[time-nuts] Frequency counter recommendation

[Chris Albertson]

I looked.   I think we should keep the design goals modest for a first
revision.  Shoot for a spec that can be hand built on perf board.  So
I'd relax those numbers by a factor of 1000.  The top frequency is in
Mhz, not Ghz and the time resolution closer to ns than ps.  It's good
to have a cheap option.  Many people are happy with an FCC1  Try for
the next step after that with a goal of actually matching the state of
the art in steps.

Why no through holes?  I don't see the point of banishing them.  I to
agree with the rest.  SMT that is hand solderable by a skilled tech
but now reflow ovens or solder past masks should be required .  You
might place a limit on component size too like 0.5mm lead pitch or
whatever is reasonable.

Mechanical part is not easy.  Need to re-purpose some mass produced
chassis.  That keeps leading me back to computer hard drives.  What if
you made the PCB the same size as a disk drive and then got some 1" x
1/4" aluminum L extrusion and screwed some of the aluminum around
three sides of the PCB.  low-tech metal work but they might slide into
a disk drive enclosure that is made to house SATA drives.   These
enclosures come in any size for one drive all the way up to 6 foot
racks.

If yu also place a aluminum L across the short side you have space for
conectors and switches

On Mon, Dec 20, 2010 at 6:20 PM, Bob Bownes <bownes at gmail.com> wrote:
> Well said Chris. Take a look at the initial spec in the OpenCounter Gogle
> group and tell me what you think with respect to your item #1. I think the
> core counter is going to be the really difficult part of the module list.
>
> Item #2 is going to be a tough one methinks. I love Eurocard, but, as you
> say, it is very expensive, if only for the connectors. In cases like this
> I'm a fan of either repurposing commercially available connectors (PCI and
> memory DIMMS are two I have used in the past) because they can be a)
> purchased off the shelf, b) are manufactured in enough volume to make cheap,
> and c) are common enough that the really cheap amongst us can get them off
> of scrap boards someplace for little or nothing. The N2PK VNA is built to
> fit into a particular HAmmond enclosure that I like but again, there are
> many options. My feeling is that the enclosure should not dictate any
> functional design decisions.
>
> #3 - I've created a group and appointed myself benevolent dictator. We can
> discuss things, propose designs or design criteria, call for a concensus,
> accept, and draft volunteers to design that section to the defined spec. If
> there are multiple competing designs, so much the better, as long as we all
> agree on the interfaces. Sound like a process? Can you tell I've done this
> once or twice? :)
>
> Step one will be to agree on the overall functional spec. If we get enough
> participants, I'd like to nail that down by mid January. The next step is to
> agree on the interfaces between the modules. Same process, discuss, propose,
> draft, get concensus, close and move on.
> Then we get folks working on the individual modules.
>
>
> On Mon, Dec 20, 2010 at 8:43 PM, Chris Albertson
> <albertson.chris at gmail.com>wrote:
>
>> On Mon, Dec 20, 2010 at 2:51 PM, Dave M <dgminala at mediacombb.net> wrote:
>> >
>> .. never got off the launchpad because of their inability to come to
>> > consensus on a set of features. I had to conclude that too many cooks
>> > spoiled the broth. Everyone that had input to the project was unwilling
>> to
>> > yield on anyone else's ideas.   Hopefully, our project won't degrade into
>> > another such fiasco.
>>
>>
>> THAT is the number one problem to solve.  Technical issues are easy
>>
>> I think the solution is to
>> (1) chop the project up into small enough parts, each on it's own PCB
>> so that each part is "easy" and has some wider user outside the
>> project.
>> (2) Find a mechanical standard so all the PCBs can be mounted in some
>> kind of chassis.  I'm thinking now that maybe a 160-3U Eurocard would
>> be about right size.  But the parts are expensive.
>> (3) Need some sort of design process that allows everyone to
>> contribute.   And everyone can.  Projects always are lacking technical
>> writers and quality control people
>>
>> Of those a "process" and "mechanical standard", I think are the
>> hardest.   We always give managers a hard time but that is what is
>> needed.  The person who will make this happen will be a manager and
>> organizer maybe not a designer.
>>
>>
>> --
>> =====
>> Chris Albertson
>> Redondo Beach, California
>>
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-- 
=====
Chris Albertson
Redondo Beach, California