Scope Wars

[2N3055]

This is 50 MHz AM modulated with 100 Hz. It has very well functioning antialiasing filter.

(Attachment Link)

But, if you enable FFT, it starts aliasing.

(Attachment Link)

That means that it is mindful of the fact that FFT needs clean signal sampled under certain rules, so it disables mumbo jumbo and feeds FFT clean data. Antialiased "envelope display mode" is gone.

Also, on cursory glance, it doesn't seem Peak detect is fed to FFT. Averaging and Hires are, but for Peak detect and Normal FFT look pretty much the same.

So scope manufacturers know a bit about these things.

But the FFT is not showing anything at either 50MHz or 100Hz?

I wasn't trying to get usable FFT, but demonstrating that switching on FFT changes how scope handles aliasing.

[David Hess]

Are you saying it would be a bad idea for the scope to apply another, second filter that depends on the maximum frequency that the display is able to show at the selected sweep speed?

I think David Hess is referring to the situation where the samplerate has to drop because the memory is too short to capture a full screen at the maximum samplerate.

I am saying that applying a filter before decimation to prevent aliasing due to the lower sample rate after decimation is worse than not filtering at all because it corrupts the histogram of the input signal.  That is what an anti-aliasing filter would have to do.

OTOH I wonder what good peak-detect does on the FFT operation anyway; do you want to have both enabled at the same time?

Peak detection is incompatible with many but not all measurements including FFTs; it also corrupts the signal histogram.  Some very recent DSOs from R&S implement multiple decimation operations in parallel to produce multiple acquisition records, like sample, peak detect, high resolution, etc., simultaneously.

The design which I have been looking into produces multiple histograms whereas a DPO type of oscilloscope produces one, with the fastest histogram replacing peak detection and the others having higher resolution at lower sample rates.  This makes the best use of limited hardware resources to produce an analog type display which captures as many characteristics of the input signal as possible.

I would prefer my digital scope to default the trigger position to one division from the left side of the screen, so you can see a little bit of "before" the trigger, and still use almost the whole screen for the rest of the signal.

You can of course manually move the trigger location horizontally, but that messes up with zooming in and out on a digital scope.

I am not sure what you are doing but most DSOs allow the trigger position within the acquisition record to be adjusted.  In the photograph I posted earlier, it is difficult to see but the the trigger position is marked with a "T" one division from the left and about one division below the center horizontal graticule line.

As far as magnification not being aligned with the trigger, analog oscilloscopes always magnify starting at the center of the CRT which has nothing to do with the trigger position.

[bdunham7]

Here is the DS1202Z-E and the MSO-2204EA being fed a 200 MHz and 300 MHz signal from an HP 8648C.

It's as good a demonstration of aliasing as you can get.  I've got the scopes in dot mode with infinite persistence. Both scopes have all channels enabled to force 500 MSa/s so Nyquist is at 250 MHz.

I didn't think the Rigol was turning the anti-alias filter on and off when I was looking at the step response.  The two photos of the Rigol screen prove that it does not work. I reset the persistence between photos and rest the frequency.

So, do you want a scope that shows you the truth or one that lies? These both lie.  They indicate that the 300 MHz signal is 200 MHz.

Have Fun!
Reg

And you would 'fix' this how?  DSP isn't going to help.

These are budget brand devices that deliver a lot of 'bang for the buck' but can get you into trouble if you approach their limits unwarily.  There are plenty of instruments that 'lie' to you if you don't understand their limitation and characteristics.  Granted, the marketing on these things is borderline criminal, but I don't think there are any cheap fixes.

You have to respect ALL of the Nyquist criteria.  You can use a sampling rate of 10X rated bandwidth with a gentler 6db/octave or so filter, or you can try to squeeze up closer to the limit with a fancier, more expen$ive analog front end.  Either way, the filtering has to be done ahead of the ADC and either way, it costs money.

[rhb]

I started this as a comparison of DSOs, not a debate about what people *think* a scope should do.  My frame of reference is a good analog scope.  So I am comparing DSOs to good analog scope signals.

The purpose of a DSO is to faithfully represent an *analog* signal.  That requires low pass filtering to prevent aliasing.

[...]

Can you show us an example of one of those scopes showing aliasing on the screen due to decimation of a signal that was within Nyquist at the native sample rate but is now aliased because of decimation?  Is that happening?  If so, I'll grant that to be an undesirable result.

Sorry for the interruption and although USB-oscilloscopes are probably off topic, but at this point I have to vent my disappointment about Agilent's U2702A (200MHz, 1GS/s, 32Mpts) in conjunction with Agilent Measurement Manager 2.2.4.0. This USB-oscilloscope can store a waveform from a single-shot-acquisition in its internal memory, then the software on the computer retrieves some amount of this data to display the waveform on the screen. You can zoom in and out, but unfortunately the decimation involved in this is done wrong, so aliasing occurs. The data is there (in the device), but the presentation is a failure. Unnecessarily. PicoScope handles this better.

The pictures show the same acquisition in different time/div settings (200µs/div and 500ns/div).

No DSO is "off topic".  I'm on the warpath because I'm so ticked off at all the really bad DSOs from all the OEMs including Keysight.  Thanks for the demonstrating the issue.

The limitation on what I test is having to buy the junk as it's hard to get a demo unit for a few months and I don't want to have my life dominated by a short loan period.

Have Fun!
Reg

[SilverSolder]

This is 50 MHz AM modulated with 100 Hz. It has very well functioning antialiasing filter.

(Attachment Link)

But, if you enable FFT, it starts aliasing.

(Attachment Link)

That means that it is mindful of the fact that FFT needs clean signal sampled under certain rules, so it disables mumbo jumbo and feeds FFT clean data. Antialiased "envelope display mode" is gone.

Also, on cursory glance, it doesn't seem Peak detect is fed to FFT. Averaging and Hires are, but for Peak detect and Normal FFT look pretty much the same.

So scope manufacturers know a bit about these things.

But the FFT is not showing anything at either 50MHz or 100Hz?

I wasn't trying to get usable FFT, but demonstrating that switching on FFT changes how scope handles aliasing.

I am seeing exactly the same thing on the 54622D.  Good to see that Keysight is still using the same code 20 years later...

20MHz carrier with 100Hz modulation.

Both the FFT and the time domain signals are deeply wrong and misleading here - is it trying to show us an 800Hz carrier, with side bands 100Hz away?

[rhb]

Here is the DS1202Z-E and the MSO-2204EA being fed a 200 MHz and 300 MHz signal from an HP 8648C.

It's as good a demonstration of aliasing as you can get.  I've got the scopes in dot mode with infinite persistence. Both scopes have all channels enabled to force 500 MSa/s so Nyquist is at 250 MHz.

I didn't think the Rigol was turning the anti-alias filter on and off when I was looking at the step response.  The two photos of the Rigol screen prove that it does not work. I reset the persistence between photos and rest the frequency.

So, do you want a scope that shows you the truth or one that lies? These both lie.  They indicate that the 300 MHz signal is 200 MHz.

Have Fun!
Reg

And you would 'fix' this how?  DSP isn't going to help.

These are budget brand devices that deliver a lot of 'bang for the buck' but can get you into trouble if you approach their limits unwarily.  There are plenty of instruments that 'lie' to you if you don't understand their limitation and characteristics.  Granted, the marketing on these things is borderline criminal, but I don't think there are any cheap fixes.

You have to respect ALL of the Nyquist criteria.  You can use a sampling rate of 10X rated bandwidth with a gentler 6db/octave or so filter, or you can try to squeeze up closer to the limit with a fancier, more expen$ive analog front end.  Either way, the filtering has to be done ahead of the ADC and either way, it costs money.

Actually DSP can do the job.  You can combine a  modest analog filter followed by a digital filter to zero out the region in which the aliasing is present.   Just give  the user the control of the corner frequency of a digital filter applied to the live trace so they can control overshoot.  It's only a problem for marketing and accounting.   The former are inclined to lie and the latter are greedy.  Neither the Instek nor Rigol is even 3 dB down from specified BW at Nyquist.  That is sad.  I'll measure the actual corner later.  That's time consuming as I need to check the 8648C against my 438A and DDA-125 to make sure they all agree on levels at stated BW and Nyquist.

As I noted earlier, I've been working on this for some time and have more than enough experience to know what to do, how and what it costs in FPGA real estate.

It costs a bit.  You can't claim that your 2 GSa/s scope has a 1 GHz BW.  Realistically 500 MHz is the best you can do with a 1 GHz Nyquist when you take the cost of the analog filter into account.  My issue is with $20K DSOs which have total crap performance.

When I bought a Keysight "Premium Used" MSOX3104T and put my <40 ps pulser on it I was shocked at the 450+ ps rise time.  So I  reread the datasheet.  The "calculated" rise time is 0.35/BW *except* when you get to the 1 GHz version.  Then it's 0.45/BW!  Given my respect and trust of  HP it was like discovering my wife had been cheating on me.  The net result was I bought a huge pile of kit that says "HP".  I've not been disappointed.

Have Fun!
Reg

[SilverSolder]

Here is the DS1202Z-E and the MSO-2204EA being fed a 200 MHz and 300 MHz signal from an HP 8648C.

It's as good a demonstration of aliasing as you can get.  I've got the scopes in dot mode with infinite persistence. Both scopes have all channels enabled to force 500 MSa/s so Nyquist is at 250 MHz.

I didn't think the Rigol was turning the anti-alias filter on and off when I was looking at the step response.  The two photos of the Rigol screen prove that it does not work. I reset the persistence between photos and rest the frequency.

So, do you want a scope that shows you the truth or one that lies? These both lie.  They indicate that the 300 MHz signal is 200 MHz.

Have Fun!
Reg

And you would 'fix' this how?  DSP isn't going to help.

These are budget brand devices that deliver a lot of 'bang for the buck' but can get you into trouble if you approach their limits unwarily.  There are plenty of instruments that 'lie' to you if you don't understand their limitation and characteristics.  Granted, the marketing on these things is borderline criminal, but I don't think there are any cheap fixes.

You have to respect ALL of the Nyquist criteria.  You can use a sampling rate of 10X rated bandwidth with a gentler 6db/octave or so filter, or you can try to squeeze up closer to the limit with a fancier, more expen$ive analog front end.  Either way, the filtering has to be done ahead of the ADC and either way, it costs money.

Actually DSP can do the job.  You can combine a  modest analog filter followed by a digital filter to zero out the region in which the aliasing is present.   Just give  the user the control of the corner frequency of a digital filter applied to the live trace so they can control overshoot.  It's only a problem for marketing and accounting.   The former are inclined to lie and the latter are greedy.  Neither the Instek nor Rigol is even 3 dB down from specified BW at Nyquist.  That is sad.  I'll measure the actual corner later.  That's time consuming as I need to check the 8648C against my 438A and DDA-125 to make sure they all agree on levels at stated BW and Nyquist.

As I noted earlier, I've been working on this for some time and have more than enough experience to know what to do, how and what it costs in FPGA real estate.

It costs a bit.  You can't claim that your 2 GSa/s scope has a 1 GHz BW.  Realistically 500 MHz is the best you can do with a 1 GHz Nyquist when you take the cost of the analog filter into account.  My issue is with $20K DSOs which have total crap performance.

When I bought a Keysight "Premium Used" MSOX3104T and put my <40 ps pulser on it I was shocked at the 450+ ps rise time.  So I  reread the datasheet.  The "calculated" rise time is 0.35/BW *except* when you get to the 1 GHz version.  Then it's 0.45/BW!  Given my respect and trust of  HP it was like discovering my wife had been cheating on me.  The net result was I bought a huge pile of kit that says "HP".  I've not been disappointed.

Have Fun!
Reg

That's why I ended up with an older model scope.  -  Basically,  450+ ps rise time is only ~10x better than a modest 20 year old 100MHz scope can deliver.  But you pay much more than 10x the price for that....  and in return, you get a lower voltage rated, less solid feeling instrument.

I think a modern scope should be 100x or 1,000x better than 20 year old models...   and not be ridiculously priced.

[Jay_Diddy_B]

Hi,

I am going to speculate that more fundamental issue is the ratio between bandwidth and the sampling rate.

The Nyquist Sampling theorem tell us the bandwidth is half the sampling frequency. Then you get folding and aliasing.

But that is an absolute minimum requirement.

As a thought experiment consider this model:



It is a sample and hold circuit driven by a 1MHz sampling clock.
There is no need to worry about anti-aliasing filters because we are going to sample a pure sinewave so there is nothing to filter out.
The output of the sample and hold represents the data points that are stored in the scopes acquisition memory.
I have included a very simple reconstruction filter, a double pole filter at Fs/2.

This model helps us visualize the process.

I ran the model with different input frequencies.

100kHz

This is a fairly easy one. There are 10 samples of the input in the period and the sampling frequency is a multiple of the input frequency.



The circuit can construct a reasonable representation of the input signal from the samples.
So a ratio of 10 sample per period gives very good results.

107kHz

There are 9.34 samples per period, not a multiple.



You can still get a very reasonable representation of the input signal.

203KHz

Here just less than 5 samples period. Injecting a pure sinewave, so anti-aliasing will not help.



There are barely enough data points to reconstruct the input signal.

303kHz

Still above the Nyquist limit about 3.3 samples period.



There is some modulation caused by the sampling frequency.
If you look at V(sample) waveform, You have to guess at the input waveform from the sampled data.
There isn't enough data to create the waveform with any degree of confidence.

A 100Mhz scope with 500Msps isn't enough data points.

Regards,
Jay_Diddy_B

[bdunham7]

Actually DSP can do the job.  You can combine a  modest analog filter followed by a digital filter to zero out the region in which the aliasing is present.   Just give  the user the control of the corner frequency of a digital filter applied to the live trace so they can control overshoot.

If you have 500GSa/S on a 200MHz scope, a 350 MHz signal will fold down to 150MHz and I don't see how you can filter that out digitally without also zeroing out real 150MHz signals. 

Neither the Instek nor Rigol is even 3 dB down from specified BW at Nyquist.  That is sad.  I'll measure the actual corner later.

How could they be?  Even if the corner were at 200MHz, it would only be down another 1-2 db at 250MHz for a first-order filter.  You would need a 24db/octave filter to even get close to proper solution to the specs they claim.

When I bought a Keysight "Premium Used" MSOX3104T and put my <40 ps pulser on it I was shocked at the 450+ ps rise time.  So I  reread the datasheet.  The "calculated" rise time is 0.35/BW *except* when you get to the 1 GHz version.  Then it's 0.45/BW!  Given my respect and trust of  HP it was like discovering my wife had been cheating on me.  The net result was I bought a huge pile of kit that says "HP".  I've not been disappointed.

Tektronix and others have application notes on this subject.  They state that high bandwidth scopes that have lower sample rate to BW ratios need to use steeper low pass filters which affects the step response.  They aren't lying--the scopes likely do have the bandwidth that they claim, they just won't have any 'extra' and step response is affected, thus the '0.45' rule for high bandwidth scopes.  I don't think it is straight out specsmanship and my one Tek scope (200MHz, 2GSa/S) does actually roll off pretty hard.  It's a flat line at 400MHz even with a 1GHz Nyquist.

[Elasia]

There is some modulation caused by the sampling frequency.
If you look at V(sample) waveform, You have to guess at the input waveform from the sampled data.
There isn't enough data to create the waveform with any degree of confidence.

A 100Mhz scope with 500Msps isn't enough data points.

Regards,
Jay_Diddy_B

Bingo.. My minimum is at least 10:1 for this reason, preferably higher.. Yes mathematically 2 is the bare minimum but your structural resolution is shit and is really only good for a repeating fixed frequency signal.. The more dynamic the more resolution you actually need

[SilverSolder]

Hi,

I am going to speculate that more fundamental issue is the ratio between bandwidth and the sampling rate.

The Nyquist Sampling theorem tell us the bandwidth is half the sampling frequency. Then you get folding and aliasing.

But that is an absolute minimum requirement.

As a thought experiment consider this model:

(Attachment Link)

It is a sample and hold circuit driven by a 1MHz sampling clock.
There is no need to worry about anti-aliasing filters because we are going to sample a pure sinewave so there is nothing to filter out.
The output of the sample and hold represents the data points that are stored in the scopes acquisition memory.
I have included a very simple reconstruction filter, a double pole filter at Fs/2.

This model helps us visualize the process.

I ran the model with different input frequencies.

100kHz

This is a fairly easy one. There are 10 samples of the input in the period and the sampling frequency is a multiple of the input frequency.

(Attachment Link)

The circuit can construct a reasonable representation of the input signal from the samples.
So a ratio of 10 sample per period gives very good results.

107kHz

There are 9.34 samples per period, not a multiple.

(Attachment Link)

You can still get a very reasonable representation of the input signal.

203KHz

Here just less than 5 samples period. Injecting a pure sinewave, so anti-aliasing will not help.

(Attachment Link)

There are barely enough data points to reconstruct the input signal.

303kHz

Still above the Nyquist limit about 3.3 samples period.

(Attachment Link)

There is some modulation caused by the sampling frequency.
If you look at V(sample) waveform, You have to guess at the input waveform from the sampled data.
There isn't enough data to create the waveform with any degree of confidence.

A 100Mhz scope with 500Msps isn't enough data points.

Regards,
Jay_Diddy_B

Awesome simulation.

I guess matters improve a little bit if you introduce dithering and other magic tricks into the mix...   but there's really no substitute for having some sample rate headroom.

When you get close to Nyquist, you are mostly looking at the characteristics of the reconstruction filter...

[tomato]

Basically,  450+ ps rise time is only ~10x better than a modest 20 year old 100MHz scope can deliver.  But you pay much more than 10x the price for that....  and in return, you get a lower voltage rated, less solid feeling instrument.

I think a modern scope should be 100x or 1,000x better than 20 year old models...   and not be ridiculously priced.

So, you think modern scopes should have 10 GHz (100x) or 100 GHz (1000x) bandwidth and not be ridiculously priced?  Cool.

[rhb]

I posted demonstrations of the relationship of filter profile and overshoot a couple of weeks ago.  No one seemed to pay any attention.  Left me thinking, why bother.  Someone did make an important point that if you see overshoot you need a faster scope, but in some cases a user controllable LP filter would do the trick.  For example, if there is an impedance mismatch on a transmission line you can get a reflection that is pretty much impossible to see if the AFE rings too much.  You can see it if you know exactly what to look for, but it is really hard.  But if you suppress the ringing it's obvious.

A good friend from grad school in Austin is a manager for a seismic instrument maker.  I'll ask him what their AFE performance is.  With 10's of billions of dollars riding on the results, the seismic industry is very stringent about accurately reproducing the analog waveform.  At 32 bits of resolution in today's market.  Only possible if your data is below 120 Hz.  And even then difficult and expensive.

Have Fun!
Reg

[Elasia]

I posted demonstrations of the relationship of filter profile and overshoot a couple of weeks ago.  No one seemed to pay any attention.  Left me thinking, why bother.  Someone did make an important point that if you see overshoot you need a faster scope, but in some cases a user controllable LP filter would do the trick.  For example, if there is an impedance mismatch on a transmission line you can get a reflection that is pretty much impossible to see if the AFE rings too much.  You can see it if you know exactly what to look for, but it is really hard.  But if you suppress the ringing it's obvious.

A good friend from grad school in Austin is a manager for a seismic instrument maker.  I'll ask him what their AFE performance is.  With 10's of billions of dollars riding on the results, the seismic industry is very stringent about accurately reproducing the analog waveform.  At 32 bits of resolution in today's market.  Only possible if your data is below 120 Hz.  And even then difficult and expensive.

Have Fun!
Reg

On the contrary you are forcing useful discussion of theory and practice.. I'm sure im not the only one that is finding it interesting but just staying out of the kitchen 

[SilverSolder]

Basically,  450+ ps rise time is only ~10x better than a modest 20 year old 100MHz scope can deliver.  But you pay much more than 10x the price for that....  and in return, you get a lower voltage rated, less solid feeling instrument.

I think a modern scope should be 100x or 1,000x better than 20 year old models...   and not be ridiculously priced.

So, you think modern scopes should have 10 GHz (100x) or 100 GHz (1000x) bandwidth and not be ridiculously priced?  Cool.

Well, a Pentium Pro CPU of 1995 managed a 150Mhz clock frequency.  I would guess (but haven't done the math) that a modern processor is roughly 100x to 1000x better, given increased clock frequencies, higher IPC (instructions per clock), and high amounts of parallelism / multiple cores.

Fair enough, it probably isn't fair to expect an entire instrument to evolve as fast as a single chip, especially ones that have as much interest and development budget behind them as PC CPUs.

Let's turn the question around, do you think the state of the art in oscilloscopes has advanced significantly over the last 20 years?  Long obsolete models still command high prices on eBay, which indicates that the market doesn't seem to think so.  Maybe it's the kind of work we do with them that hasn't evolved all that much?

[tomato]

Well, a Pentium Pro CPU of 1995 managed a 150Mhz clock frequency.  I would guess (but haven't done the math) that a modern processor is roughly 100x to 1000x better, given increased clock frequencies, higher IPC (instructions per clock), and high amounts of parallelism / multiple cores.

Processor speed is not what limits the performance of an oscilloscope.

Let's turn the question around, do you think the state of the art in oscilloscopes has advanced significantly over the last 20 years?  Long obsolete models still command high prices on eBay, which indicates that the market doesn't seem to think so.  Maybe it's the kind of work we do with them that hasn't evolved all that much?

I paid over $30,000 for a new 1 GHz LeCroy just over 20 years ago.  They can be purchased on eBay now for under $1,000.  I wouldn't say they are commanding high prices.

At the time, 1 GHz was the fastest scope LeCroy made.  Now you can buy one that has 100 GHz bandwidth.  I'd say that's a significant advancement.

[rhb]

I recently bought a working 1 GHz DDA-120 for $303 delivered with tax.  Quite amazing.

Of course, as they get faster it goes up rapidly.  The 110 GHz Keysight is well over a million dollars.

Have Fun!
Reg

[SilverSolder]

Well, a Pentium Pro CPU of 1995 managed a 150Mhz clock frequency.  I would guess (but haven't done the math) that a modern processor is roughly 100x to 1000x better, given increased clock frequencies, higher IPC (instructions per clock), and high amounts of parallelism / multiple cores.

Processor speed is not what limits the performance of an oscilloscope.

That's an interesting comment - there are no opportunities for more processing, more parallelism -  no opportunities for integration with other instruments (e.g. spectrum analyzer, VNA)?

Picture an instrument from the year 2030 or 2040.  It isn't going to be depending on massive amounts of processing power?

Let's turn the question around, do you think the state of the art in oscilloscopes has advanced significantly over the last 20 years?  Long obsolete models still command high prices on eBay, which indicates that the market doesn't seem to think so.  Maybe it's the kind of work we do with them that hasn't evolved all that much?

I paid over $30,000 for a new 1 GHz LeCroy just over 20 years ago.  They can be purchased on eBay now for under $1,000.  I wouldn't say they are commanding high prices.

At the time, 1 GHz was the fastest scope LeCroy made.  Now you can buy one that has 100 GHz bandwidth.  I'd say that's a significant advancement.

So the high end is about 100x better?  -  why not the entry level.

[SilverSolder]

I recently bought a working 1 GHz DDA-120 for $303 delivered with tax.  Quite amazing.

Of course, as they get faster it goes up rapidly.  The 110 GHz Keysight is well over a million dollars.

Have Fun!
Reg

That DDA-120 was quite a bargain!

How does something like that perform compared with a modern "affordable" model from A or B brands?

[Fungus]

So the high end is about 100x better?  -  why not the entry level.

You can get a 4-channel, 100MHz DSO with lots of memory and features for under $350. How is that not an improvement? What would that have cost 20 years ago?

[tautech]

So the high end is about 100x better?  -  why not the entry level.

You can get a 4-channel, 100MHz DSO with lots of memory and features for under $350.

That's misleading as it needs be hacked.

[0culus]

So the high end is about 100x better?  -  why not the entry level.

You can get a 4-channel, 100MHz DSO with lots of memory and features for under $350.

That's misleading as it needs be hacked.

 

How the hell is that misleading? You can still buy the damn thing for the quoted price...

[tautech]

So the high end is about 100x better?  -  why not the entry level.

You can get a 4-channel, 100MHz DSO with lots of memory and features for under $350.

That's misleading as it needs be hacked.

 

How the hell is that misleading?

Show us a listing for a new 100 MHz 4ch DSO for $350. 

[0culus]

Wow really? Snipping out the rest of my post to take it out of context?  You buy the $350 one and hack it. How is that possibly misleading??

Here's what I *actually* wrote:

So the high end is about 100x better?  -  why not the entry level.

You can get a 4-channel, 100MHz DSO with lots of memory and features for under $350.

That's misleading as it needs be hacked.

 

How the hell is that misleading? You can still buy the damn thing for the quoted price...

[tautech]

Wow really? Snipping out the rest of my post to take it out of context?  You buy the $350 one and hack it. How is that possibly misleading??

Again, portraying a 100 MHz 4ch scope is available for $350 IS misleading without mention of a hack.
That's what Fungus did.

So now do we all quote prices and BW of hacked scopes as standard conversation, I think not.

We go that road and $499 for 4ch 200 MHz, $619 for 2ch 350 MHz, $1400 for 4ch 500 MHz and $3500 for 1 GHz 4ch.
Best we stick with unhacked rated BW and retail prices to avoid all confusion.