Certainly an interesting thread. But so far nothing about the QSD/QSE approach. Which performs better a Flex 5000 or a QS1R?
Chris --- In [email protected], "dharmaBum" <dharma...@...> wrote: > > Marco > > Thanks for a very understandable reply. I would also like to thank other > people for adding their knowledge and opinions. > > This is certainly an interesting thread... > > Wayne > > --- In [email protected], Marco IK1ODO -2 <ik1odo@> wrote: > > > > At 10:31 13-05-10, you wrote: > > > > > > > > >Alberto > > > > > >Thanks for a great reply. I'm familiar with the analysis that you > > >detailed. I should have mentioned that I'm interested in SSB and PSK. > > > > > >You mentioned that 86 db might not be enough for HF. What drives the > > >quest for dynamic range? Is it the ability to dig out a weak station > > >next to a powerful one? > > > > Hello Waine, > > > > your receiver ADC gets all the signals that are present at his input. > > That may be the antenna, or the output of a preselection filter if > > there is one between antenna and ADC. > > You want to have a receiver sensitive enough to hear the band noise; > > that requires a noise figure in the order of 10 dB in HF. That means > > approx. -129 dBm of input power in 3 kHz BW. > > On the other side, the ADC has to handle the strongest signals that > > reach the input. If you listen to 40m by the evening in EU, you get > > up to +10 dBm peak (1 V pk, measured...) due to BC signals close to > > the amateur bands. > > So the required dynamic range is of the order of 139 dB in 3 kHz. > > Since it is currently unreachable, you need a preselector to limit > > the signals that the ADC sees, and an attenuator to work on low bands > > (where the band noise is higher and a loss of sensitivity is acceptable). > > To have 139 dB of dynamic range one needs a 100 MS/s ADC with 16 bits > > of ENOB, or 94 dB dynamic range ... current 16 bit ADCs have far > > less, at the point that there is a very little difference in dynamic > > range between 14 and 16 bit converters. > > > > 73 - Marco IK1ODO / AI4YF > > >
