Hi, the block diagram of the K2 can be found in the owners manual page 148. http://www.elecraft.com/manual/E740001_K2%20Owner's%20Manual%20Rev%20I.pdf
73 de Hajo DL1SDZ Gruss Hajo --- Cela est bien dit, mais il faut cultiver notre jardin. On Sat, Dec 12, 2015 at 12:55 PM, David Woolley <[email protected]> wrote: > I don't think these descriptions are accurate, particularly the K2 versus > K3 one. > > The K2 is a fairly conventional, single conversion, analogue design. As > stated, it uses the crystal filter for primary selectivity. It typically > has up to two crystal filter options, one hard wired, and the other as an > integral part of the SSB adapter. The hard wired one is adjustable, and > the SSB one is fixed. The filters are constructed by the final assembler, > from individual crystals. Although there is a DSP option, it works purely > on the audio. > > The K3 and K3X are software defined radios (SDRs) of the non-direct > sampling variety. I use SDR in the technical sense, not in the amateur > radio community sense; the latter requires the digital processing to be > performed on a PC. This means they have an analogue front end with at > least one analogue mixer, but the final processing is done digitally. > > The K3 has a double conversion superhet architecture, with an HF first IF > and an extremely low second one. There is a selectable crystal filter > (using commercial sub-assemblies) in the first IF, which provides coarse > selectivity. The final IF processing is digital. There is a quadrature > path starting from the second mixer, analogue at that stage. Combined with > digital processing, this creates an analogue of a phasing design receiver > to suppress the final IF image, rather than the audio image. As the signal > continues in quadrature, the digital processing may also act analogously to > a phasing receiver to do the final conversion and audio image stripping, > but it may be that the internal logic is more complex than that - the fine > details are a trade secret, although they may or may not have release > information about that part of it. > > The K3 also does digital processing on the recovered audio, but this is > done within the same digital processor as the final IF processing. > > The K3X, for CW at least, implements a hybrid analogue/SDR direct > conversion, phasing design. For SSB it may do the same, but it is also > possible that it actually implements a final passband centre at 0Hz, and > then does a final frequency shift to move the centre of the passband to the > correct audio frequency (i.e. they could have implemented it as a single > conversion architecture). Selectivity is provided entirely by digital > processing. > > For both the K2 and K3, first mixer image rejection is provided by a > combination of band pass filters, optimised for each band, and a low pass > filter, also optimised for the band. For the KX3, the image is the one > removed by the phasing, although there is also analogue band and low pass > filtering - I'm not sure whether this is switched, or there is a single, > compromise, filter. > > Block diagrams for all three are fairly easy to find. I have the K2, so > did that from memory, but the K3 one is at < > http://www.qsl.net/wb4kdi/Elecraft/K3/K3_Block.png> and the KX3 at < > http://www.elecraft.com/manual/KX3%20Manual%20Block%20Diagram.pdf>. There > are likely other places, including a better K3 image. > > -- > David Woolley > Owner K2 06123 > > On 11/12/15 21:40, Ron D'Eau Claire wrote: > >> The K3 and K2 and conventional superhetrodyne formats with an Intermediate >> Frequency in the H.F. range and crystal filters to set the passband. The >> K2 >> has an adjustable crystal filter and the K3 uses fixed crystal filter >> bandwidths. The basic K2 bandwidth is established by the crystal filter >> while the K3 adds an adjustable DSP filter after the crystal filter. (The >> K2 >> has an optional audio DSP for enhanced filtering.) >> > > ______________________________________________________________ > 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] > ______________________________________________________________ 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]
