Author Topic: Test Equipment Anonymous (TEA) group therapy thread  (Read 1709594 times)

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Offline factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29350 on: April 15, 2019, 11:07:54 am »
Finally, a couple of weeks ago I was going to bid on an item when the auction was shown as being in Aylesbury. Then it "moved" to Scotland, and it wasn't worth a 700 mile trek. I bid on something similar a couple of weeks ago, but it went for £95. But at Kempton I saw the first item; the vendor had indeed gone to Scotland and filled up a van with many of the items from a college that was shutting down.

Anyway, I am now the proud possessor of a Griffin Timer Scaler containing some of the same technology used in the world's oldest operating computer, the WITCH in TNMoC. Yes, it does work, and looks as retro cute as I would hope :) 

Since pictures are required, here's one at 1/250s:



And I still haven't got the blasted handle off!

I guess the £95 one was the Advance Counter-Timer SC1, it was on my watch list to just to see how much it would make and to save the pictures later.

This one was bought one years ago for about £24;



A replacement dekatron needed for it cost more than the unit (the Argon had escaped), I seem to remember the voltage selector was missing and the mains lead had been cropped off too.
Here are some pictures of the insides;




Sadly service manuals for Advance stuff are pretty hard to find, I've never found anything for the SC1, maybe I'll have to go through it component by component one day to find out why it only counts with low mains/line voltage (i.e. with the lamp limiter in circuit).

David
« Last Edit: April 15, 2019, 11:14:11 am by factory »
 
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29351 on: April 15, 2019, 11:27:21 am »
We're all Motorola TETRA here at the moment. Coordinated across all emergency services. What's cool is the TETRA sets work underground on the public transport as well now. Ambulance driver gets a call at a tube station and can relay stuff and call for assistance while they're underground etc. This goes as far as working in the tunnels between stations. Same with police / BTP / fire etc.

Believe it or not....for all the money they spend on security.....the NYC 911 radio system is still for the most part on VHF and in the clear. It's too bad I'm too far away to listen in because I'm sure I'll hear some interesting stuff.  ;D
Yeah you sure would, I used to listen into our emergency services when they were in the open on VHF especially exciting if something was happening your own area as well but of course now that they are using TETRA I can no longer do that, hmmm just wish someone would develop a scanner that could cover TETRA as well the military air bands and was reasonably priced. I don't think that I have ever heard of anyone selling a radio capable of receiving and decoding TETRA ?

From what I understand to be even in simple possession of the decryption key for one of those systems will land you in jail.  :scared:
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Offline factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29352 on: April 15, 2019, 11:37:29 am »
This evenings TEA Foot making tools include Fusion with a Helping hand from a Coopers Stout or two or ....  :popcorn:

Rough Prototype as per the photo is on the printer.


I'm curious as to what you are going to use for the spring loaded retainer for the HP feet, maybe it was mentioned in the 3D parts printing thread, but I can't find that now.
Pictures below of the retainer & spring from a broken foot, just need to work out how to attach it to another foot that is missing these.

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Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29353 on: April 15, 2019, 11:42:49 am »
Yeah I've heard that as well. When it is on FM, is was OK to listen to their broadcasts but to play it on speakers in public or to others about what you hear on it would land you in hot water. Having said that, it's much the same thing with Airband scanners, especially military transmissions but that said, when I go to Airshows or a trip to one of the Airbases near me to photograph the planes, the scanners are on speakers all the time and nobody bothers about it so what is the real truth here?
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Online beanflying

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29354 on: April 15, 2019, 11:48:55 am »
This evenings TEA Foot making tools include Fusion with a Helping hand from a Coopers Stout or two or ....  :popcorn:

Rough Prototype as per the photo is on the printer.


I'm curious as to what you are going to use for the spring loaded retainer for the HP feet, maybe it was mentioned in the 3D parts printing thread, but I can't find that now.
Pictures below of the retainer & spring from a broken foot, just need to work out how to attach it to another foot that is missing these.

David

I have a small stash of Aluminium rivets from some other past jobs will do the job. Search '3mm flat head aluminium rivets' on Google will find plenty. A short correct diameter sleeve of some sort and peen the end over.

Edit: Prototype clip in foot sample fits and the pin hole lines up. Cosmetic bit tomorrow when I work out some angles.



« Last Edit: April 15, 2019, 12:19:02 pm by beanflying »
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29355 on: April 15, 2019, 01:02:49 pm »
That 427A is looking pretty good. I like the old battery. The last one I had someone had removed the battery which was a good thing. I worried that it was going to have leaked. Mine did however have the mains supply option so I just used that in the end. I had the idea of building a 15x AA cell pack for it but couldn't be bothered in the end. It takes bugger all current and works over a wide range so 3x 9v batteries would probably be fine too.
« Last Edit: April 15, 2019, 01:04:54 pm by bd139 »
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29356 on: April 15, 2019, 01:14:46 pm »
Mine has option 001 fitted too and I am unlikely to ever want to run it on batteries. Amazed at the pricing on the Battery still. Not sure what to do with it longer term as at 2% accuracy it won't get a lot of use on my bench other than a gap filler ;)

Will be making a foot version for the 1" wider 419A body too. Unsure if there is any wider bodies with that same bail and foot design? If anyone has or knows of one let me know?
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Online mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29357 on: April 15, 2019, 01:26:18 pm »
Things that make you go, hmmm...

(Unsure of the scale, but an appropriately sized version of that might work as a cover for a 454 screen.)
You don't say...  >:D
Yeah, well, I just had to, since you left it in that post so teasingly without even so much as an "ahem." :-DD

ahem.  >:D

Today's cleanup background video. Baofeng leads to SDR leads to wireless data hacking. Interesting and uber nerdy.

https://youtu.be/N0p3_ES2dBU

Thank you! I actually stopped my morning music burn to watch that... SDR and the wireless infrastructure are something I've been meaning to investigate for some time. a VERY interesting watch; plus I got to find out what actually happened with the ISEE-3 reboot (nothing; propulsion inoperable even though fuel present)  :(.

www.spacecraftforall.com


Very neat stuff...those ettus boards are not cheap either...
Seems they are now owned by National Instruments won't be helping. I think I will settle for one of these eBay auction: #172813499296 and maybe add a discone antenna (unless anyone has a better suggestion?) of some sort to it at some stage. I mainly want access to weather, local emergency services and airband.
Yeah...I was thinking of getting a hackrf. A little more expensive but a lot less than ettus.

I was reading just the other day about how emergency services here in the states are switch to encrypted channels all around. Not just a few tactical channels for the fuzz...police, fire, and EMS all using encrypted links. :--
Our State Police and I assume most others have gone to encrypted some years ago. Emergency Services are generally still open https://www.radioreference.com/apps/db/?stid=152

We don't need a license for Tx on the standard 70cm band Channels but to use the 2m band including the channels used for Marine (and rescue) we need a license  :palm: While I am currently boatless apart from a Hobie Kayak a waterproof bag with a marine capable radio for $60 is still sensible, care factor of a fine if I am in the poo is Zero.

Yeah, the general sentiment in the stuff I've seen (and I tend to agree) is that taxpayer funded public servants shouldn't be on encrypted radio for general stuff. Tactical channels for SWAT teams and pursuits makes sense but everything else should be in the clear. I can't sleep tonight, so kit building therapy time. I think the next kit I get has to be one of those giant transistor-level 555 timers.  ;D
   www.RTL-SDR.com   www.airspy.com

Happy I could contribute to your post-juvenile delinquency.  >:D

mnem
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29358 on: April 15, 2019, 01:40:02 pm »
Mine has option 001 fitted too and I am unlikely to ever want to run it on batteries. Amazed at the pricing on the Battery still. Not sure what to do with it longer term as at 2% accuracy it won't get a lot of use on my bench other than a gap filler ;)

They're great for watching fluctuating values. Also the noise immunity is much much better than any digital meter.

TBH 2% is fine for most jobs. Hell 5% is probably fine (I will inflame most of the voltnuts with that).

I noticed with the HP 400E on the sensitivity front - if you put a 2m antenna on it and key up in the same room it'll give a deflection :)
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29359 on: April 15, 2019, 02:13:36 pm »
Here are some pictures of the insides;


Veroboard?  :o

Keyboard error: Press F1 to continue.
 

Offline tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29360 on: April 15, 2019, 02:37:28 pm »
I guess the £95 one was the Advance Counter-Timer SC1, it was on my watch list to just to see how much it would make and to save the pictures later.

Yup.

Quote
This one was bought one years ago for about £24;
...
A replacement dekatron needed for it cost more than the unit (the Argon had escaped), I seem to remember the voltage selector was missing and the mains lead had been cropped off too.
Here are some pictures of the insides;

Very similar construction techniques to the Griffin, although I can only get the backplate off.

The handle on the lid is still firmly attached. I suspect a numpty has tried to force the cover off, and part of it has bent under the screw hidden by the cover. If that's the case then destructive force would be required.

Since it is working as a timer, I can't think of a good enough reason to use destructive force; mere curiosity is insufficient.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Offline Specmaster

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29361 on: April 15, 2019, 02:40:12 pm »
Mine has option 001 fitted too and I am unlikely to ever want to run it on batteries. Amazed at the pricing on the Battery still. Not sure what to do with it longer term as at 2% accuracy it won't get a lot of use on my bench other than a gap filler ;)

They're great for watching fluctuating values. Also the noise immunity is much much better than any digital meter.

TBH 2% is fine for most jobs. Hell 5% is probably fine (I will inflame most of the voltnuts with that).

I noticed with the HP 400E on the sensitivity front - if you put a 2m antenna on it and key up in the same room it'll give a deflection :)
You beat me to it, I was going to say that is better for flactulating signals and 2% is perfect for most jobs and I will soon have 6.5 digit meters but the extra  resolution for me is only useful in certain applications, otherwise 2 or 3 dps is perfectly fine for 99% of jobs
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Online mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29362 on: April 15, 2019, 02:43:52 pm »
They are cute, and have the usual colour more often seen in delicious Panaplex displays.

They were frequently seen in the background of 50s and 60s movies/TV. The good ones showed them performing some scientific/military job. The bad ones (e.g. excreble SF / cold war propaganda) used them as blinkenlights.

Anyway, feast your eyes here http://www.tnmoc.org/special-projects/harwell-dekatron-witch including a video of the computer being rebooted with some of its original designers. A shorter version is


   ALSO a very interesting watch... So wait a minute. This thing... the Dekatrons themselves are the registers. So this prehistoric Turing-age machine... it actually used decimal-coded logic as opposed to binary-coded? Clearly the pulses used to advance the register are binary; but the register itself is inherently decimal (or, apparently, many more states are possible; it appears Russian-made tubes are available with many more "poles"), so it must be decimal, right?

Interesting thing: Now that we're trying to make ever-larger SSDs... we're going back to that kind of logic... where each "bit" (cell), instead of having a binary state, can be one of 8 (TLC) or even 16 states (QLC) now dependent upon the voltage stored in a single cell. Of course that is still converted back & forth through a more traditional binary buffer; but still... the idea of modern machines that "think" in something other than binary has always fascinated me.

   Oooooh... tripped over these while looking into the mechanics of the Dekatron:

http://www.tube-tester.com/sites/nixie/nixie-tubes.htm

https://threeneurons.wordpress.com/dekatron-stuff/dekatron-dohickie/

mnem
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Online med6753

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29363 on: April 15, 2019, 02:53:42 pm »
The 465B is done and buttoned up. Checked both channel's attenuator compensation and it was perfect. No adjustments required. Here's 10Mhz square from the Heath IG-4244. Obviously I'm not going to use this scope as a parts mule. I've put too much work into it plus it works damn near perfect. So now all my Tek's are functional except the 465B requiring the 4x attenuator. Speaking of which....it's STILL sitting at JFK. Been there since April 9th. If it doesn't move today I'm going to my local PO tomorrow and ask them what's up?  :wtf:



And a quick follow up. Here's the 2430. Still working perfectly after about 6 days and many power cycles. So it was an overheat problem from improper mounting that destroyed those CCD hybrids.    :palm:

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Offline tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29364 on: April 15, 2019, 02:59:11 pm »
They are cute, and have the usual colour more often seen in delicious Panaplex displays.

They were frequently seen in the background of 50s and 60s movies/TV. The good ones showed them performing some scientific/military job. The bad ones (e.g. excreble SF / cold war propaganda) used them as blinkenlights.

Anyway, feast your eyes here http://www.tnmoc.org/special-projects/harwell-dekatron-witch including a video of the computer being rebooted with some of its original designers. A shorter version is


   ALSO a very interesting watch... So wait a minute. This thing... the Dekatrons themselves are the registers. So this prehistoric Turing-age machine... it actually used decimal-coded logic as opposed to binary-coded?

Yes, yes, and yes.

Quote
Clearly the pulses used to advance the register are binary;

Nope, they are simple analogue pulses. The input to one dekatron can be derived from another dekatron' s output.

Quote
but the register itself is inherently decimal (or, apparently, many more states are possible; it appears Russian-made tubes are available with many more "poles"), so it must be decimal, right?

Yup.

Quote
Interesting thing: Now that we're trying to make ever-larger SSDs... we're going back to that kind of logic... where each "bit" (cell), instead of having a binary state, can be one of 8 (TLC) or even 16 states (QLC) now dependent upon the voltage stored in a single cell.

Everything is analogue, except for photon counters and femtoamp circuits. In most cases the analogue voltage or current is interpreted as a binary signal and then regenerated before being passed downstream.

Yes, that is an exaggeration, but not much of an exaggeration.

Quote
Of course that is still converted back & forth through a more traditional binary buffer;

That binary buffer is called an ADC :)

Quote
but still... the idea of modern machines that "think" in something other than binary has always fascinated me.

Your next assignment is to design a circuit that divides a pulse train by 5 so that a 10MHz input becomes a 2MHz output. Your junkbox contains three transistors, plus diodes, resistors and capacitors.

You will lose points if the circuit closely resembles that of a Tek 184 time mark generator.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Online bd139

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29365 on: April 15, 2019, 03:09:12 pm »
Your next assignment is to design a circuit that divides a pulse train by 5 so that a 10MHz input becomes a 2MHz output. Your junkbox contains three transistors, plus diodes, resistors and capacitors.

You will lose points if the circuit closely resembles that of a Tek 184 time mark generator.

On this subject, I found this beauty a while ago digging around in my somewhat extensive book collection. This is from "Test Equipment for the Radio Amateur":

I've left this full size as it's a schematic:



I'd build this but Droitwich is on 198KHz now instead of 200KHz (changed on February 1st 1988). Plus it's on its last transmitting tubes. I was considering building it anyway and just using a DG1022Z as the RF source as it would be fun poking it with a scope and reverse engineering.

I've used the charge storage divider by accident before trying to emulate a unijunction transistor ramp generator.
« Last Edit: April 15, 2019, 03:13:17 pm by bd139 »
 

Online mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29366 on: April 15, 2019, 03:15:25 pm »
The 465B is done and buttoned up. Checked both channel's attenuator compensation and it was perfect. No adjustments required. Here's 10Mhz square from the Heath IG-4244. Obviously I'm not going to use this scope as a parts mule. I've put too much work into it plus it works damn near perfect. So now all my Tek's are functional except the 465B requiring the 4x attenuator. Speaking of which....it's STILL sitting at JFK. Been there since April 9th. If it doesn't move today I'm going to my local PO tomorrow and ask them what's up?  :wtf:

   

And a quick follow up. Here's the 2430. Still working perfectly after about 6 days and many power cycles. So it was an overheat problem from improper mounting that destroyed those CCD hybrids.    :palm:

*In best 'The Count' Voice* "Two... twoooo wooorking Cathode-Ray Oscilloscopes... Ahhh-Ahh-Ahhh!!!"    ;)

Bummer about the unnecessary parts death... but that's the role of failure in design.  :-+

Hope you get your parts soon... maybe have to go downtown and jump somebody's shit!

mnem
 >:D
 

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29367 on: April 15, 2019, 03:20:48 pm »
The old CRT has been cleaned up and is now a display piece. I'm considering breaking the exhaust tip to make it "safe" but I put it where it can't get knocked over (easily).  :-DD

Perhaps put it in an acrylic display case with a nice wood base.

+1

once I have more space I'm going to get some kind of a display case for my vacuum tube collection. Keep the dust off and the cats out...

As in https://entertaininghacks.wordpress.com/2016/03/09/rescuing-a-broken-tektronix-465-crt/ which also indicates how and where to cut.



Ought to upload a better image now I've got a decent camera.

If I do decide to "fancy up" the CRT I'm not going to separate the gun from the ceramic bell. If I do anything to it I'll cut off the HV anode lead flush with the CRT.
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Offline factory

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29368 on: April 15, 2019, 03:49:14 pm »
Here are some pictures of the insides;


Veroboard?  :o



It is indeed, here is a picture showing the back of the veroboard and another with the lights off (only just noticed the lamp limiter dimly glowing in the background).

David
 

Online mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29369 on: April 15, 2019, 04:21:15 pm »
   ALSO a very interesting watch... So wait a minute. This thing... the Dekatrons themselves are the registers. So this prehistoric Turing-age machine... it actually used decimal-coded logic as opposed to binary-coded?
Yes, yes, and yes.
Quote
Clearly the pulses used to advance the register are binary;
Nope, they are simple analogue pulses. The input to one dekatron can be derived from another dekatron' s output.
Quote
but the register itself is inherently decimal (or, apparently, many more states are possible; it appears Russian-made tubes are available with many more "poles"), so it must be decimal, right?
Yup.
Quote
Interesting thing: Now that we're trying to make ever-larger SSDs... we're going back to that kind of logic... where each "bit" (cell), instead of having a binary state, can be one of 8 (TLC) or even 16 states (QLC) now dependent upon the voltage stored in a single cell.
Everything is analogue, except for photon counters and femtoamp circuits. In most cases the analogue voltage or current is interpreted as a binary signal and then regenerated before being passed downstream.

Yes, that is an exaggeration, but not much of an exaggeration.
Quote
Of course that is still converted back & forth through a more traditional binary buffer;
That binary buffer is called an ADC :)
Quote
but still... the idea of modern machines that "think" in something other than binary has always fascinated me.

Your next assignment is to design a circuit that divides a pulse train by 5 so that a 10MHz input becomes a 2MHz output. Your junkbox contains three transistors, plus diodes, resistors and capacitors.

You will lose points if the circuit closely resembles that of a Tek 184 time mark generator.

You don't have to tell me this; I've long been an evangelist of the concept that "All digital signals must first exist in the analog domain." I don't want to rehash the ages-old argument over whether adding the time domain makes a signal inherently digital or not; obviously, as with all circuits, that depends entirely on what you do with the signal.  ;)

Well, actually I was thinking more about the octal/hex register those values are stored in, but okay.  :P

Okaaaayyy... I'm a little busy packing a 454 for shipping to its new home, but of course I've built a Mod-5 using flip-flops. Normally need at least two transistors to make a discrete flip-flop, and then something for the reset, but I remember reading a Hackaday about a DTL circuit that uses a single transistor as a flip-flop, but as tested it was limited to under 1 MHz operation. Not sure if that's what you had in mind, or something more along the lines of "analog computer" design wherein "operations" are performed as a function of RC/LC,etc time constants and LF heterodyning.

mnem
Fuck... that's a big box.
« Last Edit: April 15, 2019, 04:44:37 pm by mnementh »
 

Offline wch

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29370 on: April 15, 2019, 04:46:06 pm »
The 465B is done and buttoned up. Checked both channel's attenuator compensation and it was perfect. No adjustments required. Here's 10Mhz square from the Heath IG-4244. Obviously I'm not going to use this scope as a parts mule. I've put too much work into it plus it works damn near perfect. So now all my Tek's are functional except the 465B requiring the 4x attenuator. Speaking of which....it's STILL sitting at JFK. Been there since April 9th. If it doesn't move today I'm going to my local PO tomorrow and ask them what's up?  :wtf:

That's a nice piece of work!  :-+

After going through your photos, I went back and read BD139's thread, and others, on restoring 4XX gear. A ton of useful info in all of it. I am still working my way through the pile of TM500 plugins and sorting the Tektronix probes, calibration fixtures and so on. I will probably tackle the 485 first, which doesn't work, before tackling the 475A which does.

And just to keep things interesting, I am picking up a Tek 466 this evening. Free. Current owner says, It was working, then died. I have a couple of working scopes, don't know much about these, don't want to take the time to figure it out. Its yours if you want it.   :-BROKE  Silly bloke, of course I want it!   :-DD


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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29371 on: April 15, 2019, 04:59:35 pm »
I got an RTL-SDR Blog V3 kit a few months ago. I don't know if it's better or worse than the NESDR or others. Apparently there are knockoffs of the RTL-SDR Blog V3, so I bought mine from the RTL-SDR Blog's eBay store.

For software, I use it with SDR#. It seems the original SDR# URL now redirects to airspy.com. I'm not sure what that means. You can still get SDR# on their download page, but it seems to be bundled with other stuff, now.

I got the dongle primarily to be able to check if a transmitter (e.g., RF remote) is functioning. But, using it to listen to FM and shortwave works as expected, too.

RTL-SDR V3 is pretty good. A bit more expensive than the generic one but with the metal enclosure heat dissipation is a lot better (A problem to be able to lock the pll at different frequencies).

The creator of SDR# was eventually hired by AirSpy and is now developing software over there. SDR# is still available for free and you can use it with generic R820T based hardware (ex RTL-SDR V3).

For a overview of the different SDR platforms, check this link https://www.rtl-sdr.com/roundup-software-defined-radios/
 
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Offline tggzzz

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29372 on: April 15, 2019, 05:00:22 pm »
   ALSO a very interesting watch... So wait a minute. This thing... the Dekatrons themselves are the registers. So this prehistoric Turing-age machine... it actually used decimal-coded logic as opposed to binary-coded?
Yes, yes, and yes.
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Clearly the pulses used to advance the register are binary;
Nope, they are simple analogue pulses. The input to one dekatron can be derived from another dekatron' s output.
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but the register itself is inherently decimal (or, apparently, many more states are possible; it appears Russian-made tubes are available with many more "poles"), so it must be decimal, right?
Yup.
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Interesting thing: Now that we're trying to make ever-larger SSDs... we're going back to that kind of logic... where each "bit" (cell), instead of having a binary state, can be one of 8 (TLC) or even 16 states (QLC) now dependent upon the voltage stored in a single cell.
Everything is analogue, except for photon counters and femtoamp circuits. In most cases the analogue voltage or current is interpreted as a binary signal and then regenerated before being passed downstream.

Yes, that is an exaggeration, but not much of an exaggeration.
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Of course that is still converted back & forth through a more traditional binary buffer;
That binary buffer is called an ADC :)
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but still... the idea of modern machines that "think" in something other than binary has always fascinated me.

Your next assignment is to design a circuit that divides a pulse train by 5 so that a 10MHz input becomes a 2MHz output. Your junkbox contains three transistors, plus diodes, resistors and capacitors.

You will lose points if the circuit closely resembles that of a Tek 184 time mark generator.

You don't have to tell me this; I've long been an evangelist of the concept that "All digital signals must first exist in the analog domain." I don't want to rehash the ages-old argument over whether adding the time domain makes a signal inherently digital or not; obviously, as with all circuits, that depends entirely on what you do with the signal.  ;)


Er... Digital signals exist in the digital domain, by definition. There is nothing analogue about 0, 1, 0xdeadbeef etc.

Adding the time domain changes absolutely nothing of that.

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Okaaaayyy... I'm a little busy packing a 454 for shipping to its new home, but of course I've built a Mod-5 using flip-flops. Normally need at least two transistors to make a discrete flip-flop, and then something for the reset, but I remember reading a Hackaday about a DTL circuit that uses a single transistor as a flip-flop, but as tested it was limited to under 1 MHz operation. Not sure if that's what you had in mind, or something more along the lines of "analog computer" design wherein "operations" are performed as a function of RC/LC,etc time constants and LF heterodyning.

The circuit bd139 showed indicated one way. I think (without verifying it) that the Tek 184 uses a different way.

No flip flops involved, only "glugs" - to use the lovely and descriptive) term frequently found in high precision voltmeters.
There are lies, damned lies, statistics - and ADC/DAC specs.
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Online Kosmic

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29373 on: April 15, 2019, 05:04:02 pm »
How does the RTL-SDR do at lower frequencies? The NooElec NESDR is specced at 65MHz bottom end and they sell an up converter for covering HF and the lower end.

Most of them don't go below 24Mhz. This is due to the R820T chip. Was initially designed to receive digital TV and was suposed to only work between 42Mhz and 1000Mhz. Can actually do 24 - 1700Mhz

https://rtl-sdr.com/wp-content/uploads/2013/04/R820T_datasheet-Non_R-20111130_unlocked.pdf
« Last Edit: April 15, 2019, 05:09:20 pm by Kosmic »
 

Online mnementh

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Re: Test Equipment Anonymous (TEA) group therapy thread
« Reply #29374 on: April 15, 2019, 05:09:56 pm »
In Other News...

"snap... crackle...crunnnnch.... crackle... pop..." emanating from the back room indicates that my print is cooling and "releasing" from the mirror tile. I plan to ignore it assiduously for the next 15 minutes or so, allowing it to "do its thing..."

Unfortunately, it appears I've killed part of my printer... In hopes of maintaining adhesion over such a long, large print... I cranked up the bed heat to 75°C to compensate for the heat lost by passing through 3 layers. It worked... but as many have warned it would do, the Tevo "Build-Tak" clone print surface has bubbled. I'm going to have to remove it.  |O

Guess I'll get to see how well it prints directly on the ceramic bed now.  >:D

mnem
Damn... I need to dust my printer.
« Last Edit: April 15, 2019, 05:14:13 pm by mnementh »
 


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