> BRUCE WW8II <wa8...@gmail.com> wrote: > > The question is will the K4 or K4D be as good or better on receive than my > K3s with the > 2.1kHz and the 200Hz filters. > > Bruce WW8II
Bruce, First, a bit of background would help since they're two different architectures. The K4/K4D are "pure" SDRs, meaning they're more agile in frequency, operating modes, modulation and demodulation, features in general, and extensibility. A lot of the flexibility of the design is in service of the built-in and external displays as well as remote control. The K4/K4D also have a lot more digital and RF I/O, satisfying the demand for a modern, integrated station. For example you can directly attach a keyboard, mouse, HDMI monitor, and flash storage drives or other USB devices. By contrast, the K3S is a superhet, with emphasis primarily on receive close-in dynamic range performance rather than integration, agility, extensibility. The use of crystal filters is an advantage in raw performance, at the expense of passband flatness, available bandwidths, and group delay. The K4HD will be a hybrid of the two: When the extra dynamic range is needed, you can turn on the HDR module, which is essentially two superhet downconverters, one for the main receiver and the other for the sub. But the HDR module is, in practice, rarely needed unless you have high-power transmitters in close proximity. Examples of this situation include multi-transmitter contest or DXpedition stations, those living in the shadow of a broadcast station, and those with very nearby ham neighbors. With this context we can now talk about receiver performance. - The K4/K4D are very similar to competing pure SDRs using 16 bit, wide-band A-to-D converters: signal handling is excellent by any measure, and there's plenty of headroom in all but the most heavily impacted RF environments. - Compared to *any* pure SDR, the K3S (and a few other superhets) will have a few dB higher third-order intercept point. (Note that Sherwood's chart still shows the Flex 6700, a pure SDR, at 108 dB. He corrected this later to a much lower number -- see the '6700 footnotes in the far right column.) - The K4HD will be in the same ballpark as the K3S, though we're still refining the design and our goal is for it to be higher. (The limitation with any superhet is the crystal filters, and we carefully control the quality of our suppliers.) 73, Wayne N6KR ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
