The IC-7300 uses a 14-bit ADC. My ANAN-100D uses 16-bit ADC and overload of ADC occurs at a signal level of -10dBm, which I never see in my single transmitter environment. I do prefer the K3s for contesting, but not for lack of front-end robustness on the part of the ANAN.
73, Barry N1EU On Wed, Apr 27, 2016 at 3:48 AM, Barry LaZar <[email protected]> wrote: > Joe, > I agree with you basically. I think it's just the manor in which you > state the problem. > > You touch on the real problem 14-16 bits of sampling vice having more > bits in the sample. It's not specifically the direct sampling architecture. > I think the radio companies just can't get 24 bit ADCs fast enough to do > direct sampling at commodity pricing which would allow direct sampling with > out the baggage. If I can do 24 bit sampling and high and low pass > filtering, I can simplify receiver design AND have a an acceptable dynamic > range. Multiple instances of DSP processing of the 24 bit samples will > allow as many virtual receivers, slices, as processor power will allow. My > guess is we are on the verge of getting to where we would like to be. > > Flex is using a 16 bit ADC and I'm not sure what the 7300 is using, > but I infer it, too, is 16 bit. I do believe that the Elecraft > architectures are all based on 24 bit sampling. The Elecraft designs should > be tolerant to serious environmental abuse short of a local thunderstorm. > > Our comments reflect a rigorous tech discussion. But, there is another > issue that has not been discussed in anything I've read so far, ultimate > filter rejection. Flex, Kenwood, and Elecraft have filtering that runs in > the 100 db region, or a little better. I saw that the IC-7300 is about 20 > db worse. What that means if you are a CW operator, serious or otherwise, > and there is a pile up on a DX station, a contest, or just a really busy > weekend, you may have problems from strong stations not too far away while > you are trying to work an S1-3 station. SSB operators have other problems > like splatter and no amount of superb design will fix that. > > I'm pleased there is a vigorous discussion on the new radios. It helps > push the designers and the technology. > > 73, > Barry > K3NDM > > > ------ Original Message ------ > From: "Joe Subich, W4TV" <[email protected]> > To: [email protected] > Sent: 4/26/2016 10:10:32 PM an > Subject: Re: [Elecraft] Sherwood's receiver performance table updated > > On 4/26/2016 8:08 PM, Kevin Stover wrote: >> >>> Everybody is ignoring W4TV's 800lb Gorilla, ADC overload. >>> >> >> I can't take credit for that ... the warning comes from some of the >> best RF designers in the world. Direct sampling receivers are very >> good in controlled situations. Unfortunately, those who are used to >> analog superhetrodyne receivers do not recognize the symptoms of ADC >> overload/overflow in many cases. >> >> The overflow can show up as an occasional click or pop if the number >> and strength of signals continues to increase conditions go down hill >> very rapidly. The best 16 bit ADC based SDRs can and do show very >> significant overload issues when run without effective front end >> bandpass filtering in high RF environments (160 meters near AM BC >> stations, 40 meters in Europe, 160 meters in New England during a >> contest, etc.). >> >> One can apply filtering (which Icom seems to have done in the 7300), >> apply attenuation (which Flex seems to have done in the 6000 series) >> or both. Filtering limits the number and width of "slice receivers" >> while attenuation kills weak signal performance. >> >> I find Icom's implementation interesting in that they are using the >> technology as a single band, single channel receiver (they could have >> added Dual RX within the same band at practically no hardware cost) - an >> application where, with tight bandpass filtering, direct sampling >> may be ready to compete as indicated by the fact that Sherwood's tests >> place the 7300's above some "good" conventional rigs like the Ten-Tec >> Eagle, Kenwood TS-590SG and TS-990 in MDS, LO Phase noise and IMD DR. >> >> However, for the ultimate multi-channel receiver, ADC technology is >> still 4 to 6 bits short as witnessed by the need for 12 to 20 dB of >> attenuation in the Flex 6000 or the 0 to 30 dB electronically stepped >> attenuators in some of the other products like the Anan, Hermes, etc. >> Sherwood's results hint at this when comparing the MDS with the >> preamp on and preamp off ... even with its preamp on the Flex 6700 >> MDS is the same as the K3S with *no preamp*! >> >> 73, >> >> ... Joe, W4TV >> >> ______________________________________________________________ >> 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] > ______________________________________________________________ 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]
