Make a very simple test for me

[Lucien Nunes]

Dont worry man, its fine.

I think this means you are using a voltage divider that is not isolated from the mains. Please don't. In real industry it would get you fired because it's an unnecessary risk. The key point is 'unnecessary.'

I am following with interest and I admire your determination to build logic blocks from discrete components. It is, in theory, a good way to understand what goes on inside and I would think it good exercise to build a few gates using different technologies. But to build a reliable multi-stage frequency divider is truly hard work. It was done in the past, yes, but in the days when only a large multinational corporation could afford to own a computer, and they had to hire a full-time technician to keep it functioning.

I have electronic organs from the 1960s that use discrete-transistor frequency dividers. Each stage of division uses about 15 components and needs to be set up for a particular frequency range, like the blocking monostable idea with the 555. |The best of those organs cost as much as a good car, and you got a total of 72 divider stages. At the time it was 'hi-tech' but immediately became obsolete when ICs were designed to do the same job.

So experiment if you wish, but do not beat yourself up if your discrete multistage divider takes too much time or misbehaves at higher frequencies. It was always like that.

 

[_q12x_]

Interesting... but I still have to see a circuit with discrete components. That's what I'm after.
See if you can help me with one (or more if possible).

 

[Lucien Nunes]

OK, no schematics but here you go, this is the sort of thing you want to build. I had forgotten about this organ, it was a very good model from 1967 that cost as much as a house. It uses about 300 transistors in total. Each divider stage has two transistors for the multivibrator and one as an output buffer. Each divider board has 7 stages plus an oscillator. It is only designed for frequencies up to about 12kHz and would not operate at 20MHz.

 

[_q12x_]

So with a 555 then.........

 

[Lucien Nunes]

If a man was holding a gun to your head saying: "Make a prescaler NOW! Divide by 8192. NOW!" and you had only 555s, then, maybe. But later you would be saying "OK sir, here it is, I think it's dividing by, let's see, 13 x 7 x 9 x 10 which is 8190, that's very close, or it might be 11 x 12 x 6 x 9 which is 7920, that's not as close but is it OK sir? Please will you let me go now sir?

Only it will be you holding the gun to your own head.

 

[marconi]

So with a 555 then.........

If I remember well, you used a 555 in your wings project, without a capacitor as a two state/bistable and thus as a flip flop to control a relay. You may be able therefore to adapt that circuit and have a number cascaded together ie the output of one feeding the input of the next and thereby form a divide by 2expN circuit where N is the number of 555s. I do not have time now to research or think further on using 555s as FFs but you are good at doing these and negotiating the 'Innovation Funnel' to success -

 

[marconi]

View attachment 97610

I will have a go at constructing this circuit tomorrow.

q12x: I have just spent an hour trying this circuit out but without success. Re values of 2.2kR and 10kR and Rc values of 47KR and 10kR. Tr1 and Tr2 BC549s. VB between 1.5 and 15V. I have given up with it.

 

[pc1966]

q12x: I have just spent an hour trying this circuit out but without success. Re values of 2.2kR and 10kR and Rc values of 47KR and 10kR. Tr1 and Tr2 BC549s. VB between 1.5 and 15V. I have given up with it.

You need Rc to be significantly less than Re for it to have any chance of working.

For 20MHz crystal try Rc = 1k and Re = 4.7k from 5V and see if you get anywhere.

 

[_q12x_]

An important update.
I didn't check this before, because I was thinking on a bigger picture, but... today for 2h or so, I was desperately trying to find a way of measuring the frequency.
I have 2 instruments here:
Number 1, the famous golden boy toy
DSO 138 Oscilloscope

that is showing the waveform alright but it doesnt put the numbers !
Or at least I don't think I know very well how to get them from only its waveform.
And number 2:
GM328A Transistor Tester

And I completely forget I have a fv counter build in, until I checked its menu today. And I checked its manual as well and it doesnt say anything useful for my problem with fv counter. I had to literally guess every port it has, and multiple times, switching polarities, and all that shi...fun. But looking now more carefully on its naked picture posted here, I noticed it has a BACK port as well.... I have a cardboard cover on him, I made it myself and I didnt see the back port. Oh my god. Haha. And indeed that was the Input port for the frequncy counter. Ohoha. What a ride. Im happy to report I have a way of measuring the fv now. But this is also limited 1Hz-2MHz. But it is good I discovered this somewhat hidden functionality. I had a very vague idea I have something related to frequency counting but I was not very sure what I had. It appears I read its menu some years ago and something remained like a shadow memory about it. Im so Lucky I even remember it. Those who have this functionality ready build into your osciloscope, kiss all his 4 rubber feet !
The fv counter that is coming should be much better than this one I have, 1Hz-50MHz.... Hmmm now that I can see and compare the 2, its not that bigger difference. I should have something to Giga or TeraHz, to really see a difference. Eh well.
What a experience.
So, I measured my newly PWM with the 555, @5V, and I got 953Hz(max) to 850Hz(min). So 100Hz range. It was not the reading I was expecting. But I had planB, with a astable flipflop, also @5V and that give me straight 9Hz not variable. So I tested 2 diferent pulsating and oscilating devices that I know for sure their value and that they work. I wished I had a more larger fv range with my 555 PWM.
Im thinking to make another board that is a pure frequency variable generator with greater range than 100Hz and not a PWM. I also think what I have already is good enough as well. So this new board remains in plan.
I am thinking out loud here a bit... thinking a little bit more on my options, I also have a fv generator in my small GM328A. But the problem is that I also have to measure with it as well, so I should have 2 of these GM328A, one for fv gen and one for fv counter.... hmmm. But the other fv counter is arriving so in theory, this GM328A can be the fv gen and that will be the fv counter. So 2 devices after all. I didn't stop to analyze these problems until now.
In conclusion, Im good. Haha.

 

[marconi]

You need Rc to be significantly less than Re for it to have any chance of working.

For 20MHz crystal try Rc = 1k and Re = 4.7k from 5V and see if you get anywhere.

PC1966: I had another try with Rc = 1kR and Re = 4.7kR, 10kR and 22kR over a range of voltages from 3-15V. Not a twitter at 20MHz. I also tried two other crystals.

Next I will try keeping Re at 4.7kR and reducing Rc but at the moment it is too hot in my shed to do so.

 

[pc1966]

PC1966: I had another try with Rc = 1kR and Re = 4.7kR, 10kR and 22kR over a range of voltages from 3-15V. Not a twitter at 20MHz. I also tried two other crystals.

Next I will try keeping Re at 4.7kR and reducing Rc but at the moment it is too hot in my shed to do so.

OK, I will see if I have the parts to try it as well.

At one point we had loads of stuff for this sort of experiment but sadly it was thrown out when my last work ended. We saved some stuff "just in case" but space did not permit all of the items I wish we had kept.

 

[pc1966]

@marconi Was the DC bias condition much as expected? I guess around (Vcc - 0.7) / (Rc + Re) per transistor current, at 5V supply around 3.5V over emitter resistors?

 

[marconi]

@marconi Was the DC bias condition much as expected? I guess around (Vcc - 0.7) / (Rc + Re) per transistor current, at 5V supply around 3.5V over emitter resistors?

I will check tomorrow morning. We are heading for thunder and lightning this evening and it feels very muggy right now.

 

[pc1966]

This is a handy web site for current activity:

Lightning & Thunderstorms - United Kingdom, England, Scotland, Wales, Ireland

Blitzortung.org provides lightning and thunderstorm information in real-time on maps for USA, United Kingdom, Australia, new Zealand, Europa, Africa, Asia and other Countries.

www.blitzortung.org

However we have seen the odd flash here that did not register on their detectors.

 

[_q12x_]

Im loughing how everyone is preoccupied: me with the fv reading, marconi with lightning and pc1966 with stuff that doesnt find or have anymore. Hahaha.

 

[marconi]

Regarding the circuit Symmetrischer Oszillator I have included below again. I don't think this is the working circuit - it is an outline schematic of a circuit missing some key detail. I reckon the circuit idea is a classical astable transistor circuit - see second circuit - which has resistance and capacitance to make it oscillate at a frequency close to that of the quartz crystal as in the second image. The purpose of the crystal connected between emitters is to 'force' operation at its frequency. This is what I am going to pursue.

 

[Lucien Nunes]

I was just going to say, it looks like a circuit from a patent which shows enough to define the principle that is claimed, but not enough to construct a replica directly. I too would be inclined to provide AC feedback and bias in the usual way, and probably make the emitter coupling somewhat tunable.

It seems a very long time ago that I had the opportunity to make with circuits that might not function, to see whether something can be done some particular way. In my work I am so often against time pressure that the solution has to be guaranteed to work first time even it is technically ridiculous or extravagant. I have used a 14-bit 40-pin PIC running at 20MHz as a monostable to generate a 10 second pulse, because it was already built and reprogramming took 2 minutes vs. 5 minutes to make something specific.

If you asked me to test the frequency of a vanilla-flavour crystal now I would reach for the PIC prototyping board again and have an answer in 20 seconds.

 

[_q12x_]

We know that is a symbol of a BJT NPN but try with 2 N-ch Mosfets.
Also... Im thinking to use different types of npn's. 1 BC548 and another BD139. To induce a instability in the circuit...
Just putting some ideas on the table.

 

[pc1966]

A crude simulation attempt, did not work at 20MHz with 2N2222 but OK with BC548, also used low-Q crystal model so faster to build up (along with 1mV kick at t=0)

Time-domain for test point in Tr1 collector:

 

[Lucien Nunes]

I gave myself 5 minutes to do this, just to prove we can all build a discrete transistor crystal oscillator that doesn't work...
First transistors I came to - ZTX753s - should have enough zing to work. The circuit has a name but I can't remember it, a common-base stage driving an emitter follower. I made the values up as I went along, they won't be far out but it still doesn't work. I've no interest in simulating it or debugging it, time's up!

 

[Lucien Nunes]

So then I decided to give myself another 5 minutes to build a crystal oscillator the way I would have done if somebody had said: "Build a simple crystal oscillator." I.e. with an 'HC00. Of course this one works just fine. I didn't bother tuning it, I used the first capacitors that I picked up from the drawer, which turned out to be 22pF. Build time was just under 3 minutes including stripping some wire to make links.

 

[Lucien Nunes]

And this is how it looks with a 4MHz xtal.

*BONUS POINTS for anyone who noticed I had the scope's 20MHz bandwidth limiting switched on. The actual output waveform is very ringy because I did a lousy job of decoupling the power supply (stood a ceramic 0.1 across the IC without chopping its leads down). You can change the W/F just by bending this component about. It could be fixed but... time's up!

E2A, I semi-fixed it (relocated the bypass cap and poked the probe direct into the breadboard)

 

[_q12x_]

very interesting update.
I managed to split 1/10 of my test PWM original fv. From its 850Hz down to 85Hz
Now Im playing with some capacitors values to bring it down to 1/100.
My target end result will be 1/1000.
And, I did managed to --average-- the 1/100 values. I say average because the fv counter is jumping a couple of Hz up and down. It should be 8.5Hz but is heavily fluctuating with diverse values between 10Hz and 6Hz. So I am theoretically at 8 but because is jumping all around these values, it was hard in the beginning to understand where I stand. But staying and watching these values for a while, a couple of minutes, I concluded it is jumping around these margins. That might be from the High resolution of the splitting, all the circuit(s) combined might present some tolerances, especially the capacitors and resistors and why not the chip(s).
At 1/10, it does not jump at all, it stays put at that fv. So.... I think im good at this point.
I might have to make a second circuit that will split another 1/10 from this one that is 1/100 and in the final output will get 1/1000. And I expect it will be extremely jumpy at that Very High resolution. If it is a way of "average" all these jumping, especially at 1/100 stage I am right now. That will give a good clear chance for the 1/1000 stage. Hmmm. But it is in plan. For now, I have to reach that 1/1000 target and Im GOOD, literally. Haha.

 

[marconi]

A crude simulation attempt, did not work at 20MHz with 2N2222 but OK with BC548, also used low-Q crystal model so faster to build up (along with 1mV kick at t=0)
View attachment 97652

Time-domain for test point in Tr1 collector:
View attachment 97653

I had another go this morning after thinking about the small signal model of this circuit and why the ratio of Rc to Re matters so much- see first attachment. I tried Rc = 1kR and Re = 4.7kR and even exchanged the BC549s for two new but in my construction it did not oscillate. Not enough feedback methinks so I swapped Rc for 100R and the symmetrischer oszillator found its 20MHz voice. We did it Sir and self starting to boot!

 

[pc1966]

Not enough feedback methinks so I swapped Rc for 100R and the symmetrischer oszillator found its 20MHz voice. We did it Sir and self starting to boot!

Excellent!

While the E-E impedance should be roughly -2*Rc quite possibly the higher Rc values along with stray capacitance might cause too much phase shift. I seem to recall that 10-20MHz crystals are below 100R series resistance so indeed 100R values for Rc would be adequate, as you have so well demonstrated!

 

[marconi]

q12x. : My next step is to take the small amplitude 20MHz sine wave and turn it into 20MHz pulse stream of TTL logic 0 and 1s to feed into the divider circuit.

 

[_q12x_]

Congratulation mister @marconi I am really happy you made it !
But I am not sure I understand completely your values.
So I grabbed all the information you provided so far:

Rc for 100R and the symmetrischer oszillator found its 20MHz voice.

did not work at 20MHz with 2N2222 but OK with BC548

I tried Rc = 1kR and Re = 4.7kR

and I redraw the circuit with the new values:
- Are these the values you used?

 

[marconi]

Congratulation mister @marconi I am really happy you made it !
But I am not sure I understand completely your values.
So I grabbed all the information you provided so far:



and I redraw the circuit with the new values:
- Are these the values you used?
View attachment 97682

Yes. VB is 5 Volts not 1.35V. The npn transistors are BC548B types. the letter A, B or C after BC548 indicates the so-called direct current gain of the transistor - the hFE - and relates the emitter-collector current flow to the base-emitter current flow eg: Ice/Ibe. Which BC548s do you have? Cs have higher gain than Bs than As so I used the mid-range gain type.

See top of page 2 of:

BC548B datasheet - https://datasheetspdf.com/pdf-file/1292183/Kingtronics/BC548B/1

 

[marconi]

Which operational amplifiers do you have please and I will use the same ones to amplify the small amplitude 20MHz sine wave.

 

[_q12x_]

Mine are BC548 B - coincidence! like yours.
I have uA741(not that used anymore) and LM358(most used)
Updated circuit after your last specifications:
Ive added + and 5V and gnd symbol. Also B after tr name.

 

[_q12x_]

My last night progress:

The fv Counter is reading the output of the frequency divider and is reading 1/100 = (around) 8.5Hz
(The osciloscope reading is intermittent for this 8.5Hz output, not the same every time)
The osciloscope shown here is reading the output of the PWM at 850Hz

And now, Im building the board of the frequency divider:

 

[_q12x_]

Mister @marconi and @pc1966 , in my post #73 I had a problem:
"..I might have to make a second circuit that will split another 1/10 from this one that is 1/100 and in the final output will get 1/1000. And I expect it will be extremely jumpy at that Very High resolution. If it is a way of "average" all these jumpings, especially at 1/100 stage I am right now. That will give a good clear chance for the 1/1000 stage. Hmmm. But it is in plan. For now, I have to reach that 1/1000.. "
- Can you give me an answer to this problem?
I have an idea but I think is a bit too complicated.... and is incomplete as well.
I want to see what are your thoughts.

 

[marconi]

Impressive progress and great dedication.

 

[_q12x_]

deleted post ______

 

[_q12x_]

Impressive progress and great dedication.

True, true,
The same to you
haha

 

[marconi]

To use a 555 as a frequency divider of a known and constant frequency pulse train you have to make sure that the 555 is ready to be triggered again after n input pulses where n is the division factor.

This means that one has to ensure the 555 output (shown in green) has changed to zero after a further n input pulses (shown in yellow) since it was last triggered so the 555 is ready to be triggered again by first pulse of the next group of n pulses.

The way the 555 retriggerable monostable circuit operates to divide by n means that the time constant/period of the monostable 555 - x - must satisfy this equation:

(n x T) - t < x < (n x T)

What this says is the 555 output must transition to zero after the trailing edge of the nth pulse and before the leading edge of the (n+1)th pulse - that is in the gap between them when the input is zero.

Attached is an example for a divide by 3 scheme which shows the meaning of n, T, t and x.

It is probable better then for your PWM input to keep t short with respect to T so that there is a relatively big time gap between input pulses so that variations in the 555 timer function which creates the interval x will generally fall clearly after n pulses and nicely before the (n+1)th.

Or something close to this explanation - I am bit rushed.

 

[_q12x_]

So... no answer. Ok.
And I finished the board. it took me exactly 3h to make it (continuous work, no brakes).

Is the small right (card)board

Not bad !
Now I can make another division, 1/10 to get a total of 1/1000.
It would be nice if you could look over the "average" problem, but... you are busy as well I guess.
I will probably not implement it, but it will had give me a very clean result in the final stage....
As I said, we'll see after I finish the whole 1/1000 process then.

 

[marconi]

So... no answer. Maybe not the complete answer you were expecting but something for you to consider. The explanation suggests pointers on what you might do to 'tweak' your design so that division by n actually occurs in the real circumstances of the circuit when the input period T and pulse duration t are varying randomly and the monostable duration x is subject to random lengthening and shortening in time. In plain English/Romanian make sure the on to off ratio of the input pulse stream is less than 5%(say) and n is high.

 

[_q12x_]

I still don get it.... make me a clear circuit... or a continuation of the one that I have already, Like another module to add after the last 1/100 output (that Im actually measure with the fv counter).
Draw on paper and make a picture and post it.

 

[marconi]

I and you do not know whether the variation in division result is due to variation of the input from your PWM circuit or in your 555 divider circuit or both. All I can say is the variation becomes less significant if the mark-space ratio of the input is low and n is higher. That is how the mathematics works.

To do the averaging one would need to store values over an interval which can be done but at the moment I do not think you have the ics to do that. When my parcel arrives maybe but then you can do the division in a much more practical way to not bother.

 

[_q12x_]

I and you do not know whether the variation in division result is due to variation of the input from your PWM circuit or in your 555 divider circuit or both.

That is true. We cant know for certain. BUT...my very best guess, is this signal, created by the PWM is like a picture of 800x600. When you look at it from afar, from distance, it looks detailed and good to watch, and no problems, right? Now, when I add a magnifying glass, which is our "splitter"/ fv divider here, that is magnifying by 100 times in my practical case (1/100), NOW we can see the bloody pixels in that image. Right? So again, my best guess, the source of the signal is good to a point or to a magnification. After that is crapping itself down. But...
- Doesnt matter from where is the source !!! We must add a "silencer" / "a filter" that will let flow only the important thing.
Again, im not the math guy here so you'll have to understand this aspect about me. Im better at visual representation more than anything. Im trained on it all my life actually.
My idea that is not finished yet, but I will expose it as unfinished as it is, is the folowing: we dont go in the range of 10Hz to 6Hz where the fluctuations are the worst. We go a bit higher. Let's say to 20Hz just to be sure. Right? Now, from this "sure" position, we can start trim and cut and filter what we need and send out only a constant flow of impulses at 20Hz and the rest of fluctuations trim off or avoided somehow. And this is where my idea stops.
Actually it is in my plan to try a very simple approach, like we deal with 240V filtering, after all this is also a fluctuating current, right? and I will add a filtering capacitor in the output of this fluctuating crapping itself signal. It is in plan, I have to try it. This is the simplest idea I could think.

 

[_q12x_]

Hmmm. I managed to clean the output of the PWM and get a VERY stable output reading from the fv counter for the 1/100 level.
But I could not make it to 1/1000. I tried many ways.
First I hooked up the 1/100 board I just built to the breadboard with a 1/10. And it kept showing me the same output as the input. Very-Very strange. Logically you would expect another division. But noooo.
Then I said, blaimy, I leave only the breadboard circuit and tried to bring it down to 1/1000 as a single circuit. It didnt work because the fv counter can't count 0.x x x fv. It just stops at 0 and thats it. It actually jumps from 8 to 0. The most I could get it down was 2Hz, and I thought on a logical RC arangement of values to try for the 1/1000, that it wasnt working for the fv I had to test with, but MAYBE, it will work with the crystal.
Then I hooked up the crystal and ... nothing. I put it at 1/100 and it should have giving me something around 200kHz, what the maximum of this device could see, I was hunting for some variations at the border, but nothing. Then I tried a 14MHz crystal with also 1/100 model and it should had shown something. And it didnt. Then I tried my theoretical RC values for 1/1000 and nothing worked either. Also put both crystals and again, nothing. It was staying on 0 Hz all the time.
Then I measured the output of the circuit, oh, I used your circuit mister @marconi with 1 transistor, and it give me 4V, so it was an output from that, no doubt.
I made so many permutations today, I am tired.
Funny story: I unhooked everything from the fv splitter circuit but I touched the input wire with my fingers. And the fv counter showed a clear 50Hz - hahahaha, I dont even have to plug it on the mains, I am vibrating at this fv anyway. Now that Im thinking it should have been 5Hz since it supposed to be splitting. I noticed sometimes, in certain conditions, the output is equal with the input of the fv splitter.
Then, I had another bright idea, to check the maximum fv of the 555 ! And I checked the internet, and it says "500-kHz to 2-MHz ", ok, then I looked in its datasheet and it says:

and I didnt find nowere the fv of the 555 mentioned in its datasheet. This values here, the 100ns are the only ones I could find and I thought I can convert that into Hz, and I did, and guess what, 100ns = 10000000Hz = 10Mhz . I beat the internet with this finding, but still not good enough for my 20MHz crystal. So.... Im screwed with this experiment. Its a test anyway. But I am not happy that logic splitting didnt work. It should had. I was counting on it. Eh well, life lesson, never expect anything.

 

[marconi]

Deleted post and some extra words

 

[_q12x_]

How is your progress, signore @marconi ?

 

[_q12x_]

And, we are turning back to some of my previous ideas.
My greatest suspicion is that 555 circuit could not do its job do to a much greater fv in its input than he is designed to support and see.
So....my previous idea that someone here laughed at, was to make a discrete fv splitter. We need it for a couple of times, not the entire 1/1000 range.
- So I ask again, give me your best discrete circuit that is capable reliable to split a very high fv !
My plan is simple: I will split it a couple of time using discrete fv splitter circuits, and after is down under 10MHz as the datasheet of the 555 mentioned (or 2MHz as the internet says) after that, I will input my 555 fv splitter circuit. Simple. And this is a good plan. I will do the work anyway.

 

[marconi]

How is your progress, signore @marconi ?

Good morning. I had a day off yesterday. But I was thinking about whether:

a. to use an opamp or transistor to amplify the signal;

b. to pause on (a) and make a crystal oscillator instead using a 74HC04 as Lucien did from which one can produce a square wave very easily 5V-0V to drive the 74 series divider. This approach keeps things very simple whereas (a) would require more tinkering* around. Alas I do not have as much patience as you do so prefer to keep things simple these days. I have posted you some 74LS04s and 74LS00s so it may be possible to use these instead of the HC04s. I will have a rummage now in my shed for some.

*tinker around with - https://idioms.thefreedictionary.com/tinker+around+with

 

[pc1966]

The simplest divider I can think of would need at least 3 transistors (without resorting to odd devices like the unijunction transistor), two for the state memory (i.e. flip-flop) and a 3rd to try and steer it to change state on each edge. Others seem to have the same idea as here is an example of a T-flop (scroll down the page):

Flip-Flops Using Discrete Transistors

Flip-Flops Using Discrete Transistors: Hello everyone, Now we are living in the world of digital. But what is a digital ? Is is far away from analog ? I saw many people, which believes that the digital electronics is different from analog electronics and the analog is a waste one. So her…

www.instructables.com

But, as Lucian pointed out, they end up with RC time constants that limit the useful frequency range. The example on the link above would not operate anywhere close to 20MHz due to the high-ish R and stray capacitance, device capacitance, etc.

If you get a 74HC4060 then its input gate can be an oscillator or simply an amplifier for squaring-up the output of a transistor oscillator, and then you get the dividers all working as part of the deal.

 

[marconi]

q12x Here is 74LS00 crystal oscillator which you can make when the box of ics arrives. Now you have three circuits you can make to test your crystals with.

 

[_q12x_]

Thank you signore @marconi , very good progress so far. Don't forget to actually post the circuit for this last experiment with the 74LS00 in the video. Drawing on paper is the fastest way.
To mister @pc1966 , yes I found the exact same page. Its good that you mentioned that RC limiting problem, not reaching 20MHz. Then what would a circuit be not limited? Can you guys think on creating and also testing (having all that nice osciloscopes) such a circuit for me?
I was thinking, how the light measuring devices are functioning?
What circuits they have inside that actually measure such great fv values? Yes, visible light
Electromagnetic_spectrum

Maybe we can use something that they use, you know? That's my idea. A special sensor or a special circuit.
- The conclusion so far, is that I can Not build a discrete fv divider ? That sucks...
- To be totally sincere, I didn't put quite all my energy into discrete fv divider either, I choose the fastest routes as a coward as I am, using the 555's and next the IC's are about to come. It bugs me the 555 is not up to the task. Aaah.
- The 20MHz osc is the test osc ! I have other osc at different fv, some are greater some are less. I have one for ex at 40MHz. So our circuit must read up to 100MHz or more, to be able to deal with all the common osc values. I also have a lot of unknown values, which was the starting point for all this adventure here. Keep this little detail in mind all the time. FUN, right? Hahahahaha.

 

[marconi]

q12x Here is 74LS00 crystal oscillator which you can make when the box of ics arrives. Now you have three circuits you can make to test your crystals with.

Here is the circuit which uses three of four 2 input nand gates in the 74LS00. The fourth gate is unused so its two inputs are connected to 0V so that they do not float. The crystal is in the series resonance mode so low impedance at 20MHz.

I will look at the ics in the box to you and think about which one to use to do the division of fv and then construct the circuit. I am a bit slower off the mark than you are so be patient. I like to read the datasheets. I quick glance at the 74LS93 4 bit counter specification and it looks like it can operate the first divide by 2 stage with an input between 32 and 42 MHz so it might cope with your 40MHz crystal if the crystal test rigs will still perform at 40MHz. The last circuit using the 74LS00 was oscillating at 32MHz without the crystal in circuit - need to check again though to be sure.

https://www.ti.com/lit/ds/symlink/sn5400.pdf?ts=1653117913729