment about audio derived AGC in general, which is used in all of the rigs in this class (NC40, Sierra, SST etc., and even by the the NC20, QRP+ and SG-2020. (The DSW-20, 40 etc. and the SW40 series have no AGC. They rely on manual RF gain and diode clipping limiting in their AF stages.) We worked hard optimizing the K1's audio AGC performance to be the best in this category. IF derived AGC will always have a better attack time, but it would have added significantly to the size, complexity and cost the the K1. The bottom line is that we designed the K1 with the following goals in mind: 1. Very low RX current drain for battery / portable operation 2. Very easy to build, understand and debug - even for first time builders. 3. Reasonable cost - well below the K2 and other full feature rigs. 4. Good RX operation in over 95% of operating situations. 5. Excellent TX characteristics (excellent harmonics and a great keying waveform.) 6. Unmatched features in a single, very small, package: Built in memory keyer, digital display and options for a noise blanker and internal auto tuner. You can basically throw the K1 into your briefcase, knapsack or lunch box, along with a battery and spool of wire, and be on the air where ever you choose to go! All reviews are subjective. What is excellent about Russ's ARS review is that while he voices his opinion about RX designs strongly, he follows his subjective opinions it with lab data. While I wish he had made it clearer he wasn't singling out the K1 RX performance versus other rigs in its category, I think most readers, after reviewing the data and comparing the K1 to the other rigs in its class, will not be disappointed at all. So far our K1 customer feedback has been exceedingly positive. A final note: Wayne and I are obsessive optimizers. If there is a way to squeeze more RX performance out of rigs designed for this class (small, portable and easy to build and understand), you can be sure we will find it! 73, Eric WA6HHQ www.elecraft.com +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Fri, 08 Dec 2000 11:44:43 -0800 From: Wayne Burdick Subject: [Elecraft] K1 vs. Sierra Hi Phil, There's been some discussion recently weighing the K1 vs. the Sierra. A while back I put together a Q & A for just this occasion (see below). All of this information is available from on-line sources already, but I think this is a useful summary. Feel free to forward it to any interested parties. Given that I designed the Sierra, and was also priniciple designer of the K1, I could be perceived as biased either way. Get additional opinions ;) Clearly, both rigs have their place. 73, Wayne N6KR * * * Q: Overall, how does the K1 compare to the Sierra? A: The K1 is about what you'd get if you put a Sierra, two band modules, and a KC2 all into a smaller box, improved the performance, and gave it a modern user interface. (We think of it as a "Next-Generation" ultra-portable CW transceiver.) The design is modular and extensible, so that different types of filter boards and other options can be added in the future. The basic Sierra kit (less KC2) is somewhat simpler, it has a single PC board and no microcontroller. It operates on all bands but requires manually-inserted modules. Q: What additional features does the K1 offer? A: The K1: - uses internal band-switching using latching relays - puts out a full five watts or more on each band - has plenty of audio output, and includes an internal speaker - has excellent receive I.F. gain--enough to provide good sensitivity even with the -14 dB attenuator turned on (and in this mode, the "headroom" should be about 20 dB better than other active-mixer rigs) - has internal ATU and noise blanker options - has both RIT and XIT for working DX split - has a full-featured memory keyer with auto-repeat - has an easy-to-use menu system that provides many ways to customize features and performance for the individual operator - has an optional wide-range tilt stand (KTS1) that makes it the world's first true "Trail-Friendly Radio"; a featherweight keyer paddle can be attached directly to the tilt stand Q: How easy is the K1 to build? A: The K1's digital display and microcontroller are completely integrated into the design, with no hand-wiring Q: Does the Sierra have any other advantages over the K1? A: The Sierra has slightly lower current drain (35 mA vs. 50 mA), and you can get band modules for 160-10 meters. There are fewer bands available for the K1 at present. ++++++++++++++++++++++++++++++++++++++++++++++++++++ Date: Sun, 10 Dec 2000 11:37:36 -0800 From: Wayne Burdick Subject: Re: [Elecraft] ARS Sojourner K1 Review - Comments Julian, Peter, et al, I just wanted to add that we recently designed tighter filters for the K2 on some bands, in response to some European K2 users who had near-band interference on 17 and 20 meters. We're still testing these filters, but it's clear that the present filters can be narrowed significantly on 40 meters and higher. Additional loss is very low (< 1 dB typ.), and only capacitor changes are needed. We may make some of these filter changes permanent, but we won't know until we've completed testing. If you have specific questions about the new narrower filters, contact gary at elecraft.com. Gary has the new component values and is doing the tests. 73, Wayne N6KR +++++++++++++++++++++++++++++++++++++++++++++++++++++++