Paul
I agree. That is my main frustration, lot of talk no results. The good part
of time nuts is that I have made some very good contacts that share my
interest  of actually building some things and results are great.
Remember the Loran simulator?

Bert Kehren

In a message dated 12/6/2012 1:17:14 P.M. Eastern Standard Time,
paulswedb@gmail.com writes:

Boy do I  have to agree. uProcs by the dozens and with all kinds of
counters
onboard.
I think it was Bob who said none of thats the  challenge.
It is the phase comparison method and a stable D/A converter and  reference.

have D/As but the quality is simply OK.
The other comment  is that whoever writes the software gets to choose the
software and  everything else. Its actually not really democratic at all.
Cause we will  all use it if its reasonably good. ;-)
If I do it it will be basic! Though  it will run at very high speeds. Now
someone should be jumping in with  Forth real soon now.
Last tidbit the Rasberry is a pretty interesting  widget and there had been
a thread about a time server. Was looking forward  to the results. Nothing
ever  happened.
Regards
Paul
WB8TSL

On Thu, Dec 6, 2012 at 1:00 PM,  Bob Camp lists@rtty.us wrote:

with

all

with

resistor

experts.

transparent

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I'm excited, for sure.

I've got a whole box of goodies over here I bought full of the Arduino uP
and a ton of its 'shields'.  Been collecting, so-to-speak.

I just new I could use it for a, down-and-dirty GPSDO.  The Trimble Lassen
looks good down to 20ns UTC (I got two for $10); then add a cheap datum
ocxo; coupled that with the Arduino.  Voilà.

I can't wait, ..and you guys are reinforcing that just because its' cheap
won't mean it won't work.

-Don

From: EWKehren@aol.com
Sent: Thursday, December 06, 2012 1:38 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPSDO Alternatives

Don wrote:

Of course it doesn't.  But keep in mind that "working" spans several
orders of magnitude in this area, and what one needs to design and
build depends on what degree of "working" one needs to support the
uses to which the finished standard will be put.  First, there is
performance during normal operation (good, continuous satellite
tracking) -- ADEV at all taus of interest, PN at all offsets of
interest, distortion and spurs, residual AM, stability over
temperature, PPS jitter, etc.  Then, there is performance with poor
satellite visibility, and finally performance in holdover (no
satellite visibility) for however long one needs it (if one needs it
at all, which many amateurs may not).  For some, there will be power
consumption issues.  There may also be issues of interfacing to
monitoring devices, both simple (e.g., LCD status displays) and
sophisticated (e.g., computer running Lady Heather or Z38xx).  Does
it need to work with existing programs, or is writing a new
monitoring program part of the project?  Then there are the
construction issues.  Does it need to be assembled entirely from
connectorized modules, no soldering required?  Or capable of being
thrown together on a scrap of perfboard?  Or will a PC card be
designed?  If so, can it use SMT parts?  How adaptable must it be,
particularly in accommodating different oscillators?  Does it need to
support rubidium oscillators as well as quartz?  Etc., etc., etc.

Thunderbolt and Z38xx commercial GPSDOs are plentiful and relatively
affordable, so they are natural benchmarks for any DIY project.

From my perspective, the most interesting development would be an
offer by someone with a very well equipped lab to test any DIY GPSDO
with a consistent protocol and publish the results.  That way, we
could all see how the various approaches compare with respect to the
characteristics that are most important to each of us.

Best regards,

Charles

Hi

The single best thing about a TBolt is Lady Heather.

Consider how many years it's taken to get it to where it is today. Consider
how many people have worked extensively on it. It's a wonderful thing to
have available.

Could you make a homebrew gizmo look "just like a TBolt"? Sure you could. It
might well take you forever to do all the reverse engineering, validation,
and testing, but it can be done. I'd guess it would take less time to
re-write a version of LH from scratch....

Another thing to consider:

Z3801's got scrapped out, flooded the market, and the price went to "real
good". The supply dried up and prices climbed. This took years.

TBolts went through the same cycle. Again over a time period of many years.

In both cases you had a long time to look at them and make a decision about
weather you wanted one or not. It was never a "buy it this week or they are
gone" thing.

These aren't the only things that will ever get scrapped. There's something
somewhere in the world that's going to get junked. Some sort of GPSDO will
flood the market in the future. It will be around for many years at low
prices.

What ever you do as a project needs to be pretty good to survive the
competition. Otherwise it'll die before anybody ever sees one.

Bob

-----Original Message-----
From: time-nuts-bounces@febo.com [mailto:time-nuts-bounces@febo.com] On
Behalf Of Charles P. Steinmetz
Sent: Thursday, December 06, 2012 4:36 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPSDO Alternatives

Don wrote:

Of course it doesn't.  But keep in mind that "working" spans several
orders of magnitude in this area, and what one needs to design and
build depends on what degree of "working" one needs to support the
uses to which the finished standard will be put.  First, there is
performance during normal operation (good, continuous satellite
tracking) -- ADEV at all taus of interest, PN at all offsets of
interest, distortion and spurs, residual AM, stability over
temperature, PPS jitter, etc.  Then, there is performance with poor
satellite visibility, and finally performance in holdover (no
satellite visibility) for however long one needs it (if one needs it
at all, which many amateurs may not).  For some, there will be power
consumption issues.  There may also be issues of interfacing to
monitoring devices, both simple (e.g., LCD status displays) and
sophisticated (e.g., computer running Lady Heather or Z38xx).  Does
it need to work with existing programs, or is writing a new
monitoring program part of the project?  Then there are the
construction issues.  Does it need to be assembled entirely from
connectorized modules, no soldering required?  Or capable of being
thrown together on a scrap of perfboard?  Or will a PC card be
designed?  If so, can it use SMT parts?  How adaptable must it be,
particularly in accommodating different oscillators?  Does it need to
support rubidium oscillators as well as quartz?  Etc., etc., etc.

Thunderbolt and Z38xx commercial GPSDOs are plentiful and relatively
affordable, so they are natural benchmarks for any DIY project.

From my perspective, the most interesting development would be an
offer by someone with a very well equipped lab to test any DIY GPSDO
with a consistent protocol and publish the results.  That way, we
could all see how the various approaches compare with respect to the
characteristics that are most important to each of us.

Best regards,

Charles

time-nuts mailing list -- time-nuts@febo.com
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https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
and follow the instructions there.

On 12/6/2012 4:35 PM, Charles P. Steinmetz wrote:

This is interesting, and I could bite -- for a limited definition of
"very well equipped."

What's really interesting, though, is the idea that collectively we
might develop some standard measurement protocols that would be
reproducible in a number of (amateur) labs.

John

On 12/6/12 1:56 PM, Bob Camp wrote:

Of course, the process of experimenting and trying to duplicate the
Tbolt is fairly educational.  It touches a lot of interesting areas in
RF design and metrology, as well as software algorithms.  One might do
it for the same reason that someone builds a fusor in their garage.
There are easier ways to get neutrons, but building a fusor is a nice
combination of learning about high vacuum, high voltage, nuclear physics
and metrology, etc.

Both are a heck of a lot cheaper than building and flying a CubeSat, for
instance.

John wrote:

I agree, but I didn't dare to dream so large when I wrote:

At bottom, any such testing requires (i) a comparison standard at
least as good (and hopefully at least somewhat better) than the DUT
at all taus and offsets (which may, in reality, be several standards,
each doing part of that job), (ii) a reliable TIC (and, potentially
usefully, frequency counter) that can exploit the stability of the
comparison standard, and (iii) the capability to process the raw data
to produce meaningful information.  [Additionally, to characterize
poor-signal behavior one would presumably use attenuators and a
well-situated antenna.  Some may not have good antenna sites to begin
with, and in any case, it would be hard to standardize the signal
strength between locations.]

My thoughts were (1) for many (most?) of the people who would want to
build a DIY GPSDO, it would likely be their first "really good"
standard, and therefore their best; and (2) the range of
TICs/frequency counters owned by the target base is so wide, and
covers such a large range of capabilities (to say nothing of whether
any given counter is in good repair and being used to best
advantage), that obtaining comparable results from one amateur lab to
another would be just as much if not more dependent on the individual
counters involved than on the GPSDOs under test.

However, that is no reason not to push forward with standardized
measurement protocols, which would focus all of us on what the
relevant desiderata are and how to measure them.

Best regards,

Charles

On Fri, 07 Dec 2012 17:50:55 -0500, "Charles P. Steinmetz"
charles_steinmetz@lavabit.com wrote:

For myself:

1. My current lack a comparison standard is the reason I would design
   and build a GPSDO.  At best I might buy a used rubidium oscillator at
   some point.  People talk about good deals on Thunderbolts but I have
   yet to see one.  It seems peak Thunderbolt passed before I was
   seriously looking.

2. So far my best universal counter is a rebuilt Racal Dana 1992 with
   a TCXO but it lacks GPIB.  It might be easier and cheaper for me to
   duplicate my GPSDO phase detector and add a counter chain and trigger
   so it can make and report its own time interval measurements against a
   secondary asynchronous source but that would hardly be reproducible by
   a third party.

3. I am less interested in this since I will be at the mercy of
   whatever timing GPS I use and my current antenna environment.