>
> From Flex, my questions in red:
> "A number of people have asked how you can get more than 96 dB of
> instantaneous dynamic range out of a 16-bit A/D converter. You may think
> that one can only achieve 6 dB per bit, which would be 96 dB. Technically
> the theoretical maximum limit is 6.02n +1.67 dB (wheren is the number of
> bits).[1,2] What many people fail to understand is that dynamic range is a
> meaningless term without knowing the final detection bandwidth (i.e. 500 Hz
> CW filter). Indeed narrowing the final detection bandwidth reduces noise as
> well. That was true with analog filters too. The only problem with this
> approach in analog signal filtering was that added electronic again was
> required to offset the filter loss, often with an INCREASE in overall noise
> due to the added noise from the amplifier’s noise figure. DSP filtering does
> not suffer in this regard.
>
> Instantaneous dynamic range increases with decreasing bandwidth by a factor
> of 10*log*(bandwidth change). That means that a 50 Hz filter will provide 10
> dB higher dynamic range than a 500 Hz filter. That is why you hear less
> noise in the smaller filter. The actual receiver noise figure (NF) of the
> radio has not changed but the detection bandwidth has. Thus the SNR and
> dynamic range improves accordingly. Within the bandwidth being detected!
> Therefore, yes, the dynamic range does improve at narrower bandwidths if the
> dynamic range is noise limited. This would, of course, be true on 40 meters
> in the summer. However, unless I messed something, this answer does not
> address the problems that take place when a signal whose amplitude is 148 dB
> above the LSB (least significant bit) voltage. An A/D converter has a voltage
> change for each bit. If the span of the A/D is 10 volts, then each bit in a
> 16 bit A/D accounts for a change in amplitude of 10V/65536 = 0.0015 V/bit
> (1.5 mV/bit). If you assume that a signal on the antenna of 1 uV is
> “copyable” in CW, and is thus at least a few dB above the noise floor, S1,
> for example, on a quiet band, then there would need to be some sort of gain
> stage (~1000X or 30 dB) to bring this up to one least significant bit.
> Alternatively, you design so that the LSB step size is 1/1000 of 10 volts or
> 10 mV. That is allowing only 1 bit to give you your CW signal. Realistically
> you need 4 bits to give a readable signal on CW, about 6 to 8 bits for SSB.
> So when you are detecting this 1 uV signal with a 50 Hz filter in place, all
> is well and you have good instantaneous dynamic range.
>
>
>
> However, the A/D is simultaneously looking at the entire HF spectrum all of
> the time. It is digitizing that entire spectrum all of the time at twice (or
> more) the Nyquist frequency, and is extracting each individual signal using
> the DSP to unravel the complex waveform (which is the Fourier transform of
> the entire waveform that is digitized). If a signal appears anywhere between
> 0 and 30 MHz with an amplitude greater than 96 dB above 1 uV, with a 16 bit
> A/D, you have a problem. A signal 148 dB greater than 1 uV, quite often the
> case for the large shortwave station down the block, presents a signal
> voltage of 25 volts. Houston, we have a problem.
>
> The law of linear superposition, essential for any of this stuff to work,
> simply states that the instantaneous value of any sampled point is the linear
> sum of all of the components at the sampling point. Thus, the 25 volt signal
> from that shortwave station rides on top of the 1 uV signal you are trying to
> hear. In reality, this will be well outside the“ maximum peak signal handling
> capability” of the A/D converter.
>
>
>
> When you get outside the“ maximum peak signal handling capability” of the A/D
> converter, the law of linear superposition is still true, but the A/D cannot
> measure that signal because it is out of range. Very non-linear things happen
> when an A/D converter gets outside the“ maximum peak signal handling
> capability”. That would be known in analog days as “overload” or “blocking”.
>
>
>
> The dynamic range of any ADC is normally assumed to be specified over the
> Nyquist bandwidth, which is equal to 1/2 of the converter’s sampling rate.
> With the ADC used in the FLEX-6000 series, the Nyquist bandwidth is 122.88
> MHz. To calculate instantaneous dynamic range, one needs to know the
> converter’s specified signal to noise ratio (SNR), maximum peak signal
> handling capability, sampling rate, and final detection bandwidth. There are
> many application notes available from Analog Devices, Linear Technology,
> Texas Instruments, etc. that aid in these calculations. It is beyond the
> scope of this newsletter to provide the detailed education and analysis."
>
> Sent from my iPad
>
> On Aug 16, 2016, at 7:59 AM, Barry N1EU <barry.n1eu@gmail.com> wrote:
>
> You don't need a PC. You can use Maestro or an iPad.
>
> Violated the laws of mathematics? I suggest reading this:
> https://www.flex-radio.nl/flex-6000-serie/dynamicrange/
>
> Barry N1EU
>
> On Tue, Aug 16, 2016 at 8:55 AM, Gary J FollettDukes HiFi <
> dukeshifi@comcast.net> wrote:
>
>
> Flex has never been shy about touting their own perfection, ala' the 2
> hour on-air infomercials on 20 meters every Saturday afternoon.
>
> And you still need a PC to run one…
>
> Apparently someone has devised a way to get more than 96 dB dynamic range
> out of 16 bits and my congratulations to them for having successfully
> violated the laws of mathematics.
>
> I wish they would apply that to the sub-par Compact Disk format with which
> we are stuck…
>
> Gary
>
>
>
>
> On Aug 16, 2016, at 4:25 AM, Barry N1EU <barry.n1eu@gmail.com> wrote:
>
> The argument that the current 16-bit digital sampling offerings (Flex 6K,
> ANAN-100/200, MB-1, etc) are insufficient in bit depth and sampling rate
> doesn't hold water IMHO. Besides my own experience of no observable
> overload during major DX and 160M contests, here are a few more tidbits
> to
> consider:
>
> http://www.eham.net/ehamforum/smf/index.php/topic,110479.0.html
>
> https://community.flexradio.com/flexradio/topics/adc-
> overload-myths-debunked
>
> etc etc
>
> Barry N1EU
>
> On Tue, Aug 16, 2016 at 7:43 AM, rick@dj0ip.de <Rick@dj0ip.de> wrote:
>
> EXCELLENT Gary. Thanks.
>
> I only disagree on the timeline. I don't think it will take so long.
>
> The MB-1 from Sun SDR or Sun Expert (not sure which brand they are
> pushing) "claims" to be what you described, but it costs $5K. However
> prices will drop rapidly as soon as competition is there.
>
> Within 3 years we will have it.
>
> In the year 2020, SDR with knobs a'plenty. (no computer required)
>
> BTW, has anyone actually seen or used the MB-1?
> I haven't heard a single user review yet.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt, Germany)
>
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Gary J
> FollettDukes HiFi
> Sent: Tuesday, August 16, 2016 7:23 AM
> To: Discussion of Ten-Tec Equipment
> Sub
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