Sherwood has posted his measurements of the K4D's receiver performance in his table:
http://www.sherweng.com/table.html We're quite pleased with his test results, which confirm that the K4/K4D is near the top of its class (direct-sampling SDRs). A K4HD would provide somewhat higher dynamic range for those stations in extreme signal environments, but the vast majority of operators will find that the K4/K4D more than meets their needs. I'd like to highlight a few important items in Rob's chart. First, the K4D has a high 2 and 20 kHz dynamic range value of 101 dB. Because it's a direct-sampling radio, this figure will hold at nearly all offsets from strong signals. Second is the block dynamic range number (128 dB), higher than almost every other "pure" SDR measured. Finally, there's the LO noise (local oscillator; 148 to 155 dB) -- again, very favorable compared to all competing SDRs. This is an important number correlated with reciprocal mixing dynamic range (RMDR). Taken together these demonstrate that the K4D will offer excellent performance in crowded band conditions. Inevitably a question will arise regarding the chart position of the K4D relative to a couple of our other transceivers: the K3S and KX3. There's a bit of "apples to oranges" in both comparisons. The K3S uses a superhet receiver architecture. The K4HD will provide a receive setting that emulates this superhet performance when and if it's needed. But the "pure" (direct sampling) method used by the K4 (all models) has many advantages. One is the elimination of artifacts associated with crystal filters. Another is that, as a pure SDR, the K4 has a far more flexible architecture. We'll be able to provide updates to the receive and transmit digital signal chains that cannot be added to a superhet like the K3S or its competitors. The KX3 is another Elecraft radio high on Sherwood's chart. Its performance is excellent, especially at its price point. But its numbers relative to the K4 are somewhat misleading, as hinted at by Rob's footnotes. The KX3 uses a quadrature downsampling architecture, which digitally samples at baseband audio rather than at RF. This is ideal for a radio like the KX3 that has to have very low current drain for portable operations. The K4 uses a direct-samping architecture that requires a higher power digital signal chain, resulting in important benefits over quadrature downsampling including much higher and more consistent opposite sideband image suppression and 2nd-order intermod rejection. So the two are really designed for different applications. Overall, this first independent test of the K4 validates the performance of our SDR architecture. Feel free to send us any further performance questions. 73, Wayne N6KR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to [email protected]
