Re: [time-nuts] (UK) NPL open house

[Dr. David Kirkby]

The visitor guide is now available.

Even if you are not going, the guide might be of interest.

http://www.npl.co.uk/upload/pdf/open-house-2018-visitor-guide.pdf

I've had a reasonable amount of success today phoning NPL and trying to
visit a couple of labs that will not be open, but interest me. No absolute
confirmations yet, as one of the people I wanted to visit is going on jury
service tomorrow, but I'm hopeful one of his colleagues can show me around.


Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, CHELMSFORD,
Essex, CM3 6DT, United Kingdom.
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621-680100 / +44 1621-680100


On 11 May 2018 at 12:57, Adrian Godwin <artgod...@gmail.com> wrote:

> Next thursday :
>
> https://www.eventbrite.co.uk/e/national-physical-
> laboratory-open-house-2018-prepare-to-be-amazed-tickets-42330306085
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Re: [time-nuts] Dual GPSDO - any advantage?

[Dr. David Kirkby]

On 10 April 2018 at 16:56, donald collie  wrote:

> I have the Chinapost tracking numbers, so I don`t think it`s a scam - just
> real good value.


I hope you are right, but I doubt you are.

It is not uncommon to be sent fake tracking numbers.

I was 99% sure a Keithley 2002 8.5 digit meter for £900 was a scam, but
decided to play along with it, just in case it was not. The seller claimed
to have sent it, send me a FedEx tracking number, but said if he did not
receive payment by bank transfer within 24 hours he would cancel the
shipment. The tracking number was NOT to the real FedEx site, but something
made to look like FedEx.

Even if you have the real Chinese post office tracking number, it could be
the same number sent to 100 people. I doubt it has your detailed location
on it.

I hope you are right, and they are a good buy, as I bought 10 of them. But
I doubt they are real. I'm 99% sure they are a scam, but are not bothered,
as a scam like that would easily result in one willing an eBay dispute.

Dave
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Re: [time-nuts] Dual GPSDO - any advantage?

[Dr. David Kirkby]

On 10 April 2018 at 17:11, Clint Jay  wrote:

> Sad to say I think I was right, the listings have been pulled already and
> the seller now has zero items for sale.
>

The listing has not been pulled. Yes the seller has 0 to sell, but because
he has sold out of the 100. I still have the purchase in my purchase
history, and no messages from eBay about fraud.

>
> Get those paypal refund cases logged.
>

One would need to wait until they don't arrive. Luckily they were not much.

Then it is better to complain to eBay first. If you don't get any
satisfaction from eBay, then you can go to PayPal. But by going directly to
PayPal, you will have lost the chance to get a refund via eBay. So the
sensible order to try to get refunds is

1) eBay
2) PayPal
3) Chargeback on credit card.

Never advance to stage PayPal unless you have exhaused attempts at eBay.
Never make a chargeback unless you have exhaused atttempts at both eBay and
PayPal.

Sometimes it can be a bit of an uphill struggle to get refunds from eBay
for dodgy sellers, but in this case it should be fairly easy if the goods
don't arrive. On the off-chance they do, we have scored well.


Clint. M0UAW IO83
>


Dave G8WRB.
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Re: [time-nuts] Dual GPSDO - any advantage?

[Dr. David Kirkby]

On 10 April 2018 at 16:23, Dr. David Kirkby <drkir...@kirkbymicrowave.co.uk>
wrote:

> On 10 April 2018 at 15:32, Clint Jay <cjaysh...@gmail.com> wrote:
>
>> Ahh, I've found the listing, has anyone received one?
>>
>> I hate to say this but I'm highly sceptical that they will ever turn up,
>> looks and smells very much like the standard eBay scam to me.
>>
> --
>
>> Clint. M0UAW IO83
>>
>
>
> I'm VERY skeptical too of the item
>


The more I look at this, the more I think it is a scam.

* Description says orders shipped after April 2016 will be a new design,
yet the seller was not registered until 27th February 2018 - almost 2 years
later.
* Feedback is zero.

I phoned eBay. The guy I spoke too was highly suspicious too, and has past
it along to a team that deals with possible scams.

Dave
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Re: [time-nuts] Dual GPSDO - any advantage?

[Dr. David Kirkby]

On 10 April 2018 at 15:32, Clint Jay  wrote:

> Ahh, I've found the listing, has anyone received one?
>
> I hate to say this but I'm highly sceptical that they will ever turn up,
> looks and smells very much like the standard eBay scam to me.
>
--

> Clint. M0UAW IO83
>


I'm VERY skeptical too of the item

https://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-sine-and-square-wave/273145006434

I have bought 10, on the assumption if they don't show up, I will get my
money back. Note the seller has a feedback of zero, and had not been
registered that long. So I'm thinking there's a 95% chance its a scam.

Also listed by the same seller is a rubidium source

https://www.ebay.com/itm/New-FE-5650A-OPTION-58-RUBIDIUM-FREQUENCY-STD-FREQUENCY-ELECTRONICS-INC/273145001650

which looking nothing like one.

Perhaps with hindsight, I wish I had not ordered 10, but then I would kick
myself if I did not order them, and find out later they are genuine.

Dave
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Re: [time-nuts] Weird Stuff WareHouse shutting down

[Dr. David Kirkby]

On 8 Apr 2018 16:56, "jimlux"  wrote:
>

> Test equipment tends to be aged - Unless you have a particular need for a
HP 600 series microwave signal generator, there are probably better sources
available much cheaper that use more modern components. In this day and
age, I don't think people should suffer through 141T spectrum analyzers or
even a 8568- Spend your money an a nice USB unit instead.

I think people learn more with old test equipment.  I know someone who has
a 1 GHz LeCroy scope,  as well as a high end Agilent, but can't seem to
measure the simplest of signals, that I could easily measure with a 50 year
old scope.

I heard about someone who could not use an analogue multimeter as it could
not measure negative voltages.

The above said,  I don't entirely disagree with you either.

Dave, G8WRB.
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Re: [time-nuts] Environmental sensor recommendations.

[Dr. David Kirkby]

On 5 April 2018 at 15:44, John Green  wrote:

> Why has no one mentioned thermocouples?
> I had some experience with thermistors a few years back designing thermal
> attenuators and equalizers for CATV. NTC thermistors can have a large
> change of resistance for a unit change in temperature. They aren't linear,
> but there are formulas for computing resistance vs temp. PTC thermistors
> have a much smaller change per unit change in temp., but are much more
> linear. And, they are susceptible to self heating, which makes things
> interesting. If I remember correctly, in my research something called an
> RTD was supposed to be the king when it came to accuracy and repeatability.
> As someone else has stated, the IC devices are supposed to be quite good,
> but you have to interface with them.
>


Keysights nano volt / micro ohm meter takes

https://www.keysight.com/en/pd-101296%3Aepsg%3Apro-pn-34420A/micro-ohm-meter?cc=ZA=eng

can do direct SPRT, RTD, Thermistor, and Thermocouple measurements

SPRT = Standard Platinum Resistance Thermometer

I don't claim to know much about this, but the uncertainty quoted for the
SPRT probes with that meter is 0.003 deg C.

When I Google SPRT probes, I see they are incredibly expensive - many
thousands of USD each.

I'm a bit puzzled there seem to be a number of 3-wire platinum resistance
thermometers. I can understand using 4-wires for a Kelvin connection, but
can't understand the use of 3-wires.

Of course, for environmental monitor in a lab, one is most unlikely to need
very high accuracy.

Dave
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[time-nuts] Open day at the National Physical Laboratory (NPL) on Thursday 17 May 2018.

[Dr. David Kirkby]

NPL opens their doors to the public once every 2 years. It is well worth
going. Tickets are only 3.00 each, and that money is donated to a cancer
charity. More details at

http://www.npl.co.uk/open-house/

To make the most of it, you need to

1) Arrive early (14:00)
2) Leave when they close (20:00)
3) Walk around the many labs. Even 6 hours is not enough time to visit
everything.

I think you need to be reasonably fit, since it is not a place where you
sit down in a chair and listen to lectures all day.

I think NPL do a really good job, as they manage to put on something that
is interesting to both children and professional scientists. Lots of
schools have trips there for the day.

Dave
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Re: [time-nuts] WWV/CHU

[Dr. David Kirkby]

On 30 March 2018 at 06:49, Tom Van Baak  wrote:

>
> FYI: for the original spam-free version, please use:
>
> https://tf.nist.gov/general/pdf/469.pdf
>
> In general, if the author or paper is related to NIST, the original
> copyright-free PDF will be available in the NIST Time and Frequency
> Publication Database. That easily searchable database, and the thousands of
> papers it contains, is probably the greatest asset we time nuts have. For
> those of you that don't know it yet, check it out:
>
> https://tf.nist.gov/general/publications.htm


That's useful to know.

I have been in contact with someone at NPL, who provided papers by either

1) Attaching a copy.
2) Mentioning it was on Research Gate - a site I personally find annoying.
3) A link to IEEE (or similar), which will has a paywall.

This suggests to me NPL don't have all their papers available online,
although at least some can be found at

http://www.npl.co.uk/publications/

For anyone interested in metrology, and I assume that includes everyone on
this list, this NPL publication,

"A beginner's guide to uncertainty of measurement." by Stephanie Bell

http://www.npl.co.uk/publications/a-beginners-guide-to-uncertainty-in-measurement

is well worth a read. This is far more readable than "Guide to the
expression of uncertainty in measurement (GUM)", which is heavy going.


>
> As a non-academic working from home one of the greatest frustrations is
> getting copies of old and new scientific articles.
>

You obviously share the same frustrations as Alexandra Elbakyan

https://en.wikipedia.org/wiki/Alexandra_Elbakyan

Because of her inability to get some papers, she set up sci-hub.

https://en.wikipedia.org/wiki/Sci-Hub

Alexandra Elbakyan makes the very valid point that authors do not get paid
for submitting papers, reviewers do not get paid for reviewing them, yet
the publishers charge significant amounts of money for distribution of
electronic copies of papers. This is VERY different to books or music,
where authors get royalties from copies sold.

You can debate the ethics of sci-hub, with many scientists having strong
and opposing views on sci-hub. The site does allow one to get virtually any
academic paper for free. There are no ads, but donations are accepted by
bitcoin - which reminds me, I must set up a bitcoin wallet so I can donate
to sci-hub.

Dave
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Re: [time-nuts] Need a Watch Recommendation

[Dr. David Kirkby]

On 5 March 2018 at 16:50, William H. Fite  wrote:

> And that is just my point--well, part of it, anyway--ultra-precise
> measurement of time is profoundly important, and rightly the primary focus
> of this group. But for the wrist, very, very few of us need pin-point
> accuracy--though many seem to perceive that we do. My Tissot mechanical
> chronograph is right now doing a fantastic job of timing the eggs I'm
> boiling for my lunch.
>

What is the most demanding task one would use a wrist watch for? The doors
on trains in the UK lock up to 30 s before the train is due to leave. It is
most frustrating to arrive at a platform, with the train stationary, but no
way to get in. I would estimate that about 20 seconds is good enough for
making a decision about just how fast one has to run for a train.

Buying tickets for events like Wimbledon tennis in the UK can demand one
attempts at the right time, as tickets become available and sold out very
quickly. But one would be using a computer to purchase them, so I don't
think that comes under the requirements of a wrist watch.

Dave
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Re: [time-nuts] eBay GPS antenna test results.

[Dr. David Kirkby]

On 9 February 2018 at 21:43, John Green  wrote:

> To those who doubted that the antenna was actually a 3.3 to 18 volt design,
> it seems you were correct. Today, I hooked it up to a variable power supply
> and slowly raised the DC voltage fed to the antenna. It began to pull
> current at about 2.9 volts and at 3.3 volts, took about 40 mA. I continued
> to slowly raise the voltage. At about 7.5 volts, the current suddenly
> dropped to 10 mA. At just below 12 volts, it suddenly increased to 80 mA
> and the supply went into current limit. I increased the current limit to
> 130 mA and repeated the exercise. Everything went as above until I reached
> 12 volts and the current went to 130 mA and the supply went into current
> limit. Lowering the voltage didn't lower the current. I disconnected it,
> waited a minute, and tried again. Yep, shorted. It would have worked well
> with the T bolt, but would have blown anyway if I tried to use it with my
> 12 volt supply and bias T. I guess I will get inside it somehow to see if
> it can be repaired. My first attempt ended in failure. I guess I need a
> bigger screwdriver with which to pry the top off. I am going to contact the
> seller and tell them it was not as advertised. I kind of doubt that will
> get me anything, but it won't hurt to try. There is a saying about
> experience being a cruel teacher. You get the results first, and the lesson
> after. Oh well.
>


You should not open it up, but open an eBay case for item not as described.
If it said it would do 3-18 V, but does not, then its not as described, and
you should get your money back. The chances are the seller will not want to
arrange collection, so you will probably get to keep it anyway. But you
should get a refund before opening it up.

Dave
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Re: [time-nuts] Anyone have experience with this antenna?

[Dr. David Kirkby]

On 6 February 2018 at 03:33, John Green <wpxs...@gmail.com> wrote:

> https://www.ebay.com/itm/High-Precision-L1-L2-GNSS-GPS-GLONA
> SS-BeiDou-RTK-CORS-survey-antenna/162718512935?ssPageNam
> e=STRK%3AMEBIDX%3AIT&_trksid=p2060353.m2749.l2649
>
> Listed on eBay as a L1/L2 antenna with decent specs.


I used to work in the antenna industry selling 'professional' antennas -
not aimed at the amateur radio market. Many specifications are invented to
be better than a competitor. The competitors do it too, so it is not just
one company. If you sell antennas with valid specifications, it would be
next to impossible to sell them, as competitors will have higher
specifications.

Another RF engineer, who I don't know from working with antennas, said to
me that antennas are a still a charlatan's paradise.

With antennas, probably more than any other device, I would believe the
specifications if I could verify them. Unfortunately, for that sort of
antenna, I don't know how to verify them.

If nothing else, I would ask the seller for a copy of the test reports that
back up the specifications.

I got a couple of WiFi antennas free from eBay, after proving the gain
specifications were vastly exaggerated. Depending on the phase of the moon,
the numbers that came up in last months lottery, eBay policy changes with
reguard to who pays the return shipping fee on items that are not as
described. If you can show its the seller, then in many cases they will not
wish to pay the return cost.

Dr David Kirkby Ph.D C.Eng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3
6DT, United Kingdom
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 01621'680100 / +44 1621-680100 <01621%20680100>
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Re: [time-nuts] Stable32 now available

[Dr. David Kirkby]

On 5 January 2018 at 14:21, Graham  wrote:

> Lulu is currently having a promotion with free postage for those
> contemplating ordering a copy of the manual from Lulu.
>
> Get free mail or 50% off ground shipping!
> Use promo code *SHIPIT2018*
> Expires Jan 8 at 11:59 pm ET
>


>
> http://www.lulu.com/shop/william-riley/stable32-user-manual/
> paperback/product-3507840.html
>
> Lulu frequently has specials, sometimes a percentage discount plus reduced
> or no shipping.
>
> https://www.lulu.com/
>
> cheers, Graham


Thank you for that.

I entered the code, and it worked, but then I see a notice that promotion
codes CAN be combined with other promotion codes! That seems unusual, as
most places only let you use one promo code. Anyway, a quick Google

https://couponfollow.com/site/lulu.com?ref=3497047

and I found another code for Lulu. First I tried JAN15, but that was
rejected. Then I tried FWD15, and that was accepted. So with the
combination of FWD15 and SHIPIT2018, it cost me a total of just £10.39
(GBP) with free shipping.

I did not bother trying any more codes, but perhaps with patience, the cost
could be reduced even more, but I was more than happy to pay that.

Dave
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Re: [time-nuts] Stable32 now available

[Dr. David Kirkby]

On 3 January 2018 at 11:08, Poul-Henning Kamp  wrote:

>
> Anyway, code like this can be written to compile and work across all the
> relevant *IX operating systems with a minimum of effort, so I don't think
> a separate port to any of *BSD, Linux, Solaris or AIX should be necessary.
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
>


But to achieve code to work on those platforms, it needs regular testing on
those platforms, because otherwise non-portable code will be introduced.
That's been my experience, both on projects I have managed, and the
SageMath mathematical software.

I have here machines running Solaris (both x86 and SPARC), one that runs
AIX, and another another that runs HP-UX, although I have not powered up
the AIX or HP-UX machines for a few years, so I don't know if they still
work. But if there was interest, I could make any of these available by
remote access to others using ssh, although due to power consumption, I
would not run them 24/7/365. The UK is pretty expensive for energy.

Dave
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Re: [time-nuts] Stable32 now available

[Dr. David Kirkby]

On 3 January 2018 at 04:09, Tom Van Baak  wrote:

> I asked Bill for clarification and here's some of what he shared:
>
> > Tom:
> >
> > I’m glad that the word is getting out that Stable32 is now freely
> available.
>
>
> > My donation to the IEEE UFFC included all source code, and it is up to
> them
> > to decide whether and how to make it available.  That has not yet been
> done.
>
>
Great news.


> > My motivation was to see that it lived at least in its present form
> without
> > my having to remain involved.


That's really good of Bill.

I will continue to support the commercial
> > version for a year more, but not the free one.
>
> > The IEEE UFFC Stable32 distribution is  released under a form of the “MIT
> > License” which is as free as can be.  That was made possible last year by
> > Scientific Endeavors Corporation who agreed to end my obligations under a
> > royalty payment agreement for the GraphiC scientific plotting functions
> that
> > Stable32 uses.  No other such issues exist for the Stable32
> distribution, so
> > it became possible to make it free.
>
>
Nice of Scientific Endeavors Corporation.


> > The Stable32 source code is organized into two basic parts, the
> top-level Windows
> > user interface and a DLL that contains the core analysis functionality.
> It is
> > likely that the latter is the more valuable for future versions and
> other purposes.
> > For example, I have ported that Windows FrequenC.dll (which is
> distributed with
> > Stable32) to Linux as a libfrequenc.so shared object library that can be
> used by
> > GCC/G++.  I have also created a wrapper function for that so it can be
> used with
> > Python.  I hope to make these (and the critical FrequenC function
> documentation)
> > available soon.
>
>
Several technologies come to my mind, that could give a multi-platform
version.

1) WxWidgits in C++

2) Qt in C++

3) Mathplotlib in Python.

4) GNUplot

5) Command line version for UNIX and UNIX-like systems.

> I hope this explains things a bit.  The Stable32 distribution package is
> now freely
> > available for all to use.  The Stable32 source code is under the control
> of the
> > IEEE UFFC AdCom.  I plan to make the core Stable32  FrequenC Library
> documentation
> > and functionality available for Windows, Linux and Python.
>

I would not be surprised if Poul-Henning Kamp would be interested in
porting to FreeBSD too.

Solaris is pretty much dying since Oracle bought Sun, so there are
arguments for not bothering with a Solaris port. But from my experience,
testing software on multiple platforms often highlights bugs that exist in
all platforms, but have not been discovered. I lost count of the number of
hours I spent porting Sagemath to Solaris, but a number of bugs were
discovered by me whilst porting to the Solaris. Those bugs existed on
Linux, but had just not manifested themselves.



> > Best regards,
> > Bill Riley
>
> My comments:
>
> 1) I use both Stable32 and TimeLab equally; and now that Stable32 is free,
> everyone can now enjoy both of them too. They overlap somewhat, but each
> has its own set of strengths and target audience. Both show evolutionary
> bloat by now but for the small subset of features one typically uses the
> learning curve is not high. Each includes a comprehensive user guide. Both
> are native Windows apps, and run under emulation on Unix.
>

I assume, but perhaps are mistaken, you mean Linux here. Strictly speaking,
a system is not UNIX unless certified by The Open Group. Linux is certainty
not UNIX, and in several cases the code breaks UNIX compatibility. For
example, on Linux, the df command reports sizes in kb, but for UNIX system
it is 512 byte blocks. I don't know, but I suspect FreeBSD conforms to the
UNIX standard more than Linux. Also on Linux, people tend to use tools like
'which'

drkirkby@hawk:~$ which ls
/usr/bin/ls

to find the path to an executable. But 'which' is not part of the UNIX
standard, so may not be available on a UNIX system.  But the following
gives the same information

drkirkby@hawk:~$ command -v ls
/usr/bin/ls

but works on UNIX systems in addition to Linux systems.

Dave
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Re: [time-nuts] Stable32 now available

[Dr. David Kirkby]

On 2 January 2018 at 14:10, paul swed  wrote:

> Jelen
> Thank you for informing us about Stable32. I have been busy downloading
> details.
> I was surprised by the size of the use manual at some 348 pages.
> I believe I have a very long way to. I suspect we need a Stable32 for
> dummies book.
> Regards
> Paul
> WB8TSL
>

The manual is available as a book.

http://www.lulu.com/shop/william-riley/stable32-user-manual/paperback/product-3507840.html

I don't know about others, but I often find I absorb information better
reading a book than I do a computer screen, and at the cost of the book, it
is not really worth the hassle of printing it oneself. That said, the
software is 2017, and the book published in 2008, so there might be
significant differences between the book and software. Perhaps someone who
has both the book and the software, would comment if the book is very out
of date, or would still be useful.

Dave
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Re: [time-nuts] Stable32 now available

[Dr. David Kirkby]

On 2 January 2018 at 09:30, Matthias Jelen  wrote:

> Dear Time-Nuts,
>
> Happy New Year!
>
> Maybe this is of interest for some of you:
>
> A copy of Stable32 was on my wish-list for Christmas and I asked for the
> possibility of a non-profit-license. Bill Riley informed me that he donated
> Stable32 to IEEE UFFC and it will be available for free download with the
> beginning of 2018. And here it is:
>
> https://ieee-uffc.org/frequency-control/frequency-control-
> software/stable-32/
>
> Many thanks to Bill Riley!
>

Given Hamilton Technical Services are no longer selling this, I wonder if
the author could be persuaded to release the source code under a GPL or
similar license.


>
> Best regards,
>
> Matthias
>

Dave
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[time-nuts] Cheap ($90) time interval counter on eBay

[Dr. David Kirkby]

I can't possibly imagine that this is going to have the performance of the
high end TI counters,  but it might interest someone to have a play without
breaking the bank.

https://m.ebay.com/itm/ADC-100A-Time-Interval-Analyzer-Tested-Working-/261303897956

Dave
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Re: [time-nuts] External cooling fans - source

[Dr. David Kirkby]

On 18 December 2017 at 23:11, Charles Steinmetz 
wrote:

> From time to time, the subject of external cooling fans comes up -- for
> example, in discussions of the HP 5370A/B with their steaming hot
> heatsinks.  I have several times recommended very quiet, all-metal, 4" desk
> fans as ideal for the job, but have not been able to suggest a source.
>

For what it is worth, my 5370B run very hot, which forced me to check my
mains voltage as I knew every time I had done a quick measurement, the
voltage was above 230 V. So for a few days I logged the voltage, and found
it was consistently high. The maximum permitted here in the UK is 253 V,
but I measured mine at 255.x volts. It was the heat of the 5370B that
forced me to contact the electricity supply company (UK Power Networks),
who logged the voltage for 4 days. I have a 3-phase supply here, which is
unusual for a domestic property, but each of the 3 phases was consistently
high. I managed to get the supply company to reduce the voltage by 5%. That
made a *significant* difference in the heatsink temperature of the 5370B,
and a significant difference to to the exhaust temperature of my HP 7
series system.

I'm not saying an extra fan is not a good idea, but it is certainly worth
ensuring the mains voltage is not too high. I was told by UK Power Networks
that they aim for 245-250 V in rural areas - this is despite the UK is
supposed to be 230 -6%/+10%. On equipment with linear power supplies, a few
extra volts can lead to a significant increase in the amount of heat the
regulators produce. 10% extra voltage does *not* equate to 10% extra power
dissipation, but considerably more.

I found quite a reluctance on the part of the UK Power Networks to reduce
the voltage. Even though it was was on average more than 5% high, the
technical manager who took ownership of the problem only wanted to reduce
the voltage by 2.5%, despite they could easily reduce it 5%. Luckily, when
the engineers came to adjust the supply voltage, (which they do by changing
the taps on the 11 kV primary), I managed to convince them that there were
very few properties on the transformer, and the furthest was an old couple
that used very little electricity. So they did reduce it 5%, which is the
maximum they could. But they warned me that if there were complaints of low
voltage, they would have to increase it 2.5%. Luckily for me, nobody
locally noticed the reduction in mains voltage, and it is still on average
over 230 V.

It would be interesting to know how low the AC input can go on a 5370B
before the regulators fail to regulate. Given they are the sort of
instrument one might want to run for long periods, running one on a UPS,
with a transformer to reduce the output of the UPS, might not be such a bad
idea.


> Charles
>

Dave
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[time-nuts] "Timekeeping today – from stars to atoms" lecture by Peter Whibberley of NPL, organised by IET.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

This might interest some. It's on 6th December in London.

http://www.theiet.org/events/local/251136.cfm?utm_source=Adestra_campaign=Copy%20of%20Copy%20of%20London%20New%20Template_medium=Local%20Networks_content=London%20Local%20Network_term=http%3A%2F%2Fwww.theiet.org%2Fevents%2Flocal%2F251136.cfm

Unfortunately (for me), its not at the IET's headquarter's in Savoy Place,
central London, but in Teddington, South West London.

The Adelaide
57 Park Road, Teddington,
London, TW11 0AU
United Kingdom

It's near NPL, but not at NPL.

I'm not sure if I'll go or not. Because of the location, I could not get
home without spending £40 on a Taxis and arriving home around 2 AM the next
day.  Add that to the £30 train fare, and it is not that attractive, but I
might end up going.

Dave
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Re: [time-nuts] Favorite counters (current production)?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 10 November 2017 at 16:37, Bob Camp  wrote:

> Hi
>
> There is no perfect answer. I’d go with the 53230 simply because it
> *might* be supported
> the longest.
>
> Bob
>


If I had to take a bet, I would say the SR620 will be supported longer.
Stanford Research seem to be selling the same products they have for
decades. I started my Ph.D. in about 1994, and bought what was a very new
product - the SR830 lock in amplifier.

http://www.thinksrs.com/products/SR810830.htm

23 years later, it is still a current product.

Stanford Research also sell a couple of LCR meters

http://www.thinksrs.com/products/SR715720.htm

The SR720 looks remarkably like the long obsolete HP E4925A LCR meter.

There's no doubt in my mind that Stanford Research sell their products much
longer than HP/Agilent/Keysight. Of course, that does mean Stanford
Research are using older technology.

I would add, when I have contacted Keysight about obsolete products they
have always been helpful. When I contacted Stanford Research to ask what
was the latest firmware for an SR620, I was ignored. They also ignored some
other email I sent them. So their support does not seem as good as
Keysight, but I assume, with persistence, one could get support on a
current product.

Dave
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Re: [time-nuts] R XSRM Rubidium Standard

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 15 Sep 2017 10:45, "Scott McGrath"  wrote:
>
> Precisely my point,   But when purchasing i expect to pay for a
calibration at a minimum.

I have on occasions requested sellers to send an item to the manufacturer
(Agilent or Keysight) for calibration *before* shipping it to me, offering
to pay the calibration cost, but stating that I expect a full refund if the
item fails the calibration.

If a test equipment dealer is confident that something is working well,
they should not object to sending it to the manufacturer for calibration,
as long as the buyer is willing to pay.

Of course if a seller knows little about something,  they are not going to
do this,  but the item should be appropriately priced.

One UK seller (grace1403) declined to send an Agilent N9912A FieldFox to
Agilent, because "Agilent were too fussy"., failing items for trivual
issues.   But he did agree to send it to one of the cal labs he uses. I
thought it was a waste of time going to one of the less fussy outfits,  but
bought it anyway. It was then clear on receipt that it was faulty. (The
spectrum analyser functionality was ok, but it didn't work as a network
analyzer).  He took it back,  but then advertised it on eBay 6 months
later. When asked, he said nothing had been done to it.

eBay rules about who pays the return shipping charge for an item that is
"not as described' keep changing, and may be different on different sites.
But on a heavy item shipped internationally,  the postage cost can be
comparable or exceed the calibration cost.

Dave.
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Re: [time-nuts] Something for all TIME NUTS!!

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 27 June 2017 at 23:02, Don Murray via time-nuts 
wrote:

> Hello all...
>
> For the SERIOUS time nut...  you might want to give yourself a few hours
> before you go check out this site...  and beyond!!
>
> 73
> Don
> W4WJ
>
>
> https://www.nist.gov/pml/time-and-frequency-division/time-
> services/manufacturers-time-and-frequency-receivers
>

I'm surprised by the omission of units that use Loran-C, such as those from
Stanford Research.

Dave.
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Re: [time-nuts] SR620 TCXO calibration

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 19 June 2017 at 21:43, David C. Partridge <david.partri...@perdrix.co.uk>
wrote:

> Yes please. ...
>

OK, the code is here

http://www.kirkbymicrowave.co.uk/tmp/srs-0.02.tar.gz

Note

1) It has only be tested on Solaris SPARC, with a National Instruments GPIB
card.

2) I would expect it to run under Linux, with few if any changes. If any
are needed for an NI card, please let me know. I don't mind trying to get
it to run under Linux, or any Unix system.

3) I've no idea how easy it would be to run under Windoze, and have no
intention of trying to help getting it to run under Windoze.

4) There's no man page, but there is some rudimentary in-built help, if you
run it with the wrong number of arguments. Below I run it with none, so it
generates a semi-helpful help message. It needs at least one option, and a
GPIB address. So something like

srs --time 12

would run it time-internval mode, and expect to find the SR620 on address
12.

I've NOT distributed this before, and have made no attempt to clean it up
to consider it in a fit state to distribute. But feel free to try it. Send
any comments directly to me.

Consider it released under the GPL version 2, or at your option any later
version.

drkirkby@buzzard:~/srs-0.02/src$ ./srs
srs - Version 0.02, by David Kirkby, G8WRB, drkir...@kirkbymicrowave.co.uk
Dumps data from a Stanford Research SR620 time-interval counter
Usage: srs [options] GPIB_address
**MODE**
  --time
  --width
  --risefall
  --frequency (or use --freq)
  --phase
  --count

**SOURCE (or start)**
  --A
  --B
  --reference (or use --ref)
  --ratio

**SAMPLE SIZE**
  --size n (n=1 to 100)

**DISPLAY**
  --mean
  --rel
  --jitter
  --max
  --min
  --trig
  --dvm
**OTHERS**
  --autocal
  --readcalbyte n
  --setcalbyte n m (sets calbye n to the value m)
  --settimebase (Put 10 MHz into input A before running this, to correct
the timebase)
  --help
  -h, --help
  -v, --version
  -V, --verbose
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Re: [time-nuts] SR620 TCXO calibration

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I should have added, mine had an OCXO - I just see you had a TCXO.

I don't have the SR620 any more. I swapped it, along with a HP 4.2 GHz
signal generator, for an HP 4291B impedance and material analyzer.

Dave
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Re: [time-nuts] SR620 TCXO calibration

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 19 June 2017 at 15:35, David C. Partridge 
wrote:

> I think I'm being dense, but I can't work out how to get this thing to
> display CalDat 04.   I have managed to get it to display CalDat 0 value,
> but
> can't work out how to step through to view adjust CalDat 04.
>
> Once I do  get there, how do I manage to adjust the CalDat value while
> observing the output of measuring my GPSDO 10MHz output at the same time?
>
> Please could someone put me out of my misery?
>
> Thanks
> Dave
>


I can't recall how you step the data, but it must be in the manual.

I wrote a bit of C code that attempts to correct the timebase, if 10 MHz is
put into channel A. It measures the frequency on channel A, then adjust the
crystal frequency until the frequency is 10 MHz. That's probably not the
best way on a TI counter, but seems to work reasonably well - at least any
errors are small compared to the fact that only integer values may be
programmed into the calbytes. Hence it seems impossible to fully correct
this.

One issue is that frequency shift is non-linear with respect to the
calbytes. So the approach I took was to shift the value by 4, see the
effect of the shift, and then use that to try to work out a suitable
correction.

Below is the bit of C-code. If you want the complete set of code, which
reads data from the SR620, I can send you it. I don't think it is well
commented, and in any case has only been tested on Solaris. It will only
work with an NI card, but I would expect it to work under

case SETTIMEBASE:
  output(device_descriptor,"MODE3;"); /* Set frequency mode */
  output(device_descriptor,"SRCE0;");  /* Measure source A */
  do {
calbyte_4=read_calbyte(device_descriptor,4);
frequency=read_frequency(device_descriptor);
frequency_error=frequency-1e7;
if (fabs(frequency_error) < 0.0008)  {
  printf("GOOD ENNOUGH frequency error=%lf\n\n",frequency_error);
  exit(0);
}
printf("cb4=%d f=%lf\n",calbyte_4, frequency);

if(frequency_error > 0)
  set_calbyte(device_descriptor, 4, calbyte_4+3);
else
  set_calbyte(device_descriptor, 4, calbyte_4-3);

printf("Changed calbyte 4 a little cb4=%d f=%lf\n",calbyte_4,
frequency);
new_frequency=read_frequency(device_descriptor);
new_frequency_error=new_frequency-1e7;

if(frequency_error > 0)
  frequency_change_per_calbyte=(new_frequency-frequency)/3; /* in
Hz/calbyte */
else
  frequency_change_per_calbyte=-(new_frequency-frequency)/3; /* in
Hz/calbyte */

printf("frequency_change_per_calbyte=%lf\n",frequency_change_per_calbyte);
/* Do a correction of half the value calculated */
calbyte_change=-(int)
((new_frequency_error/frequency_change_per_calbyte)+0.5);

/* Attempt to correct the frequency */
set_calbyte(device_descriptor, 4, calbyte_4+calbyte_change);


/* Read the frequency, then exit if within an acceptable tollerence
*/
frequency=read_frequency(device_descriptor);
frequency_error=frequency-1e7;
calbyte_4=read_calbyte(device_descriptor,4);
printf("new cb4=%d frequency error=%lf\n\n",calbyte_4,
frequency_error);
  } while (fabs(frequency_error) > 0.0008);
  exit(0);
break;
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Re: [time-nuts] Temperature sensors and quartz crystals (was: HP5061B Versus HP5071 Cesium Line Frequencies)

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 5 June 2017 at 00:59, Attila Kinali  wrote:

> Moin,
>
> This discussion is kind of getting heated.
> Let's put some facts in, to steer it away from
> opinion based discussion.
>

I can't find it now, but I know someone said thermocouples are obsolete. I
spoke to a friend tonight who services industrial boilders. He said
thermocouples are far from obsolesce, at temperatures of a few hundred deg
C, as nothing else works.


Dave
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Re: [time-nuts] Measuring coax temperature coefficient with a TICC

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 15 April 2017 at 02:34, Mark Sims <hol...@hotmail.com> wrote:

> I finally got around to using a TICC to measure the temperature
> coefficient of 100 feet of generic RG-58 coax using a TICC.   The TICC was
> clocked by a HP 5071A 10 MHz output.  The 1PPS output was connected to the
> input of the coax and the TICC chB input.  The TICC chA input was connected
> to the coax output via an inline terminator.   The TICC was set to "debug"
> mode  and Lady Heather plotted the chB-chA timestamp difference (hence the
> negative cable delay values).
>
> The coax had been chilled down for 2 hours in a 5 degrees F in a freezer,
> connected to the TICC, and left to warm up in a 75 degree F room.   Over
> the 10F to 70F temperature range (measured with an IR thermometer) the coax
> delay spanned around 300 ps... so figure around 5 ps per degree F (10 ps
> per degree C) for 100 feet of cable.
>
> I'm adding currently adding the ability for Heather to use an external
> temperature sensor...
>

I would not assume that a reel of coax that is coiled up will behave the
same as when used in  in a lab environment in the usual way. So whilst this
might be an interesting experiment, I believe some caution would need to be
applied before assuming that such a measurement is representative of how
coax is normally used. When not on a reel, a heated coax is free to expand
radially with no external pressure force applied, apart from that due to
air pressure. When on a reel, that's not the case, as the coax is the
middle of the reel is going to have forces applied that are much greater
due to the mass of the coax. To take an extreme example, if you use a foam
dielectric coax, when on a  real, the airgaps in the foam are likely to
become smaller as the cable will experience mechanical forces as it tries
to expand, constrained by the coax around it.

Also, when the coax tries to expand under heat, it is likely to deform to
take up the space between the turns on the reel, so possibly become more
square.

Unfortunately cable is likely to behave very differently at 10 MHz than 10
GHz, so it not necessarily useful to repeat a measurement with a small
piece of coax at 10 GHz, where its phase change could easily be measured on
a vector network analyzer.

Another spanner in the works is that the impedance of coax (usually 50
Ohms), is given by the equation

Z=sqrt( (R + 2 pi f L)/(G + 2 Pi f C) )

where R is the resistance per unit length, L is the inductance per unit
length, G is the conductance per unit length and C is the capacitance per
unit length. The high frequency approximation is that 2 pi f L >> R, and 2
Pi f C >> G, so it simplifies to sqrt(L/C). Those two assumptions become
less valid at low frequencies.

Overall, what you are doing seems interesting, but I would question how
much the results will relate to real-world use of coax, where its not
normal to have great real of it.

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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Re: [time-nuts] Vintage Frequency Measurement

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 12 February 2017 at 06:08, Scott Stobbe  wrote:

> I was inspired recently coming across a Lampkin 105 frequency meter, as to
> how  frequency measurement was done before counters.
>
> Certainly zero-beating a dial calibrated oscillator, would be one approach.
>
> Is there a standout methodology or instrument predating counters?
>

How about the diffraction grating? Natural ones have probably existed
billions of years, but they were made by man in the 18th century. These are
still in use today in instruments like optical spectrum analyzers.

The wavemeter must have been around a long time too. These are still used
at THz wavelengths.


Dave.
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Re: [time-nuts] Line Frequency standard change - Possible ?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 9 February 2017 at 21:31, Poul-Henning Kamp  wrote:

>
> The only other possible "balance signal" is the voltage, and it
> suffers from a host of noise mechanisms, from bad contacts and
> lightning strikes to temperature, but worst of all, it takes double
> hit when you start big induction motors, thus oversignalling the
> power deficit.
>
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20

I'm not sure what you mean by "balance signal" here. But I was chatting to
a friend, who used to control generators at two power stations in the UK -
one coal, the other nuclear. It is fairly obvious that the power put into
the grid must equal the power consumed, plus losses. What is also true, and
less obvious, is that the V*A must balance too. He said that he would
receive a call from the CEGB, saying they wanted X Watts, and a power
factor of Y.


Dave
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[time-nuts] HP 58503A GPS time and frequency receiver - How do I determine why the ALARM LED is on?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I've got an HP 58503A purchased from China a couple of years ago. It has a
bit of a hard life, having been in water at some time. But it seems to work
ok, as far as I can tell. Today there was a power failure for 5 minutes or
so. The red ALARM LED is on. It is not clear to me why, although of course
I'm aware there was a power outage, which almost certainly caused this,
although I can't be 100% sure.

Could it be that the log is full? I had a program running trying to get the
position multiple times in a loop, to get some sort of average, so I can
well believe I filled the log up. But this was a few weeks ago. The log is
clearly full .

scpi > diag:log:read:all?
Log status: Full

Log 001:19970504.00:00:00:  Log cleared
Log 002:19970504.00:00:00:  System preset
Log 003:19970504.00:00:00:  Power on

Log 219:20170107.05:30:17:  Position hold mode started
Log 220:20170107.05:30:57:  Holdover started, not tracking GPS
Log 221:20170107.05:31:03:  Survey mode started
Log 222:20170107.05:33:04:  GPS lock started

Nothing has been logged since 7th January. I know for a fact there was a
power outage on the 19th and today (25th), so I suspect the log being full
has NOT caused the ALARM light to come on. A fault, that is not logged, has
caused it.

scpi > SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION . [ Outputs
Valid ]
SmartClock Mode ___   Reference Outputs
___
>> Locked to GPS  TFOM 3
FFOM 0
   Recovery   1PPS TI +9.5 ns relative to
GPS
   Holdover   HOLD THR 1.000 us
   Power-up   Holdover Uncertainty

  Predict  432.0 us/initial 24
hrs

ACQUISITION  [ GPS 1PPS
Valid ]
Tracking: 6    Not Tracking: 1    Time

PRN  El  Az   SS   PRN  El  AzUTC  15:03:50 25 Jan
2017
  5  23 186   7324  21 252GPS 1PPS Synchronized to UTC
 13  84 110   81  ANT DLY  0 ns
 15  59 289   94  Position

 20  45 245   96  MODE Hold
 28  51  76  104
 30  27  68   83  LAT  N  51:39:04.155
  LON  E   0:46:36.381
ELEV MASK 20 deg  HGT   +45.55 m
(MSL)
HEALTH MONITOR .. [
ERROR ]
Self Test: Err   Int Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK
scpi >


The self-test shows an error, but no indication what the error was, as the
log was full.

I have a fairly good idea what may have happened. Sometimes when the unit
is powered on, the voltages on the PSU appear to go out of spec. I'm not
convinced this is really happening, as a multimeter on peak hold could not
catch any glitch, but I have not tried a fast scope.

I'm just wondering if there's anything else I can do to see what caused the
LED to come on. I suspect if I execute the self-test, it will pass and the
light go out, but I'd rather find the reason before doing that.

Dave
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Re: [time-nuts] Thermal effects on cables

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 23 January 2017 at 17:29, Tim Shoppa  wrote:

>
> Funny how people always want to put the words "dielectric" and "constant"
> right next to each other but we know it isn't constant :-)
>
> Tim N3QE
>

Yes. I will have to look into this, as I see some quite widely different
values quoted for the dielectric constant of PTFE. I have an HP 4291B
impedance/material analyzer

http://www.keysight.com/en/pd-100857%3Aepsg%3Apro-pn-4291B/rf-impedance-material-analyzer?cc=US=eng=true=4291b

and  16453A dielectric material test fixture

http://www.keysight.com/en/pd-100508%3Aepsg%3Apro-pn-16453A/dielectric-material-test-fixture?cc=US=eng

To make a measurement of the permittivity of a material, the calibration
procedure is a bit complicated, needing 6 or 7 standards, but at one point
you need to use a dielectric of known thickness and known permittivity. I
believe it defaults to 2.1, which is supposed to be what the bit of PTFE
Keysight supply is. Needless to say I don't have that, and I'm not spending
the best part of £500 for a bit of PTFE that's 1 mm thick. But I've seen
values of Er of PTFE quoted from 2.0 to 2.2.

Dave
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Re: [time-nuts] Thermal effects on cables

[Dr. David Kirkby (Kirkby Microwave Ltd)]

  oI On 23 Jan 2017 17:02, "REEVES Paul" 
wrote:
>
> Hi David,

Hi Paul

> Surely the impedance of the cable is only affected by the ratio of the
inner conductor and outer conductor diameters modified by the internal
dielectric constant, nothing to do with the frequency of operation.

No, that is incorrect.

There are two complications with coax, which mean that you can't trust the
"normal" equations at very low or very high frequencies.

1) LOW FREQUENCY

An accurate equation for the impedance of the cable is

Zo=sqrt ((R+j w L)/(G+j w C))

w = 2 Pi f
R = Resistance per metre (ohms/metre)
C = Capacitance per metre (Farads/metre)
G = Conductance per metre (Mho/metre)

If the frequency is high enough (above a few MHz),

j w L >> R and
j w C >>  G

so the R & G terms are insignificant and one gets the usual equation we know

Zo=sqrt (L/C)

At low frequencies the assumption that the resistive losses (R) are
insignificant is no longer valid, so impedance rises at frequency
decreases.

At DC a bit of coax is just a capacitor..

2) HIGH FREQUENCY

At high frequencies!the best of9 higher order modes can propagate.  The
reasons for this are more complicated to explain,  but are a result of the
breakdown of the assumption of the boundary conditions used to arrive at
the impedance.

The maths of this effort is more complicated,  needing Bessel functions.

> You might well have problems converting the larger diameters down to a
suitable size for the connectors at the higher frequencies though

Yes, but small connectors are used for the very same reason small cables
must be used.

> I thought that the HP cabling for the 8510 series VNAs was air spaced but
I might well be wrong - I just tried not to damage them :-)

You might well be right about the air spacing.  Of course there needs to be
some support for the centre conductor,  but it might be  beads like in 3.5
mm connectors. I really don't know.

> Regards,
>
> Paul Reeves

Dave, G8WRB.
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Re: [time-nuts] Thermal effects on cables

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 13 January 2017 at 06:52, Ole Petter Ronningen 
wrote:

> Hi, all
>
> The question of phase shifts in cables pops up every now and then on this
> list - I stumbled across a good table of measured phase shifts with
> temperature in different cable types in this paper:
> http://www.ira.inaf.it/eratec/gothenburg/presentations/ERATEC_2014_
> PresentationWSchaefer.pdf
> that I though would be of interest to others.
>
>
I've like to know how VNA cables compare. They are expensive enough - a
couple of cables around 600 mm long (24") for my VNA are over $5000. They
are much larger diameter than normal cables, but much more flexible too.
The construction is obviously very different. Since mine are designed for
use to 26.5 GHz, the internal diameter of the outer conductor can be no
more than a couple of mm, yet the overall cable has a diameter of about 15
mm.

Dave
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Re: [time-nuts] HP 55300A Date Problem

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 21 January 2017 at 17:29, Gary Neilson  wrote:

> I have a HP 55300A Telecom Primary Reference Standard that I am using as a
> frequency reference (10 mhz) in my lab.
>

I suppose this is one of those open-ended questions, but what the
definition of a "Primary Reference"?  It seems a rather presumptuous name
to attach to a GPS frequency source. When I google the part number, I
actually get " *55300A* GPS Telecom Primary. Reference Source" but it still
have the "primary reference" name in there.

Dave
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Re: [time-nuts] General questions about making measurements with time interval counter.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 12 January 2017 at 02:31, Bob Camp  wrote:

> Hi
>

Hi Bob


>
> The most basic issue you are going to run into is that your counter is not
> high enough
> resolution / accuracy to give you meaningful data for time intervals under
> a few hundred
> seconds.


Is that true if I'm not testing very high quality sources? There are
significant differences observed between these two setups

1) START and STOP from distribution amplifier.
2) START from distribution amplifier. STOP from Stanford Research SR345 30
MHz function generator set to produce 10 MHz.

1) ADEV plot at http://www.kirkbymicrowave.co.uk/time-stuff/ADEV.PNG
where ADEV is about 5x poorer on the function generator at 100 seconds

2) MDEV plot at http://www.kirkbymicrowave.co.uk/time-stuff/MDEV.PNG
where MDEV is about 5 x poorer on the function generator at 10 seconds.

The raw data is in the same directory
http://www.kirkbymicrowave.co.uk/time-stuff/ . I should have zipped that,
as it is quite large

I'm pretty sure the HP 83623A 20 GHz sweep generator will be a lot worst
than either of those, as a simple check of the standard deviation on the
display of the HP 5370B (no data collected from GPIB), showed much higher
SD on the microwave sweeper than the function generator.

I can see if I were testing masers, Cs source, and decent GPS receivers,
what you say would be true. But is it true for lesser quality sources?
Maybe testing lesser quality sources is not such a stupid idea, as the
instrumentation is less of a limiting factor.

I admit I did say in my original post SHORT/MEDIUM time scales, and I guess
10/100s is not short.



> I would focus on improving on that part of things before I went off on a
> major
> “test everything” adventure.


But is there any way without spending lots of cash? The following
instruments are out of the question due to price

* Keysight 53230A 350 MHz Universal Frequency Counter/Timer, 12 digits/s,
20 ps
* John's Timepod

A Stanford Research SR620 is not out of the question. I did have one
before, but swapped it, along with a 4.2 GHz signal generator for an
HP4391B impedance/material analyzer. The 5370B came along fairly cheap
($300), but I don't mind spending more on  a SR620. But will that gain me
much? I know the single shot resolution is a bit better than the 5370B, but
it does not appear to be a massive improvement, given they are 3~4 x the
cost.on the used market.

I also have many other contraiints, which limit what I can realistically
achieve

* Small lab in my garmage- opening door on lab will change temperature.
* Single glazed window
* Air con that is a standard unit designed for offices - not metrology
labs.

Simply collecting a lot of data that is resolution limited is
> not a lot of fun …..
>

Agreed. But am I doing that at > 10 seconds? Is the counter my limit on
those two sets of data? I will collect some from the HP 83623A 20 GHz sweep
generator later today, but that generates a lot of heat, and I'd rather let
that warm up for a couple of hours before doing anything with that.


>
> Bob
>

You clearly have a lot of knowledge Bob. Can I learn anything useful with
what I have, or am I wasting my time?

Dave
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[time-nuts] General questions about making measurements with time interval counter.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

MY AIMS

1) Try to learn about the various statistical tests (ADEV, MDEV etc), and
how best to compare oscillators, by making some measurements on various
oscillators I have.

2) Investigate the short/medium term stability of the output of  various
bits of test kit. All are locked to GPS by feeding 10 MHz to their timebase
inputs, so long term drift should not be relevant.

These istrumuments are:

a) The GPS itself - primarily a test of the 5370B time interval counter,
distribution amplifier and general temperature fluctuations in the lab.

b) Other GPS(s) when I get 1 or 2 more.

c) 10 MHz to 20 GHz Microwave signal generator.

d) 0.001 Hz to 30 MHz function generator.

e) A VNA that will work at 10 MHz. Turn sweeping off

f) A VNA that has a minimum frequency of 50 MHz. Again turn sweeping off.

METHOD - Suggestion for improvements welcome.

* Where possible set all instruments to 10 MHz, which is the same as the
GPS reference. (Obviously since one of the VNAs will not go below 50 MHz, I
would need to use a higher frequency)
* Feed GPS to the start input of the 5370B TI counter and the DUT into the
stop input
* Use the 5370B time interval counter to measre the time difference between
one output of the distribution amplifier and the output of the instrument
being tested .
* Collect data from 5370B and use John's Timelab to plot various graphs and
try to understand the differences between the various statical measurements
(ADEV, MDEV etc.)

MY QUESTIONS.

1) Should I use the GPS to provide a reference for the 5370B time interval
counter,  or would it be better to use the internal OCXO? Currently I have
the 5370B locked to GPS too, but I am wondering if this is a bad idea and I
should run it from its own oscillator.

2) Is there any advantage in a 10 MHz DUT going into the start or stop
input? I assume that it is irrelevant, as long as the GPS goes into the
other. But maybe not.

3) If the DUT is higher in frequency (eg 50 MHz) than the 10  MHz GPS,  is
there any advantage in going in the start ot stop input?

4) If the DUT is lower in frequency (eg 5 MHz) than the 10  MHz GPS,  is
there any advantage in going in the start ot stop input?

Dave
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Re: [time-nuts] hm H Maser

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 10 January 2017 at 15:35, Ole Petter Rønningen 
wrote:

> ... having said that, I for one think I'm with Bob on this one. The thing
> about masers are that they are big. At least active masers. And they
> require a substantial volume be kept at ultra high vacuum - which is not
> trivial, especially not in a homeshop. The cavity needs to be kept at a
> temperature stable to 0.001 degree C. With 4-5 magnetic shields. Add to
> this costly pumps to keep the vacuum this low even if you succeed at
> reaching that vacuum.. There's easily 1-2KUSD running cost per year just to
> keep the maser running.
>

Looking at the Microsemi MHM 2010 Active Hydogen Maser data sheet, the
maser has a peak power of 150 W and an operating power of 75 W.  Based on a
power consumption of 75 W, that is 657 kW hr / year of energy. I pay around
£0.20 (GBP) per kW hr for electricity, so that's £131 (GBP) annually. I
believe electricity is cheaper in the USA than here in the UK, but
converting £131 (GBP) to USD, that's around $161/year in electricity. So
running costs don't seem to be an issue.

But I must admit, the thought of spending a lot of time/money to build
something I could have bought for a lot less with higher performance is not
that attractive, although of course there would be a satisfaction from
building it yourself.

Dave
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Re: [time-nuts] hm H Maser

[Dr. David Kirkby (Kirkby Microwave Ltd)]

Once 9 Jan 2017 12:59, "Bob Camp" <kb...@n1k.org> wrote:
>
> Hi
>
> Ok here are some rough numbers:
>
> > On Jan 9, 2017, at 4:35 AM, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkir...@kirkbymicrowave.co.uk> wrote:

> > It would be interesting to see your breakdown of the costs and man hours
> > for an H2 maser. I suspect that others would find cheaper/faster
solutions.
>
> $100M for the H2
>
> $25M for the Rb

With all due respect,  and I apprectiate you have a good knowledge of this
field, but that's not a breakdown of costs or man hours I wanted to see,
but a cost which appears to be plucked from the air.

There's a BIG difference between a volunteer effort where

* Salaries are not paid
* Items of test equipment are likely to be borrowed or people provide
access to them for no charge etc,
* Academics are likely to provide consultancy for free, in return for being
on papers published.
* Software licenses could probably be obtained free,  or enough people get
trials.

compared to a commercial company building a maser where

* Salaries are paid
* All equipment is purchased new
* Bench power supplies with 3.5 digit displays are sent out for calibration
each year.
*  No outside body will do anything except at a commercial rate.
* Flights are booked for meetings which could be done over the Internet.
* High end software licenses are huge.

> $500M for the fountain.

But on what basis do you arrive at that figure?

> To get sponsorship for anything remotely close to those numbers, you
> need to have some massively good credentials.
>
> Bob

Yes agreed at $500M. But someone like Tom, who does have massively good
credentials, could perhaps get $500,000, and perhaps that wisely spent
could get a fountain built.  Without knowing how you arrive at $500M, it is
not possible for anyone to look at ways of shaving that cost.

The Lovell Telescope at Jodrell Bank in the UK was built on a shoestring
budget. It was at the time the world's  largest steerable radio telephone.
Half a century later only 2 larger ones have been built.

Maybe I am too nieve.

Dave.
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Re: [time-nuts] What signals if any are on the unpopulated SMC pads onthe 58503A motherboard?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 9 January 2017 at 10:44, Roy Phillips  wrote:

> I would be grateful for an answer to this question, as I also have a an HP
> 58503  - is the manual for the instrument available for download ?
> Thank you
> Roy
>

I know its a bit unlikely to use SMC in such a case, but I believe there
are some versions of the 58503A which have a clock, and perhaps some
buttons on the front. I would have expected them to be via a multi-way
cable, but maybe not.

There are at least two relevant manuals on Tom's website

http://www.leapsecond.com/museum/hp59551a/097-59551-02-iss-1.pdf
http://www.leapsecond.com/museum/hp58503a/097-58503-08-iss-1.pdf

I also have another one - not sure where I got that from. It might have
been on Tom's site too, but if not, I put a copy here.

http://www.kirkbymicrowave.co.uk/58503B-GPS-disiplined-OCXO-frequency-standard-097-58503-13-iss-1.pdf
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Re: [time-nuts] hm H Maser

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 8 Jan 2017 17:34, "Bob Camp"  wrote:

> You are talking about a project that will take many years and likely
> more money than the price of a new home. If that is “fun money”, then
> fine. For most people that sort of commitment is a bit outside the range
> of do it for fun.

It would be interesting to see your breakdown of the costs and man hours
for an H2 maser. I suspect that others would find cheaper/faster solutions.

> Even as a “fun project”, I question the bang for the buck. If cost and
time
> are no object, why not do an optical ion standard or a Cesium fountain?
> I would suggest that both are more cool than than a maser and likely
> have a lot more fun aspects to them. You then would have something
> truly unique and not simply a more expensive / poorer performing example
> of something you could have bought.

You raise an interesting point.

I suspect that if a serious attempt was made at a caesium fountain by a
*group* of people, they might end up with donated parts from places like
NIST, NPL etc.

Commercial sponsorship  could conceivability be an option to funding such a
project, as could wealthy individuals like Richard Branson or James Dyson,
both of whom are interested in technically challenging projects.

$100 would not go far, but I personally would be willing to donate $100
towards the cost of such a project, just to feel part of it.

> Bob

Dave
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Re: [time-nuts] hm H Maser

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 8 January 2017 at 15:22, Bob Camp  wrote:

> Hi
>
> I guess the question then would be:
>
> Is a H Maser that runs 6.6 x 10^-12 at 1 second worth the trouble?
>
> With 100 KHz / C temperature coefficients running around, getting
> good stability in a real world setting at 1 day will be “interesting”.
>
> Just for reference:  The MH-2010 data sheet shows 1.5x10^-13 at
> 1 second for the “cheap” version and 8x10^-14 at one second for
> the low noise version.  Data showing the 5065 Rb at 1x10^-12 at
> 1 second is running around on various web sites.
>
> The NIST paper suggests that they made several prototypes before
> they got one good one working. That’s a lot of “fun and games” with
> ceramic machine lathes and Rb magnetometers…..
>
> The punch line being - would the same effort / cost / many years of time
> be more
> fruitful (ADEV wise) doing a large package Rb (like a 5065) ?  Based on
> the number of people making them in volume over the years, Rb’s appear to
> be the easier item to debug, design, and build.
>
> Bob
>

If you build a H2 maser, you would learn a lot more than building a bunch
of rubidiums. That sounds a good enough reason to me.

I've been contemplating buying one of the older HP 5061A or 5061B cesium
frequency standards from eBay. Almost all are sold as "for spares or
repair", and are probably not going to be economically viable to get
working due to the fact the tubes are probably useless. But I'd sure learn
a lot from playing around inside one of the older ones.

Dave
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Re: [time-nuts] Line Voltage - USA

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 4 January 2017 at 14:25, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkir...@kirkbymicrowave.co.uk> wrote:

>
> I just phoned Tektronix and they want £160 (GBP) + VAT to calibrate this
> 6000 count handheld DMM. Ouch. I will not bother with that.
>

Sorry, 60,000 touch - 4 3/4 digits.
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Re: [time-nuts] Line Voltage - USA

[Dr. David Kirkby (Kirkby Microwave Ltd)]

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)

On 4 January 2017 at 14:06, David C. Partridge <
david.partri...@perdrix.co.uk> wrote:

> Time to call your supply co.
>
> Dave
>

I think I'll wait a few more days and collect some more data. I'm just too
close to the upper limit to be confident it is not the uncertainty in my
instruments.

I'd also feel a bit happier if the meter was not 20 years old and had a
valid calibration certificate. I just phoned Tektronix and they want £160
(GBP) + VAT to calibrate this 6000 count handheld DMM. Ouch. I will not
bother with that.

Keysight are quoting $210.00 (USD) to do a 6.5 digit 3457A. That's more
attractive, but a 3457A is not really suited to logging data next to an
electricity meter. It is just not practical to get a GPIB connection there.

Dave




>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr.
> David Kirkby (Kirkby Microwave Ltd)
> Sent: 04 January 2017 13:42
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Line Voltage - USA
>
> I measured my voltage overnight in a peak hold at 255.10 V RMS as close to
> the meter as I could.
>
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Re: [time-nuts] Line Voltage - USA

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 4 January 2017 at 09:34, Poul-Henning Kamp  wrote:

> 
>
> >Do you have a reference to this +6%? I've heard from various sources that
> >the UK is 230 -6%/+10%.  If the EU dictates otherwise, then I'm certainly
> >over the 6% limit. I may or may not be over the 10% limit.
>
> There was a transitional range, but I belive it has expired.
>
> In 240V countries it was -6%/+10%.
>
> In 220V countries it was -10%/+6%
>
>
> --
> Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
>

I measured my voltage overnight in a peak hold at 255.10 V RMS as close to
the meter as I could. One of the phases goes via a 100 A switch to the
garage. I measured on the input of that switch. At 230+10% the maximum
permissible is 253 V, but mine went to 255.10 V. That was measured on a
Tektronix DMM916 (40,000 counter) meter, which has not been calibrated
since I bought it new about 20 years ago.

I spoke to a friend of mine who worked at the CEGB. He thought I might have
a tough time getting the electricity company to do anything about 2.1 V if
it was expensive for them to do.

I was going to report my findings today at

http://www.ukpowernetworks.co.uk/internet/en/power-cuts/report-it/report-general-issue-form/

but having spoken to him, I think I'll monitor for a few more nights and
see if the problem gets worst than 2.1 V outside the specification.

The specification of the meter is +/- 0.7% + 4 counts, so measuring at 253
V (maximum permissible mains voltage), the meter specification is +/- 1.81
V, so there's no doubt that a measurement of 2.10 V above the maximum with
a meter that's not recently been calibrated, is a bit on the dubious side.

Perhaps I need something a bit more convincing before reporting this. I was
thinking of buying a Keysight handheld, but whilst some are cheap, anything
with a reasonable amount of functionality is quite expensive.

Dave
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Re: [time-nuts] Line Voltage - USA

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 2 January 2017 at 05:15, Jeremy Nichols  wrote:

> Thank you for the detailed analysis, Bill. The voltage measurements I made
> in my garage laboratory were duplicated by the utility with their meter,
> which was connected at the service entrance.


I have just been chatting to a friend who was a controller at two power
stations in the UK - Darlington (coal) and Bradwell (nuclear). He tells me
that the voltage is likely to be higher in the summer around 2-3 am in the
morning. Now it might seem obvious that the load is smaller in summer than
in the middle of winter, but this is NOT the reason the voltage rises more
in summer. I must admit though, I could still not understand it, and he
admits he could not explain it, but just tells me it is so. But a few
things I did get, which are not all obvious - some are.

1) The real power consumed by the users + losses must balance the power
generated. That's pretty obvious.

2) The reactive power (V*A) must also balance - perhaps less obvious.

3) The voltage generated by a generator when it is not providing any load
is controlled by the current in the field winding.

4) Before connecting a generator to the grid it is necessary to ensure the
voltage and phases are matched.

5) Once the generator is on the grid, there's nothing the generator can do
that has any practical effect on the voltage. Even with a nuclear power
station, the output power it is a small fraction of the overall power being
generated by the all the power stations, so one power station coming on/off
line does not have any significant effect on the voltage of the grid.

6) What the operator can do is

* Generator more power, by increasing the steam that drivers the generator.
* Change the reactive power by changing the field current


7) As soon as the generator is connector, he would increase the steam to
provide at least  5 MW at Bradwell (nuclear, 2 MW at Darlington (coal), as
failing to do so risks the generator going unstable due to disturbances on
the grid.  This could easily result in the generator becoming a motor,
which is not good. So there's a minimum power a generator can practically
provide - in his case 2 or 5 MW.

8) If there were no uses on the grid, so nobody using any electricity, the
capacitance of the cables would make the load capacitive.

9) Users are generally inductive, so in practice the current lags the
voltage, as the reactive power of users is greater than the the grid.

10) The higher power usage in winter means that the power factor is further
from 1.0.

I get the feeling that the voltage might go up more in summer as the
generator are running closer to a point of instability, with small changes
in load causes significantly more change in power factor than in the
winter.

As I say, I never really seemed to get to the bottom of fully understanding
this, but he assures me that voltages will be less stable at light load
than at heavy load.

I guess if I do report a problem, I will get them to measure all 3 phases.
That must increase the chances of at least one phase going outside
specification. I am rugulary going over 250 V, but not 10% more which would
be 253 V.

Dave
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Re: [time-nuts] Line Voltage - USA

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 2 January 2017 at 18:14, Poul-Henning Kamp  wrote:

> 
> In message  qnosgqvz...@mail.gmail.com>
> , Tim Shoppa writes:
>
> >What modern loads are actually sensitive to high (say, +10 to +20%) line
> >voltage?
>
> In EU you're supposed to have 230V +/- 6% in your outlet.
>
> The way this was arrived at was:
>
> A lot of europe used 220V +/- 10% = [198..242] V
>
> Brittain used 240V +/- 10% = [216..264] V
>
> Take the average of the two, and use the low max and high min as limits
>
> QED:  230V +/- 6% = [216..244]
>

Do you have a reference to this +6%? I've heard from various sources that
the UK is 230 -6%/+10%.  If the EU dictates otherwise, then I'm certainly
over the 6% limit. I may or may not be over the 10% limit.

While the UK is still in the EU, it would be good to get this resolved,
since we will be leaving in just over 2 years.

Rules in Brussels override those made in the UK, which is one of the
complaints we have in the UK. But +/- 6% could actually be beneficial, if
it is correct.

I will be measuring at the incoming terminals some time soon. For now I
have added a variac, which has lengthened  the time I can hold my fingers
on the 8970B from 2 seconds to 9 seconds!!! So a very marked difference in
heatsink temperature since dropping the voltage.

Dave
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Re: [time-nuts] Anyone (ideally in the UK) got a spare rotary knob for the 5370B TI counter?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 30 December 2016 at 23:58, Dr. David Kirkby - Kirkby Microwave Ltd <
drkir...@kirkbymicrowave.co.uk> wrote:

> I bought a 5370B TI counter which arrived today. It needs a bit of TLC,
> but nothing too bad. But one of the rotary knobs is incomplete. Does anyone
> have a spare knob? Contact me off list if you do.
>

It has been great to see the response of many people offering me a free
knob, or the knob for just the postage cost. But this is now resolved.
Robert Atkinson is kindly putting one for me in the post, so I have no need
for any other offers, but thank you anyone that did offer one. In the event
the one Robert sends is not suitable, I will contact the many other that
offered knobs.

It is great to see the generosity of people to help someone else. Not a
single person asked for any money except postage costs.

Dave
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Re: [time-nuts] Anyone (ideally in the UK) got a spare rotary knob for the 5370B TI counter?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 2 January 2017 at 18:21, Robert Atkinson  wrote:

> I've a spare knob and it's on it's way to Dave. f
>

Cheers Robert. I'll send you some money. Drop me a private email with your
PayPal address.


> 5370 counters do seem to run hot so I don't think you have a fault. As
> suggested a little external airflow can help a lot.
>
> Robert G8RPI.
>

I'll have to check now I have put a variac on the supply voltage to the
equipment. I set the variac last night, and have set my Tektrononix
handheld to record min/max/average readings

So far
* Min = 216.71
* Max = 232.75
* Average = 227.88
* Min-Max=16.04.

Obviously the change of 16.04 V is a bit lower than the real swing, as the
variac is reducing this. Perhaps I might need to increase the variac
voltage slightly, but I suspect that running a significantly lower voltage
than before can only help. Maybe just a bit too low though.

I also ordered a couple of those GPIB extenders. It would seem totally
impossbile to get a GPIB cable on otherwise. Sticking the GPIB connect
right next to the heatsink, with the cables coming out the side of the
heatsink seems a bit odd. Unless there are any cables which come out the
other side, so away from the heatsink. Anyway, I have an HP and a Keysight
10834A on order, which should give me enough room to get a GPIB cable out.
A 5370B without a GPIB connection is a bit of a useless bit of kit.

Dave
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[time-nuts] Reproducibility of position data from multiple surveys of HP 58503A GPS receiver

[Dr. David Kirkby - Kirkby Microwave Ltd]

I put my HP 58503A into an infinite loop where

1) Forced GPS receiver to do a survey (GPS:POS:SURVEY ONCE)
2) Waited until survey was complete (GPS:POS:HOLD? returns 1)  This takes about 
2 hour.

3) Recorded date (SYST:DATE?), time (SYST:TIME?) and location (GPS:POS?)

For about 4 hours before the leap second, I stopped this, so the clock was right 
at the time of the leap second. Then I restarted some time after midnight.


The actual data file is here

http://www.kirkbymicrowave.co.uk/HP-58503A/gps.log

which is being updated whenever a survey is complete, and new data collected - 
about once every 2 hours.


A plot of the height from the first 19 data points is here.

http://www.kirkbymicrowave.co.uk/HP-58503A/gps-height.pdf

Unlike hte log, this is not being updated dynamically - I should have used 
another machine which has gnuplot on it for that.


Anyway, based on the first 19 data points, the antenna height appears to be 
anywhere from 40 to 48.5 m. I'm pretty sure it is not bouncing up and down 8.5 
metres! The latitude and longitude move too. I've not converted them into 
metres, so I don't know how much they represent.


The antenna is about 3.5 m above ground level, mounted to the side of a garage, 
which is higher. I could push it another 2 m or so by mounting it on the garage, 
but not without drilling holes in the garage which will not exactly make the XYL 
happy, although I guess if I do it when she is not looking, its a bit late to 
moan then!


I was thinking of telling the receiver the location is an "average" of the data 
points. Some thought would need to be given to averaging, although I would have 
thought in my latitude (51 deg, 39' N), and distance from the meridian (0 deg, 
41' E), a simple mean would not be a bad figure. But I stand to be corrected.


--
Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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Re: [time-nuts] Line Voltage [Was: Anyone (ideally in the UK) ...]

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 1 Jan 2017 11:10, "Hal Murray"  wrote:
>
> The nice thing about the APC units is that they are close to free if you
are
> already going to purchase a UPS.
>
> I agree that something like the Dranetz 658 would be better, but a quick
peek
> at eBay shows prices far beyond what I'm willing to pay.
>
> > What's the sample rate on your APC UPS?
>
> I don't know what the internal sampling rate is.  The API is
>   tell me the current voltage
>   tell me the lowest voltage since the last time I asked
>   tell me the highest voltage since the last time I asked

Em, not a lot. My handheld true RMS Tektronix can give me the average. (One
assumes an average of RMS values).

> I have a hack that reads as fast as it can.  If nothing interesting has
> happened, it adds a line to the log file every 5 minutes.

Again,  I think if attending presenting data for others,  one wants to
avoid hacks like that. One can always post-proces to indicate the points of
particular interest.
My biggest problem is that it is not very practical to log data at the
incoming point, which is just above my back door.  If I lived on my own,  I
could set up equipment easily to do this. But sharing a house with a my
wife and a large German Shepherd dog, it is not practical to do it with the
equipment I have.

I think measuring voltage elsewhere would give someone more reason to
question its accuracy.  In my case, measuring in my lab would almost
certainly give a power supply voltage lower than that coming in.

Anyway,  short term I will use a variac to lower the voltage to test
equipment with linear power supplies.  I am less concerned about equipment
with switch mode supplies.

Dave.
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Re: [time-nuts] Line Voltage [Was: Anyone (ideally in the UK) ...]

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 1 Jan 2017 05:07, "Chris Albertson"  wrote:
>
> Just a comment for anyone who wants to log line voltage v. time.   If
> you have an APC "Smart UPS" battery backup unit these will log voltage
> and frequency to a file.

If the information is for your own use only, that is probably fine.  But if
you intend challenging the electricity supply company over it, I would use
a laboratory multimeter with a valid calibration certificate. It will give
your measurements far more credibility than the data from a UPS.

I would suggest that a 5.5 digit laboratory multimeter with a current
certificate from Keysight would be better than an 8.5 digit 3458A that is
out of the calibration period by a day, despite the latter having lower
uncertainty.

The point where you measure the voltage is probably important too.
Obviously wire resistance in a ring main reduces the voltage, so there's
not much point reporting that the voltage is low unless measured at the
point of the incoming supply. I suspect that it is better to measure there
whatever ones cause  for complete is. Possibly a motor run internally could
act as a generator and push the supply above the incoming voltage.

I don't know what (if any) averaging should be done.  Does one sample every
cycle?  I would probably set my 3457A  to sample 10 power line cycles (200
ms) here in the UK.  I think collecting data every cycle would be a bit
excessive, but maybe not.  One can always post process the data later to do
some averaging.

What's the sample rate on your APC UPS?

Dave
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Re: [time-nuts] Capture of leapsecond on HP 58503A time and frequency reference receiver

[Dr. David Kirkby (Kirkby Microwave Ltd)]

Reposting the output in a fixed width font. It looked fixed on my other
client.

I note the clock says "Time _ +1 leap second pending" at 23:59:60,
which one can argue is wrong.


*Status reports a couple of times before the leap second. *

scpi > SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION . [ Outputs
Valid ]
SmartClock Mode ___   Reference Outputs
___
>> Locked to GPS  TFOM 3 FFOM
   0
   Recovery   1PPS TI +8.7 ns relative to
GPS
   Holdover   HOLD THR 1.000 us
   Power-up   Holdover Uncertainty

  Predict  11.1 us/initial 24
hrs

ACQUISITION  [ GPS 1PPS
Valid ]
Tracking: 6    Not Tracking: 2    Time _ +1 leap second
pending
PRN  El  Az   SS   PRN  El  AzUTC  23:56:00 31 Dec
2016
 16  12 287   45 2  12  37GPS 1PPS Synchronized to UTC
 21  28 171   6623  11 323ANT DLY  0 ns
 25  44 106  101  Position

 26  40 290  123  MODE Hold
 29  73  68  114
 31  61 236   85  LAT  N  51:39:04.132
  LON  E   0:46:36.343
ELEV MASK 10 deg  HGT   +44.72 m
(MSL)
HEALTH MONITOR . [
OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK
scpi > SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION . [ Outputs
Valid ]
SmartClock Mode ___   Reference Outputs
___
>> Locked to GPS  TFOM 3 FFOM
   0
   Recovery   1PPS TI +11.4 ns relative to
GPS
   Holdover   HOLD THR 1.000 us
   Power-up   Holdover Uncertainty

  Predict  11.1 us/initial 24
hrs

ACQUISITION  [ GPS 1PPS
Valid ]
Tracking: 6    Not Tracking: 2    Time _ +1 leap second
pending
PRN  El  Az   SS   PRN  El  AzUTC  23:59:00 31 Dec
2016
 16  13 288   37 2  11  37GPS 1PPS Synchronized to UTC
 21  29 171   9523  11 322ANT DLY  0 ns
 25  42 107  110  Position

 26  41 290   85  MODE Hold
 29  72  67  120
 31  61 234  101  LAT  N  51:39:04.132
  LON  E   0:46:36.343
ELEV MASK 10 deg  HGT   +44.72 m
(MSL)
HEALTH MONITOR . [
OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK

*Here's the actual leap second. *

scpi > SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION . [ Outputs
Valid ]
SmartClock Mode ___   Reference Outputs
___
>> Locked to GPS  TFOM 3 FFOM
   0
   Recovery   1PPS TI -3.3 ns relative to
GPS
   Holdover   HOLD THR 1.000 us
   Power-up   Holdover Uncertainty

  Predict  11.1 us/initial 24
hrs

ACQUISITION  [ GPS 1PPS
Valid ]
Tracking: 6    Not Tracking: 2    Time _ +1 leap second
pending
PRN  El  Az   SS   PRN  El  AzUTC  23:59:60 31 Dec
2016
 16  14 288   51 2  11  37GPS 1PPS Synchronized to UTC
 21  30 171   5423  11 322ANT DLY  0 ns
 25  42 107   95  Position

 26  42 291   73  MODE Hold
 29  72  66  124
 31  60 233  120  LAT  N  51:39:04.132
  LON  E   0:46:36.343
ELEV MASK 10 deg  HGT   +44.72 m
(MSL)
HEALTH MONITOR . [
OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK

*Now one after the leap second. The notice about a 

Re: [time-nuts] Leap-second capture on laptop

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 1 January 2017 at 01:00, Magnus Danielson 
wrote:

> Fellow time-nuts,
>
> While not fancy by any means, my laptop captured the leap-second being
> inserted by this message in the /var/log/syslog:
> Jan  1 00:59:59 greytop kernel: [78458.839942] Clock: inserting leap
> second 23:59:60 UTC
>

Noting reported on my Sun Ultra 27 running OpenSolaris.

Dec 31 23:55:02 hawk sendmail[4016]: [ID 801593 mail.info] uBVNt2jv004015:
to=, ctladdr= (0/0), delay=00:00:00,
xdelay=00:00:00, mailer=local, pri=30730, relay=local, dsn=2.0.0, stat=Sent
Jan  1 00:00:02 hawk sendmail[4055]: [ID 801593 mail.info] v01002rm004055:
from=root, size=319, class=0, nrcpts=1,
msgid=<20170101.v01002rm004055@hawk.local>, relay=root@localhost


This OS has not been updated for years

drkirkby@hawk:~$ cat /etc/release
   OpenSolaris Development snv_134 X86
   Copyright 2010 Sun Microsystems, Inc.  All Rights Reserved.
Use is subject to license terms.
 Assembled 01 March 2010


Dave
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[time-nuts] Capture of leapsecond on HP 58503A time and frequency reference receiver

[Dr. David Kirkby - Kirkby Microwave Ltd]

cv: OK
scpi > SYSTEM:STATUS?
--- Receiver Status ---

SYNCHRONIZATION . [ Outputs Valid ]
SmartClock Mode ___   Reference Outputs ___
>> Locked to GPS  TFOM 3 FFOM 0
   Recovery   1PPS TI +3.2 ns relative to GPS
   Holdover   HOLD THR 1.000 us
   Power-up   Holdover Uncertainty 
  Predict  11.1 us/initial 24 hrs

ACQUISITION  [ GPS 1PPS Valid ]
Tracking: 6    Not Tracking: 2    Time 
PRN  El  Az   SS   PRN  El  AzUTC  00:00:15 01 Jan 2017
 16  14 288   47 2  11  36GPS 1PPS Synchronized to UTC
 21  30 171   6823  11 321ANT DLY  0 ns
 25  42 107   99  Position 
 26  42 291   70  MODE Hold
 29  71  66  125
 31  60 233  105  LAT  N  51:39:04.132
  LON  E   0:46:36.343
ELEV MASK 10 deg  HGT   +44.72 m  (MSL)
HEALTH MONITOR . [ OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv: OK
scpi >



--
Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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Re: [time-nuts] Anyone (ideally in the UK) got a spare rotary knob for the 5370B TI counter?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 31 December 2016 at 13:03, EB4APL  wrote:

> Hi,
>
> I'm not totally sure about the limits, but I have read several times that
> in the UK the nominal supply voltage is 230 V +10%/−6% to accommodate the
> fact that most supplies are in fact still 240 V. The context was that a lot
> of test equipment failed when operated at around 250 V and many input
> capacitors (particularly the ones inside a know brand IEC socket - filter)
> caught fire.
>
> Wikipedia says that several areas in UK still have 250 V because this
> value is withing the current limits.
>
> I think that the governing document is British Standard BS 7697: Nominal
> voltages for low voltage public electricity supply systems —
> (Implementation of HD 472 S1).
>
> Regards,
>
> Ignacio, EB4APL



Hi,
I have just been on to the phone of a friend of mine who spent much of his
like working in the electricity generating industry. Working at both
Darlington (coal) and Bradwell (nuclear) power stations in the UK. Among
many other things he said

* He did not know the current specifications limits for certain, but he
said easy to check. (What you say - 230 -6%/+10% does seem to be quoted in
many places, but I guess I should check it out.)
* Supply voltage is likely to be highest about at 2-3 am in Summer
* Supply voltage is likely to be lowest on a cold Winter's afternoon.
* Voltages in use around the county include at the least 11, 22, 33, 66,
132, 275 and 400 kV.
* There's not much standardization of generator voltage - Bradwell nuclear
power station was 11.1 kV.
* There are taps on the 275 kV transformers to keep the 132 kV close to 132
kV
* There are 6 taps on the 11 kV transformers feeding my house to adjust the
voltage. Those can only be adjusted with the 11 kV off - they can't be done
with it online. Essentially this means to change the taps, an area would
need to be powered off.
* If voltage is out of spec, it should be possible to get something done
about it.
* The electricity board can install monitor equipment.
* Since I am right by the 11 kV transformer, and other places further away,
dropping the voltage at my place might put other places too low.

I think short-term I will put the auto transformer in line. I will monitor
the mains, and report it in the summer, when I'm told it is likely to go
higher.

It hit 250.04 V in the last hour or so, but I have not seen the magic
figure of 253 V.

I'll get my 3457A calibrated by Keysight, then look to measure this and if
appropriate make a formal request to have the voltage checked, and
hopefully the problems would occur during the time it was monitored.

Dave
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Re: [time-nuts] Anyone (ideally in the UK) got a spare rotary knob for the 5370B TI counter?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 31 Dec 2016 02:03, "Bob Stewart"  wrote:
>
> If you can touch the heat sink for 2 seconds, you're made of sterner
stuff than I am!  They run very hot.  It's a good idea to get a GPIB
extender so your GPIB cable can clear the heat sink.  Somebody, can't
remember who, worked up a nice looking conversion to a pair of switching
supplies.

SMPSs tend to be less clean than a linear supply. I would be somewhat
reluctant to take that route on test equipment. But I will search for the
conversion.

I have a 13 A variac sitting around that's not been used in the last 25
years. I think as a short term measure I will drop the voltage to a few
bits of the equipment with linear power supplies. The spectrum analyzer has
linear supplies and puts out a lot of heat.  As someone else said,  a 20 V
transformer would work. Adding the variac will take me 5 minutes to do,
which has an advantage over anything I need to build.

I will also log the mains voltage over a period of a few weeks and see if
it high enough to ask the electricity supply company to do something about
it.  I do know someone that measured his voltage and found it was outside
the legal limits. He advised the electricity supplier,  they agreed,  but
said that they were not going to do anything about it.  He wired his whole
house on an auto transformer.  I would be speaking to my Membrr of
Parliament (MP) if it was outside the legal limits. I don't know what legal
limits exist in the UK for voltage,  but I can find out.

It is unusual in the UK for a domestic property to have a phase supply, but
mine does.  I don't know whether any one phase is consistently lower than
any other. If so phases could be switched.  But given my close promptly to
the 11 kV transformer,  I doubt it.

I know at one point I had a dispute with the electricity supply company as
the 415 V overhead power lines used to be regularly hit by farm vehicles
down a private road where my property is. This would pull the cables away
from my house and make a mess of the house. The electricity supplier would
always repair the damage,  but after this happened a few times I
complained. I was initially told they would do nothing as it is not a road.
But I discovered that the cables needed to be a minimum height if there was
vehicular access. So whether the electricity supplier considered it a road
or not was irrelevant.  Eventually they extended a pole and raised the
cables up, which appears to have solved the problem.  Whether I can
convince them to move the transformer taps is another matter.  I suspect
that it might be hard if my supply is consistently high, but not outside
the legal limits.

Dave
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[time-nuts] Anyone (ideally in the UK) got a spare rotary knob for the 5370B TI counter?

[Dr. David Kirkby - Kirkby Microwave Ltd]

I bought a 5370B TI counter which arrived today. It needs a bit of TLC, but 
nothing too bad. But one of the rotary knobs is incomplete. Does anyone have a 
spare knob? Contact me off list if you do.


I had one of these things about 10 years ago. I have forgotten how to drive it.

It is running very warm. I can hold my fingers on the heatsink for only a couple 
of seconds - not a very scientific test I must admit.


Obviously the mains voltage varies a bit, but it is usually well over the 230 
VAC we are supposed to be. I just measured it at 248 VAC. Unfortunately I'm 
right on top of the 11 kV transformer, so other properties around me probably 
get poorer voltage regulation, but a few less volts.



Dave


--
Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT, UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 December 2016 at 20:54, Bill Byrom  wrote:

> Read about the synthesizer design of that generator here:
>
> https://ia600407.us.archive.org/10/items/Hewlett-Packard_
> Journal_Vol._42_No._2_1991-04_Hewlett-Packard/Hewlett-
> Packard_Journal_Vol._42_No._2_1991-04_Hewlett-Packard.pdf
>

Cheers, I will do that.


>
> Dave, looking at the graph you posted it appears to me that the shift is
> 10 Hz, not 100 Hz. It appears to me that is an audio spectrogram. I have
> no idea if the frequency shift is in the generator or receiver.
>

Well done!. I thought I was told it was 100 Hz, but looking at the diagram,
it is closer to about 10~15 Hz. The setup his end is a software defined
radio, so the measurement of frequency is being done at audio.
Unfortunately, I've been unable to get a response by phone, so I can't seem
to get much in the way of technical details at this minute.

I have an HP 5342A -- 10Hz to 18GHz Microwave Frequency Counter with 1 Hz
resolution, but I belive this is moving (it is is), is quicker than the
time it would take to measure to 10 GHz to 1 Hz. I can lock that to GPS
easy enough, so the signal generator would be fed from the same reference
as the frequency counter, but I don't think that would help.

It would appear that measuring such small changes at microwave frequencies
is not easy. Mixing with very good quality signal generator or known
performance would probably be ok, but even old 20 GHz units are expensive.
To get a good quality new signal generator would be a small fortune.

I don't think even sending this to Keysight for calibration would achieve
anything useful. I have not looked at the specification in detail, but
phase noise is specification is -76 dBc at 10 kHz offset at 20 GHz. The
calibration of this is high too ($1600 in the USA).

>
> Bill Byrom N5BB
>

Dave
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 December 2016 at 01:35, Brooke Clarke  wrote:

> Hi David:
>
> Do you have a comb generator?
>

No.

Dave
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 December 2016 at 03:51, Tom Knox  wrote:

> If it is any help, the 836XXA/B series are all capable of 1Hz resolution
> but are locked at 1KHz unless you enter the license key for option 008. So
> it could be software/firmware related.
>
> Happy Merry;
>
> Thomas Knox
>

I have the license key - not exactly via an official means I might add. I
would not be surprised if that changed the behavior in some way, but I'd
like to resolve this problem, if one exists, before the upgrade.

Dave
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 December 2016 at 03:17, paul swed  wrote:

> Dave Congratulations on 10 Ghz SSB.
>

This was not a QSO at all. It was simply a one way transmission from a
signal generator at my end to a receiver at his end. No QSO was attempted.


> Now to your question. I will fully believe you are seeing normal behavior
> of the generators. Even if its dithering 100 Hz thats pretty amazing. Sweep
> gens simply are not stable enough for narrow work like you are trying.
> Now I am sure comments will prove me totally wrong.
>

But I find it a bit odd that HP would have a 1 Hz software option on this
instrument, if the instrument jumped up/down 100 Hz.

Now I don't yet have the 1 Hz option programmed in, and it might well
change the behavior completely, but I'd still like to find a way, if one
exists, of checking this with the equipment I have.

The signal generator is no longer supported, but I could try my luck seeing
if there are any known problems with this unit, or firmware upgrades
available - currently revision 29, May 1991.



> But I don't think so. (Have been on 10G SSB over the years also. Only 60
> watts plus. Nothing fancy. ;-)  )
> Regards
> Paul
> WB8TSL
>

60 W is clearly some setup. I also know a lot of people run portable stuff
on 10 GHz, where achieving frequency stability is more of a challenge,
although less so with GPS. But this is a laboratory instrument, from a
reputable manufacturer. I personally would not expected this behavior. I
actually purchased this very cheaply (£650 GBP, which would have been about
$900 at the time), but they are not cheap to buy now.


Dave
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[time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I run a test over the weekend with a fellow radio ham. I transmitted 100 mW
or so at 10368.115 MHz from an HP 83623A 10 MHz to 20 GHz sweep generator

http://www.keysight.com/en/pd-101862%3Aepsg%3Apro-pn-83623A/synthesized-sweeper-10-mhz-to-20-ghz-high-power?cc=GB=eng

into a small horn antenna inside my lab.

He was able to receive me about 7 km away, although the signal was quite
week - it was 20 dB above the noise in a 2.9 Hz bandwidth.

What is odd, is that his transceiver + transverter combination indicates
the signal generator is shifting frequency up/down 100 Hz. This is not slow
drift, but a step change - see waterfall picture, where time is on the
vertical axis, and frequency is on the horizontal. Unfortunately I don't
know what the scale is on the vertical axis - I am trying to find out. The
frequency on the x-axis is not the true frequency, but that shown on an 2 m
amateur transceiver, so the true frequency is more than 10 GHz higher.

The step size on this HP sweeper is 1 kHz, so the 100 Hz up/down shift is
not due to a rotary encoder that might be just on the limit of two
frequencies.  Both the internal oscillator and a GPS locked frequency
standard were used during this test. Going from internal to external
reference caused a 450 Hz step in frequency, but did not change this
up/down 100 Hz behavior. So the problem is certainly not the crystal in a
10 MHz reference oscillator, as two have been tried, one of which was
locked to GPS.

Does anyone have an idea what may cause this behavior?

Does anyone have any ideas on the best way to investigate this, given the
signal is at more than 10 GHz?

What I do *not* have is any other signal generator capable of operation at
10 GHz. The only other sig gen I have is a 30 MHz Stanford Research DS345
function generator.

I don't have a TI counter at the minute, but had an offer of $300 accepted
on eBay for a 5370B a couple of days back, so should have a TI counter
soon. (Yes, I have had an 5370B and SR620 in the past, but for various
reasons no longer have them). The 5370B at $300 was a lot cheaper than an
SR620.

Other equipment I have include

* 22 GHz spectrum analyzer
* 30 MHz signal generator
* 20 GHz VNA

but no other signal generator capable of anywhere near 10 GHz.

I do have a couple of double balanced mixers which have RF and IF inputs
that will take 10 GHz, and an IF output that will go from DC to 4 GHz.
Introducing a REALLY long delay might allow the steps to be seen, as the
frequency at the LO and RF inputs of the mixers will be different. But
that's not really practical, as I'd need an awfully long bit of coax.

The 20 GHz vector network analyzer, which could be pressed into service as
a poor (rich) mans microwave signal source, but I suspect the output of
that is quite dirty, as the output is generated from a step recovery diode.
I have not yet tested it on a spectrum analyzer, but the SA has quite a few
spurious signals, so I'm never exactly confident of the SA. But one thing
to possibly is

* Set sweep generator to 10.368 GHz
* Set sweep generator to 10.378 GHz, so there's a 10 MHz difference.
* Mix the VNA + sweeper down to 10 MHz using a double balanced mixer
* Compare the 10 MHz at the output of a mixer to that of a 10 MHz crystal.
Steps of 100 Hz should then be seen I guess.

Any better suggestions?

Someone had kindly given me a key to change the step size of the signal
generator from 1 kHz to 1 Hz. I've not applied that yet, as it is quite a
complex procedure. But the fact the step size of this is 1 kHz, but it is
shifting up/down 100 Hz, does not make sense. Especially given the unit is
capable of 1 Hz resolution, but HP decided to charge extra for 1 Hz steps.
Luckily this is just a software option.

I did wonder if the signal generator was incapable of output the exact
frequency needed, so it was stepped up/down periodically so it gave the
right number of cycles over a long duration. But again, the fact it can
step 1 Hz with just a software upgrade suggest that's not the case.

The radio ham that noticed this step change in frequency is well used to
listening on 10 GHz, and hearing beacons. So I think its reasonable to
assume that the problem is not his end, but my end.

Any thoughts, which do NOT include purchasing a second expensive 20 GHz
signal generator. They are around $10,000 each, so a bit out of my price
range.

Dave
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Re: [time-nuts] Problem with HP 83623A 20 GHz sweep generator stepping up/down 100 Hz when not wanted.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 21 December 2016 at 23:42, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkir...@kirkbymicrowave.co.uk> wrote:


> But one thing to possibly is
>
> * Set sweep generator to 10.368 GHz
> * Set sweep generator to 10.378 GHz, so there's a 10 MHz difference.
>


I mean set the VNA to  10.378 GHz, so there's a 10 MHz difference between
the VNA and sweep generator.

Dave
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Re: [time-nuts] Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 18 December 2016 at 22:41, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkir...@kirkbymicrowave.co.uk> wrote:

> It is looking much better now. I
>
> 1) Powered off
> 2) Left off for 30 s
> 3) Pulled antenna out.
> 4) Powered on
> 5) Connected antenna, making sure if was firmly screwed in.
>
> It then got GPS lock in a few minutes. It is running at reduced accuracy,
> with the survey only 9.7% complete, but it is looking more hopeful.
>

This does appear now to be working - see below. I'm not exactly sure what
was the secret to getting this to work, but the above procedure seemed ok.


scpi >  SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION . [ Outputs
Valid ]
SmartClock Mode ___   Reference Outputs
___
>> Locked to GPS  TFOM 3
FFOM 0
   Recovery   1PPS TI -8.3 ns relative to
GPS
   Holdover   HOLD THR 1.000 us
   Power-up   Holdover Uncertainty

  Predict  9.6 us/initial 24 hrs

ACQUISITION  [ GPS 1PPS
Valid ]
Tracking: 6    Not Tracking: 2    Time _ +1 leap second
pending
PRN  El  Az   SS   PRN  El  AzUTC  23:11:07 19 Dec
2016
  2  31  69   83 6  15  34GPS 1PPS Synchronized to UTC
 12  41  80  11032  27 234ANT DLY  0 ns
 14  37 266   81  Position

 25  83  33  127  MODE Hold
 29  55 195  135
 31  42 301   75  LAT  N  51:39:04.198
  LON  E   0:46:36.358
ELEV MASK 10 deg  HGT   +45.42 m
(MSL)
HEALTH MONITOR . [
OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK
scpi >
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Re: [time-nuts] Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

It is looking much better now. I

1) Powered off
2) Left off for 30 s
3) Pulled antenna out.
4) Powered on
5) Connected antenna, making sure if was firmly screwed in.

It then got GPS lock in a few minutes. It is running at reduced accuracy,
with the survey only 9.7% complete, but it is looking more hopeful.

I can't help feeling there should have been more informative status
available by the LEDs. The fact it is locked, but at reduced accuracy,
should really be visable from the front panel IMHO. Anyway, it seems to be
getting there - see below.

scpi >  SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION  [ Outputs Valid/Reduced
Accuracy ]
SmartClock Mode ___   Reference Outputs
___
>> Locked to GPS: stabilizing frequency   TFOM 3
FFOM 1
   Recovery   1PPS TI -15.9 ns relative to
GPS
   Holdover   HOLD THR 1.000 us
   Power-up   Holdover Uncertainty

  Predict  432.0 us/initial 24
hrs

ACQUISITION  [ GPS 1PPS
Valid ]
Tracking: 6    Not Tracking: 3    Time _ +1 leap second
pending
PRN  El  Az   SS   PRN  El  AzUTC  22:39:23 18 Dec
2016
  2  28  87   86 6  20  48GPS 1PPS Synchronized to UTC
 12  57  70  11924  24 137ANT DLY  0 ns
 14  39 287  10631  27 303Position

 25  76 284   96  MODE Survey:9.7%
complete
 29  37 194   79
 32  39 249  109  AVG LAT  N  51:39:04.205
  AVG LON  E   0:46:36.347
ELEV MASK 10 deg  AVG HGT   +42.42 m
(MSL)
HEALTH MONITOR . [
OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK
scpi >
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Re: [time-nuts] Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 18 December 2016 at 18:19, Dan Rae <dan...@verizon.net> wrote:

> On 12/18/2016 9:34 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:
>
>> 
>> *12  -- ---MODE Survey:  0%
>> complete
>>
>>
> If it's still showing that after being on for five hours, maybe it needs
> to be explicitly told to start a survey?
>
> dr
>


I seem to be having some issues now with this. I've reset it, and entered
the approximate latitude, longitude, height, as well as date and time. The
commands below were executed, although NOT necessarily in the order give.


E-113> GPS:INIT:DATe 2016,12,18
E-113> gps:init:time 19,18,35
E-113> SYSTEM:PRESET
scpi > DIAG:LOG:READ:ALL?
Log status: 2   entries

Log 001:19970504.00:00:00:  Log cleared
Log 002:19970504.00:00:00:  System preset

The receiver seems to find satellites fairly quickly, tries to track them,
and is showing reasonable values for the things I set, like date, time,
position etc. However,  the receiver doesn't seem able to track any
satellites, so not surprisingly the survey never starts. I assume it wont
start until it has tracked sufficient number of satellites.

scpi > SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION ... [ Outputs
Invalid ]
SmartClock Mode ___   Reference Outputs
___
   Locked TFOM 9
FFOM 3
   Recovery   1PPS TI  --
   Holdover   HOLD THR 1.000 us
>> Power-up: GPS acquisition  Holdover Uncertainty

  Predict  --

ACQUISITION .. [ GPS 1PPS
Invalid ]
Tracking: 0    Not Tracking: 12 ___   Time

   PRN  El  Az  PRN  El  Az   UTC  21:57:41 [?] 18 Dec
2016
 6  20  67   12  76  56   GPS 1PPS Invalid: not tracking
   * 7  -- ---   14  32 307   ANT DLY  0 ns
   * 8  -- ---   24  42 129   Position

   * 9  -- ---   25  58 259   MODE Survey:  0%
complete
   *10  -- ---  *31  10 299Suspended: track <4
sats
   *11  -- ---   32  45 274   INIT LAT N  51:39:03.825
  INIT LON E   0:46:36.277
ELEV MASK 10 deg   *attempting to track   INIT HGT  +29.99 m
(MSL)
HEALTH MONITOR . [
OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK


It will run overnight. Perhaps tomorrow it will sort itself out, but I'm
not too hopeful.


Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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Re: [time-nuts] Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 18 December 2016 at 14:31, Tim Shoppa  wrote:

> A common misconception, is that holdover is the opposite of GPS lock.
> Sometimes we might even talk about the two as if we're in one or the other.
> But really the power-on state, is that we're in neither holdover or GPS
> lock.
>
> Holdover means the smartclock previously had GPS lock and had used it to
> characterize the aging of the OCXO, and is maintaining the EFC
> extrapolation, such that it believes it can still produce accurate time and
> frequency through the GPS loss.
>
> The state of your clock at the moment, is that it has never had GPS lock
> since regaining power, it does not know what time it is, and it has not
> characterized or extrapolated the aging of the OCXO. So it is definitely
> not in holdover.
>
> Tim N3QE
>

Cheers Tim, that makes sense.

I'm a bit concerned it has not managed to track a single satellite, despite
it has been on 5 hours or so. But perhaps things have improved, as its not
attempting to track 6 (PRN=15, 2, 21, 25, 26 and 28), whereas before it was
attempting to track just with a PRN of 32. I'm hoping its current status
(see below), is looking more hopeful than what it was before.

scpi >
scpi > SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION ... [ Outputs
Invalid ]
SmartClock Mode ___   Reference Outputs
___
   Locked TFOM 9
FFOM 3
   Recovery   1PPS TI  --
   Holdover   HOLD THR 1.000 us
>> Power-up: GPS acquisition  Holdover Uncertainty

  Predict  --

ACQUISITION .. [ GPS 1PPS
Invalid ]
Tracking: 0    Not Tracking: 6    Time _ +1 leap second
pending
   PRN  El  AzUTC  14:43:22 [?] 01 Jan
1998
   *15  -- ---GPS 1PPS Invalid: not tracking
   *20  -- ---ANT DLY  0 ns
   *21  -- ---Position

   *25  -- ---MODE Survey:  0%
complete
   *26  -- --- Suspended: track <4
sats
   *28  -- ---INIT LAT N  51:39:03.825
  INIT LON E   0:46:36.278
ELEV MASK 10 deg   *attempting to track   INIT HGT  -14.04 m
(MSL)
HEALTH MONITOR . [
OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK
scpi > SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION ... [ Outputs
Invalid ]
SmartClock Mode ___   Reference Outputs
___
   Locked TFOM 9
FFOM 3
   Recovery   1PPS TI  --
   Holdover   HOLD THR 1.000 us
>> Power-up: GPS acquisition  Holdover Uncertainty

  Predict  --

ACQUISITION .. [ GPS 1PPS
Invalid ]
Tracking: 0    Not Tracking: 6    Time _ +1 leap second
pending
   PRN  El  AzUTC  16:59:08 [?] 01 Jan
1998
   * 8  -- ---GPS 1PPS Invalid: not tracking
   *10  -- ---ANT DLY  0 ns
   *11  -- ---Position

   *12  -- ---MODE Survey:  0%
complete
   *13  -- --- Suspended: track <4
sats
   *30  -- ---INIT LAT N  51:39:03.825
  INIT LON E   0:46:36.278
ELEV MASK 10 deg   *attempting to track   INIT HGT  -14.04 m
(MSL)
HEALTH MONITOR . [
OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK
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Re: [time-nuts] Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 18 December 2016 at 17:34, Dr. David Kirkby (Kirkby Microwave Ltd) <
drkir...@kirkbymicrowave.co.uk> wrote:

> But perhaps things have improved, as its not attempting to track 6
> (PRN=15, 2, 21, 25, 26 and 28), whereas before it was attempting to track
> just with a PRN of 32. I'm hoping its current status (see below), is
> looking more hopeful than what it was before.
>

I mean it is NOW attempting to track 6 !!! Almost the opposite of what I
wrote.

I'm guessing it gave up attempting to track the satellite with a PRN of 32.

Dave
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[time-nuts] Why is holdover LED on HP 58503A not lit, when GPS lock is unlit too?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

My 58503 GPS time/frequency reference had its power disconnected a few
times yesterday as I moved things in the lab. At the modem the status of
the LEDs are

* Power green
* GPS lock - not lit
* Holdover - not lit
* Alarm - not lit.

That is what the manual says will happen  when power is first applied, but
I'm puzzled why.

The SYSTEM:STATUS? shows the information at the end of this email. What I
can't understand is why the holdover light is not lit, when clearly its not
tracking any satellites. It seems logical to me that holdover should be on,
when GPS lock is not, and visa versa. But that does not seem to be the
case.

Looking at the data below, the date/time is obviously wrong (01 Jan 1998),
the height at -14.04 m  (MSL) is wrong, but latitude and longitude look
about right, although they are certainly not exactly agreeing with Google
maps, which show 51°39'04.1"N+0°46'36.4"E.

I must be misunderstanding the purpose of these lights.

I'm also a bit puzzled it has been on about 1.5 hours, and can't seem to
find a single satellite. The antenna is fairly clear of anything else, and
it was certainly working yesterday, with the power and GPS lock LEDs both
lit.

Any ideas what's going on?

scpi > SYSTEM:STATUS?
--- Receiver Status
---

SYNCHRONIZATION ... [ Outputs
Invalid ]
SmartClock Mode ___   Reference Outputs
___
   Locked TFOM 9
FFOM 3
   Recovery   1PPS TI  --
   Holdover   HOLD THR 1.000 us
>> Power-up: GPS acquisition  Holdover Uncertainty

  Predict  --

ACQUISITION .. [ GPS 1PPS
Invalid ]
Tracking: 0    Not Tracking: 1    Time _ +1 leap second
pending
   PRN  El  AzUTC  12:59:16 [?] 01 Jan
1998
   *32  -- ---GPS 1PPS Invalid: not tracking
  ANT DLY  0 ns
  Position

  MODE Survey:  0%
complete
   Suspended: track <4
sats
  INIT LAT N  51:39:03.825
  INIT LON E   0:46:36.278
ELEV MASK 10 deg   *attempting to track   INIT HGT  -14.04 m
(MSL)
HEALTH MONITOR . [
OK ]
Self Test: OKInt Pwr: OK   Oven Pwr: OK   OCXO: OK   EFC: OK   GPS Rcv:
OK
scpi >



Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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Re: [time-nuts] OT: ExpressPCB (cross-post from volts-nuts)

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 9 December 2016 at 19:58, BIll Ezell  wrote:
> Sorry if I'm behind the times, just did a new project that required a pcb,
> and ExpressPCB is my go-to vendor for one-off boards. I just noticed they
> now provide the low-cost boards (fixed size, 3x5, quantity 3) that I've
> always ordered with silk screen and solder mask for $71. I got my latest
> boards that way and they're beautiful. No relationship to them, just a happy
> customer. You can still get the barebones boards for $51.

You also lock yourself into one vendor. There's other free software,
like Kicad, where you can export files that many PCB manufacturers
use. So you avoid vendor lock-in.

https://en.wikipedia.org/wiki/Vendor_lock-in

If the company goes belly up, where are you going to get any more
boards made, without starting from scratch?

Anyway, it is a bit off topic.

Dave
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Re: [time-nuts] Need for a document comparing time interval counters

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 21 November 2016 at 21:10, Bob Camp  wrote:

> Hi
>
> With both counters running on the same external standard (and no internal
> OCXO), the 53230
> beats the 53132 both on frequency and time. It also has slightly better
> isolation of the 10 MHz
> internals so the “dead zone” at 10 MHz is not quite as bad. I have no idea
> how either one
> works with the OCXO option … I’ve never seen either one with an OCXO.
>
> Bob
>

This sort of information is useful. Perhaps a Wiki is the best document,
where people can put comments like this. I don't have a Wiki set up myself,
but I'd guess the sort of information one would want would be:

* Description
Described what a TI counter is

* Uses
No doubt with an emphasis on time nuts uses, but I don't see any need to
restrict it just to that. (I did consider using one of mine to record the
speed of the traffic near my house!)

* Understanding the specifications and their importance.
Lots of them.

* Items to be considered when purchasing new vs used.

* Description of model X
Include any options that are available for model X.
Also any known issues - e.g. for both the SR620 and 8970B, they do in my
experience run quite warm.

* Description of model Y
* Description of model Z

Table comparing specifications between all models

* Models worth considering if your budget is < $250
* Models worth considering if your budget is < $500
* Models worth considering if your budget is < $1000
* Models worth considering if your budget is < $2000
* Models worth considering if you budget is unlimited.

* Conclusions.




Dave
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[time-nuts] Do reflections up/down the antenna cable cause a problem with GPS?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

People state it is desirable to have a GPS antenna well clear of
obstructions, which I believe is to stop reflections. But there is another
source of reflections which I suspect could be just as problematic.

Whilst the input impedance of the antenna input terminal on a GPS receiver
is probably marked 50 Ohms, I'd be somewhat surprised if it was very close
to 50 Ohms. Antenna cables have an impedance, which is typically 50 +/- 2
Ohms, but this varies, not only between different makes/models of cables,
but even on the same real of cable.The output of the pre-amp is most
unlikely to have a 50 Ohm source impedance. In fact, the output impedance
might be close to 0 Ohms, as it may be driven by a voltage source, without
any 50 Ohm resistor.

Anything not immediately absorbed by the GPS receiver is going to be
reflected back up the coax, and could be reflected multiple times.

I just looked on my HP 8720D VNA, and see I can reduce the output power to
-70 dBm, which would should not do any damage. It will be interesting to
see just what the input impedance of the GPS receiver is. I'm tied up with
doing my accounts over the next few days, but later I will look.

If reflections on the antenna/cable/receiver are a problem, then
attenuators can improve the match, but of course they reduce the signal
level too. A more intelligent, but more difficult solution, is to build a
matching network. For that one would need a VNA to measure the impedance in
the first place.

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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[time-nuts] Need for a document comparing time interval counters

[Dr. David Kirkby]

If anyone has the time & inclination, a document comparing different time 
interval counters would be useful to budding time nuts. There are quite a few 
different models at prices that are affordable to many.

I have had a HP 5370B and a Stanford Research  SR620, but have neither now. I 
regretted selling the HP, but then after buying the SR620, I swapped that and a 
4.2 GHz HP signal generator for an HP 4291B 1.8 GHz impedance and material 
analyzer. 

I was looking for something cheap,  but see a used Keysight 53230A on eBay for 
considerably more than a new one from Keysight. It had a "make offer" so I 
could not resist pointing out a new one is much less, and making a redicously 
low offer of $1000. I doubt it will be accepted,  but one never knows.  I once 
got a current Ketsight product for 2% of the current price,  so anything is 
possible.  

But a  comparison of TI counters,  and a discussion of the important 
specifications would be njce. 


.Dave. 
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[time-nuts] Do the HP 5334A & 5335A counter/timers take the same oven oscillator?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

Would it be possible to remove an OCXO from an 8334A 100 MHz counter/timer
and fit it in a 8335A 200 MHz counter/timer?

Would the TXCO from the 8335A then fit in the 8334A so that the 100 MHz
unit?

Are the OCXOs similar,  identical or incompatible?

I expect a detailed look at the service manuals would answer at least some
of the questions,  but I only have access to a mobile phone now, so are
hoping that someone might know.  In any case, different part numbers might
actually work,  even if not as stable as the correct OCXO.

Dave

Dr David Kirkby
Managing Director
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3
6DT, United Kingdom
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 07910 441670 / +44 7910 441670 (0900-2100 GMT)
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[time-nuts] Any reference to many/all ways of measuring frequency?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

Is anyone aware of any references to review papers or other sources that
describes a large number of ways of measuring the frequency of oscillators?
Ideally something with lots of pretty pictures,  but that's not essential.
Ideally something that covers various techniques from 50 Hz to light.

Unfortunately I have lost access to the university source I once had that
allowed downloads of almost any scientific paper.  So if you have something
that's not easy to download,  please email it to me.

I was looking to give a talk about frequency measurements to my amateur
radio club. Whilst I am sure that those at the club will only use a
commercial frequency counter,  I thought it sensible to mention a large
number of ways,  as I think that would be interesting to some.

I am not well qualified to do such a talk, but I know more than any others
at my club on this matter.  If anyone who feels that they could give a good
talk on the subject to a radio club in Essex,  please contact me off list.
At least some of it would need to be understandable to those without a
great electronics knowledge.  A talk suitable for a scientific conference
on the topic would not be useful. We can pay reasonable travelling
expenses.

Dr David Kirkby
Managing Director
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3
6DT, United Kingdom
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 07910 441670 / +44 7910 441670 (0900-2100 GMT)
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Re: [time-nuts] Man with too many clocks.

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 4 Nov 2016 17:48, "Bob Camp"  wrote:
>
> Hi
>
> The only practical way to set the 10811 or 10544 is with a >= 10 turn pot
on the EFC. I
> never have worked out just why there are so many instruments that don’t
have a pot on
> the EFC.
>
> Bob

I'm amazed my 18 GHz HP 5342A counter has no pot. IIRC the standard TCXO
does, but the counter drifts a lot with that.  After fitting the optional
10811A OCXO, I discovered it is almost impossible to set the frequency from
the mechanical control. I guess I should modify the counter and add a
control. It really is odd that there's no such facility.

That said,  the difference in value between this old counter and the newer
microwave counters like the 5351B has fallen.  The newer ones are much more
sensitive too.

Dave.
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Re: [time-nuts] Temp/Humidity control systems?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 31 October 2016 at 10:37, Poul-Henning Kamp  wrote:

> 
> In message  gmail.com>, "Dr. David K
> irkby (Kirkby Microwave Ltd)" writes:
>
> >> > [...] so it might be a relatively cheap way to measure humidity.
> >>
> >> 80m wave-guide is neither cheap, nor in most circumstances, practical
> :-)
> >
> >But you don't need 80 m of waveguide. 100 mm or so would be sufficient.
>
> Then it would require a quite high frequency...
>

If you try to do an attenuation measurement in the normal operating
wavelength of the guide, then I agree you would need a huge length unless
at very high frequency (100 GHz+), where water absorption becomes high  But
that's not the approach I would take.

I would look at trying to exploit the variation of cutoff frequency of
waveguide with humidity. WR90, which has an internal width of 0.900"
(that's where the 90 comes from),  has a cutoff frequency around 6.5 GHz. I
would expect that to be pretty dependent on the permittivity in the guide.
6.5 GHz is not a ridiculously high frequency to generate, and WR90 is not
unmanageably large. Making the guide bigger would reduce the frequency you
need to generate.

. .
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Re: [time-nuts] Temp/Humidity control systems?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 31 Oct 2016 06:07, "Poul-Henning Kamp"  wrote:
>
> 
> In message <
canx10hcpa5sozukqe00c5hcm-zrwkblnsojcoljokdriols...@mail.gmail.com>, "Dr.
David K
> irkby (Kirkby Microwave Ltd)" writes:
>
> > [...] so it might be a relatively cheap way to measure humidity.
>
> 80m wave-guide is neither cheap, nor in most circumstances, practical :-)

But you don't need 80 m of waveguide. 100 mm or so would be sufficient.

I have not looked at any of the papers someone have a link to, but I would
imagine one problem would be there's litter airflow in the waveguide,  so
it would be very slow to respond.

Dave
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Re: [time-nuts] Temp/Humidity control systems?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 28 October 2016 at 01:05, Poul-Henning Kamp  wrote:

>The exception is the "cold mirror" type of sensor, which measures the
> >dewpoint by cooling a mirror and bouncing a light off it to sense the
> >temperature where dew condenses on it. Those are expensive, and they
> >require maintenance to keep the mirror clean.
>
> And they are comparatively slow, last I saw one it could only do
> a measurement every second minute.
>

I was just reading the Keysight forum on VNAs. Someone was having issues
measuring a bit of waveguide 80 m long. Dr. Joel Dunsmore pointed out that
humidity has an effect in waveguide.

I'm guessing this is due to the change in permittivity in the air, which
would be most noticeable near the cutoff frequency of the waveguide. That
should change the magnitude of the reflection, not just the phase, so it
might be a relatively cheap way to measure humidity.

Just thinking aloud. I'm probably talking rubbish.

Dave
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Re: [time-nuts] Has anybody checked this? GPSDO in kit

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 October 2016 at 17:22, Chris Albertson 
wrote:

>
> You have to remember what this thing replaces.   In ham radio, some people
> are using vacuum tube oscillators with mechanical variable capacitor
> tuning.  Maybe some advanced rigs use gear drive on the capacitor shaft to
> allow more exact tuning  This Si chip is considerably better then 1940's
> technology.
>


Well, as someone else pointed out, hams are not using this sort of thing
now - or at least not in any significant numbers.

I recently bought a "new" 2 m transceiver - which is actually a 40 year old
Yaesu FT-225RD. When fitted with a Mutek front end (GW4DGU), they were
arguably the best 2 m transceiver ever made.

Mine drifts quite a bit, and I need to look into why. It can be two things

* Crystal - 100 and odd MHz
* VFO  - around 8 MHz

I heard of someone replacing the VFO with a cheap Chinese DDS as an
"upgrade". Actually, I suspect it was probably a downgrade, as I would
expect the VFO to be a lot cleaner.

I've not taken it apart to fix mine, but from what I have read, it would
appear the crystal is the main source of drift, and not the VFO. A
frequency counter will soon determine if that's the case in mine.

Dave
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Re: [time-nuts] Prologix USB-GPIB Controller

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 10 October 2016 at 09:35, Charles Steinmetz 
wrote:

> Poul-Henning wrote:
>
> And for voltage references, "pre-owned" is likely to mean "better".
>>
>
> Perhaps, but third-world recyclers are not known for gentle treatment
> during the parts removal process.


I had some cheap ($10) GPS receiver boards shipped to me in a plastic
kitchen bag from yikunhk on eBay. 4 boards in the same bag, all scratching
each other. The bag was not anti-static.

There are all number of possible explanations of why boards can be made so
cheaply, when the ICs appear to cost more than the boards.

* The chips are counterfeit
* The chips are similar to what they are supposed to be, but have been
relabeled.
* They are made at the same factory as the real devices, on what I've heard
described as the "ghost shift", where they are not officially made, but are
the same devices.
* They are recycled.
* They are stolen.

It is anyone's guess once you start buying semiconductor devices from eBay.
Maybe you are lucky, maybe you are not.

You dramatically increase the probability a part is good if sourced from a
reputable source (e.g. RS or Farnell in the UK). That is not to say that
the parts are not counterfeits, as even the best suppliers can get caught,
but they are more likely to be ok.

I recently bought a supposedly original Samsung battery for my Samsung
Galazy S3 phone from a local shop. The phone had all sorts of issues with
this battery, so I concluded it was a poor counterfeit.  I thought I'd be
safe buying directory from Amazon (not a 3rd party), but on reading reviews
on Amazon, I was not convinced those were genuine Samsung batteries either,
so I did not buy from Amazon.

Eventually I bought a battery from the Samsung website. The phone now works
ok.  I don't know if  Samsung actually make the batteries themselves, but I
think I have a better chance of buying from the Samsung website than from
anywhere else.

I've had "Duracell" batteries leak. At one time I used to blame Duracell,
but now it has cross my mind whether they might have been bought on eBay
and were counterfeits. I can't recall where they were purchased, but now I
will only purchase batteries from sources I consider reputable.

Dave.
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Re: [time-nuts] Prologix USB-GPIB Controller

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 8 October 2016 at 02:13, Hal Murray <hmur...@megapathdsl.net> wrote:

> > They get counterfeited a *lot*.
>
> Is that true for relatively obscure things like the Prologix GPIB
> controllers
> that aren't high volume?
>

I would have thought the Prologix GPIB controllers no more obscure than the
NI GBPIB-USB controllers, but the NI ones from China have definitely been
counterfeited. There was a report here, the HP list or similar where the
latest National Instruments software reported the GPIB-USB adapters were
counterfeit! The eBay seller said send it back, and the buyer got a refund.
(Personally I would have not sent it back, and still got a refund.)

There was some even more obscure Analog devices chips that were marked as
something else - see the UK microwave list for the details reported by Andy
Talbot.

There was a design published in the latest RadCom (RSGB publication) of a
voltage reference. The sort of thing volt-nuts would make, although not
such high quality as the LTZ1000 chips. The author said it was cheaper to
buy a complete voltage reference board, than the chip. When I looked on
eBay, the board was £2.25 delivered from China. The Analog Devices website
shows the chip having a budgetary price of $7 in quantities of 1000 or
more. So if the chips are $7 (£5-£6), how can they make a complete board,
and pay the postage from China for £2.25? It seems to me highly likely
those voltage reference chips are counterfeit. If not counterfeit, they are
hardly legal devices.

Like Bob Camp said, it is better to pay more money and get a genuine
product.

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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[time-nuts] What's the best Windows 10 ntp client?

[Dr. David Kirkby]

At my amateur radio club we have Internet access via a WiFi dongle with a Pay 
As You Go card. A Windows 10 PC is only powered up while we are there, so on 
around 2-4 hours per week. 

Does anyone have any thoughts on what might be the most suitable software to 
run on our Windows 10 PC to set the time correct? 

Someone installed "Dimension 4" 

http://www.thinkman.com/dimension4/

As far as I can see, this takes the time from one single NTP server, which I 
believe is not a good idea.  However,  given we only run the PC on 2-4 hours 
per week,  maybe no ntp client will work well,  but I would have thought using 
multiple servers being better than one. 

I am wondering if anyone has any better suggestions for software. .

Dave.
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Re: [time-nuts] Anybody want a Thunderbolt power supply?

[Dr. David Kirkby]

 Original message 
From: Charles Steinmetz 
Date:09/01/2016 06:07 (GMT+00:00) 
To: time-nuts@febo.com 
Subject: Re: [time-nuts] Anybody want a Thunderbolt power supply? 

Randall wrote:



> Tested and guaranteed samples of all of these can be bought for $25-100 
if you are patient (pay no attention to the loonies who list them for 
$250-350).

The problem on eBay is "tested" means something quite different to what I know 
as "tested'. 

> There are two potential disadvantages.  The first is size (particularly 
WRT the Power Designs units -- the HPs are much smaller).  The second is 
their adjustability.  You would not want to brush against one of the 
voltage-setting knobs accidentally and send your Tbolt to GPS heaven. 
The cure for this is a small dab of RTV on each knob.  

There are a number of HP power supplies that have over voltage trips.  You. can 
program them to switch on with an output voltage of V1 and a trip of V2, where 
V2 > V1. So even if you accidentally turn the knob and increase the voltage, no 
damage will occur as the PSU voltage drops to zrro. 

The above said, I set up an HP 6674A  option J02 (70 V, 30 A, 2100 W) supply to 
switch on at 13.8 V. Setting the trip at anything less than 14.1 V (from 
memory), meant it would trip at startup. If one wanted it to trip at 13.85 V, 
one would need to set the voltage lower,  then slowly increase to 13.8 V.

I have a number of HP/Agilent PSUs, and they all have over voltage trips. None 
of the PSUs I have are their "precision" ones.

The units I have do I believe have a local lockout facility which can be 
programmed by GPIB. 


Dave
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Re: [time-nuts] negative mention of products (was: DIY VNA design)

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 August 2016 at 23:15, Attila Kinali <att...@kinali.ch> wrote:

> On Mon, 22 Aug 2016 16:16:16 +0100
> "Dr. David Kirkby (Kirkby Microwave Ltd)" <drkir...@kirkbymicrowave.co.uk>
> wrote:
>
> > That resulted in the manufacturer of the RigExpert contacting Tom, as
> they
> > were unhappy about my comments. (Strangely they never contacted me!) I
> > received a phone call from Jan, the UK distributor about it. Basically
> they
> > did not want to get into a war with other companies like RigExpert. I can
> > see that discussions about VNAs in general could lead to discussions
> > comparing products.
>
> Yes, lots of companies do get very unhappy when they see negative
> mentiones of their product. Quite a few of them also do not get that
> a mailinglist/forum/... is not responsible for what their users write.
> Some even threaten to sue, in case a negative remark is not removed
> IMEDIATELY!!!1!einself
>

Yes. It is interesting to note that one of the reviews by G3GXG on eHam of
the RigExpert AA-600, which is the product I was referring to, says

"I tried sharing my concerns on the RigExpert site but every time I did, my
comments were removed. This is clearly a raw subject for them."

Personally, I write what I think is fair, and if that offends them, let
them try to sue me. But I can understand others not wishing to take the
same view - especially if in the USA. But unfortunately we have a lot of
"no win no fee" lawyers here now in the UK. It is a big "industry". I've
not seen it move to things like technical comments about products, but it
could well happen.

Dave
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Re: [time-nuts] DIY VNA design

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 22 August 2016 at 02:51, bownes <bow...@gmail.com> wrote:

>
> Comment inline
>
>
> > On Aug 21, 2016, at 18:59, Dr. David Kirkby (Kirkby Microwave Ltd) <
> drkir...@kirkbymicrowave.co.uk> wrote:
> >
> > I am not convinced that this is time-nuts related,  although I am sure
> many
> > time-nuts either have a VNA or would like one. Such a project needs its
> own
> > forum.
> >
>
> v...@yahoogroups.com would be the place.
>

I doubt it would be, although one should ask Tom Baier. I don't suppose he
would mind some discussion, but the topic of VNA design is so large and
complex that it could generate a huge volume of messages, which are way
outside the scope of the VNWA group.

I do know of another possible reason he might be a bit reluctant too. I
made a post on there once about the fact I had measured the N connector on
a brand new competitive product (RigExpert AA-600) and found it was out of
spec - photos at

http://www.dhars.org.uk/RigExpert-AA-600/

That resulted in the manufacturer of the RigExpert contacting Tom, as they
were unhappy about my comments. (Strangely they never contacted me!) I
received a phone call from Jan, the UK distributor about it. Basically they
did not want to get into a war with other companies like RigExpert. I can
see that discussions about VNAs in general could lead to discussions
comparing products.

In some ways it would be good if there was a forum for VNAs, and similar
instruments, which is not tied to any particular manufacturer. I'm not
aware of any. There's the HP/Yahoo list, VNWA and there's the Keysight
forums. Those are all specific to one manufacturer.

There are a number of techniques for measuring impedance, and the VNA is
just one of them. Keysight have no forums for LCR meters or impedance
analyzers, despite they sell the things.


>
> The intersection of HP equipment && Time-Nuts && VNWA mailing lists is >>
> 1 :)
>
>
Yes, very true. I'm certainly one of them, but as you say, it would be >>
1.

Dr. David Kirkby Ph.D CEng MIET
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Althorne, Essex, CM3 6DT,
UK.
Registered in England and Wales, company number 08914892.
http://www.kirkbymicrowave.co.uk/
Tel: 07910 441670 / +44 7910 441670 (0900 to 2100 GMT only please)
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Re: [time-nuts] DIY VNA design

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 21 Aug 2016 03:19, "Attila Kinali"  wrote:
>
> Moin,
>
> I stumbled over a new open hardware/source VNA design:
>
http://hforsten.com/cheap-homemade-30-mhz-6-ghz-vector-network-analyzer.html
>
> Unlike other designs out there, this one is very well done and has very
> little room for improvement, without increasing the price considerably.

I am not convinced that this is time-nuts related,  although I am sure many
time-nuts either have a VNA or would like one. Such a project needs its own
forum.

That said, I don't know why the author is using directional couplers.  A
bridge is much wider bandwidth.  It is more lossy though.

The software is I believe the tricky part. The VNWA software is very
sophisticated, with a lot of useful features like it can design matching
networks,   The software in the PNA-X is very sophisticated too, but in
different ways.

I don't know what the author uses, but Qt seems like best choice to me,
which can be be built on OSX, Linux and Windows.

For many measurements power levelling is not required, so that bit could be
dispensed with.

The author seems of the opinion that a lot of the hardware imperfections
can be corrected in software. Thak is true, but the the residual errors
that remain are a function of the quality of the hardware.

Anyway,  it is an interesting project,  but personally if I were going to
go to the effort of building a 2-port VNA, I would build one with 4
receivers.

Dave
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Re: [time-nuts] HP5370 power supply measurements

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 13 Jul 2016 08:31, "Charles Steinmetz"  wrote:

> An external fan blowing on the heatsink keeps my 5370s nice and cool, for
about $10 each.

So more noise.

> *if the counters were operated 24/7/365*.  I sometimes take data for a
few months straight, but very, very far from 24/7/365 on average.  So for
me, break-even would be more like 50 years.

I don't suppose Poul's main motivation is to reduce his electric bill.

> Speaking of fan noise -- you can't really get away with replacing the
internal fan with one that moves less air, so it is hard to find a
replacement that generates significantly less noise.  If you find one,
please share the make and model -- all 5370 owners would love to know.
>
> Best regards,
>
> Charles

Surely one of the main  advantages of the SMPS route is the higher
efficiently means less cooling air is required.  That means less noise.

I often here of people replacing fans with quiter ones, but I suspect that
all they really do is reduce the airflow. I believe that most of the noise
one hears is the movement of the air.  From what I have read, sleve bearing
fans make a bit less noise than ball bearings fans.  However,  although the
MTBF of both types is similar at 20 degree C, the MTBF of sleve bearing
fans decreases quite a bit with only a modest increase in temperature.

Dave.
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Re: [time-nuts] Visiting Greenwich

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 5 Jul 2016 00:43, "Dave Martindale"  wrote:
>
> I am in London England at the moment, playing tourist with the rest of my
> family.  I want one day to be a visit to the National Maritime Museum at
> Greenwich, which includes the Royal Observatory Greenwich.  I am
> particularly interested in seeing Harrison's H1 through H4, plus other
> high-precision mechanical timekeepers (pendulum clocks, etc).

There's an interesting clock at Cambridge university too:

http://www.corpus.cam.ac.uk/about-us/the-corpus-clock/

you might consider visiting.  Cambridge is not too far from London,  and a
nice place to visit,  especially on a warm sunny day when punting on the
river Cam would be particularly enjoyable.

I am sure that you will visit Big Ben.

The clocks at NPL were open to the public at the recent open day, but will
not generally be open.  But if you tried a personal phone call,  and said
that you were a tourist with a particular interest in precision
timekeeping,  you might be offered the chance to look around.

Dave.
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Re: [time-nuts] Cable length calibration

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 30 June 2016 at 09:19, Scott McGrath  wrote:

> If the nominal velocity of propagation is known and length is known delay
> is easily determined mathematically
>

Except that coax does not have a uniform impedance or velocity factor. Both
will vary as a function of position and frequency. How relevant this is
depends on the accuracy you require, but since it is time-nuts, it is
reasonable to assume that such a simplistic method is not of the standard
expected on time-nuts.

Dave
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Re: [time-nuts] buying a time interval counter

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 29 Jun 2016 17:02, "Stéphane Rey"  wrote:
>
> Hello there,
>
> I'm planning to buy a such instrument in order to do some frequency
stability measurement at work. The SR620 seems to be discontinued.

It still looks available to me
http://www.thinksrs.com/products/SR620.htm

There is also a Keysight 53230A with a slightly better (20 ps vs 25 ps)
single shot resolution.  It looks more modern,  but I don't know how well
they compare.

Dave.
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Re: [time-nuts] Phase noise measurements on the cheap with an Agilent E4406A VSA Transmitter Tester?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 18 June 2016 at 21:01, John Miles  wrote:

> > and looked at what was used to make the phase noise measurements. It was
> an
> > Agilent E4406A. The noise floor is nowhere near as low as the more
> > expensive instruments, but the E4406A is available for under $500, which
> is
> > more than two orders of magnitudes cheaper than an E5052B.
>
> It appears that Leo's using a notch filter to remove the carrier before
> measuring it with the E4406A, so it's not quite a plug-and-play sort of
> measurement.  But yes, the E4406A is a really cool piece of gear given the
> prices they sell for.  It's not meant to be a general-purpose spectrum
> analyzer -- and Agilent went well out of their way to make sure of that --
> but it can still handle many common SA measurement tasks including SSB
> noise.
>

Thank you. In which case it may or may not be better than  the HP 7
series SA I have, consisting of:

* 70004A display,
* 70905A 50 kHz to 22 RF GHz front end
* 70902A (10 Hz to 300 kHz) IF
* 70903A (100 kHz to 3 MHz) IF
* 70310A precision frequency reference.
+ some irrelevant bits.

I was not looking for a general purchase SA, as I have one of them already.



> The plot on that page came from my freeware phase noise app from
> http://www.ke5fx.com/gpib/pn.htm , which is a (very) distant ancestor of
> TimeLab.  The last two FAQ entries at http://www.ke5fx.com/gpib/faq.htm
> offer some hints for suppressed-carrier measurements that can be used with
> the E4406A and other analyzers.  There's nothing special about the E4406A
> with respect to this type of measurement, except that it's an unusually
> cost-effective way to get the job done.
>

I note your software works with the HP 7 too. As I say, I already have
one of them, but was thinking the E4406A would be a worthwhile addition.
But perhaps not in that case. Although maybe it will outperform my 7
system for phase noise measurements. I expect you will know the answer to
that.

BTW, the link to the  "Wenzel Associates, BluePhase 1000 Phase Noise Test
System Operations Manual
 (30
pages, 1.3 MB)" PDF is broken.


> The E5052A/B's most immediate predecessor was probably the HP 4352A/B.
> They were made specifically for VCO and PLL transient analysis and noise
> measurement, and they've been selling in the $1K-$3K


It seems the HP 4352Bs are available for a little under $1000 now, but are
but still twice the price of a E4406A.

neighborhood for several years.  Their measurement floor is better than a
> conventional spectrum analyzer, but still not adequate for "time
> nuts"-class measurements on 10 MHz sources.
>

OK, I will give this idea a miss. I was actually looking to compare 116 MHz
oscillators. but I guess the same principles apply.

Cheers John.


>
> -- john, KE5FX
> Miles Design LLC
>


Dave, G8WRB
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[time-nuts] Phase noise measurements on the cheap with an Agilent E4406A VSA Transmitter Tester?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I was looking at some high end commercial low noise oscillators and see
they use instrument like the Agilent E5052B signal source analyzer for
phase noise measurements. When I looked for them on eBay, it soon because
apparently they were very expensive.

Then I see this oscillator that locks to GPS

http://www.leobodnar.com/shop/index.php?main_page=product_info=107_id=234

and looked at what was used to make the phase noise measurements. It was an
Agilent E4406A. The noise floor is nowhere near as low as the more
expensive instruments, but the E4406A is available for under $500, which is
more than two orders of magnitudes cheaper than an E5052B.

I'm wondering if there are other more suitable commercial instruments
around that don't cost a fortune, yet would allow lower levels of phase
noise to be measured. I tend to preference HP/Agilent kit, as it is better
supported, both by the manufacturer and places like the HP/Agilent Yahoo
group.

Dave
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Re: [time-nuts] How can I generate a very clean 1 W signal @ 116 MHz ?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 30 May 2016 17:01, "Richard (Rick) Karlquist" <rich...@karlquist.com>
wrote:
>
> On 5/30/2016 4:06 AM, Dr. David Kirkby (Kirkby Microwave Ltd) wrote:

>> I'm wondering what's the best way to generate 116 MHz with very low phase
>> noise. Phase noise at < 20 kHz offset is particularly important, but 200
>
> The "best" way is clearly to use a 116 MHz 5th overtone crystal
> oscillator, which can be locked to 10 MHz with no difficulty.
> I designed hundreds of these sorts of things 40 years ago when
> I worked for Zeta Labs.

Please excuse my ignorance,  but how would one lock a 116 MHz 5th overtone
crystal oscillator to 10 MHz with no difficulty?  Do you have a circuit you
share that would give low phase noise, and if so how low?

>From what I have read here before,  amplifiers degrade the phase noise if
driven to near the 1 dB compression point. So would the final amplifier
need to have a 1dB compression point of 33, 36, 40 dBm?

My next problem would be measuring the phase noise, but that's a different
topic for another day.

Dave.
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[time-nuts] How can I generate a very clean 1 W signal @ 116 MHz ?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

I was thinking about designing a 2 m (144-146 MHz) ->HF (28-30 MHz)
transverter, using a 116 MHz local oscillator feeding a level 30 mixer.

116 + 28 = 144
116 + 30 = 146

I'm wondering what's the best way to generate 116 MHz with very low phase
noise. Phase noise at < 20 kHz offset is particularly important, but 200
kHz would be fairly important. Outside that, it does not matter too much.

The ability to lock to 10 MHz would be "nice", but certainly not essential,
as absolute frequency stability would not be of prime importance. Getting
the phase noise as low as possible would be more important. I expect better
performance can be achieved if one forgets about locking the signal source
to something else, but I may be wrong.

An HP 8663A sig gen has <-147 dBc/Hz at 10 kHz offset, but I'd hope its
possible to produce something better than is possible in a commercial sig
gen that covers up to 2.5 GHz.

Dave
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Re: [time-nuts] NPL open day

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 15 May 2016 22:06, "Adrian Godwin" <artgod...@gmail.com> wrote:
>
> In case anyone's in London this week, the NPL have an open day :
>
> http://www.npl.co.uk/openhouse

Thanks for that. I was not aware of it but have noe registeted (which is
essential) and will be going.

Say hello if you see me.

Dr David Kirkby
Managing Director
Kirkby Microwave Ltd
Registered office: Stokes Hall Lodge, Burnham Rd, Chelmsford, Essex, CM3
6DT, United Kingdom
Registered in England and Wales as company number 08914892
http://www.kirkbymicrowave.co.uk/
Tel 07910 441670 / +44 7910 441670 (0900-2100 GMT)
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Re: [time-nuts] Using lasers for data transmission

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 1 May 2016 15:02, "Bruce Griffiths"  wrote:
>
> The solution with high power is to use a beam expander so that the
unaided eye cannot collect a power greater than the safe limit. Using near
IR beams also helps.
> Bruce

It is a long time since I worked with lasers, so my knowledge is both out
of date and my memory not perfect. But I was a long while ago regularly
using and sometimes aligning a picosecond pulsed laser at about 800 nm. The
average output power was 1 W, so a very dangerous class IV laser. It
certainly hurt if one had the beam on ones skin, but it was not
sufficiently powerful to noticeably burn the skin if one did the obvious
thing and moves ones hand away.

But I believe people need to be particularly careful using IR lasers. The
lens in the eye will not focus Iinfra red on the retina,  so that is
probably why you say IR is safer. However one of the protective methods the
eye has is a "blink response". One blinks if one perceives a light source
as bright. Blinking offers some protection to the eye. But since one does
not see an IR laser source, one  does not blink, so IR lasers disable one
of the eyes protective mechanisms.

Hence there are various complications that arrive when discussing laser
safety issues.  I don't have the knowledge to advise on what is or not
safe,  but will warn there are several effects which are important,  and
many people don't realise this.

Laser safety is a nontrivial subject.

Dave.
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Re: [time-nuts] Using lasers for data transmission

[Dr. David Kirkby (Kirkby Microwave Ltd)]

> Hi,
> Several (many?) years ago National Geographic magazine show a picture
taken here in southern California of the state government sending red laser
signals between different mountain tops to keep track what was going on
near fault lines
> There were no technical details on what was taking place.  So it can be
done.
> At a hamfest a few years ago I bought both a red and green 35 mW laser
pen for about $15 each.  They do shine a long, long way.

35 mW is certainly unsafe to the eyes, so be very careful.  There maybe
legal issues about doing this.

> Whether these are powerful enough, or can be properly modulated for what
is needed, I have no idea.

You can pretty much modulate any laser diode. There are two important
currents to know about

* Threshold current I_th - below which it will not lase.
* Maximum operating current I_max - above which the device will be
destroyed.

You can AM modulate them by applying a DC current

I_th + (I_max - I_th)/2.

Then superimpose the modulation which has a peak value of (I_max - I_th)/2.

Those currents ensure that the laser is always lasing,  and gets you
theoretically 100% modulation.  For best lifetime,  run at lower levels of
peak modulation current.

Watch out for transient currents - lasers make transistors look like
antisurge fuses!

For point to point contact you want a beam which diverges as little as
possible.  IIRC the divergence is something like inversely proportion to
the cavity length.  For this reason a diode laser with its short cavity is
not optimal. But of course they are cheap.

A veey long time ago I used to know quite a lot about lasers,  but not
using them for years I realise that I have forgotten an awful lot!

FWIW, at university we had a 10 W argon ion laser. I think it took about 50
kW to produce those 10 W. When it was disposed of, it was sold to a company
that put on light shows.

Dave
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Re: [time-nuts] RG6 or LMR400 for GPS Antenna (Symmetricom 58532A and T-bolt)

[Dr. David Kirkby (Kirkby Microwave Ltd)]

On 21 Apr 2016 01:00, "Bob Camp"  wrote:
>
> Hi
>
> RG-6 Quad Shield should be fine as long as it’s meeting the published
specs. The advantage of LRM-400 is that you likely *know* where it came
from and what the specs are.

There is plenty of coax marked LMR400 that is produced in China and not by
Times Microwave.  Judging by the amount of counterfeit electronic devices
around,  I would nit in the least be surprised if there's stuff around
printed "Times Microwave" that is made in China, but with no relationship
to the company whose name is on it.

Dave.
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