Test Equipment Anonymous (TEA) group therapy thread

[bd139]

Heads up for UK TE folk. New museum: https://www.museumofeverythingelse.com/

Full of Nixie tubes, VFDs, scopes and weird stuff. Run by the dude with the Furby organ.

It is in Kent, which saves Debbie from being dragged down there. 

Still hoping to visit Blechley Park.  Been on my list for ages, but it is too darn far for a day trip and never seems to fit in the schedule for a weekend in London.    Debbie might actually enjoy Blechley.    (She is a statistics guru and does all sorts of number crunching...)

It’s a good day out. Don’t forget TNMOC as well. Lots of cool stuff in there.  Attached a couple of photos:

[beanflying]

I am fairly well covered as far as good quality Resistors but these are a good set of bits in Oz for not a lot of $ eBay auction: #184603695622

[capt bullshot]

Remember the frequency difference meter I've made to test my GPSDO?



Now I've made another one, looks way more simple, doesn't it?



Not only it's less complex, it has about one decade better noise floor in comparison with the 100MHz PLL based device. I'll redo the PLLs some day, because there's some major flaws inside causing that high noise floor.



The new one uses simple divide-by-four circuits to provide in-phase and quadrature of the 10MHz input signals (now at 2.5MHz). These are fed into simple XOR gates and RC lowpass filtered. You get two triangle waveforms at 90° phase shift, these are input to an AD7793 high-resolution ADC. Do the math and get the frequency difference.
The new unit has three inputs, one reference and two frequencies that are compared to the reference. So I can monitor two devices vs. a third one at the same time (hopefully saving a few of these 24h debug sessions ).

For the first test, I'll be comparing one of the GPSDO radio clock vs. an FRS rubidium and the TruePosition GPSDO.

[capt bullshot]

This is the first measurement, with all the devices been just powered on:



Yellow is TruePosition GPSDO vs. mine, green is FRS vs. mine. Left axis is frequency difference in Hz, so one division equals 0.1ppb (or 1e-10).

Edit: second graph showing the noise floor of the new difference meter, for visual comparison (same axis): green is zero difference, yellow is 0.0001Hz difference (or 0.01ppb / 1e-11)

[mnementh]

If I really wanted to attack... there would be a much easier target ..... The MARMITE !!!   Just the smell of it had me puke ! Seeing people actually not only EATING the stuff,  but even seemingly highly ENJOYING IT..... has me baffled !!

Yeah.  I tried Marmite once .... bleeeaaaggghhh.

Do it right - go for the Vegemite!!   

(No, they are NOT the same thing - not by a long chalk!)

Nothing at all wrong with Marmite, it's lovely really, trust me, just not at breakfast though.

Time of day has nothing to do with it.  To me, Marmite just tastes "off" once you've had Vegemite.

I heard Marmite was made of ground up Marmots and recycled Masonite, hence the name...

Wartime Austerity Measures and all that... wot, wot...

mnem
 

[ch_scr]

[...]

The new one uses simple divide-by-four circuits to provide in-phase and quadrature of the 10MHz input signals (now at 2.5MHz). These are fed into simple XOR gates and RC lowpass filtered. You get two triangle waveforms at 90° phase shift, these are input to an AD7793 high-resolution ADC. Do the math and get the frequency difference.
The new unit has three inputs, one reference and two frequencies that are compared to the reference. So I can monitor two devices vs. a third one at the same time (hopefully saving a few of these 24h debug sessions ).

Great results and project in general   
To me it sounds like it is related to a Dual Mixer Time Difference DMTD?
Where the two signals to be measured are mixed with an offset oscillator and the resulting waveforms LPF'd and compared by a counter?
With your contraption they are mixed each with the reference as well? but as I and Q components and the output digitized,
but you have no amplitude difference (it's all square anyway?) so only phase information is what is relevant and used?

[mnementh]

So how come every time there is a spike in the cases you Aussies clean out all the toilet paper? 

Surprisingly last short break TP only became reduced stock not wiped out. I am hoping around the country there is some idiots unable to put cars in Garages for years to come and have to look over their shoulders to make sure no one is watching their embarrassment every time they open the door 

He's covering up. Truth is, because they place the bog roll in the incorrect underhand orientation and their toilets swirl backwards, every time they flush it empties the whole fucking roll.

As one might imagine, that does place a high emphasis on making sure you have adequate stocks in case you have to go more than two days between TP runs. 

mnem

[tggzzz]

Vegemite is Marmite with lots more salt and sugar, as less of the ingredients with the interesting flavours

[xrunner]

This oughta be fun. A cobbled-together 3D print / soup can cutter to trim nicely around my irrigation heads in the yard. Attaches to the B&D weed eater.

Texas chain saw massacre guy step aside - there's a new guy in town. 

[capt bullshot]

[...]

The new one uses simple divide-by-four circuits to provide in-phase and quadrature of the 10MHz input signals (now at 2.5MHz). These are fed into simple XOR gates and RC lowpass filtered. You get two triangle waveforms at 90° phase shift, these are input to an AD7793 high-resolution ADC. Do the math and get the frequency difference.
The new unit has three inputs, one reference and two frequencies that are compared to the reference. So I can monitor two devices vs. a third one at the same time (hopefully saving a few of these 24h debug sessions ).

Great results and project in general   
To me it sounds like it is related to a Dual Mixer Time Difference DMTD?
Where the two signals to be measured are mixed with an offset oscillator and the resulting waveforms LPF'd and compared by a counter?
With your contraption they are mixed each with the reference as well? but as I and Q components and the output digitized,
but you have no amplitude difference (it's all square anyway?) so only phase information is what is relevant and used?

Thanks!
I've read some papers about the DMTD (before and while I built the first one).

Anyway, the first one (100MHz PLL) isn't a DMTD, I've had some ideas on my own that I wanted to test:

One 100MHz PLL is offset by a slightly variable 125Hz signal, the other one is just 10x the input frequency. Then it's mixed down to a 125Hz beat frequency. Within the uC, there's another I/Q mixer that mixes the 125Hz beat frequency down to DC. Its output drives a control loop that keeps the phase constant (e.g. Q is alway zero) by varying the 125Hz signal frequency. As a result, the 125Hz offset signal frequency minus 125Hz equals 10 times the frequency difference of the inputs. The problem is the not-so-good 125Hz subtraction stage (by an I/Q mixer) to offset the first 100MHz PLL, it produces quite an amount of noise.
Next iteration will use DMTD principles.

The new one directly compares the input frequencies by mixing them down to DC (all digital). Each input is fed into an divide-by-four circuit with I/Q output. Two XOR gates do the mixing part (one input I / Q, other input I only), after RC filtering in a triangle wave proportional to the phase difference of the input signals. ADC and software measure du/dt of the mixed down signal and calculate frequency difference. Theoretically one needs only the I (or Q) part, but the triangle isn't very linear at the ends (near GND / VCC), so software automatically switches between them, and by having both signals one can derive the sign of the difference. Amplitude is "1" by definition.

[mnementh]

Just watched a local sparky firm on youtube, out on a "fire in junction box" call -- screw terminals badly applied, replaced with Wago 221, of course. "They won't fail and heat up like screw terminals." 



dragon-ticklingishly,

/M

mnem
"...for thou art crunchy and taste good with ketchup."

[tggzzz]

Went to a provincial hamfest today, the first one for years.

Lots of stuff that should be put in recycling waste bins, lots of beer bellies, too few masks, fortunately most stalls were outside.

Was about to look a brass and mahogany box with many an in resistors, but the bloke in front of me nabbed it. Got something else that I don't need, condition unknown. If it works I'll flip it, if not then it cost less than the petrol any way.

[mnementh]

Heads up for UK TE folk. New museum: https://www.museumofeverythingelse.com/

Full of Nixie tubes, VFDs, scopes and weird stuff. Run by the dude with the Furby organ.

I posted that in here almost a year ago, when he did the megaDrone. All y'all motherfuckers dogpiled me cuz of all the old TE you assumed he was busting up for circuits to make oscillators out of.

mnem

[beanflying]

Vegemite is Marmite with lots more salt and sugar, as less of the ingredients with the interesting flavours

We have done this before and you were WRONG about the Sugar last time!

[Robert763]

OK enough of the foodie stuff, back to TEA.
I went to my first hamfest/radio rally in over two years this morning (missed a bunch pre-covid due to being overseas for work). Only a small one and didn't stay long. I took the new dog and she was not totally happy, still a bit nervous.
I did however score big time. A HP 8640B. I've been after a low phase noise generator (at the right price) either a 8640B or TF2017 for many years.  This one has option 001 the wide range udio oscillator. I'm not bothered abot the internal doubler, 'Ive plenty of UHF signal generators and an external doubler if I need it.
The photo is as bought, I' slowly bringing it up to temperature. Supposed to be workig and the RAF calibration stickers are in place so it's not been messed with.
The big question (other than will it work) how much? £40, yes forty, I didn't miss a digit. I had the cash out before he changed his mind.   
Also picked up a Rapco 1804 P2 GPSDO for £20  no I don't need another GPSDO but this is TEA

Wow, if that actually works then you did very well getting that one 

Just been running some tests and it looks lke I have a fully functional, very tidy, post 1984 (from serial #) HP 8640B 
On of my best rally buys for years.

[mnementh]

This oughta be fun. A cobbled-together 3D print / soup can cutter to trim nicely around my irrigation heads in the yard. Attaches to the B&D weed eater.

Texas chain saw massacre guy step aside - there's a new guy in town. 

Doubles as a cup-digger for your own personal Mini-golf in the back yard, too ehhh...? 

mnem
3DP FTW!

[factory]

Heads up for UK TE folk. New museum: https://www.museumofeverythingelse.com/

Full of Nixie tubes, VFDs, scopes and weird stuff. Run by the dude with the Furby organ.

I posted that in here almost a year ago, when he did the megaDrone. All y'all motherfuckers dogpiled me cuz of all the old TE he was busting up for circuits to make oscillators out of.

mnem

Yes I've know about this for a long time, as I do watch some of the videos on both the LMNC & second channel for the museum he has been working on. https://www.youtube.com/channel/UC0-QuVLhCc4hmJaiLSCMwcw
The Solartron LM1420 voltmeter & Tek 585 scope are amongst the items he has acquired for the museum.
Bit surprised he hasn't flogged the Bradley calibrators to fund his other purchases.

Not sure he knows what this is  ; 


David

[Robert763]

Went to a provincial hamfest today, the first one for years.

Lots of stuff that should be put in recycling waste bins, lots of beer bellies, too few masks, fortunately most stalls were outside.

Was about to look a brass and mahogany box with many an in resistors, but the bloke in front of me nabbed it. Got something else that I don't need, condition unknown. If it works I'll flip it, if not then it cost less than the petrol any way.

If it was Kings Lynn you missed a nice 8640B 

[mnementh]

Vegemite is Marmite with lots more salt and sugar, as less of the ingredients with the interesting flavours

By "the ingredients with the interesting flavours" you mean "the stuff that tastes like ass", right...? 

mnem
"Thanks folks... I'll be here all week..."   

[Specmaster]

Vegemite is Marmite with lots more salt and sugar, as less of the ingredients with the interesting flavours

We have done this before and you were WRONG about the Sugar last time!

Truth is that both products are VERY similar and both derived out of waste products from beer brewing process
https://en.wikipedia.org/wiki/Marmite
https://en.wikipedia.org/wiki/Vegemite

[mnementh]

I rest my case.

mnem
 

[Brumby]

But, as Bean said, the lockdown rush this time around has been fleeting.  I was at Aldi a couple of days ago and their TP stock was FULL.  Two weeks earlier, it was very thin ... but not empty.

Pancake thin, or crêpe thin..?   

Paper thin ...
Tissue thin ...

(What I'm talking about is not fit for ingestion by anything other than a septic tank)

[Robert763]

Heads up for UK TE folk. New museum: https://www.museumofeverythingelse.com/

Full of Nixie tubes, VFDs, scopes and weird stuff. Run by the dude with the Furby organ.

I posted that in here almost a year ago, when he did the megaDrone. All y'all motherfuckers dogpiled me cuz of all the old TE he was busting up for circuits to make oscillators out of.

mnem

Yes I've know about this for a long time, as I do watch some of the videos on both the LMNC & second channel for the museum he has been working on. https://www.youtube.com/channel/UC0-QuVLhCc4hmJaiLSCMwcw
The Solartron LM1420 voltmeter & Tek 585 scope are amongst the items he has acquired for the museum.
Bit surprised he hasn't flogged the Bradley calibrators to fund his other purchases.

Not sure he knows what this is  ; 


David

Strange that somone into electronic music doesn't know the difference between a voltage divider and a decade box. 

[mnementh]

Heads up for UK TE folk. New museum: https://www.museumofeverythingelse.com/

Full of Nixie tubes, VFDs, scopes and weird stuff. Run by the dude with the Furby organ.

I posted that in here almost a year ago, when he did the megaDrone. All y'all motherfuckers dogpiled me cuz of all the old TE you assumed he was busting up for circuits to make oscillators out of.

mnem

Yes I've know about this for a long time, as I do watch some of the videos on both the LMNC & second channel for the museum he has been working on. https://www.youtube.com/channel/UC0-QuVLhCc4hmJaiLSCMwcw
The Solartron LM1420 voltmeter & Tek 585 scope are amongst the items he has acquired for the museum. Bit surprised he hasn't flogged the Bradley calibrators to fund his other purchases. Not sure he knows what this is  ; 

https://youtu.be/5lMrZh5gKXE

David

I think he knows a bit more than is apparent; he made a trillion years countup timer out of timer modules and knew enough to make the circuit and have the PCBs made up. Not sure how much of that was him vs his friends, but hey... that's what design is all aboot. You do what you know how to, and tap friends or hire people who know what you don't. 

Point being that I suspect the whole "What the hell is this thing...?" cheerfully ignorant noob bit is mostly part of his online persona; how he sells his yoobToob.

mnem
 

[mnementh]

...Now I've made another one, looks way more simple, doesn't it?



Not only it's less complex, it has about one decade better noise floor in comparison with the 100MHz PLL based device. I'll redo the PLLs some day, because there's some major flaws inside causing that high noise floor...

So does that mean you'll finally be able to tell us which one of these is showing you what time it is right now...?   

No, seriously... it's good to see someone doing actual EE stuff in here... 

mnem
Ifni knows I can't be arsed to... Even with stuff I know how to do.