[time-nuts] Thunderbolt Monitor (Didier Juges)

[WB6BNQ]

Bruce Griffiths wrote:

> Bill
>
> If one is going to do all this in one instrument then care should be
> taken to avoid inadvertent coupling via low frequency ground loops.
> RF transformers on all RF inputs can be very effective in minimising
> such problems.
> Isolating the instrument from the PC by using either LAN or isolated
> serial link(RS232/RS485 etc) for communications would also be useful.
> USB is less useful in that it can be somewhat more expensive to isolate
> satisfactorily.
>
> If one requires even higher resolution when comparing standards then a
> dual (or N channel) mixer system is easily constructed using carefully
> designed modular parts.
> Isolation amplifiers, mixer preamps, zero crossing detectors etc are
> required. However the zero crossing detectors can be replaced by a high
> resolution sound card.
> For low frequency (< 100kHz) beat signals a capacitive mixer IF port
> termination is best.
> With some substitutions the same modules can be rearranged to create a
> phase noise measurement system.
>
> Bruce
>
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Hi Bruce,

Well I think you missed my point !  As I mentioned there are a few who have the
ability to deal with the H and Cs devices.

However, I was really targeting the low end of the spectrum.  I referred to them
as the "normal guy" but perhaps I should have said the "casual guy" meaning those
who have a passing interest but are not going to run out and buy a Cs or even a
Rb but would be happy with a GPS disciplined crystal with 3 to 4 times the
accuracy they really need.  This person may have a less than stellar counter or
two laying around who would want to calibrate them against his GPSDO every now
and then.  Or may want to monitor and calibrate their HF rig for a ARRL frequency
contest or some such.  Even those with a Rb may not need more then what i
suggested.

I think the Shera controller with some upgrades is probably more then good enough
for the targeted level to discipline a crystal house standard or two.  Not that I
am saying something else could not be used.  Particularly for the third channel
which would be intended for non disciplined purposes.  I should have made
reference to the TRACOR 895 for that third position.

I was also thinking at the kit level.  If things were done at the "thru-hole"
level maybe more people would be interested in building such a kit.  Usually the
people left these days that tinker around (i.e., quasi hobbyist) are older with
failing eye sight, a little more jitter in their step (if you know what I mean)
and not interested in fooling around with those damn surface mount items {such as
myself}.  Sticking to "thru-hole" means those putting the kit together do not
have to figure out how to handle the surface mount stuff for those who do not or
cannot deal with it.

The largest problem is just coming up with a chart recorder.  I have a couple of
them and cannot find paper for them.  Standard office calculator/cash register
paper is expensive enough, chart paper with holes on the side and a specific grid
pattern is even worse.

So, the way I see it, there are a number of people (Timenuts and Amateur radio
operators via TAPR) who would probably be interested if it is not too involved.
To handle those who are in the upper category, perhaps a second project aimed
solely at them would also be appropriate.

I am not dismissing your commentary, just noticing that it got way too involved
too quickly.  Some of the stuff you were suggesting would involved some really
serious work with programming not only the CPLDs or FPGAs (for which I have no
knowledge) but much more effort dealing with the ADCs and such.  Well seems that
way to me anyhow.

Mainly I was really trying to get people to see that it should be a group
effort.  Otherwise you have 3 or 4 people duplicating the wheel so to speak.  If
those 3 or 4 could channel their efforts into one project perhaps we would end up
with the best out of all 3 or 4.

regards,

Bill....WB6BNQ