Re: [time-nuts] Time-nut going England!

[John Lofgren]

Seconded.  Did both last August and it was great.  The amount of restored 
hardware that's operational is impressive and docents are knowledgeable.
If you get to the computing museum, having a chat with whoever is in the 
Colossus gallery is worth your time.

Admission to BP is £17.75 and the Computing Museum is £7.50.  Both are well 
worth the admission price plus the train ride.

Cheers,
John

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Clint Jay
Sent: Thursday, April 27, 2017 6:16 AM
To: Discussion of precise time and frequency measurement ; 
Dave B 
Subject: Re: [time-nuts] Time-nut going England!

Yes, Bletchley is a good day out but be aware the national museum of computing 
is a separate entity and has its own entry fee.

On 27 Apr 2017 12:00 pm, "Dave B via time-nuts"  wrote:

> On 26/04/17 17:00, time-nuts-requ...@febo.com wrote:
>
> > Message: 12
> > Date: Wed, 26 Apr 2017 15:05:52 +0200
> > From: Attila Kinali 
> > To: time-nuts@febo.com
> > Subject: [time-nuts] Time-nut going England!
> > Message-ID: <20170426150552.93c33e4cbe356663386bb...@kinali.ch>
> > Content-Type: text/plain; charset=US-ASCII
> >
> > Hi
> >
> > I'll be in the UK for three weeks and will have a "free" week 
> > between 13th and 20th of May. I will most probably be around the 
> > London area and maybe spend a day or two in Southampton.
> >
> > If someone wants to meet for a beer or cup of hot chocolate, or 
> > knows of time-nutty things to do, please let me know.
> >
> > I would also appreciate if someone knows an affordable place to stay 
> > at in London, so that it doesn't strain the purse of this poor 
> > student too much.
> >
> >   Attila Kinali
>
> --
> -- Not exactly "TN" material, but you'd find this an interesting day 
> out.
>
> https://www.bletchleypark.org.uk/
>
> Get an off peak return rail ticket from Euston to Bletchley, it's a 
> short walk from the rail station.
>
> The National museum of computing (and other special interests) are 
> there too.
>
> Else the various museums in London will more than keep you occupied!
>
> Regards.
>
> Dave B, not that far from BP, but no idea what I'll be doing the time 
> you plan to be in the UK. "Domestic Management" has not told me the 
> plans for that far ahead yet!  :)
>
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Re: [time-nuts] End Of The World

[John Lofgren]

 As expected, on the leap second the display on the 8183 showed 6:59:60 (the
 8183-A showed 23:59:60), but the TV400 displayed 7:00:00 at that moment.
 The TV400 remained one second ahead until it displayed 7:00:03 for a two-
 second period, then from 7:00:04 forward it was properly synced.

On the 2012 event my HP 55300A did the same thing on the IRIG output.  The :03 
second was repeated and then normal operation resumed.

I did attempt to view the event on a 3.5 Tomtom GPS, without much joy.  
There's a setup screen that shows all SVs in view as well as the current UTC.  
When it came time to roll from 23:59:59 to 23:59:60 the time line just went 
blank for 1 second, then rolled to 00:00:00.  Their code must be checking for 
'invalid' time.  Bummer ...

-John


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Re: [time-nuts] Better gps antennas than a Symmetricom 58532A

[John Lofgren]

Should I make it a habbit of TDRing my GPS antennas, receivers and 
splitters?

Cheers,
Magnus

I think that question ties into some of the other responses to the original 
post.  The value of doing the TDR measurement would probably depend on your 
cable lengths and how likely you think it is that a connector mismatch would 
cause cable reflections that might smear the GPS signals.

Since you're fortunate enough to have a TDR, it might be interesting to do it 
just to see how much mismatch there really is.  If the resolution of the 
measurement is good enough you should be able to see all of the connectors.  If 
nothing else, it might tell you if you have a bad cable end or a loose 
connection.

Maybe the Italian guys should have run an optical TDR on their timing setup 
before doing the neutrino measurements :)

-John
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Re: [time-nuts] Better gps antennas than a Symmetricom 58532A

[John Lofgren]

 snip 
And it's not clear that there's actually loss due to mismatch.  Most 
antennas/preamps/receivers don't have exactly 50 ohm impedances.  75/50 
is only 1.5:1, and there's an awful lot of antennas and receivers out 
there that only claim 2:1 VSWR.  The usual spec for the antenna is 
1.5:1, so for all you know the Antenna and Receiver is already 75 ohms, 
and RG6 will give you a better match than 50 ohm LMR400.
 snip 

An excellent point.  A similar issue is the connectors.  If you read the data 
sheets for many common connectors and adapters you'll find that a lot of them 
are only rated for a 1.2:1 VSWR.  I ran into this issue a few years ago when 
trying to measure reflection coefficient in a system using TNC connectors.  It 
turned out that the connectors set the VSWR limit, not the test of the 
measuring system.

-John



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Re: [time-nuts] Better gps antennas than a Symmetricom 58532A

[John Lofgren]

Fat fingers.  Replace test with rest.

 snip 
And it's not clear that there's actually loss due to mismatch.  Most 
antennas/preamps/receivers don't have exactly 50 ohm impedances.  75/50 
is only 1.5:1, and there's an awful lot of antennas and receivers out 
there that only claim 2:1 VSWR.  The usual spec for the antenna is 
1.5:1, so for all you know the Antenna and Receiver is already 75 ohms, 
and RG6 will give you a better match than 50 ohm LMR400.
 snip 

An excellent point.  A similar issue is the connectors.  If you read the data 
sheets for many common connectors and adapters you'll find that a lot of them 
are only rated for a 1.2:1 VSWR.  I ran into this issue a few years ago when 
trying to measure reflection coefficient in a system using TNC connectors.  It 
turned out that the connectors set the VSWR limit, not the test of the 
measuring system.

-John



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Re: [time-nuts] Thunderbolt Monitor

[John Lofgren]

I can't help you with the outboard monitor, but I can help with the haywire / 
mouse situation.

Windows thinks that the serial port has a mouse connected because of the 1 / 
second transmissions from the T-Bolt.  At boot time Win looks for serial mice 
and it gets fooled by seeing something active on that COM port.  There was an 
answer about this issue from Nov. 1, 2010.

==
 NOTE:  If you boot Windows with your ThunderBolt connected to the Com 
 port, Windows will think it is a serial mouse and grab the port.  It 
 can lead to some interesting Windows behavior as the T-Bolt outputs 
 data.


 Mike - AA8K

Easy fix. Add the following to your Boot.ini file. Obviously, the x stands 
for the COM port you are using.

NoSerialMice:COMx

Joe Gray
W5JG
==

This didn't always work for me.  Another way to get it to stop using the mouse 
is to boot, let it find the mouse, and then disable it in the Device Manager. 
 After opening Device Manager you'll find a mouse that doesn't belong there 
connected to whatever COM port your serial adapter was assigned.  If you move 
the adapter to a different USB port you'll need to do the process again.

-John



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Major L. McGee III
Sent: Wednesday, January 23, 2013 10:32 AM
To: time-nuts@febo.com
Subject: [time-nuts] Thunderbolt Monitor

I have been following this on the list for a while now and was curious 
if anyone is actively working on a open source monitor.  I see the one 
made by Adam VK4GHZ is no longer being sold.  This got me back on track 
for wanting to make one of my own.

I have been using either tbmon or lady heather but always have issues 
with a usb to serial converter when I start the computer.  It will go 
haywire and cause it to freeze and make the mouse malfunction.  Once I 
disconnect the converter (I have tried other makes as well) it works 
fine.  Usually I can reconnect the converter and things will work again.

What I would like to do is make a 2 or 4 line lcd readout to display 
various info.  I really liked VK4GHZ's page type selector knob.  I can 
see that being very useful.  On a youtube video by n6vmo said the 
thunderbolt used a ASCII Hex and needs to be converted by using 64 bit 
floating point math.

So are any of you currently working on this or have decided to quit and 
have any information to share?


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Re: [time-nuts] HP-53132A Faded and flickering display

[John Lofgren]

Edgardo,

Two possibilities: Cathode poisoning or bad tantalum caps.  I'm not sure if 
cathode poisoning is really the correct term for this effect, but it's 
similar.  There have been a number of tutorials out there about rejuvenating VF 
displays.

The one I have direct experience with is bad caps.  We bought an HP 6612C power 
supply with a bad display for an automated test setup.  It's basically the same 
VF display used in a lot of the instruments from that family.

We didn't really need the display because it was for an automated setup, but I 
wanted to fix it anyway.  When I removed the display board I found that it had 
3 or 4 large tantalum caps on one edge.  One of the caps was toasted a crispy 
brown color instead of the usual yellow.  After replacing that cap the display 
came right back to life and has been working fine for a couple of years, now.

BTW: those display and button boards are a bit of a trick to remove.  They're 
slide in from the side under some L shaped plastic features in the case 
front.  There are instructions in the service manual for dealing with them.

-John


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Edgardo Molina
Sent: Friday, November 02, 2012 11:24 AM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] HP-53132A Faded and flickering display

Dear Group,

Good morning! I just got my first HP-53132A frequency counter and Prologix 
GPIB-USB converter. Now I can do some measurements and I am excited about it.  
Everything looks promising. Condition of the instrument on the outside is like 
new, controls responsive and no fading in lettering at the buttons. Connectors 
are not worn or damaged, original connectors. The unit has been tested and 
works OK, probably not with adequate calibration but that is not an issue now, 
I can always calibrate it later.

What worries me is the display. Even though being an Agilent built unit, it has 
probably more hours on it than a seldom used HP built unit. The flourescent 
display is fading, not all the digits show consistent illumination levels. The 
left-most digits show some flickering at some of their segments. It is readable 
in the end, but I am terribly disappointed about it. 

Does anybody know if there is a cure for this? Or should I start saving for a 
better unit.

I am not afraid of the screwdriver or the soldering iron if someones suggests a 
display overhaul. Thank you!


Regards,



Edgardo Molina
Dirección IPTEL

www.iptel.net.mx

T : 55 55 55202444
M : 04455 20501854

Piensa en Bits SA de CV



Información anexa:




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Re: [time-nuts] HP-53132A Faded and flickering display

[John Lofgren]

- snip -

Two possibilities: Cathode poisoning or bad tantalum caps.  I'm not sure if 
cathode poisoning is really the correct term for this effect, but it's 
similar.  There have been a number of tutorials out there about rejuvenating VF 
displays.

- snip -

It appears that the military parts system has the EL displays listed for 
replacement purposes.
http://www.wbparts.com/rfq/5980-01-396-4645.html
http://www.iso-group.com/Public/PartDetail/CP3033A/12619547/12619547.aspx

Should the display prove to be beyond recovery it might be possible to buy a 
new one.  Now, the cost may be another matter ...

These are made by Noritake-Itron.  The generic part number is CP3033A, but it 
does not show up in their product line on their web site.  It might be worth 
contacting them to see if there's any possibility of still getting them.
http://www.noritake-elec.com/contact_us.htm

Searching for Itron CP3033A turns up some parts brokers that claim to have 
access to 251 of them.

-John


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Re: [time-nuts] GPS receiver testing

[John Lofgren]

Thank you to all of the respondents.  There is a lot of great information in 
the replies.  Based on more interaction with our customer it's looking like we 
may need to send the unit(s) out to a facility that specializes in this area.

Best regards,

John




-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Jim Lux
Sent: Wednesday, October 31, 2012 8:39 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPS receiver testing


 Hello  Said,

 I'm familiar with your postings on the Time Nuts list, so I  thought I'd
 ask your advice.  I searched the Time Nuts archive, but  didn't come up with
 what I was looking for (reference to a good GPS  tutotial).

 We have a GPS project in-house that requires us to  characterize receiver
 module performance.  We have a Litepoint IQ-Nav box  with several stored
 scenarios, but no other signal generators with GPS  personalities in them.  We
 need to measure position accuracy and time  accuracy.  We may also need to
 get some characterization of the 1 PPS  output.


There's folks at JPL who do this kind of thing all the time.. I'll ask 
who you should contact..  It kind of matters on what you're testing for, 
but I'm sure there's someone who can point you in the right direction.

Jim


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Re: [time-nuts] GPS receiver testing

[John Lofgren]

Thank you very much for the thorough reply.

Best Regards,
John

From: saidj...@aol.com [mailto:saidj...@aol.com]
Sent: Wednesday, October 31, 2012 3:17 PM
To: John Lofgren; time-nuts@febo.com
Subject: Re: GPS receiver testing

John,

thanks for your email, I am replying to Time Nuts as well as there is a lot of 
knowledgeable folks here that can help.

In terms of a GPSDO tutorial, take a look at the HP papers linked on the JLT 
website under the Links Of Interest and Related Whitepaper sections:

  http://www.jackson-labs.com/index.php/support

In terms of how to measure the 1PPS accuracy and how to set up the equipment, 
see the paper labeled Critical evaluation of the Motorola M12+ receiver on 
that page. Explains how to set up the Agilent counter I mention below.

There is a lot of threads in the time nuts archives discussing the pro's and 
con's of different equipment, but let me give you a quick guide to what worked 
well for me:

For 1PPS measurements and frequency stability down to the ~2E-010 level per 
second you can get a low-costAgilent 53132A counter.

In order to check GPS position accuracy, you may want to get a timing GPS 
receiver that can do position-averaging using Auto Survey features. Such as the 
Trimble Thunderbolts, the JLT Mini-JLT GPSDO, or the HP58503A units. The JLT 
unit is the only unit using WAAS augmentation, so it probably has a much 
quicker and more accurate position indication than the other units mentioned. 
Let it average the position of your antenna for a day or two, and you will 
likely have an accuracy at the centimeter level (horizontal) and at the foot 
level vertical. Beware of different GPS datums, e.g. MSL versus GPS height 
indications etc.

You can use those GPSDO as a reference for your counter as well.

The above equipment can be had with a couple of days shipping time from Ebay, 
at around $1500 to $2000 totaland will serve you well for a very long time, and 
the resolution of the counter (150ps) is likely much higher than the GPS 
sawtooth error from the GPS you mentioned.

If you need much more accuracy and resolution, get a Wavecrest DTS time 
interval analyzer from Ebay for around $800, those have picosecond averaged 
noise floors, femtosecond hardware resolution, and 10ps single shot resolution.

In order to measure the 1PPS stability and accuracy, you would input the GPSDO 
reference 1PPS and your GPS 1PPS into the counter, and set it to T1 to T2 time 
interval measurement can capture that data. You may or may not use an external 
10MHz reference for the counter doing this measurement, it shouldn'tmake a 
difference to your results.Then download Ulrich Bangerts excellent freeware 
Plotter program to do the time-stability analysis (search Google for Bangert 
Plotter and you will find his website).

Please note that you may or may not want to use the GPS receiver sawtooth 
correction data on your dataset, either manually (using Excel to subtract the 
offset error), viaa delay line, or other mechanism in your system. It will make 
a significant difference in your stability.

To measure frequency, feed the GPSDO reference into the ref-in port of the 
counter, your DUTto the A input, then use the offset feature to remove the 
carrier frequency, then capture the frequency offset of your source to a file, 
and again use Ulrich's plotter to give you the time-stability info etc.

Be warned, once you start on above path, you are likely never to stop searching 
for the holy grailof references, and measurement equipment..

Hope that helps,
Said



In a message dated 10/31/2012 12:36:55 Pacific Daylight Time, jlofg...@lsr.com 
writes:
Hello Said,

I'm familiar with your postings on the Time Nuts list, so I thought I'd ask 
your advice.  I searched the Time Nuts archive, but didn't come up with what I 
was looking for (reference to a good GPS tutotial).

We have a GPS project in-house that requires us to characterize receiver module 
performance.  We have a Litepoint IQ-Nav box with several stored scenarios, but 
no other signal generators with GPS personalities in them.  We need to measure 
position accuracy and time accuracy.  We may also need to get some 
characterization of the 1 PPS output.

I know that you do these types of measurements frequently.  Could you point me 
to a good reference on correctly performing these tests and, maybe, describe 
the equipment you are using?  We're checking through Agilent and RS 
application papers, but you seem to have a lot of the required knowledge 
readily available.

Any help you could provide would be appreciated.


Best regards,

John

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Re: [time-nuts] GPS Jammer

[John Lofgren]

The 0.5 W and + 10 dBm numbers in the specs don't work out.  +10 dBm is 10 mW.  
I suspect that the 1/2 watt is really the DC input power.

And, I'd agree about the range.  +10 dBm into a dipole at 10 meters gets you 
about -44 dBm at the receiver antenna in a free-space model.  That's really 
loud compared to the nominal -130 to -140 dBm you'd hear from the satellites.

-John

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Magnus Danielson
Sent: Tuesday, October 02, 2012 4:02 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] GPS Jammer

On 10/02/2012 10:43 PM, J. Forster wrote:
 Take a look at the specs of this unit:

 http://www.mobilephonejammer.com.au/covert-gps-jammer-portable-p-119.html

 The Power Output is 0.5 Watts and it claims a jamming range of 1-10 Meters.

 Anybody think there is something wrong?

For a 500 mW jammer your jamming range should be much better. That's wrong.

Cheers,
Magnus

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Re: [time-nuts] Hi Power LED Light power supply...

[John Lofgren]

snip
I would hence believe that a 50 Hz flicker must be pretty close to the edge of 
what can be perceived, so I'm having trouble believing that a flicker at more 
than twice that rate would be perceptible at all by anyone.
snip

Oh, but it is.  A couple of years ago I bought one of the Chinese 30 LED spot 
light bulbs for about $8 on ebay.  I thought I'd give it a try for a workbench 
light.  When I plugged it in at work (60 Hz power, here) the two guys standing 
behind me yelled gaahhh at the same time I did.  The flicker was horrendous.  
The earlier comment about peripheral vision also applies, though.  It's worse 
in the periphery than in direct view.

The power supply is nothing more than a bridge rectifier, two current 
limiting resistors, and a filter capacitor.  The capacitor obviously wasn't big 
enough, though, because it flcikered plenty.


-John




-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Dennis Ferguson
Sent: Tuesday, September 18, 2012 1:52 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Hi Power LED Light power supply...


On 18 Sep, 2012, at 12:42 , Chris Albertson wrote:
 On Tue, Sep 18, 2012 at 5:21 AM, Bob Camp li...@rtty.us wrote:
 Hi
 
 I suspect those same 120Hz sensitive people would not be able to watch TV or
 a movie :)
 
 In the old CRT type TV sets, the phosphor has some persistence.
 Movies are modulated with a square waves, the frame blinks off and
 goes dark then blinks on.   But the LED's brightness is fast enough to
 track the sine wave and would be bright only for an instant with quick
 pulses of light.

Just to add to this...

Ontario, Canada originally ran its power grid at 25 Hz.  When they
switched the grid to 60 Hz in the 1930's some of the industrial power
users, particularly in northern Ontario where private (usually
hydroelectric) power generators were common, never got around to changing
their plants over.  Mine and paper mills using 25 Hz power were common as
recently as the 1980's, and might still be there for all I know.

Standard incandescent light bulbs don't have a lot of persistence when
run on 25 Hz power (I assume there might have been a time when you could
buy incandescent bulbs designed for 25 Hz, but not in my lifetime).  They
don't go entirely off, but they get significantly dimmer in the visible
spectrum in the dips as the output red-shifts towards the infrared; they
follow the sine pretty well.  In my teens, when visiting a place using
25 Hz power for lighting, I could initially see an incredibly annoying
flicker when I first got there but after a minute or two this would fade
and I'd no longer notice it.  Some other people would also see the flicker
but others, including my parents, couldn't see it at all so there seemed
to be variation (maybe age-related, maybe not) among individual abilities
to see this.


Dennis Ferguson
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Re: [time-nuts] RE; New Wrist watch

[John Lofgren]

Unfortunately I don't have that article, anymore, but I remember the basics 
from it.  The author used one of the Radio Shack piezo sounder elements as the 
pickup.  It was one of the 3 wire styles designed for an external oscillator 
circuit.  I think it might have been around 1 cm diameter.

The part I can't remember is the amplifier.  It could have been a PLL or may 
have just been a high gain video amplifier, like the MC1350.

Anyway, if somebody wants to look for the article it was somewhere in the 1985 
to 1995 timeframe.

There are also commercial tools from Horotec and others built for this purpose. 
 Just google watch tester and you'll find a host of products.

-John




-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Robert LaJeunesse
Sent: Wednesday, September 12, 2012 7:49 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] RE; New Wrist watch

If I recall correctly it was in RF Design magazine many years ago that a 
short article included a schematic for using an ultrasonic sensor and selective 
amplifier (narrowband PLL?) to pick up the 32KHz vibration and convert it to a 
measurable signal. I'd expect a normal microphone to pick up way too much 
extraneous noise such that the 32KHz could not be successfully recovered.
 
Bob L.



From: Azelio Boriani azelio.bori...@screen.it

Interesting: trying to hear a low frequency crystal using a microphone...
it should be hard: the crystal has to make the case vibrate and this is
energy consuming (unless it resonates). I don't expect to pick up nothing,
except the step motor driving the hands.

On Wed, Sep 12, 2012 at 9:45 AM, Hal Murray hmur...@megapathdsl.net wrote:

 Has anybody listened to such a watch?  (with a microphone)

 Can you hear both the 32KHz basic timekeeping as well as the tick when
 the
 second hand takes a step?
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Re: [time-nuts] time-nuts Digest, Vol 95, Issue 74

[John Lofgren]

Yes, Adam, you're correct.  In RF board layouts it's usually good practice to 
not allow ground fill under most components on the copper layer where the 
component is mounted.  Some specific exceptions exist for filters, amplifiers, 
etc. where the copper is needed for lowering the ground impedance or increasing 
thermal flow.

In the specific case with the crystal filters the ground was also opened up in 
the layers below the inductors.  It was either a 4 or 6 layer board and we made 
a rectangular cutout in the fill on the RF ground layer and power layer below 
each inductor.  The bottom layer ground fill was left intact.

Part of the issue with the board we were updating was that the RF ground layer 
was very close to the top component layer.  The whole board thickness was 
something less than the usual 0.062 and the height from the top to RF ground 
was something like 0.008.  In this case there's pretty strong coupling from 
the inductors into the ground.  On a 2 sided 0.062 board it's probably less of 
an issue.

The second part of the issue was the inductor type.  These were wirewound 
inductors with values in the mH range.  Their external field (and stray 
coupling) will be different than a nH range ceramic multilayer part.

As always, YMMV.  Each case will be a little different depending on frequency, 
component construction, and board stack.

-John


-Original Message-
From: Adam [mailto:ab...@gmx.com] 
Sent: Friday, June 22, 2012 10:04 AM
To: time-nuts@febo.com
Cc: John Lofgren
Subject: Re: time-nuts Digest, Vol 95, Issue 74

I'm learning a bunch here about filters and pcb techniques. Got one
question that I'm hoping somebody could help me out with:
 Date: Thu, 21 Jun 2012 13:39:01 +
 From: John Lofgren jlofg...@lsr.com

 One thing we have found that helps, though, is voiding the ground underneath 
 the inductor. 
I did some searching on Google, and found the term voiding the ground
with regard to pcb's, but I couldn't find anywhere that actually said
what that meant. Is it getting rid of the copper under the component?
Does that apply to both sides of a double sided pcb? Anybody willing to
help a newbie?

Inquiring minds . . . .

thanks,

--adam, wh6m

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Re: [time-nuts] 10 MHz low pass filter

[John Lofgren]

The inductors used in this board look like multilayer ceramic chip types.  They 
actually have a fairly low stray field around them and they're wound around 
an axis that's perpendicular to the PCB.  Most of the solenoidal coupling will 
be in the axis normal to the board.  While rotating inductors relative to each 
other is a good general practice it doesn't help much in this instance.

One thing we have found that helps, though, is voiding the ground underneath 
the inductor.  In filters where you're trying to get more than about 40 dB of 
rejection it's possible to have coupling through induced ground currents that 
will just end up bypassing the filter by coupling from one stage to the next.  
We had a case in the past where we were fixing a customer design that used a 2 
stage crystal filter.  The filter nulls were off by something like 20 dB from 
the data sheets and the measured data from the filter vendor.  Standing the 
in/out matching inductors up vertically and wiring them back down to the board 
made the response look like it should.  Voiding the ground under the inductors 
on the next board spin fixed the problem.

Self inductance and self resonance of the capacitors is always something to 
watch out for.  The general rule of thumb we use for generic NPO multilayer 
chip capacitors is an inductance on the order of 1.0 to 1.3 nH for 0402 or 0603 
size parts.  The better RF specific parts from MuRata, ATC, and Johanson will 
have lower inductance and higher SRF.  Typically a good bypass capacitor for 
900 MHz is 18 to 22 pF and for 2.4 GHz it's 6.8 or 8.2 pF.  At 10 Mhz and the 
first few harmonics values on the order of 1 to 20 nF would be below SRF.

-John



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Thomas S. Knutsen
Sent: Wednesday, June 20, 2012 6:57 PM
To: li...@lazygranch.com
Cc: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 10 MHz low pass filter

I don't have any problems with rotating the inductors, after all, that is
one of the best way to avoid coupling between them, but the main problem as
I see with that board is that there are 2 caps that would become an series
resonance with the inductance in the via to reach the ground plane.

Of course, at 10MHz this is just theoretical, since the problem most
probably would appear above 500MHz, and the 50'th harmonic of an OXCO
should be low.

My experience says that the inductance in the capacitor it self should be
low, specialy if NP0 or such capacitors caps are used.

An 10MHz sallen key lowpass may be interesting to build,and with the GHz
bandwith op-amps avaible today, it should work great.

Thomas.

2012/6/21 li...@lazygranch.com

 **
 In the days when I had access to a network analyzer with a chip component
 fixture (all calibrated of course), I tested components on hand just to see
 how ideal they were. Chip resistors are quite good. The inductance is
 basically the electrical length of the device. Caps can be decent. My
 recollection is Johanson had some really good (low parasitic) caps.
 Inductors basically suck.

 You will note in most RF board design with lumped elements, they rotate
 adjacent inductors to reduce mutual inductance.

 10MHz is probably too low in frequency for practical stripline. You could
 probably do active filters these days, but the power budget would not be
 trivial.

 --
 *From: * Thomas S. Knutsen la3...@gmail.com
 *Date: *Thu, 21 Jun 2012 01:17:02 +0200
 *To: *li...@lazygranch.com; Discussion of precise time and frequency
 measurementtime-nuts@febo.com
 *Subject: *Re: [time-nuts] 10 MHz low pass filter

 Based on that PCB, I want to see an sweep to at least 1GHz.
 The reason is that experience have shown that the inductance (perhaps
 10nH) in series with C2 and C6 would damage the stop-band rejection at UHF.

 Used with an OXCO this would not matter, but the desire to make the
 ultimate filter is still there.

 Thomas.

 2012/6/21 li...@lazygranch.com

 If the output is buffered, there really shouldn't be a problem.

 Incidentally, I can crank out high order LCR filters all day just by
 transforming prototypes out of Zverev. But it has been my experience at
 even 10MHz the parasitics of the elements will throw off the design.


 -Original Message-
 From: Bob Camp li...@rtty.us
 Sender: time-nuts-boun...@febo.com
 Date: Wed, 20 Jun 2012 17:49:37
 To: Discussion of precise time and frequency measurement
 time-nuts@febo.com
 Reply-To: Discussion of precise time and frequency measurement
time-nuts@febo.com
 Subject: Re: [time-nuts] 10 MHz low pass filter

 Hi

 That's a pretty high order filter. The output of most OCXO's already has
 a filter on it. Combining two filters (especially high order ones) without
 isolation between them is not a good idea. The resulting transfer function
 will not be what you expect it to be

 Bob

 On Jun 20, 2012, at 4:54 PM, Joseph 

Re: [time-nuts] wwvb weak on east coast especially when the pre-amps under water.

[John Lofgren]

This place has them, plus some other stuff that may be of interest to RF types 
building outdoor devices:
http://www.sealingdevices.com/products/gore-vents

Unfortunately it looks like you need to ask for a quote, so they may not be 
open to small orders.

Also, McMaster Carr has an assortment of non-Gore breathers using porous bronze 
or stainless:
http://www.mcmaster.com/#breather-vents/=hjnav7
Click on the Breather Vents in the upper left.



-John


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of George Dubovsky
Sent: Tuesday, May 15, 2012 7:03 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] wwvb weak on east coast especially when the pre-amps 
under water.

All,

W.L.Gore and Associates makes a whole line of these things, but I'm not
sure where you go to buy just one.

http://www.gore.com/en_xx/products/venting/protective/index.html?xcmp=ijdgpvmktgurl

73,

geo - n4ua



On Tue, May 15, 2012 at 2:59 AM, Attila Kinali att...@kinali.ch wrote:

 On Mon, 14 May 2012 18:01:01 -0400
 Joseph M Gwinn gw...@raytheon.com wrote:

  Modern outdoor enclosures use a filter of some kind, but the underlying
  principle is the same.

 I don't know what other types are around, but we use vents with
 a gore-tex foil over them. Keeps water out but lets the case breath.
 This prevents any pressure build up, which would then start to suck
 watter in from the seal.

 Unfortunately, i'm currently unable to find the maker or the type of
 the vent... If anyone is interested in those, i'll can ask around.

Attila Kinali

 --
 The trouble with you, Shev, is you don't say anything until you've saved
 up a whole truckload of damned heavy brick arguments and then you dump
 them all out and never look at the bleeding body mangled beneath the heap
-- Tirin, The Dispossessed, U. Le Guin

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Re: [time-nuts] Chinese Scopes

[John Lofgren]

One feature of the Agilent and Rohde scopes (maybe Tek, too?) that can help in 
some situations is segmented memory.  It allows you to capture periodic or 
random events with the full sample rate but to ignore all the dead time between 
events.  For each trigger it stores one sweep with a time stamp.  When you want 
to look at the record you can roll back through memory and look at each 
individual event with full resolution.

This isn't a cure-all because the time stamps will have limited resolution and 
some amount of jitter, but it can be helpful in some applications.  It also 
assumes that you know what you're looking for and can trigger on it :)

-John


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Jim Lux
Sent: Tuesday, April 17, 2012 9:27 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Chinese Scopes

On 4/17/12 6:56 AM, shali...@gmail.com wrote:
 I agree that memory depth is an under appreciated parameter, but even 2,500 
 points like what's available on the cheap Tek scopes is quite useful.

 On the other hand, I had a few LeCroy with 50k deep memories and there are 
 cases where that is very useful too. I can't imagine real life use cases when 
 I would need multiple MB. It would be nice to have but seldom used.


oddly enough, I had a case where very deep memory was useful last fall. 
  It was an issue with logic that was switching from one clock source to 
another where the clocks were orders of magnitude different frequency 
(10Hz and 300kHz or something like that), and it was the relative timing 
of the edges that was important, so you needed a bunch of cycles of the 
low frequency clock (i.e. record length of half a second or so), but 
enough samples to see the timing of the 300kHz at the same time.

Another deep memory use was when I used a fast 20GHz sample rate Tek 
scope a few years back (2007) debugging a radar target simulator (for 
the landing radar that's going to be used to land on Mars in August) and 
deep buffers were nice there, because we essentially needed to capture 
multiple pulses that were 4 ns to several microseconds long.   The 
requirement was that the delta phase (and time) of successive pulses be 
within a certain value (the radar used what's known as two pulse 
doppler) following a pre-programmed simulated descent profile.  We also 
wanted the pulse timing after the trigger to be accurate to, as I 
recall, 0.5 or 1 ns.

The PRF is pretty high, so you don't have time to unload the memory in 
between pulses.

So we did something like 500 pulses, captured 16,384 samples at a time 
at 20GS/sec to make a dataset of 16 million samples.

You learn a lot about what's hidden in the specs on inexpensive signal 
generators like the Agilent E4421B when you start comparing phase for 
1600 pulses 1 microsecond apart.

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Re: [time-nuts] 5370B heatsink temperature

[John Lofgren]

Check the archives on this one.  There have been several discussions in the 
past about high heatsink temperatures.  Some users have added external fans to 
them to get the temperature down.

-John


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Eric Garner
Sent: Friday, March 09, 2012 12:09 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] 5370B heatsink temperature

I just acquired my first HP 5370B off of ebay. After I had it running
for 30 min to get it warm and start doing the checkout procedures in
the manual i noticed that the heatsink was REALLY hot. I used my IR
thermometer to check it and it read ~160F(71C). This seems excessively
hot to me. What's normal? i didn't see it in the manual, but I might
have missed it.



-- 
--Eric
_
Eric Garner

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Re: [time-nuts] 5370B heatsink temperature

[John Lofgren]

I believe so.  I don't own a 5370B, but I remember the thread.

What I was thinking of starts here:
http://www.febo.com/pipermail/time-nuts/2010-September/050384.html

Or the complete thread is available here:
http://answerpot.com/showthread.php?1285452-Questions+about+HP+5370B



-John


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Eric Garner
Sent: Friday, March 09, 2012 12:22 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] 5370B heatsink temperature

This is on my HP 5370B time interval counter. it's the external
heatsink by the power inlet.

-eric

On Fri, Mar 9, 2012 at 10:16 AM, Chris Albertson
albertson.ch...@gmail.com wrote:
 On Fri, Mar 9, 2012 at 10:08 AM, Eric Garner garn...@gmail.com wrote:
.. i noticed that the heatsink was REALLY hot. I used my IR
 thermometer to check it and it read ~160F(71C).

 What heat sink?  Did you have the cover off and were measuring the
 internal bar they use as a sink or was your FE5680A screwed down to a
 large aluminum heat sink.     Were all the dozen or so screws in
 place?  Was in making good contact


 --

 Chris Albertson
 Redondo Beach, California

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-- 
--Eric
_
Eric Garner

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Re: [time-nuts] FE5680 missing PPS soln

[John Lofgren]

I did the same thing when I first tested mine.  I mounted the regulator and a 
pair of SMA jacks right to the board it came with using the big board copper as 
the heat sink for the regulator.  I didn't want to build a driver for the LED 
so I wired it directly (with resistor, of course).  Dim and logic low was way 
up at 2.3 volts.

I solved the problem using a high efficiency LED (P/N C503B-RCS-CW0Z0AA1 from 
Digi-Key).  It's running at a bit over half a mA using a 6.2k resistor to the 5 
V supply.  Now the logic low level is at about 700 mV (still a bit high) and 
the PPS output works.  The LED is bright enough to see from way across the lab. 
 The current generation of LED chemistries is really impressive.

-John


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of bob grant
Sent: Thursday, February 02, 2012 2:46 PM
To: time-nuts@febo.com
Subject: [time-nuts] FE5680 missing PPS soln

Some info...

Its tempting to attach an LED to the /LOCK signal on the DB9.
However this signal is very weak and the LED does not seem very bright
and PPS signal does not pulse...Hmm

Internally the /LOCK pin is connected the 74AC240 buffer, but with an
LED helping to keep the signal voltage high (2.3V) a logic low is never
asserted.
This logic low is needed to enable one half of the 74AC240 buffer (pin
1) that gates the PPS signal.

Don't directly drive LEDs from the LOCK signal on the DB9 and, voila,
the PPS signal reappears.

Bob
-- 
  bob grant
  bobgr...@fastmail.fm

-- 
http://www.fastmail.fm - Choose from over 50 domains or use your own


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[time-nuts] Simple Super Ripple Eater

[John Lofgren]

There have been discussions in the past about ways to reduce regulator output 
noise or clean-up oscillator or voltage reference power supplies.  Here's an 
article from Design Ideas in Electronic Design that looks promising.  It has 
pretty decent rejection even at 1 Hz.

http://electronicdesign.com/article/power/Simple-Super-Ripple-Eater-Also-Cleans-Battery-Based-Supply.aspx

Note that the figures don't display properly (at least in Firefox) with 
anything but the embedded links in the text.


- John

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Re: [time-nuts] time-nuts Digest, Vol 89, Issue 51

[John Lofgren]

There's a system that the motorcycle guys call the Whitworth Inch, but I think 
may be more correctly called Whitworth Measure.  It's an old British system 
that was used on their motorcycles and possibly cars, too.  There's a whole 
subculture of people trading in Whitworth tools for BSA and Norton owners.

-John


I've seen two other systems, but their names are eluding me at this time.
Also, I've come across bolts that are not SI, nor SAE. I believe they are
considered a british thread but i'm not certain.

Steve


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Re: [time-nuts] the care and feeding of LPRO's

[John Lofgren]

fortunately, everything in the lab(basement) is on UPSs so in theory
the input voltages to the equipment should be pretty constant and I
was already planning on using a linear supply.

Be careful, there.  Most consumer type UPSs are not line regulators.  When 
there is sufficiently high line voltage they are completely out of the circuit 
and the line voltage is passed through to the output unaffected.  They're 
usually not designed for continuous operation of the inverter circuit.  There 
was a more in-depth discussion of this a while back in a thread about running 
50 / 60 Hz clocks from a locked frequency source.

One possibility, though, would be a ferroresonant line regulator, like a Sola 
transformer.  If you can tolerate the acoustic noise and the high power 
dissipation they will do a somewhat decent job of reducing line fluctuations.  
IIRC the output is also not necessarily a sine wave (depends on the design).


-John


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Re: [time-nuts] Bob Pease

[John Lofgren]

Thank you.

A good friend of mine is a huge Bob Pease fan and also a devout non-wearer of 
seat belts.  He's already used-up one of his nine lives on an accident where he 
wasn't belted-in.

Hopefully this unfortunate reminder will cause him to change his mind about 
belt use.


-John


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Chuck Harris
Sent: Monday, June 20, 2011 9:42 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Bob Pease

One important thing to note is he wasn't wearing his seat belts.

All you old codgers, and immortal young bucks, that think not wearing
seat belts will allow you to fly free and live in an accident need
to take your blinders off and pay attention:  Flying free and living
after an accident only happens in Hollywood.  In the real world,
YOU DIE!

I have lost too many otherwise intelligent friends from this same
idiotic act of insanity.  Most in accidents under 25MPH.  Most within
a couple miles of their homes.  The only one that didn't die had serious
brain damage that left her with a stammer, crutches for life, and took
away her brilliant musical talent.  Several that did die left behind
spouses, and a host of children.  Several were childhood friends, that
were children at the time of their deaths.

Buckle up!  Wear your seat belts!  PLEASE!

-Chuck Harris

Javier Herrero wrote:
 More or less ...

 http://www.amazon.com/How-Drive-into-Accidents-Not/dp/0965564819

 Very sad that two great analog designers had passed away in the same week.

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Re: [time-nuts] Kode TCU 285 info wanted

[John Lofgren]

Hi Paul,

This one isn't a GPSDO, AFAIK.  It looks like a stand-alone tape controller 
that accepts either SLO code or IRIG input.  My main use for it was just as an 
IRIG clock display, but it doesn't seem to want to work like that.

- John

-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of paul swed
Sent: Thursday, May 05, 2011 6:30 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Kode TCU 285 info wanted

A bunch of pre 91 rcvrs used down converters at the antennas. Did you get
the antenna with your unit?

On Thu, May 5, 2011 at 5:50 PM, John Lofgren jlofg...@lsr.com wrote:

 I don't think so.  All of the chips that have date codes I can decipher are
 from late 1984, or earlier.

 I probably should have been more specific, too.  It's a model 285-202/NC
 with a serial number of 011710.


 -John


 -Original Message-
 From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
 Behalf Of paul swed
 Sent: Thursday, May 05, 2011 4:22 PM
 To: Discussion of precise time and frequency measurement
 Subject: Re: [time-nuts] Kode TCU 285 info wanted

 I have nothing. Though recently have gotten a pair of Odetics GPStars
 working with Pete Lancashires (Think thats misspelled) help.
 Can you tell if its newer then 1994?
 Regards

 On Thu, May 5, 2011 at 4:54 PM, John Lofgren jlofg...@lsr.com wrote:

 
  Does anybody have any information available for a Kode (Odetics) model
 285
  Time Code Unit?  I've checked the usual places (google, BAMA, Didier's
 site,
  etc.) and haven't come up with anything.  I see that this question was
 asked
  in 2008 and 2009, also.  Just checking to see if anything new has come to
  light.
 
  Ideally I'd like to find a service manual but a simple operating manual
  would be of some help.
 
 
  Thanks,
 
  John
 
 
 
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[time-nuts] Kode TCU 285 info wanted

[John Lofgren]

Does anybody have any information available for a Kode (Odetics) model 285 Time 
Code Unit?  I've checked the usual places (google, BAMA, Didier's site, etc.) 
and haven't come up with anything.  I see that this question was asked in 2008 
and 2009, also.  Just checking to see if anything new has come to light.

Ideally I'd like to find a service manual but a simple operating manual would 
be of some help.


Thanks,

John



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Re: [time-nuts] Kode TCU 285 info wanted

[John Lofgren]

I don't think so.  All of the chips that have date codes I can decipher are 
from late 1984, or earlier.

I probably should have been more specific, too.  It's a model 285-202/NC with a 
serial number of 011710.


-John


-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of paul swed
Sent: Thursday, May 05, 2011 4:22 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Kode TCU 285 info wanted

I have nothing. Though recently have gotten a pair of Odetics GPStars
working with Pete Lancashires (Think thats misspelled) help.
Can you tell if its newer then 1994?
Regards

On Thu, May 5, 2011 at 4:54 PM, John Lofgren jlofg...@lsr.com wrote:


 Does anybody have any information available for a Kode (Odetics) model 285
 Time Code Unit?  I've checked the usual places (google, BAMA, Didier's site,
 etc.) and haven't come up with anything.  I see that this question was asked
 in 2008 and 2009, also.  Just checking to see if anything new has come to
 light.

 Ideally I'd like to find a service manual but a simple operating manual
 would be of some help.


 Thanks,

 John



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Re: [time-nuts] NMEA reader?

[John Lofgren]

Hi Jim,

Try Serialmon:
http://www.serialmon.com/

It has a NMEA packet decoder built in.


- John



-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Jim Mandaville
Sent: Thursday, January 07, 2010 8:42 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] NMEA reader?

I'm totally new to this semi-DIY gps stuff.  Can anyone recommend any 
NMEA packet reader software that will work on my old Windows 98 
laptop (using data through the RS-232 serial)?.   Searching online I 
find a lot of rather expensive software that does much more than I 
want to do.  Any shareware or cheapware that just gives a window with 
lat, long, time and the usual other stuff?

Jim


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