General > General Technical Chat
Frequency Divider for older Oscilloscopes??
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Ian.M:
@Jorge,
First, welcome to these forums.


--- Quote from: GlennSprigg on April 02, 2020, 12:23:35 pm ---To all, point taken and understood.   ;D

--- End quote ---
I would understand that as: Glenn accepts that his original question had no cost-effective practical solutions.  However if you have built an analog sampling front end or other device to down-convert high frequency signals for display on a lower bandwitdh scope, we'd all be interested in seeing your project.   
joeqsmith:
Welcome Jorge,   

I don't mind seeing some of these more technical threads revived and am interested in hearing about what you have to offer.   

Some time ago I had downloaded the patents for LeCroy's Digital Bandwidth Interleaving and attempted to write a simulator to demonstrate how it works.  Roger Delbue from LeCroy chimed in the comments and offered a few bread crumbs.   The video starts out showing a home made Arb which can be used for this purpose.   In the end of the video I show a down converter used to monitor the output of a simple oscillator I was playing with.   



At 12:40, I show another simple down converter using a DRO.   


Jorge Ginsberg:
I am sorry to say but I too can only offer a few "crumbs"....
Many ...MANY years ago (between 1980 and 1982), I built a prescaler that obtained an almost exact copy of an analog signal but with a frequency 100 or 1000 times lower.  That mean that it was possible to observe a 100 Mhz signal as if it were a 100 Khz signal.  It was entirely made with Shotky-TTL technology, something already obsolete or almost obsolete today.
I can give the idea here but unfortunately I have sold and given away everything. Schematics included.
It happens that I have been retired for 15 years now and as soon as I started to see this equipment coming from China, at such low costs, I realized that if I didn't sell my lab quickly I was going to be left with old or obsolete junk in my hands.  Therefore, I hurried to sell everything.  Now I just read about electronics. Nothing more than that.
I regret not keeping the schematics.  I was convinced that they were worthless obsolete things.  I never imagined that someone would want to build an analog prescaler, being that nowadays you can get good sampling oscilloscopes for less than 400 dollars....
If you still want to know how I did it and you want to develop it, just let me know and I will tell you -at least what I remember- how to do it.
Greetings from Argentina
Jorge Ginsberg:

--- Quote --- what you want is not possible. You have to have 100MHz bandwidth scope, no matter if it is analog, analog sampling, digital sampling or digital real time.

So, yes, you need to get a 100MHz scope to have a 100MHz scope.

You could use current low bandwidth scope as a display for sampling head (that other already pointed to).
Problem is that ANY 100 MHz scope (even the most stupid ones, that you can get for 100 USD new) will be better than any contraption you can make cheaply...

Sorry.

--- End quote ---

2N3055 : You are wrong. (nice nickname)
It is perfectly possible to make a circuit that takes samples of the 100 MHz signal and with those samples make an exact copy but at 10 Khz, so that they can be observed by a cheap oscilloscope. And you can do it in analog form. No memory, no counter, no microprocessor. The only thing you could use is some high speed TTL chips and even not even that. And it's a relatively simple project, but very critical in terms of the semiconductors, capacitors and resistors you employ.
The problem here is not the technology but the cost.
If China sells you an oscilloscope capable of sampling a signal at a rate of 2 Gs/s, for a ridiculous price of 400 dollars, it is silly to work so hard to make a homemade prescaler that will surely cost more than that.
Just look here and be amazed at the price:
https://www.rigolna.com/products/digital-oscilloscopes/1000z/
Look also here:  https://www.renhotecic.com/HANMAKET-DOS1102-110MHz-Digital-Oscilloscope-2channel-Oscillograph-1Gsa-s-7-Tft-LCD-Osciloscope-Kit-Better-Than-Ads1102cal-0004577
But from the technological point of view there is no problem to do it.  And I know very well what I'm talking about...
The only justification for such a project is the enthusiasm for electronics and the pleasure of doing it.  Nothing more than that.

2N3055:

--- Quote from: Jorge Ginsberg on July 18, 2021, 09:10:05 am ---
--- Quote --- what you want is not possible. You have to have 100MHz bandwidth scope, no matter if it is analog, analog sampling, digital sampling or digital real time.

So, yes, you need to get a 100MHz scope to have a 100MHz scope.

You could use current low bandwidth scope as a display for sampling head (that other already pointed to).
Problem is that ANY 100 MHz scope (even the most stupid ones, that you can get for 100 USD new) will be better than any contraption you can make cheaply...

Sorry.

--- End quote ---

2N3055 : You are wrong. (nice nickname)
It is perfectly possible to make a circuit that takes samples of the 100 MHz signal and with those samples make an exact copy but at 10 Khz, so that they can be observed by a cheap oscilloscope.
The problem here is not the technology but the cost.
If China sells you an oscilloscope capable of sampling a signal at a rate of 2 Gs/s, for a ridiculous price of 400 dollars, it is silly to work so hard to make a homemade prescaler that will surely cost more than that.
Just look here and be amazed at the price:
https://www.rigolna.com/products/digital-oscilloscopes/1000z/
But from the technological point of view there is no problem to do it.  And I know very well what I'm talking about...
The only justification for such a project is the enthusiasm for electronics and the pleasure of doing it.  Nothing more than that.

--- End quote ---

You might know what you're talking about but you didn't seem to understand what I did talk about. 
You simply misunderstood. English is not native language for either of us.

Please read again: you cannot look at high frequency signal on a low bandwidth scope with a PRESCALER ( a divider like the one used in frequency counters).
Which was OP original question.
And you can't.

And few sentences later I say " You could use current low bandwidth scope as a display for sampling head (that other already pointed to)."
Which is obviously true because thousands of scopes like that exist...
At which time you're looking at 100 MHz signal with your homemade 100MHz+ sampling scope consisting of a homemade sampling head and a low bandwidth scope used as a display unit for sampler.

At home it is not too hard to make a sampling head that will sample at 1 GS/s (1GHz). But today you can buy cheapest scope that already samples at that rate, and for the price of component to make sampling head (unless you already have the parts). And then you still have only sampler and no input stages, attenuators etc...

And making a 10-20 GHz sampler at home is not that trivial..not to mention 4-8 GHz front end... That one would be useful though..

Regards,


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