DMTD board

[FriedLogic]

   There is also this post from chuckb if you just want the gerbers for any PCB manufacturer to make.
https://www.eevblog.com/forum/metrology/dmtd-board/msg3278036/#msg3278036
This is the one that I made and it works well.

   There is often no need for a fast low impedance output, particularly if it's just a short link to a counter in the same case.
   I use opto isolators for the input to the Propeller counter, which reduces noise and ground loop issues. I did not have any fast ones when I was setting it up, so added an HC132 in case the counter was not too happy with the 3.5us or so rise time. It also inverted the signal again so it was the same as it originally was.

[kpjamro]

Thanks

 ... I figured out how to look at those Gerber files in Kicad Gerber viewer.  It seems that the default file extensions the program offers do not include any of the important ones, for some reason.  I guess this is the same PCB pattern as the v19D PCB. Anyway, thanks for that info.

One thing I find strange is that in input devices are in sockets.  If this is where sub-nanosecond timing variability is important, I would think you would want to avoid sockets there.

This beastie needs 4 different voltages.  For a standalone unit I was wondering if I could just buy one PSU that covered all 4 and I found the Meanwell RQ-65B which can.   I don't know if purity of the supply voltages is an issue where you need to supply it from some low-noise dc/dc regulator chips or if the Meanwell would work.  I saw a schematic by one poster that showed what seemed to be separate regulators for every stage of this circuit. No PCB was included with that however.

I am getting close :-)

[Echo88]

Are 13dBm-mixers acceptable for the pcb from Corby or should one stay with the 7dBm ones?

[5065AGuru]

Echo88,

+13dbm mixers are OK but you may have to drive them at close to that level for the best results.

One think to be careful about. The mixers used must have isolated RF and LO inputs as you are driving them differentially!

Some mixers have one side of the RF and LO connected to the case, these wont work.

Cheers,

Corby

[Mrt12]

Hi together,
has anybody made some further experiments with the ECL input stages?
I just started to think again about this DMTD topic and I still wonder why I had this strange jitter issue with my ECL gates.

[Mrt12]

Hallo all,
today I performed a very simple experiment and I believe I found the culprit why my DMTD is so unstable.

First of all, I changed the 50 Ohm input resistor for the VBB pin of the ECL gates, as suggested in an earlier post. This brought additional stability.
Then I ran some tests, during which I left the room and closed the door. After a while I went back in, and noticed that there was a sudden jump in the TI data as soon as I opened the door!
The effect was reproducible. Obviously, opening and closing the door produced a tiny air blast, that changed the temperature of the ECL gates, altering their phase.
I am annoyed that I didn't find out this earlier. The effect is reproducible when I touch the ECL chips.

I modified my entire input stage to the mixer with flying wires, and voila, now I have the desired stability of better than 1e-12 at 1 second. At least when I do this test with 2 OCXOs as signal sources at the input.
Why couldn't I find this earlier? 
and what surprises me even more is that the board from corby doesn't seem to have this effect - why doesn't the ECL comparator change its phase when the temperature changes?
anyways, it seems like the temperature coefficient of the input stage is crucial. The MC100EL16 ECL gate doesn't seem to be stable enough for this task.
Can anybody confirm this?