Author Topic: DMTD board (Read 84826 times)

5065AGuru · « **on:** September 25, 2020, 03:42:22 am »

The boards for the DMTD mixer board arrived!

I'll be populating and testing and will post updates.

Cheers!

Corby

mark03 · « **Reply #1 on:** September 25, 2020, 04:42:21 pm »

What are all those holes for?? Seem too big to be vias.

tkamiya · « **Reply #2 on:** September 25, 2020, 05:19:03 pm »

Will you share the design of the circuit? I've been wanting to do this myself.

5065AGuru · « **Reply #3 on:** September 26, 2020, 03:48:57 am »

Yes I will be sharing the schematic/parts list/and expressPCB file.
Once assembled I'll be testing it and determining the noise floor.
I'll share some plots taken with it and some pointers on how to get the best results from the particular frequency counter you use with it.
I'm also in the process of designing a counter to go along with it so you don't have to tie up your fancy counter.

Just populated the front end and mixers and have good signals out of the mixers. Will be doing the rest of the board soon. I need to breadboard the op amp portion first so I can determine what bandwidth I want to use.

Cheers,

Corby

notfaded1 · « **Reply #4 on:** September 27, 2020, 03:25:39 pm »

Looks awesome Corby! You know I'm all over this! I'm so psyched after the bad experience with the TURN Dynamic Systems DMTD I bought!

Best Regards,

Bill

notfaded1 · « **Reply #5 on:** September 27, 2020, 03:27:33 pm »

The best part about this is we could setup multiple ones if the counter works for monitoring multiple oscillators! Good stuff!

Bill

5065AGuru · « **Reply #6 on:** September 27, 2020, 03:40:48 pm »

OK! Fully populated.
Just need to mount it in a frame with power supplies for testing.

notfaded1 · « **Reply #7 on:** September 27, 2020, 08:15:54 pm »

Dang Corby... that's some really cool stuff brother!

Bill

rubidium · « **Reply #8 on:** September 27, 2020, 11:10:25 pm »

Just curious: Were you driven to thru-hole because of your choice of passives? It will be interesting to see the test results.
Jim

thinkfat · « **Reply #9 on:** September 28, 2020, 08:37:12 am »

Huh, is that really a MC1651L at the input? Any chance to use something more contemporary? I'm not too keen on buying that device from Rochester Electronics...

tkamiya · « **Reply #10 on:** September 28, 2020, 03:37:19 pm »

Looks like major components are "pulls".

5065AGuru · « **Reply #11 on:** September 28, 2020, 08:39:34 pm »

This was only to scratch an itch of mine to see how the Efratom TS105 stages would work as a standalone Dual Mixer.
I was not trying to build "modern"!
The 1650 or 1651 were purchased on ebay for reasonable prices.
I also wanted something that could be easily assembled as Sometimes that scares people off.
Once I have done comparative testing with different types of op amps and comparators we will see if it has reasonable performance for entry level DMTD work.
First Time interval count and dirty layout for testing PIX.

5065AGuru · « **Reply #12 on:** September 28, 2020, 09:16:44 pm »

tkamiya,

Only pulls are the 2 Mixers and the 4 inductors.

My inductor kit was at work and rather than wait a day I used pulls.

Not that I think pulls are bad!

Cheers,

Corby

tkamiya · « **Reply #13 on:** September 28, 2020, 10:17:33 pm »

So.... how is it? I've been wanting to do this myself but been unable to get my feet wet.

thinkfat · « **Reply #14 on:** September 29, 2020, 07:53:37 am »

Quote from: 5065AGuru on September 28, 2020, 08:39:34 pm

This was only to scratch an itch of mine to see how the Efratom TS105 stages would work as a standalone Dual Mixer.
I was not trying to build "modern"!
The 1650 or 1651 were purchased on ebay for reasonable prices.
I also wanted something that could be easily assembled as Sometimes that scares people off.
Once I have done comparative testing with different types of op amps and comparators we will see if it has reasonable performance for entry level DMTD work.
First Time interval count and dirty layout for testing PIX.

No problem with "not modern", I was just hoping to have something that is more easily reproducible without resorting to finding "new old stock" on ebay. I don't usually buy parts from unknown sources, I stick to DigiMouser or maybe LCSC for Chinese chip vendors that are not stocked by my usual sources.

Still, when you publish the schematic at a point, I can likely come up with a "modernized" version, easier though if you provide some insight in what parameter was key to selecting a certain part over another.

For the MC1651, I'm guessing any reasonably fast dual channel comparator with differential output will do?
Do you need the latch function of the MC1651 (I'm guessing not)?

Without seeing the schematic, I figure the idea is to drive the mixer from the differential outputs of the comparator, first channel with the 10MHz from the DUT, the second channel from the transfer oscillator? The mixer output is then going into an amplifier and limiter and from there into a logic gate, probably some HCT or AHCT to have a TTL output for the counter.

5065AGuru · « **Reply #15 on:** September 29, 2020, 07:11:01 pm »

I have 4 other DMTD units and all of them have many more components and some have a lot of surface mount. One is an NBS 106D that was used in the testing of oscillators for the original GPS satellites.
I admired Efratom's design as it has minimal parts count and can tolerate a wide input amplitude range.
I wanted to offer an entry level version that would not intimidate a home brew hobbyist. Here is the first plot of an HP5065A against an FTS1200. I'll run and post a noise floor/ baseline plot next.

Cheers,

Corby

5065AGuru · « **Reply #16 on:** October 01, 2020, 11:06:28 pm »

OK, Here is a plot of the noise floor of the simple dual mixer.

This is good enough for pretty much any TimeNut!
Bill of materials will follow, Then the schematic, and then a corrected express PCB file.
(I need to enlarge a couple holes.)
The prototype is spoken for but the other two bare boards including some of the harder to find parts included will be offered for sale. (Pretty much at cost!)
This will be after I have a chance to do some more testing to make sure I'm happy with the design.

Cheers,

Corby

tkamiya · « **Reply #17 on:** October 01, 2020, 11:18:40 pm »

Pretty impressive!

Can I ask the board to have little more edge so parts aren't so close to the very edge of the board and mounting hole? Please? Whatever you end up with, I'll buy three.

5065AGuru · « **Reply #18 on:** October 02, 2020, 06:55:09 pm »

Unit is working fine but looking into a glitch in the outputs. Will update status when solved!

Cheers,

Corby

Frex · « **Reply #19 on:** October 04, 2020, 07:49:04 am »

Hello,

I don't have found many clear info about this with a Google search, so I ask you :
Does somebody can explain what is the purpose and applications of this DTMT board ?
How it work ?
Regards.

Frex

thinkfat · « **Reply #20 on:** October 04, 2020, 11:23:37 am »

Measure phase between two clocks with sub picosecond precision

5065AGuru · « **Reply #21 on:** October 04, 2020, 04:52:24 pm »

Frex,

Thinkfat is correct.

The utility of the device is to be able to compare frequency standards/oscillators and be able to reach Allan Deviation levels that most counters themselves cannot.

I just did a test a friend requested.

I wrapped 4 feet of RG58C/U around a coffee cup and measured the delay at ambient and then poured boiling water into the cup.

The cable delay changed by 40 PicoSeconds.

Resolution is 2 FemtoSeconds but noise level is in the 20 to 50 FemtoSecond range.

Ignore the scale on the left as it is not correct!

Still working on testing, BOM, and schematic.

Cheers,

Corby

thinkfat · « **Reply #22 on:** October 04, 2020, 07:49:13 pm »

At 1300s, what did you pour into the cup, liquid nitrogen? That would explain the condensation on the outside of the cup and the cable

5065AGuru · « **Reply #23 on:** October 04, 2020, 10:23:08 pm »

Let everything stabilize till 650 Sec and then poured in boiling water.
Then at 1300 Sec dumped water and then filled cup with ice cubes.
PIX of cup with condensation was just after I dumped the ice cubes.

Cheers,

Corby

KE5FX · « **Reply #24 on:** October 04, 2020, 10:35:14 pm »

Very nice. What's an MC1651L? ~~Google says it's an A/D...?~~ I see, it's a dual comparator. Haven't seen those referred to as "A/D converters" before, but I guess it's technically correct (the best kind of correct.)

The noise floor looks better than some of the more complex DMTDs I've seen. It's clearly a good part for the role.


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Author Topic: DMTD board (Read 84826 times)

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