Re: [time-nuts] Racal 9475 Rubidium

[David C. Partridge]

Most obvious issue - is the Rb "bulb" coated on the inside with a metallic 
deposit - if so it's time to use a heat gun to move it back to where it belongs.

David

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Paul Bicknell
Sent: 01 May 2018 10:19
To: time-nuts@febo.com
Subject: [time-nuts] Racal 9475 Rubidium

Hi all new member hear could any of you help with the following information

 

As I have just bought a Racal 9475 Rubidium and it has problems

 

Is there any stock faults ?

What is the life of the rubidium standard?

 

Regards Paul 

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Re: [time-nuts] Environmental sensor recommendations

[David C. Partridge]

> The OCXO is not the temperature problem with the Tbolt. It is the DAC.

So is there a better one that can be used to replace it?

David

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of ew via 
time-nuts
Sent: 05 April 2018 10:43
To: time-nuts@febo.com
Subject: Re: [time-nuts] Environmental sensor recommendations

I respectfully disagree. The OCXO is not the temperature problem with the 
Tbolt. It is the DAC. Again this is not a product developed for time nuts it 
did an excellent job for its intended purpose. Over a year we worked on the 
Tbolt using HP 10811, OSA 8600, FRK Rb, M100 Rb with excellent Warren support.
Using up to 40 000 seconds and 6 E-17 per uV we probably know more about the 
Tbolt than any time nut. The DAC on the Tbolt is worse than 1 E-10, we have 
experimented with temperature control of the board. As a matter of fact the 
OCXO contributes to a certain amount of temperate stability.
Attila visited Juerg and me on my Europe trip and observed 3 Tbolt's, original, 
8600 and M100 in operation. Tracor 527 showed the jumps of the original.
We plan on using the OCXO's pulled as offset OCXO's on our latest D/M project.
Bert Kehren 
 
In a message dated 4/4/2018 11:46:09 PM Eastern Standard Time, 
hol...@hotmail.com writes:

 
 Lady Heather has a very nice temperature control PID in it (designed by Warren 
Sarkisen). It was originally designed to stabilize the temperature of a 
Thunderbolt GPSDO. The standard Thunderbolt OCXO is rather temperature 
sensitive. 

The standard/simple implementation involves sticking the Thunderbolt in a 
cardboard box with some thermal mass and baffling. Heather then PWMs a fan (at 
1 Hz, using the serial port modem control signals and a DC solid state relay) 
to mix room temperature air into the box. It can control the temperature 
readings to around 0.01C with long term RMS errors in the low microdegree range 
(absolute accuracy depends upon the temp sensor).

---

> I would suggest that if you are looking at taking temperature sensor 
> data
and attempting to control some type of heating/cooling device that you 
implement a PID loop for stability.
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Re: [time-nuts] GPS ANTENNA

[David C. Partridge]

just use a bias tee to feed in the antenna volts :)

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani
Sent: 01 April 2018 23:29
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS ANTENNA

An unusual attenuator with a DC pass.

On Sun, Apr 1, 2018 at 10:21 PM, David C. Partridge 
<david.partri...@perdrix.co.uk> wrote:
> Or use a choke ring survey antenna and an attenuator :)
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob 
> kb8tq
> Sent: 01 April 2018 14:43
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] GPS ANTENNA
>
> Hi
>
> Indeed, it is *very* easy to put to much gain in front of a timing GNSS 
> receiver. These beasts are trying to dig out a signal that you can’t even see 
> with a spectrum analyzer.
> It’s way to far below the noise floor to detect that way. They optimize 
> things pretty tightly to get that done (and to hit a price target ….). Put to 
> much gain in front of them and they get unhappy.
>
> Making this even more crazy, the survey industry standard antenna *does* have 
> a lot of gain. Survey receivers need way more gain in front of them than 
> timing receivers. Put a survey antenna directly on a timing device and 
> trouble will likely be the outcome. Equally, a survey instrument probably 
> will not be happy with a timing receiver.
>
> Why all this nonsense? As far as I can tell, it goes back to how the very 
> early L1 / L2 survey boxes were designed back in the 1980’s and early 1990’s. 
> They made a basic decision to put a lot of gain at the antenna. Motorola came 
> along with their GPS modules later on. They made a *very* different decision 
> about how to distribute the gain. There are very good arguments on both sides 
> for why they did it this way.
> The bottom line is still - you need to match things up …
>
> Bob
>
>> On Apr 1, 2018, at 2:36 AM, cfo <xne...@luna.dyndns.dk> wrote:
>>
>> On Sat, 31 Mar 2018 10:58:19 -0500,
>> donandarline-Re5JQEeQqe8AvxtiuMwx3w
>> wrote:
>>
>>> I found a supplier for high quality GPS antennas at a very 
>>> reasonable price. PCTEL GPSL1-TMG-SPI-40NCB.
>>
>> *** SNIP ***
>>
>> I had one of those on 25m cable, and it worked fine on a Tbolt , 
>> until i got an active antenna splitter that also had some gain.
>> Then i had to replace it w. a 26dB version of same type, else the 
>> "Jackson Lite" was loosing sync.
>>
>> What i mean here, is that you can get too much gain too.
>>
>> Btw: Good price.
>>
>> CFO
>> Denmark
>>
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>
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Re: [time-nuts] GPS ANTENNA

[David C. Partridge]

Or use a choke ring survey antenna and an attenuator :)

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob kb8tq
Sent: 01 April 2018 14:43
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS ANTENNA

Hi

Indeed, it is *very* easy to put to much gain in front of a timing GNSS 
receiver. These beasts are trying to dig out a signal that you can’t even see 
with a spectrum analyzer.
It’s way to far below the noise floor to detect that way. They optimize things 
pretty tightly to get that done (and to hit a price target ….). Put to much 
gain in front of them and they get unhappy. 

Making this even more crazy, the survey industry standard antenna *does* have a 
lot of gain. Survey receivers need way more gain in front of them than timing 
receivers. Put a survey antenna directly on a timing device and trouble will 
likely be the outcome. Equally, a survey instrument probably will not be happy 
with a timing receiver. 

Why all this nonsense? As far as I can tell, it goes back to how the very early 
L1 / L2 survey boxes were designed back in the 1980’s and early 1990’s. They 
made a basic decision to put a lot of gain at the antenna. Motorola came along 
with their GPS modules later on. They made a *very* different decision about 
how to distribute the gain. There are very good arguments on both sides for why 
they did it this way. 
The bottom line is still - you need to match things up …

Bob

> On Apr 1, 2018, at 2:36 AM, cfo  wrote:
> 
> On Sat, 31 Mar 2018 10:58:19 -0500, 
> donandarline-Re5JQEeQqe8AvxtiuMwx3w
> wrote:
> 
>> I found a supplier for high quality GPS antennas at a very reasonable 
>> price. PCTEL GPSL1-TMG-SPI-40NCB.
> 
> *** SNIP ***
> 
> I had one of those on 25m cable, and it worked fine on a Tbolt , until 
> i got an active antenna splitter that also had some gain.
> Then i had to replace it w. a 26dB version of same type, else the 
> "Jackson Lite" was loosing sync.
> 
> What i mean here, is that you can get too much gain too.
> 
> Btw: Good price.
> 
> CFO
> Denmark
> 
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Re: [time-nuts] Setting correct date on Trimble Thunderbolt receiver

[David C. Partridge]

AFAIK you can't set the correct date any more - this is the 1024 week rollover 
problem.

Lady Heather does correct the displayed date, as it knows that the reported 
date is wrong..

David

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
donandarl...@gmail.com
Sent: 26 March 2018 22:18
To: time-nuts@febo.com
Subject: [time-nuts] Setting correct date on Trimble Thunderbolt receiver

Hello all,
I am new to the board and have just received a Trimble Thunderbolt GPS receiver 
today.
All is working correctly except the date shows Aug 10 1998.
How do set the proper date on this?
I am running TBoltMon to access the unit.
Any help would be appreciated.
Thanks,
Don W9BHI
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[time-nuts] 50 ohm drivers

[David C. Partridge]

Brice said:

>. Some fast CMOS devices (esp clock drivers) have an output R close to 50
ohms as they are intended to drive 50 ohm source terminated transmission
lines.

Any in particular that you'd recommend?   I need to drive a 50ohm line and a
single gate inverter doesn't have the grunt to do so ...

Thanks
David




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Re: [time-nuts] LT1016 as a pulse shaper...

[David C. Partridge]

You might consider using MC74VHC1GT14 or MC74VHC1G14 (Schmitt trigger inverting 
buffers) depending on the exact voltage levels.

They are fast (74AC logic fast) single gate devices in SC70 (SOT-353) or 
SOT23-5 case and can drive 25mA output if needed.

I've seen documents saying that using fast logic gates can result in lower 
jitter/phase noise.  Bruce - do you know ?

David

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Ulf Kylenfall 
via time-nuts
Sent: 03 March 2018 17:08
To: Discussion of Precise Time and Frequency Measurement
Subject: [time-nuts] LT1016 as a pulse shaper...

 
Gentlemen,
I have so far been using LT1016 as a pulse shaper and also whenever I needed 
toconvert a sine wave into TTL Logic levels. Some hysteresis and all the 
decouplingand layout precautions as recommended by LT.
Are there any similar or better alternatives out there that could be usedthat 
would provide lower jitter and that are less expenceive?
Ulf Kylenfall
SM6GXV
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[time-nuts] Output impedance of MC74VHC logic?

[David C. Partridge]

Using this to buffer output from an LPRO (74VHC1G14 (Schmitt trigger 3.3V
TTL compatible)), or an Efratom 105243-003 10MHz OCXO with CMS output
(74VHC1GU04 CMOS levels) in a 10MHz mod for the KS-24019 RFTGm-II.

To match well to 50R bandpass I want to add a series resistor to the output
but don't know the output impedance of these single logic gates.

Does anyone know what this is please?

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[time-nuts] Efratom 105243-003 10MHz OCXO

[David C. Partridge]

Does anyone know the specs for the 10MHz output of this?   I'm looking at a
board using it that is terminating it with a 100kOhm resistor to ground.

Yeah I know, probe it with a scope - the catch is that the equipment is
currently well disassembled so I can't do that so easily ...

Is the output of this beast 0-5V square wave?

Dave

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Re: [time-nuts] Furuno GT-8031 breakout board

[David C. Partridge]

Never having opened my TBolt, are the GT-8736 boards of use to replace the 
aging and partly deaf receiver in that? Or for a KS-24019?

Thanks
Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Gregory Maxwell
Sent: 15 February 2018 23:46
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Furuno GT-8031 breakout board

Hi Bob,

If you do a group buy of GT-8736 I'm game for 10.

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Re: [time-nuts] GPS Jamming

[David C. Partridge]

I thank Adrian was being sarcastic :)

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Azelio Boriani
Sent: 29 January 2018 10:00
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS Jamming

Wasn't the selective availability an accuracy degradation system?

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Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

[David C. Partridge]

? RasPi-4? Not released until 2019 AFAIK ...  I have RasPi-3

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David J Taylor 
via time-nuts
Sent: 01 November 2017 16:08
To: time-nuts@febo.com
Subject: Re: [time-nuts] Holdover, RTC for Pi as NTP GPS source

From: Mark Sims

I have an analytical balance that reads down to micrograms.   The weigh 
chamber is surrounded by three layers of IR absorbing glass so that radiated 
body heat does not induce convection currents in the air.   I worked on a 
balance that had nanogram resolution (mostly wishful thinking in that spec). 
It operated in a vacuum.  30 bit mass-to-digital converters are rather finicky 
beasties.

It does not take all that good of a temperature sensor to detect changes in 
room temperature due to body heat (or fetching a beer from the fridge in the 
next room).  You are basically a 100 watt space heater... even larger for the 
more corpulent folks.
==

Temperature is indeed the killer.  My best Raspberry Pis for time-keeping are 
RasPi-1 and RasPi-4, both of which are in an unheated cupboard not exposed to 
sunlight, on the north side of the house with indoor patch GPS antennas.

  http://www.satsignal.eu/mrtg/performance_ntp.php

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk
Twitter: @gm8arv 

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Re: [time-nuts] Trimble Thunderbolt no longer determines the correct date

[David C. Partridge]

> Unfortunately the unit that you have does not allow for a fw update.

Oh well it was worth asking.

Dave


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob kb8tq
Sent: 31 July 2017 17:30
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Trimble Thunderbolt no longer determines the correct 
date

Hi

Trimble, even on supported products, is pretty firm about a service contract 
being in place for updates.
The only exception seems to be security related patches. There have been a lot 
of examples of this over the years ….AFIK, there isn’t even a “public” firmware 
loader for the TBolt. 

Indeed, you might get lucky. 

Bob


> On Jul 31, 2017, at 5:27 AM, David C. Partridge 
> <david.partri...@perdrix.co.uk> wrote:
> 
> I emailed Trimble on the off chance they might have a firmware upgrade.  They 
> sent me an email which covered some units that rolled over in Feb. 2016 for 
> which they say they have no upgrade.
> 
> I sent them all the information on the label stuck to the outside of my TB 
> (one of the group buy set), to see if there's any hope ...
> 
> I'm not optimistic, but if you don't ask, you don't get.
> 
> Cheers
> Dave
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark 
> Sims
> Sent: 30 July 2017 17:18
> To: time-nuts@febo.com
> Subject: [time-nuts] Trimble Thunderbolt no longer determines the 
> correct date
> 
> That does not appear to be the case.   If it did a reset the DAC should have 
> gone to the InitV eeprom setting  of 2.800V,  but instead mine spiked to 
> 0.308V which is not close to the InitV or the last known DAC values.  
> 
> My log file shows the unit did a filter-reinit  followed two seconds later by 
> phase locking the PPS.
> 
> --
> 
>> Or maybe the TBolt reset on rollover and went back to a previously saved DAC 
>> value.
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Re: [time-nuts] Trimble Thunderbolt no longer determines the correct date

[David C. Partridge]

I emailed Trimble on the off chance they might have a firmware upgrade.  They 
sent me an email which covered some units that rolled over in Feb. 2016 for 
which they say they have no upgrade.

I sent them all the information on the label stuck to the outside of my TB (one 
of the group buy set), to see if there's any hope ...

I'm not optimistic, but if you don't ask, you don't get.

Cheers
Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Sims
Sent: 30 July 2017 17:18
To: time-nuts@febo.com
Subject: [time-nuts] Trimble Thunderbolt no longer determines the correct date

That does not appear to be the case.   If it did a reset the DAC should have 
gone to the InitV eeprom setting  of 2.800V,  but instead mine spiked to 0.308V 
which is not close to the InitV or the last known DAC values.  

My log file shows the unit did a filter-reinit  followed two seconds later by 
phase locking the PPS.

--

> Or maybe the TBolt reset on rollover and went back to a previously saved DAC 
> value.
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Re: [time-nuts] unknown GPSDO

[David C. Partridge]

ISTR that you started it with a short time constant to get locked,  and once 
you had lock you would increase the time constant in a few steps to a final 
value of (say) 1000s or so.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Volker Esper
Sent: 18 July 2017 14:15
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] unknown GPSDO

Thanks so far. I will have a look at the docs.

The machine is running well, particularly the OCXO is performing very good when 
free running (without GPS signal). It is stable and its ADEV looks good (2E-10 
at 10s). Not so the overall ADEV (when GPS locked)
(1E-5 at 10s). It seems to not having the right filter time constant what had 
to be much longer. As I understand the documents, the filter constant can be 
programmed and I will experiment whith that this afternoon.

Thank you

Volker

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Re: [time-nuts] Toggle switch wiring for RFTGm-II (KS24019)

[David C. Partridge]

<https://doc.xdevs.com/doc/Lucent/RFTG/software/rftg%20user%20manual%20novem
ber%201996.pdf>

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Alexander
Huemer
Sent: 28 June 2017 21:46
To: time-nuts@febo.com
Subject: Re: [time-nuts] Toggle switch wiring for RFTGm-II (KS24019)

Hi!

On Wed, Jun 28, 2017 at 04:17:20PM +0100, David C. Partridge wrote:
> The Lucent manual refers to a toggle switch in the frame to switch the 
> active module in the RFTGm-II (KS24019) from the Rb to the XO.

Unfortunately I cannot answer your question.
I have one myself though. You are mentioning 'the Lucent manual'.
Where is that manual? I quick skim through the ML archive and a web search
did not bring up anything.

Kind regards,
-Alex OE2AHL

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[time-nuts] Toggle switch wiring for RFTGm-II (KS24019)

[David C. Partridge]

The Lucent manual refers to a toggle switch in the frame to switch the
active module in the RFTGm-II (KS24019) from the Rb to the XO.

I have the complete shelf with both units and currently the Rb is the active
module, and the XO is standby; but sadly there's no switch on the shelf
itself.

Does anyone know how this switch this is connected to the units?

I've not yet found the spare "round-tuits" to build the beta version of LH
the Mark sent me ...

Thanks
Dave

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Re: [time-nuts] Tracor 527A and 10MHz reference input

[David C. Partridge]

I will add the information that my 527A is totally deaf when fed with 10MHz 
sine wave from my t hunderbolt (no 5MHz output from input stage).

D.
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of paul swed
Sent: 25 June 2017 20:36
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Tracor 527A and 10MHz reference input

Dave will guess you are sub sampling the 10 Mhz ref.
Yes it should be 4.7K. Not sure why but old military gear resistors were like 
that. Circa 1942 at least in schematics I have seen.
Regards
Paul
WB8TSL

On Sun, Jun 25, 2017 at 2:25 PM, David C. Partridge < 
david.partri...@perdrix.co.uk> wrote:

> Yes, does indeed look like it should be 4K7!
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David C.
> Partridge
> Sent: 25 June 2017 18:50
> To: 'Discussion of precise time and frequency measurement'
> Subject: [time-nuts] Tracor 527A and 10MHz reference input
>
> A friend says his Tracor 527A works fine with a 10MHz Ref input even 
> though it doesn't have the divide by 2 circuit from the addendum to 
> the 527E manual applied.
>
> I'm puzzled by this - I can't quite see how the reference input 
> circuit can produce a 5MHz output when fed with 10MHz (unless his 
> reference source has a large 5MHz sub-harmonic).
>
> Am I missing something here?
>
> On a related note, the schematic for the divide by 2 circuit in the 
> front of the 527E manual shows a 4R7 resistor from the base of the 
> 2N3904 to ground - this just feels all wrong!!  Has anyone built this 
> and did they change the resistor to (e.g. 47R or 4K7)?
>
> Thanks
> Dave
>
>
>
>
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Re: [time-nuts] Tracor 527A and 10MHz reference input

[David C. Partridge]

Yes, does indeed look like it should be 4K7!

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 25 June 2017 18:50
To: 'Discussion of precise time and frequency measurement'
Subject: [time-nuts] Tracor 527A and 10MHz reference input

A friend says his Tracor 527A works fine with a 10MHz Ref input even though it 
doesn't have the divide by 2 circuit from the addendum to the 527E manual 
applied.

I'm puzzled by this - I can't quite see how the reference input circuit can 
produce a 5MHz output when fed with 10MHz (unless his reference source has a 
large 5MHz sub-harmonic).

Am I missing something here?

On a related note, the schematic for the divide by 2 circuit in the front of 
the 527E manual shows a 4R7 resistor from the base of the 2N3904 to ground - 
this just feels all wrong!!  Has anyone built this and did they change the 
resistor to (e.g. 47R or 4K7)?

Thanks
Dave




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[time-nuts] Tracor 527A and 10MHz reference input

[David C. Partridge]

A friend says his Tracor 527A works fine with a 10MHz Ref input even though
it doesn't have the divide by 2 circuit from the addendum to the 527E manual
applied.

I'm puzzled by this - I can't quite see how the reference input circuit can
produce a 5MHz output when fed with 10MHz (unless his reference source has a
large 5MHz sub-harmonic).

Am I missing something here?

On a related note, the schematic for the divide by 2 circuit in the front of
the 527E manual shows a 4R7 resistor from the base of the 2N3904 to ground -
this just feels all wrong!!  Has anyone built this and did they change the
resistor to (e.g. 47R or 4K7)?

Thanks
Dave




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Re: [time-nuts] CRT for Tracor 527A

[David C. Partridge]

My message to Dan Rea are bouncing, so please forgive the BW:

Dan,

Hang fire please - I just got this baby hooked up and there's been some 
creative wire cutting done.

The supplies for the CRT have been cut at the trafo.

It needs lots of TLC as its not actually working right now - fun ahead.

If I can get the basic function working then I'll get back to you about the 
tube.

PS Sympathies for the chemo BTW, Mary (my better half) has been there twice  ...

Dave

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Re: [time-nuts] KS24019 units PSU requirements

[David C. Partridge]

Thanks, I ordered a 24V 120W power brick from eBay.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Sims
Sent: 21 June 2017 16:19
To: time-nuts@febo.com
Subject: [time-nuts] KS24019 units PSU requirements

I have not measured mine,  but I saw a spec of 2A max for each side mentioned 
somewhere (would drop considerably after warmup).  I am using a 24V 100W supply 
that came with my Z3811/Z3812 Lucent boxes.  It was already wired up with the 
proper connectors for the boxes.

--

> I  have a pair of L108 (RFTGm-II-Rb) and L109 (RFTGM-II-XO). 
What current do these bad boys draw so I don't get too skinny a 24V PSU?
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Re: [time-nuts] GPS splitter

[David C. Partridge]

Hi Magnus - what sort of inductor value did you use?  68nH or so?

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 17 June 2017 15:12
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] GPS splitter

Hi,

At one time I had to design a DC-load since the GPSDO did not experience enough 
antenna current due to a different antenna being used. So, a BNC-T was quickly 
converted with a SMD inductor and resistor to add 150 Ohm of more load, and 
that helped the telecom operator to get their GPS out of "no GPS antenna" 
warning and actually accept the GPS satellites it was already detecting fine.

Cheers,
Magnus

On 06/17/2017 02:40 PM, Bob kb8tq wrote:
> Hi
>
> The DC block requirement depends a lot on the design of the GPSDO’s 
> you are using. With some GPSDO’s a 50 ohm load on the eighth port of a 
> splitter will do a pretty good job of “antenna detect” signaling. In 
> the more general case of “I didn’t design this beast” dc blocks and dc shunts 
> to ground is the best approach.
> This fairly quickly gets you headed in the direction of the HP / 
> Symmetricom splitters.
>
> Bob
>
>
>
>> On Jun 16, 2017, at 11:54 PM, Clay Autery  wrote:
>>
>> This brings up some interesting questions:
>>
>> If sharing an active GPS antenna, do you have to DC block all but one 
>> receiver port to prevent multiple receivers trying to supply current 
>> to the antenna?
>>
>> On say a 26dB antenna (ignoring line loss, power divider insertion 
>> loss, et al), what is the effective gain to each receiver?  (Sorry, 
>> having a senior moment)
>>
>> Should ALL unused ports have 50 ohm +/- 0j terminators on them?  I 
>> assume so...  Thus, it would be "better" to always use the divider 
>> with the minimum required ports?
>>
>> I am assuming since this is a receive only situation, it will follow 
>> approximately the same rules of physics that dealing with satellite 
>> antenna installations.
>>
>> I would LIKE to share one PC-TEL 26dB GPS antenna mounted at the top 
>> of my 38 foot horiz.loop mast right  at the shack entrance, using 
>> LMR-400-DB from antenna to Narda 2-way and thence to my current 
>> hacked Nortel GPSDO and my soon to be complete RPi 2/3 w/ Adafruit 
>> Ultimate GPS Hat NTP Server.  On that mast, the antenna would have a 
>> near 360 degree view of the sky completely unobstructed.  
>> (Eventually, I expect both of those units to be replaced with commercial 
>> units).
>>
>> I'm assuming that I DC block whichever unit is capable of providing 
>> the LEAST current at 5VDC...  I suspect the Nortel unit can supply 
>> more current than the RPi, but that's not a guarantee...  And I guess 
>> I could block/turn off DC delivery on BOTH units and add a voltage 
>> adjustable, current limiting DC injection unit into the line.
>>
>> Thanks.
>>
>> 73,
>>
>> __
>> Clay Autery, KY5G
>> MONTAC Enterprises
>> (318) 518-1389
>>
>> On 6/16/2017 7:26 PM, Tim Lister wrote:
>>> On Fri, Jun 16, 2017 at 4:40 PM, Gregory Beat  wrote:
 I have reached the point that I need a 4-port splitter for my GPS antenna 
 (outdoor 5 volt).  Any recommendations of models 
 (HP/Symmertricom/Microsemi) to acquire OR to avoid??
>>> As we recommended to me when I asked a similar question, the Narda
>>> 4372A-4 was a brand I had not heard of before and didn't come up in 
>>> 'gps splitter' searches. I got one on ebay for $24 plus a bit extra 
>>> for DC blocks on the n-1 other ports and it seems to work well and 
>>> it was handy to have an SMA-based solution as most of the gps 
>>> receivers and the antenna pucks seem to use SMA. This meant I only 
>>> needed 1 N to SMA converter cable for an external antenna (which has 
>>> yet to be externalized...). I found it smaller in real life  than it 
>>> looks in a lot of the pictures, about the size of a modern 
>>> smartphone but about double or more the thickness (the connectors are on 
>>> the ends).
>>>
 greg
 ---
>>> Cheers,
>>> Tim
>>> ___
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>>
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>
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[time-nuts] KS24019 units PSU requirements

[David C. Partridge]

I have a pair of L108 (RFTGm-II-Rb) and L109 (RFTGM-II-XO). 

What current do these bad boys draw so I don't get too skinny a 24V PSU?

Thanks
Dave

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[time-nuts] CRT for Tracor 527A

[David C. Partridge]

Trying a long shot here, I'm looking for a 1" CRT type 1EP1 (or 1EP11, or?)
for a Tracor 527A Frequency Difference Meter.
 
I did spot some on eBay but the vendor had a rather high opinion of their
worth :) at over 300 dollars

Anyone got one to spare?

Thanks
Dave

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Re: [time-nuts] SR620 TCXO calibration

[David C. Partridge]

Yes please. ...

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David 
Kirkby (Kirkby Microwave Ltd)
Sent: 19 June 2017 21:03
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] SR620 TCXO calibration

On 19 June 2017 at 15:35, David C. Partridge <david.partri...@perdrix.co.uk>
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] SR620 TCXO calibration

[David C. Partridge]

actually I think mine also has an OCXO

D.

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Dr. David 
Kirkby (Kirkby Microwave Ltd)
Sent: 19 June 2017 21:21
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] SR620 TCXO calibration

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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[time-nuts] SR620 TCXO calibration

[David C. Partridge]

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





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Re: [time-nuts] GPS splitter

[David C. Partridge]

FWIW the one I chose (V26-102LED is specified to 2.4GHz and has a real DC block 
on one port and DC pass on the other.  They also do up to 8 way versions.



At an overall cost of about USD3 or so!!!

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
ziggy9+time-n...@pumpkinbrook.com
Sent: 18 June 2017 21:07
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS splitter

+1 for satellite splitters as a low cost option. But as others have mentioned, 
you do need to use a little care. 

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[time-nuts] GPS splitter

[David C. Partridge]

Anyone in UK have a spare GPS splitter?

I've decided I need more clocks :)

Dave

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Re: [time-nuts] Name of integral of timing residual

[David C. Partridge]

I think that should be "absity" (s not c)

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Jim Palfreyman
Sent: 20 April 2017 06:18
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Name of integral of timing residual

> Now if you look at *motion* of an object over time, and you integrate its 
> acceleration you get velocity, integrate again you get displacement.
> Integrate again and you get "absement" and again you get "abcity" (I only 
> recently discovered these terms).

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Re: [time-nuts] HP-59309A Clock counts only seconds

[David C. Partridge]

You can get a brand new CD4011BE from pretty much most suppliers at about 15 
cents that won't exhibit the problems of the earlier ones.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Jeremy Nichols
Sent: 04 April 2017 00:44
To: time-nuts@febo.com
Subject: [time-nuts] HP-59309A Clock counts only seconds

I have a new-to-me HP-59309A HP-IB Digital Clock. The clock works on both the 
internal crystal oscillator and on an external 10 MHz standard (GPSDO). 
However, it counts only to 60 seconds and then repeats without updating the 
minutes digit. The TIME SET (FAST and SLOW) push-buttons work but again, the 
count will not update minutes and hours, only seconds. The DAY SET procedure 
works correctly for days and months. All the other switches and buttons do what 
they are supposed to do. Using my 10526T logic pulser I can force the minutes 
and hours counters to work. 
The power supply is in good condition (after replacement of a few
components) and I see no other problems (yet).

Tracing the clock signal through the logic circuitry brought me to U3 on the A4 
board. This (U3) is a 4011 quad 2-input NAND gate in a 14-pin DIP package. It 
"connects" the seconds counter to the minutes counter and appears to have 
failed. One of the people on the email list 
 commented that the 4000 series CMOS 
chips have a known limited lifetime. Since these parts are no longer in 
production, the writer expressed the concern that any parts I might find to buy 
may be DOA.

Before I go hunting for parts, I'd appreciate hearing from anyone in the group 
who has experience with the 59309A Clock and/or the 4000-series CMOS family. In 
particular, are there modern equivalents to my 4011 chip? If the 4000's really 
do have a limited lifetime I'd rather use a substitute.

Jeremy, N6WFO


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Re: [time-nuts] GPS first LO need to be locked?

[David C. Partridge]

links [2] and [3] give 404 errors

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Attila Kinali
Sent: 31 March 2017 12:35
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] GPS first LO need to be locked?

 [2] "A Prototyping Platform for Multi-Frequency GNSS Receivers", by Akos, Ene 
and Thor, 2003 
http://waas.stanford.edu/~wwu/papers/gps/PDF/AkosIONGPS033FreqRX.pdf

[3] "Design of a GPS and Galileo Multi-Frequency Front-End", by Parada, 
Chastellain, Botteron, Tawk, Farine, 2009 
http://202.194.20.8/proc/VTC09Spring/DATA/04-04-01.PDF


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Re: [time-nuts] Time Dilation tinkering

[David C. Partridge]

Aiguille du Midi is 3842m IIRC (cable car base station at about 1000m).

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of jimlux
Sent: 22 March 2017 14:57
To: time-nuts@febo.com
Subject: Re: [time-nuts] Time Dilation tinkering

On 3/22/17 4:04 AM, Angus wrote:
> On Tue, 21 Mar 2017 13:08:56 +0100, you wrote:
>
>> On Tue, 21 Mar 2017 13:38:51 +1100
>> Hugh Blemings  wrote:
>>
>>> This got me to wondering if a Rubidium based standard might do the 
>>> trick
>>> - the Efratom SLCR-101s seem readily available for ~USD$200 mark.
>>
>> As TvB wrote, a single one will not do the trick. You will need a 
>> stability 1e-14 @1d. IIRC most Rb standards floor out at 1e-12 to 
>> 1e-13 somewhere between 1k and 100k seconds. Even the Super-5065 has 
>> a floor of about 3-4e-14 (unless our friends here improved on this already).
>>
>> There will be a few things that you will need to do, if you want to 
>> go with Rubidiums:
>> 1) Stabilize or compensate for environmental effects (temperature, 
>> air pressure)
>> 2) Build ensembles of Rb clocks.
>>
>
> Hi,
>
> Looking back at an old plot I did of a temperature controlled and air 
> pressure compensated LPRO against an M12+T, the Hadamard Deviation of 
> the 1000s averages of the 1PPS measurement was about 5E-14 at 1 day.
> A large part of that was likely the GPS, so with a better rubidium 
> like an FRK-H in a sealed and temperature controlled enclosure you 
> might be around 1E-14 at 1 day.
>
> The bit that I'm not so sure about is the travelling. A long period of 
> movement, vibration, magnetic  fields, etc. all adding in could 
> obscure the effects of time dilation.
>
> It might be quite possible, although a nearby mountain and a friend 
> with a helicopter would make it a lot easier!
>

No tall mountains in Australia, but...

Pikes Peak in the US is 14114 ft, 4304m and has a road to the top. Of course 
the base is at about 5000 ft/1600 m

In EU, there's probably a Seilbahn of some sort pretty high up in the Alps, 
although probably not to 4000m.



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Re: [time-nuts] Line Voltage - USA

[David C. Partridge]

Time to call your supply co.

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

[David C. Partridge]

I think you meant :

In 240V countries it was -10%/+6%.

In 220V countries it was -6%/+10%

Cheers
Dave



-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Poul-Henning 
Kamp
Sent: 04 January 2017 09:34
To: Discussion of precise time and frequency measurement; Dr. David Kirkby 
(Kirkby Microwave Ltd)
Subject: Re: [time-nuts] Line Voltage - USA
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%

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

[David C. Partridge]

230VAC +10% -6%, so 253 is the upper limit.  248V is not unusual as for 
historic reasons some parts of UK still actually supply 250V ...

When  we "harmonized" our mains with the EU, we changed the specification from 
240V +/- 5% (I think) and didn't actually change any equipment.

Happy New Year
Dave

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[time-nuts] Heather V5 Holdover

[David C. Partridge]

I just installed the new version of Heather, she's saying "Holdover:  51
secs"  what's she trying to tell me please?

Dave

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[time-nuts] Back to our main topic ...

[David C. Partridge]

While the recent discussion about PCBs has been interesting it would be
better continued elsewhere I think (e.g. Homebrew_PCBs group on Yahoo!).

Thanks
Dave

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Re: [time-nuts] Question on LH

[David C. Partridge]

So need to do two long surveys then - what a pain ...

Oh well
Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Caudle
Sent: 07 December 2016 19:54
To: time-nuts@febo.com
Subject: Re: [time-nuts] Question on LH

On Wed, December 7, 2016 12:51 pm, David C. Partridge wrote:
> But in any case at the end of the LH 48 hr survey, the survey location 
> will be stored into the currently connected TB.  If both TBs are 
> connected to the same antenna, I think you'll need manually to set the 
> location of the second one (lat./long./altitude) based on the survey 
> results stored in the other one.

Mark has explained previously on the list, but it is actually kind of 
convoluted.  The command to set the position does not accept enough numeric 
precision to accurately set the position which was determined from long term 
averaging, so LH causes the Thunderbolt to run short self surveys (which report 
the position to more numeric digits than the set command will allow you to 
set), and compares the reported position to the position derived from the long 
term average.  When one of the self survey results just happens to be within 
some small error of the determined position, then that self survey result is 
saved.

So if you manually set the position on a second Thunderbolt, the software will 
chop off the lower order digits of the number you give, and the two 
thunderbolts could have very slightly different performance, even running from 
the same antenna.

--
Chris Caudle




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Re: [time-nuts] Question on LH

[David C. Partridge]

I'm confused here, LH can be connected to only one TB at any one time 
(depending on command line options).

But in any case at the end of the LH 48 hr survey, the survey location will be 
stored into the currently connected TB.  If both TBs are connected to the same 
antenna, I think you'll need manually to set the location of the second one 
(lat./long./altitude) based on the survey results stored in the other one.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Don@True-Cal
Sent: 07 December 2016 17:50
To: Time Nuts Group
Subject: [time-nuts] Question on LH

I'm using the latest version of LH connected to two Thunderbolts. Whenever I do 
a precision 48-hour antenna survey, I'm confused on if the derived best 
coordinates are automatically loaded into the Lat & Lon registers when it 
completes. What is the procedure at the completion of the precision survey or 
is it completely automatic?

 

Thanks,

Don

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Re: [time-nuts] Need Time Help

[David C. Partridge]

Mark,

Do you have a likely date for the availability of the new release (other than 
RSN)?

Cheers
Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Sims
Sent: 04 October 2016 18:40
To: time-nuts@febo.com
Subject: [time-nuts] Need Time Help

Lady Heather has support for setting the system clock from the GPS receiver.  
The next release has support for analyzing and compensating for the GPS / 
system / com port message delay.  It does not use the 1PPS signal.   

It can get the Windoze clock to under 40 msecs (two times the typical Windoze 
16 msec clock interval).   It can reset the system clock on command, 
periodically, or whenever the GPS time and system time diverge by more than x 
milliseconds.  However it does not have the finesse of NTP that guarantees on 
monotonically increasing system clock... it just "jam syncs" the clock to the 
GPS time.  I know there are people using it for EME work in the field where 
there is no net connection available for NTP, etc.   

Plus the next release can give you the moon az/el/phase/age/ rise+transit+set 
times and draw a pretty picture of the moon at its current az/el and give you 
your location in Maidenhead, UTM, NATO, etc coordinates.
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Yes,  I fear a timepod is a bit out of my budget (I can dream tho').  Over here 
in the UK PN measurement kit is a bit thin on the ground too.

So I looked at  but 
that seemed a little thin on details.  Or were you referring to something else?

Dave


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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Looks like all I've managed to do is measure the baseline noise of the 
analyser.  Ho-hum looks like I need something a *lot* quieter to do these 
measurements.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David C. 
Partridge
Sent: 18 September 2016 13:43
To: 'Bruce Griffiths'; 'Discussion of precise time and frequency measurement'
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

I've just redone the measurement without the external attenuator and with 10dB 
attenuation set internally to the analyser.

The results are attached.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The signal level is also very low.
Brue 

On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
<mag...@rubidium.dyndns.org> wrote:
 

 The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:
> Now that's interesting I just re-ran the measurement, and got a quite 
> different result which is attached.  The spurs have GONE.
>
> My only guess right now is that the E4406A power supply is getting quieter as 
> it has been on for longer (I've only had it powered for short periods before 
> now).
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
> Magnus Danielson
> Sent: 18 September 2016 11:56
> To: time-nuts@febo.com
> Cc: mag...@rubidium.se
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
> from signal.
>
> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
>> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
>> just BAU harmonics?
>
> Consider full-wave rectification of 50 Hz, the power consumption load 
> on the capacitor after the rectifier creates an inverse sawtooth wave 
> of
> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it 
> though.
>
> Cheers,
> Magnus
>
>>
>>
>> Thanks
>>
>> Dave
>>
>>
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
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>
>
>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

I've just redone the measurement without the external attenuator and with 10dB 
attenuation set internally to the analyser.

The results are attached.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The signal level is also very low.
Brue 

On Sunday, 18 September 2016 11:47 PM, Magnus Danielson 
<mag...@rubidium.dyndns.org> wrote:
 

 The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

On 09/18/2016 01:27 PM, David C. Partridge wrote:
> Now that's interesting I just re-ran the measurement, and got a quite 
> different result which is attached.  The spurs have GONE.
>
> My only guess right now is that the E4406A power supply is getting quieter as 
> it has been on for longer (I've only had it powered for short periods before 
> now).
>
> Dave
>
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of 
> Magnus Danielson
> Sent: 18 September 2016 11:56
> To: time-nuts@febo.com
> Cc: mag...@rubidium.se
> Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
> from signal.
>
> Hi,
>
> On 09/18/2016 12:26 PM, David C. Partridge wrote:
>> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
>> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
>> just BAU harmonics?
>
> Consider full-wave rectification of 50 Hz, the power consumption load 
> on the capacitor after the rectifier creates an inverse sawtooth wave 
> of
> 100 Hz, and sawtooth waveshape have both even and odd harmonics.
>
> While much of this is regulated out in the next step, some of it makes it 
> though.
>
> Cheers,
> Magnus
>
>>
>>
>> Thanks
>>
>> Dave
>>
>>
>>
>> ___
>> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
>>
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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
>
>
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> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Yes, it's through a 20dB attenuator. I'll redo the measurement w/o the 
attenuator.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 18 September 2016 12:52
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The signal level is also very low.
Brue 

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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Using John Miles PN.exe and Agilent E4406A

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 18 September 2016 12:47
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

The phase-noise still looks fairly high. How do you measure this?

Cheers,
Magnus

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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Now that's interesting I just re-ran the measurement, and got a quite different 
result which is attached.  The spurs have GONE.

My only guess right now is that the E4406A power supply is getting quieter as 
it has been on for longer (I've only had it powered for short periods before 
now).

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

Hi,

On 09/18/2016 12:26 PM, David C. Partridge wrote:
> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
> just BAU harmonics?

Consider full-wave rectification of 50 Hz, the power consumption load on the 
capacitor after the rectifier creates an inverse sawtooth wave of
100 Hz, and sawtooth waveshape have both even and odd harmonics.

While much of this is regulated out in the next step, some of it makes it 
though.

Cheers,
Magnus

>
>
> Thanks
>
> Dave
>
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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>
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Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

Thanks, that makes sense.  Is the PN plot much as expected, or is it "could do 
better"?

Thanks again
Dave
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus 
Danielson
Sent: 18 September 2016 11:56
To: time-nuts@febo.com
Cc: mag...@rubidium.se
Subject: Re: [time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz 
from signal.

Hi,

On 09/18/2016 12:26 PM, David C. Partridge wrote:
> The local power is 50Hz, so I can understand the 100Hz spurs, but I 
> don't quite "get" where the 200Hz spurs are coming from.  Or is that 
> just BAU harmonics?

Consider full-wave rectification of 50 Hz, the power consumption load on the 
capacitor after the rectifier creates an inverse sawtooth wave of
100 Hz, and sawtooth waveshape have both even and odd harmonics.

While much of this is regulated out in the next step, some of it makes it 
though.

Cheers,
Magnus

>
>
> Thanks
>
> Dave
>
>
>
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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[time-nuts] Thunderbolt spurs on 10MHz output at 100Hz and 200Hz from signal.

[David C. Partridge]

The local power is 50Hz, so I can understand the 100Hz spurs, but I don't
quite "get" where the 200Hz spurs are coming from.  Or is that just BAU
harmonics?

 

Thanks

Dave

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Re: [time-nuts] 1 PPS 50-ohm driver

[David C. Partridge]

Or put another way think 4 layer boards with power and ground planes.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of ed breya
Sent: 17 April 2016 21:04
To: time-nuts@febo.com
Subject: Re: [time-nuts] 1 PPS 50-ohm driver

For high-drive outputs, my favorite is the 74AC541 octal bus driver, which is 
very nice for paralleling outputs through small series Rs. If you look at the 
pinout, you'll see why.

BTW with any of these high-drive circuits, it is essential to provide good 
bypassing of the supplies, and be sure of clean low impedance pathways for the 
signal output and return currents.

Ed
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Re: [time-nuts] Ebay GPSDO for the price of shipping.

[David C. Partridge]

Hmm not to dissuade you from selling, but have you 'scoped the PPS on the 
RS-232/SMA outputs?  My guess is you are seeing a very narrow pulse (uSecs) and 
need a pulse stretcher to actually do something like light a LED with it.

Looks to be a nicely packaged unit.

Dave

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Paul
Sent: 15 March 2016 23:43
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Ebay GPSDO for the price of shipping.

I got one of these:

http://www.ebay.com/itm/Trimble-GPS-Receiver-GPSDO-10MHz-1PPS-GPS-Disciplined-Clock-with-rs232-port-/252162780444

but the PPS output is bad.  Funny becaue the PPS LED is working just fine.
The 10MHz looks okay (the counter says 10MHz with a Fury ext-in).  This unit 
emits a selection of UBX messages which while not impossible to decode is bit 
harder than just looking for "GGA" and plucking out two fields should you want 
to continuously monitor the GPS.  UCenter works just fine but the GPS, as 
shipped, is read-only.

Like last time you send me a prepaid shipping label (for a US address) suitable 
for a USPS flat rate medium sized box  (~$13.45) and I send the GPSDO (to a US 
address).

Notable points:
0) The seller gave me a refund but said keep the GPSDO.  Economics at work.
1) It does not come with a power supply (12V,2A) or antenna.
2) It does come with three SMA to BNC adapters.
3) The 1PPS doesn't work (DB9 or SMA). It will light a random LED.  Barely.
4) I have too much of this stuff lying about and trying to fix one is of no 
value to me.

Please contact me OFF list if you're interested.
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Re: [time-nuts] Tait reference

[David C. Partridge]

Is it possible to tell by looking at the back of the unit to determine if an Rb 
is fitted?

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Stephen 
Tompsett
Sent: 11 January 2016 14:13
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Tait reference

The T801 units I have seen in the UK contained a rubidium 10MHz reference (FRS 
form factor) and a synthesizer that could produce several outputs of a nominal 
12,8MHz, but which could be individually offset slightly to allow for precise 
offsetting of the transmitter frequencies by a few Hz for use in a quasi-synch 
PMR system.

On 11 January 2016 at 11:18, Charles Steinmetz 
wrote:

> Adrian wrote:
>
> Are these the references with a rubidium oscillator ? They seem to 
> have
>> similar models with OCXOs etc.
>>
>
> Tait is a manufacturer of mobile communications gear in New Zealand.  
> The
> T801 was part of a discontinued "quasi-synchronous communications system"
> -- a form of simulcasting on the same frequency by transmitters at 
> different locations, to fill in dead spots.  Tait's application was 
> utility and public service mobile radios (not radio broadcasting, 
> where this scheme has also been used).  Here is Tait's basic description:
>
> The Tait Quasi-Synchronous Communication System works by broadcasting
>> simultaneously from several transmitters on the same frequency. The 
>> transmitters then operate as a single transmitter giving superior coverage.
>>
>> A Tait T801 Frequency Referenct Module acurately maintains the 
>> frequency of the transmitters at each site.
>>
>> Where required, the T801 allows small frequency offsets to prevent 
>> the occurrence of static nulls in the overlap area.
>>
>> The T801 module may be driven from one of a number of frequency 
>> references, such as:
>> -- Rubidium frequency standard
>> -- Broadcast frequency standard
>> -- Oven Controlled Crystal Oscillators (OCXOs)
>> -- GPS Caesium Clock
>>
>
> This suggests that the T801 does not have an internal frequency 
> reference, but rather requires a precision external reference to 
> function.  (It has a jack labeled "INTERNAL STD OUTPUT," but that may 
> simply be a reference that is derived from the external standard, or a 
> backup crystal oscillator to keep the transmitter more or less on 
> frequency if the external reference signal is lost.)
>
> Best regards,
>
> Charles
>
>
>
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>



-- 
Stephen Tompsett
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Re: [time-nuts] ACAM GP22 Chip

[David C. Partridge]

FWIW I think the two books T versus AofE complement one another quite well 

Regards,
David Partridge 

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Attila Kinali
Sent: 25 November 2015 10:25
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] ACAM GP22 Chip

On Tue, 24 Nov 2015 11:44:04 -0800
Hal Murray  wrote:

> th.allge...@gmail.com said:
> > I should say from the start that I am new to time and frequency 
> > measurements and not even an electronics engineer – but then I 
> > have been exposed to high-precision electronics for the last 25 
> > years hence have picked up some dangerous degree of half-knowledge.
> 
> Do you have a copy of Art of Electronics by Horowitz and Hill?

He is german. He most likely has Tietze, which I consider to be the 
better book than AoE* :-)

Attila Kinali

* I haven't had a look at the 3rd edition yet, so no comment on that.
--
It is upon moral qualities that a society is ultimately founded. All the 
prosperity and technological sophistication in the world is of no use without 
that foundation.
 -- Miss Matheson, The Diamond Age, Neil Stephenson 
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Re: [time-nuts] Unified VCXO Carrier Board

[David C. Partridge]

All, 

I wish that people had said that the ADCMP600 was a mediocre comparator when I 
designed the board - I’d have used a better one!

I can't find the post about the design and die level issues in a quick search 
(I've been off line for a few weeks).

Bruce,

I couldn't find your post about your measurements of my board for the same 
reason.

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Charles 
Steinmetz
Sent: 24 October 2015 14:03
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Unified VCXO Carrier Board

Bruce wrote:

>The comparator circuit measured was the front end of David Partridge's 
>divider. I merely measured the 10MHz output.

The MAX999 and ADCMP600 are the two comparator options noted on David's 
schematic.  Both parts suffer from a number of the design and die-level issues 
I noted in my previous message, and I have never obtained particularly good PN 
with either one.  Also, even the relatively direct path to the 10MHz output 
goes through two 'AC04 inverters and an 'AC541 line driver, which contribute 
additional PN.

>One thing that I have found is that at low offset frequencies the 
>measured PN is substantially reduced when air currents and other 
>sources of thermal fluctuations are reduced. Even the effect of a thin 
>piece of paper used as an air current shield can be easily seen.
>With careful shielding from thermal fluctuations I measure the low 
>frequency offset PN to be substantially lower than the datasheet values.
>I've seen this effect with everything for which I've measured the PN.

Agreed.  Whether or not it is explicitly stated, I take "all circuitry to be 
enclosed and protected from drafts, and allowed to stabilize thermally before 
testing" as a given with any sensitive time or voltage circuit.

>One problem with comparators when attempting to measure their PN is 
>that they don't have sufficient output to drive the TimePod input directly.
>An amplifier is required.

The spec sheet says both TimePod inputs accept -5 to +20dBm into 50 ohms.  
-5dBm is less than 0.4Vp-p, which requires less than +/-4mA from the source, so 
a 0-5v comparator output feeding a coupling capacitor and a 560 ohm series 
resistor should work fine as long as the comparator can source and sink at 
least 4mA.

Alternatively, a 0-5v comparator output could be buffered with three
'AC04 inverters in parallel, or an 'AC line driver -- but that adds the PN of 
the gates.

>A resistor from point A to ground in the Wenzel style shaper you 
>attached has little effect on the output symmetry due to C4.

It has just enough effect to correct the very small (<1%) asymmetry due to the 
unbalanced drive.  (With no resistor at Point A, the duty cycle is ~51%/49% 
high/low.)

>However it does allow the output amplitude to be adjusted.

According to the simulation, the resistor has no effect on the output amplitude 
until it is well below 1k ohms (at 1k ohm, the symmetry has been WAY 
overcompensated and the duty cycle is ~45%/55% high/low.

Best regards,

Charles


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[time-nuts] Serial Ballpoint issue again

[David C. Partridge]

I just installed Windows 10 (yes I know how rash), and now my Thunderbolt is
being detected as a Microsoft Serial Ballpoint Mouse (yes, just like before
inder Windows 7).  I had set something up on Windows 7 in the boot.ini to
stop this, but for the life on me I can't remember what it was.

Please could someone who's got this setup on Windows 7 remind me what the
magic incantionation is.

Thanks
Dave

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Re: [time-nuts] Serial Ballpoint issue again

[David C. Partridge]

Tahnks to John Lofgren:

 Click on start -- In the search box, type in regedit Registry editor 
 windows opens... Navigate to the location:
 HKEY_LOCAL_MACHINE
 -- SYSTEM
 -- CurrentControlSet
 -- Services
 -- sermouse
 In the right hand, you'll see stuff like:

 (default)
 DisplayName
 etc. etc. etc.

 There should be a dword (32bit) value titled:

 start

 Set the value of this to: 0004 

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Martin
Burnicki
Sent: 11 August 2015 17:25
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Serial Ballpoint issue again

David C. Partridge wrote:
 I just installed Windows 10 (yes I know how rash), and now my 
 Thunderbolt is being detected as a Microsoft Serial Ballpoint Mouse 
 (yes, just like before inder Windows 7).  I had set something up on 
 Windows 7 in the boot.ini to stop this, but for the life on me I can't
remember what it was.
 
 Please could someone who's got this setup on Windows 7 remind me what 
 the magic incantionation is.

The boot option /NoSerialMice should do the trick. See:
https://support.microsoft.com/en-en/kb/131976

However, unklike mentioned in the above article, you can't just edit a
boot.ini file in current Windows versions. Instead you have to run the
bcdedit utility shipped with Windows. See:
https://msdn.microsoft.com/en-us/library/windows/hardware/ff545492%28v=vs.85
%29.aspx

Haven't tried this under Windows 10, yet, but hope it still works.

Martin

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Re: [time-nuts] A few questions about Tboltmon

[David C. Partridge]

No, but Lady Heather will do that. 

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Waldrup
Sent: 06 August 2015 12:59
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] A few questions about Tboltmon

Hi Bryan,

I didn't do that. Is this something accessible under one of the tabs?

Chris

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Re: [time-nuts] z3801a - serial help and for sale

[David C. Partridge]

Where on the planet are you?  I'm in UK so if you are in USA shipping will make 
it uneconomic. 

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of David Andersen
Sent: 11 June 2015 21:39
To: time-nuts@febo.com
Subject: Re: [time-nuts] z3801a - serial help and for sale

Thanks for the suggestions!

It turns out the answer was my serial dongle was failing.

*head bonk*  I swapped it out for another FDTI-based dongle and suddenly 
there's a happy working z3801a.

Before I throw it on eBay, would anyone like a working (yay!) z3801a modified 
to take mains power?  I'll throw in a little puck antenna and a homebrewed 
rs232 db25-to-db9 cable.  Pictures as per my previous email about it.

(please CC: me on reply -- I'm stuck in digest subscription and having
issues.)  ((No 'issues' jokes, please. :))

I'll note there's a risk that putting the switcher in it causes added noise.  I 
haven't measured it precisely enough to tell.  I didn't need nanoseconds for 
what I was using it for, but I did want it to be pain-free to plug in and use.

 -Dave


…
On Thu, Jun 11, 2015 at 1:18 AM time-nuts-requ...@febo.com wrote:

 -- Forwarded message --
 From: James C Cotton jim.cot...@wmich.edu
 To: Discussion of precise time and frequency measurement  
 time-nuts@febo.com
 Cc:
 Date: Wed, 10 Jun 2015 16:26:17 -0400 (EDT)
 Subject: Re: [time-nuts] z3801a - serial help and for sale.

 David,

 Using a USB dongle with an Apple Mac Laptop works fine for me.

 The chip is a FTDI FT232BL.

 Drivers from the FTDI site.

 In terminal or console use one of the following commands:

 [generic $5 dongle with no serial number]

 cd /dev
 screen tty.usbserial

 [xs880 with a serial number,
 http://www.usconverters.com/usb-serial-adapter-xs880]

 cd /dev
 screen tty.usbserial-A101OFXZ

 Having one (or more) with a serial number(s) allows several to work at 
 the same time...
 I use the same USB-serial converters on windows PCs too.

 Jim



 -- Forwarded message --
 From: Scott McGrath scmcgr...@gmail.com
 To: Discussion of precise time and frequency measurement  
 time-nuts@febo.com
 Cc:
 Date: Wed, 10 Jun 2015 16:50:51 -0400
 Subject: Re: [time-nuts] z3801a - serial help and for sale.
 Try going through all the speeds starting at 300.  Sounds like a baud 
 rate mismatch to me from the symptoms

 Also try 8 bits 1 stop no parity

 Content by Scott
 Typos by Siri

  On Jun 10, 2015, at 10:28 AM, David Andersen d...@pobox.com wrote:
 
  I'm throwing my hands up in the air - I don't have the time to 
  wrestle my silly mac into trying to talk to the box, unless someone 
  has quick advice on something I might be doing wrong.
 
  z3801a, jumpered to RS232, modified with an internal switching power
 supply
  (see photos below).  Power light comes on, unit is outputting stable 
  10MHz.  Doesn't GPS lock, but that makes sense, since I haven't been 
  able to issue a SURVEY command and I don't live where I used to.
 
  The internal green status light is blinking (as normal), suggesting 
  that it's probably happy and I'm an idiot for not being able to make 
  it work, but I don't vouch for anything about it past the 10mhz 
  being there.  The double-oven oscillator is clearly happy given the 
  10mhz (compared
 against a
  working Thunderbolt).
 
  Hooked up a serial cable at 19200, 7, O, 1, but only got a garbled 
  little prompt back - no response to standard z3801a commands.  I 
  *think* I have the cable configured properly.  I opened it up and 
  checked the RS232 jumpers and they're correct.
 
  I'm open to advice on getting the serial working under my Mac or 
  Linux,
 or
  anyone who wants to relieve me of the burden of z3801a ownership and
 take a
  risk that it's a fixer-upper. :-)  I suspect that in some previous 
  life,
 I
  switched it over into a binary mode of some sort while using it to 
  sync something, but I can't for the life of me remember what I might 
  have
 done.
 
  Some reasonable price plus shipping and it's all yours... I'm trying 
  to de-clutter in preparation for a sabbatical on the other side of 
  the
 country.
 
  Pictures:
 
  https://www.dropbox.com/s/ursszjgie8m1xj8/2015-06-09%2011.57.16.jpg?
  dl=0 
  https://www.dropbox.com/s/it8d2f65ztn4rkq/2015-06-09%2011.57.24.jpg?
  dl=0 
  https://www.dropbox.com/s/1p1g6xrapzdmvzh/2015-06-09%2011.59.56.jpg?
  dl=0
 
  Thanks!
 
   -Dave
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 -- Forwarded message --
 From: Bob Camp kb...@n1k.org
 To: Discussion of precise time and frequency measurement  
 time-nuts@febo.com
 Cc:
 Date: Wed, 10 Jun 2015 17:27:36 -0400
 Subject: Re: [time-nuts] z3801a - serial help and for sale.
 Hi

 Normal drill for this sort of thing:

 1) First connect the 

Re: [time-nuts] PPS for NTP Server - How Close Is Good Enough?

[David C. Partridge]

Do you think it is OK to consider a pulse which arise 250 ns early to be close 
enough?

For NTP usage that will be no problem whatsoever.

Dave

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Re: [time-nuts] Using CPLD/FPGA or similar for frequency divider

[David C. Partridge]

I'm up for either ...  My thoughts are to try it out on a development board and 
if it works, maybe build a few for possible sale, and also release Gerbers and 
VHDL files.

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of cfo
Sent: 08 June 2015 15:09
To: time-nuts@febo.com
Subject: Re: [time-nuts] Using CPLD/FPGA or similar for frequency divider

On Sun, 07 Jun 2015 11:23:40 +0100, David C. Partridge wrote:

 My reading so far of what's been said in this thread is that you might 
 get good results using a CPLD/FPGA as a divider but ... .
..
..
..
 Thanks again Dave

Is this going to be an open source project, or something you buy  ?

CFO

--
E-mail:xne...@luna.dyndns.dk

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Re: [time-nuts] Using CPLD/FPGA or similar for frequency divider

[David C. Partridge]

My reading so far of what's been said in this thread is that you might get good 
results using a CPLD/FPGA as a divider but ... .

Bruce pointed me to Rubiola's paper 
http://rubiola.org/pdf-articles/conference/2013-ifcs-Frequency-dividers.pdf, 
and while I'm sure the lambda divider is excellent, there's a definite problem 
of needing to re-square the output after every stage if you want a multi-stage 
design.  This makes me wonder if you'd end up adding enough additional 
jitter/phase noise to more than counteract the benefit of the lambda divider 
(which produces a stepped triangle wave).  TANSTAAFL seems to apply here.

My biggest concern is that if I build a multi-stage divider (*) using a single 
CPLD or FPGA, I could end up with cross-talk problems similar that encountered 
with multi-gate logic packages.  I don't think it makes sense to use a CPLD if 
you need to use a separate package for each stage.

I'm also a bit concerned by Bob Camp's comment:

they might get to -16x dbc/ Hz region. That compares to the -174 dbc / Hz you 
could expect under similar conditions with something like AC or faster CMOS

which suggests that it will be (at least 10dB) worse than my existing design :(

I guess that it might work if the output were re-synched to the input using 
external D-flops after the main grunt work is done in a CPLD/FPGA.

I'm also a bothered by the findings in 
http://rubiola.org/pdf-articles/conference/2014-eftf-Noise-in-digital-components.pdf
 which indicate that the lowest noise devices tested were the Altera Max 3000 
series which Altera dsecribe as Mature so may be at risk of obsolescence

Thanks to all for the discussion to date.

(*) similar to my previous effort made with 74AC logic. 

Thanks again
Dave

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[time-nuts] Using CPLD/FPGA or similar for frequency divider

[David C. Partridge]

Is this a sensible thing to consider doing?  Or would I be better sticking to 
AC/HC/AHC/LVC logic?

Regards,
David Partridge 

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Re: [time-nuts] USB problems and solutions - Some what Off Topic

[David C. Partridge]

I originally replied offline, but given the level of discussion, it seems 
appropriate to put this here.

Take a look at USBOblivion which will vape all existing registry entries etc. 
for USB devices.  Next time you connect they will reload.  The only problem is 
that COM port number will most likely be changed. 

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Cash Olsen
Sent: 29 May 2015 20:18
To: time-nuts@febo.com
Subject: [time-nuts] USB problems and solutions - Some what Off Topic

I have been plagued with hard crashes of the computer when plugging in and 
unplugging USB devices. I have generally determined that some of the USB to 
serial devices are the worst offenders. I am also suspicious of some of the 
hubs. I wander if even the operating system is partly to blame.

I'm using Windows Vista, and have several different USB to serial adapters.
Most are Silicon Labs and Prolific. I thought I had the problem resolved with 
Prolific by over-riding the driver and installing an earlier version but 
Windows may have updated the driver, that seems to be a common problem.

I'm coming to time-nuts because I remember that at least one member had a very 
large number of adapters on one computer, so I'm hoping to find some help. I 
don't generally seem to have trouble with other USB devices, just the serial 
adapters.

One further issue, the COM ports are marked in use from 3 to 50+ and I'm only 
using at any one time 3 or 4. Can I clean up the assignments and can I make the 
assignments static after connect and reconnect or restarting the computer?

--
S. Cash Olsen KD5SSJ
ARRL Technical Specialist
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Re: [time-nuts] LTC6957 internal architecture

[David C. Partridge]

With all this talk of the LT6957 I'm wondering if there's interest in a re-spin 
of my frequency divider with one of these at the front end instead.

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bruce Griffiths
Sent: 26 May 2015 00:40
To: time-nuts@febo.com
Subject: [time-nuts] LTC6957 internal architecture

The following patent hints that the LTC6957 front end probably consists of 
several cascaded long tailed pair differential amplifier stages each with a 
selectable bandwidth set by capacitors shunting the collector load resistors. : 
US8319551 The input limiter is in effect a Collins style limiter with 
selectable bandwidth for each stage to reduce the noise with respect to a 
comparator which typically has several high gain wide bandwidth cascaded 
differential amplifier stages.

Bruce


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Re: [time-nuts] Divider circuit for Rubidium Standard

[David C. Partridge]

That's one of the reasons I was considering a re-spin of the board using a 
better ZCD solution.

Dave
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Richard (Rick) 
Karlquist
Sent: 05 May 2015 05:10
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Divider circuit for Rubidium Standard

This is a comparator based circuit.  This will give you worse performance than 
just about anything else, but it may be good enough anyway.

Rick Karlquist N6RK
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Re: [time-nuts] Tektronix Sample Heads

[David C. Partridge]

I doubt there is any information, but the place to ask is the Tekscopes group 
on Yahoo!  Also Tekscopes2 (schism) also on Yahoo!

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Daniel Mendes
Sent: 24 April 2015 04:01
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Tektronix Sample Heads


Does anybody in this group has any info about Tektronix sample heads like SD26? 
I´d like schematics, or at least a pinout of the centronix-like interface. My 
google-fu failed me (got only a service manual that says nothing).

Thanks

Daniel
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Re: [time-nuts] Trimble Thunderbolt question, splitting its output.

[David C. Partridge]

Yes of course, you are correct!

I'm not sure how to avoid the change in input impedance with the clipper 
involved unless I were to increase R1 to a very much higher value. 

I had intended to re-work the input clock shaper to reduce jitter if the 
proposed re-spin of the board had gone ahead, but as there wasn't enough 
interest so that's not about to happen ...

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Charles 
Steinmetz
Sent: 28 March 2015 19:56
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Trimble Thunderbolt question, splitting its output.

Dave wrote:

??? How do you get to that 45 ohm figure.  The input has a pair of 100R 
in parallel, so I can't see how it can be 45R input impedance.

Also in parallel with the 2x 100 ohm resistors (R2 and R3) is 10k
(R5) in series with 100nF, plus 475 ohms (R1) to a pair of (parallel) 
back-to-back diodes in series with a 100nF capacitor (C5).  Both 100nF 
capacitors essentially sit at the half-supply bias voltage (there is a very 
small AC component on C3, ~1mV, which can be ignored).  So, for peak input 
voltages of less than a diode drop, the input impedance is ~49.75 ohms 
(100||100|10k).  But for peak voltages greater than a diode drop, the input 
impedance is 100||100||475||10k, or about 45 ohms.  (There is a slushy 
transition zone of ~100mV as the diodes turn on.)

The TBolt puts out nominally +13dBm, or 1Vrms (2.8v peak-to-peak, 1.4v peak) 
into 50 ohms.

So, the TBolt sees a nonlinear load of ~50 ohms for the first ~600mV (plus and 
minus) of voltage excursion, then ~45 ohms from 600mV to 1.4v (plus and minus).

I'd be inclined to change R2 and R3 to 113 ohms for use with sources that put 
out +4dBm or more, although the practical effect in most cases is probably 
minor.  Note, however, that if one feeds the divider and another instrument 
using a simple BNC T, the nonlinearity of the divider's input impedance  will 
raise the distortion floor of the sine wave seen by the other instrument to ~ 
-40dBc even if the source is perfectly pure.

Best regards,

Charles



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Re: [time-nuts] Trimble Thunderbolt question, splitting its output.

[David C. Partridge]

Charles  

The input impedance of the divider board is nominally 50 ohms (closer to 45 
ohms, with 1Vrms drive

??? How do you get to that 45 ohm figure.  The input has a pair of 100R in 
parallel, so I can't see how it can be 45R input impedance.  Did you derive 
that figure based on observing the amplitude change of the Tbolt when connected 
to the board, and when disconnected?  If so I'm be more likely to suspect the 
the T output impedance isn't 50R.

Enquiring mind wishes to know :)

Cheers
Dave

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Re: [time-nuts] homebrew counter new board test result

[David C. Partridge]

You might wish to look at the LTC6957 as your input shaper device.  I think 
you'll find it far superior to either 74xx logic or fast comparator such as the 
LT1016.

Cheers, Dave 

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Re: [time-nuts] Frequency Divider Board redux

[David C. Partridge]

I've not had any replies on this for a bit, and I have only had interest 
expressed for a total of 10 boards which isn't an economically viable quantity. 
 So I'm afraid that this won't be going to production unless I get a whole lot 
more interest.

Sorry
Dave

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Re: [time-nuts] PRS10 Rubidium

[David C. Partridge]

Hmmm is it possible that a nearby board had a wet tantalum capacitor (H2SO4 
electrolyte) that failed spraying acid? 

Dave
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Jürg Kögel
Sent: 22 February 2015 15:44
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] PRS10 Rubidium

I do not understand the corrosion since it has been in a very controlled 
environment in my basement.

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Re: [time-nuts] Looking for advice to get a submillisecond setup

[David C. Partridge]

Symmetricon swallowed Navstar Systems Ltd. In 1993. So if there were any 
information available, they would likely have it, but I fear it may be long 
gone.

I did find this reference in the time-nuts archive:

http://www.navsync.com/docs/mushroom_data_sheet.pdf 

Which looks like the same animal ...

HtH
David Partridge 

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[time-nuts] Frequency Divider Board redux

[David C. Partridge]

I've been approached a few times in the recent past asking if I would do a 
re-spin of my frequency divider board.

For details of this please see: 
http://www.perdrix.co.uk/FrequencyDivider/index.html

It isn't viable to do this unless I can get orders for at least 40 and 
preferably more (the last production run was 100 units).

At this stage I'm not requesting orders, but attempting to determine interest 
levels.  If you would be interested in an re-run of these boards (possibly with 
some enhancements), please could you mail me OFF_LIST using the subject 
Frequency Divider and stating the number of boards you would want.  The last 
boards from the previous production run (of 100) were selling at around 
GBP62.50 each EXCLUDING PP. (£75 including PP to anywhere).  Fewer boards 
increases the cost (unfortunately).

My email address is david dot partridge at perdrix dot co dot uk.


Regards,
David Partridge 

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Re: [time-nuts] MIT 2 inch cesium fountain, optically pumped

[David C. Partridge]

Yes, but that one's just a GPS watch (with a humongous price tag).

Regards,
David Partridge 
-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Jason Rabel
Sent: 20 November 2014 15:58
To: time-nuts@febo.com
Subject: Re: [time-nuts] MIT 2 inch cesium fountain, optically pumped

Actually, I just looked at Hoptroff's website and guess what? Merry Christmas!

http://www.hoptroff.com/collections/atomic-timepieces/products/no-16


 Some time ago Hoptroff  produced a Cs pocket watch using the 
 Symmetricom SA45s - now how long for a wrist watch !!

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Re: [time-nuts] future NTP programs...

[David C. Partridge]

 it would not be OK to design a daemon which handles the crypto stuff or the 
 control packets in a root-process, those should go in a sandbox.

Absolutely agree, in my previous life in the data security arena (crypto, data 
security, white hat tester etc..), doing that sort of thing in a privileged 
process or similar (e.g. kernel) was a seriously discouraged - far too great a 
risk of compromise.  Keep it all in a user state process with NO write access 
to anything except the communications port (serial / UDP / TCP / w.h.y.) it is 
talking on.

Regards,
David Partridge 

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Re: [time-nuts] Anybody have experience with TimeMachines TM1000AGPS Time Server

[David C. Partridge]

If you’re referring to this:

I think he's referring to section 4.3 Resetting to Factory Defaults 

Regards,
David Partridge 

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Re: [time-nuts] Anybody have experience with TimeMachines TM1000AGPS Time Server

[David C. Partridge]

You also have to reboot after a PW change ... 

Regards,
David Partridge 

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Re: [time-nuts] Tektronix TM500 extender cable kit

[David C. Partridge]

No, you also need a GPIB extender cable for FULL function ...

Regards,
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of R.Phillips
Sent: 04 August 2014 17:11
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Tektronix TM500 extender cable kit

Am I right in thinking that two of these connector/cables would give the
full facilities on the 5000 series units.
Roy

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Re: [time-nuts] Tektronix TM500 extender cable kit

[David C. Partridge]

Hi Mark,

After all the effort you just put in, you'll be a touch annoyed that Jamma
Boards have done a kit for TM500 extenders for ages ... OTOH you may know
about them and have decided you could do better.

http://www.jammaboards.com/store/tektronix-tm500-series-extender-kit-tm500-
kit.html

Regards,
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Mark Sims
Sent: 04 August 2014 05:27
To: time-nuts@febo.com
Subject: [time-nuts] Tektronix TM500 extender cable kit

I just finished laying out a small circuit board for building an extender
cable for the Tek TM500 series mainfames / modules.  Prototypes are off
being fab'd at OSHPARK.  Should be here in a couple of weeks.  It uses two
39/40 pin ribbon cables (all the power pins use two wires)... e.g.  IDE/PATA
disk drive cables.
I know LOTs of us have and use these venerable old workhorse machines.  They
are well documented and easily maintained (particularly if you have extender
cables).  Is there any interest in purchasing a kit of all parts to build an
extender cable.   With a moderate amount of interest the price  looks like
it would be around $20 per kit plus shipping (probably around $6 for
shipping in the US for as many that can be stuffed in a small priority mail
flat rate box... most serious TM500 users will want 2 cables for the wide
modules).  Kit cables would be 18-19 long.   TM500 extender cables have
been selling on Ebay for $150-$350!   
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Re: [time-nuts] Sine to square wave converter Phase Noise

[David C. Partridge]

Bruce, 

Thank you, that was very useful information.  If I ever do a re-spin of the
divider I will likely use the LTC6957-3 or -4 instead of the ADCMP600 (I
would need interest for at least 40 boards to be able to do this at anything
like an economic price).  

Will you be putting the full details of the circuit you used up on Didier's
web site?  Did you use a transformer based circuit similar to Design Note
514 or just an input capacitor?

Regards,
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of br...@ko4bb.com
Sent: 29 July 2014 12:00
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Sine to square wave converter Phase Noise

Sorry, I meant the LTC6957-4 of course._SELA = l FILTA = L FILTB = H ie an
input stage BW of 160MHz as recommended for a 10MHz + 10dBm input.

Input for the HX4210 was +14dBm.

Comparator was that used in David Partridge's programmable divider (includes
the
74AC04 buffers).

Bruce

 On July 29, 2014 at 5:37 AM Magnus Danielson 
 mag...@rubidium.dyndns.org
 wrote:


 You alternate LTC7957-4 and LTC6957-4 and it is only the later that
exists.

 The LTC6957-4 has a single-stage amplifier stage input, with somewhat 
 programmable bandwidth. I assume you used the 50 MHz BW setting.

 Cheers,
 Magnus

 On 07/29/2014 10:55 AM, br...@ko4bb.com wrote:
  Recently I have been comparing the phase noise of the HOlzworth 
  HX4210 and the LTC7957-4.
  I have found that the performance of these devices is comparable 
  with a 10MHz sinewave input with a PN noise floor below -160dBc/Hz.
  For offsets below 100Hz the LTC6957-4 is quieter and for offsets 
  below 50Hz or so is lower than that of my measurement setup.
  I merely mounted the LTC evaluation board in a diecast metal box to 
  reduce the effect of air currents on the LTC7957-4 and used an ultra 
  low noise 3.3V power supply (Abracon) to minimise the power supply 
  contribution to the measured phase noise.
  Achieving a phase noise performance equal to that on the datasheet 
  was relatively easy.
  In fact for low offsets the phase noise is lower than that shown on 
  the datasheet.
 
  I've also measured the phase noise of a comparator based sine to 
  CMOS converter and its PN floor is about 20dB higher than that of 
  the LTC6957.
  On completion of measurements PN plots for the various sine to 
  square conveters tested will be added to the web pages I maintain on 
  Didiers site..
 
 
  Bruce
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Re: [time-nuts] Sine to square wave converter Phase Noise

[David C. Partridge]

Further to my previous post:

I note that the LTC6957 is 3.3V CMOS rather than 5V.  Do you have a
recommmendation for a level converter to 5V logic?  Would a 74AC04 using a
5V supply cope well enough in that role or is there a better solution?

Regards,
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of br...@ko4bb.com
Sent: 29 July 2014 12:00
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Sine to square wave converter Phase Noise

Sorry, I meant the LTC6957-4 of course._SELA = l FILTA = L FILTB = H ie an
input stage BW of 160MHz as recommended for a 10MHz + 10dBm input.

Input for the HX4210 was +14dBm.

Comparator was that used in David Partridge's programmable divider (includes
the
74AC04 buffers).

Bruce

 On July 29, 2014 at 5:37 AM Magnus Danielson 
 mag...@rubidium.dyndns.org
 wrote:


 You alternate LTC7957-4 and LTC6957-4 and it is only the later that
exists.

 The LTC6957-4 has a single-stage amplifier stage input, with somewhat 
 programmable bandwidth. I assume you used the 50 MHz BW setting.

 Cheers,
 Magnus

 On 07/29/2014 10:55 AM, br...@ko4bb.com wrote:
  Recently I have been comparing the phase noise of the HOlzworth 
  HX4210 and the LTC7957-4.
  I have found that the performance of these devices is comparable 
  with a 10MHz sinewave input with a PN noise floor below -160dBc/Hz.
  For offsets below 100Hz the LTC6957-4 is quieter and for offsets 
  below 50Hz or so is lower than that of my measurement setup.
  I merely mounted the LTC evaluation board in a diecast metal box to 
  reduce the effect of air currents on the LTC7957-4 and used an ultra 
  low noise 3.3V power supply (Abracon) to minimise the power supply 
  contribution to the measured phase noise.
  Achieving a phase noise performance equal to that on the datasheet 
  was relatively easy.
  In fact for low offsets the phase noise is lower than that shown on 
  the datasheet.
 
  I've also measured the phase noise of a comparator based sine to 
  CMOS converter and its PN floor is about 20dB higher than that of 
  the LTC6957.
  On completion of measurements PN plots for the various sine to 
  square conveters tested will be added to the web pages I maintain on 
  Didiers site..
 
 
  Bruce
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Re: [time-nuts] OT Gel Cell question

[David C. Partridge]

Back to time related discussions please. 

Thanks
Dave

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[time-nuts] GPS puck?

[David C. Partridge]

Slightly OT, but not much, does anyone in the UK (or close) have a GPS puck 
(mouse, sensor etc.) with serial NMEA output available cheaply?  Ideally with 
RJ11 (6P4C) connector, but I can solder ...

Thanks
Dave

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Re: [time-nuts] GPS puck?

[David C. Partridge]

Mark, 

Thank you that looks ideal, now all I need is a suitable weatherproof cover
and I'm in business. 

Regards,
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Mark Sims
Sent: 26 June 2014 18:17
To: time-nuts@febo.com
Subject: [time-nuts] GPS puck?

Check out these puppies...  $16 with logic level interface,  $17 with RS-232
interface.   Does GPS and Glonass.  Has antenna.  Has 1pps outut.  Can do 10
Hz updates.   I ordered 6 of the RS-232 units and they took about a week to
arrive.  
I have not done anything with the 1PPS output yet.  I did lay out a small
piggyback circuit board with a DB9 connector and 3.3V regulator so the unit
can be powered via a 12V signal on pin 9 of the DB9. 
http://www.ebay.com/itm/RYN25DI-10Hz-RS232-interface-high-performance-GPS-Gl
onass-antenna-module-battery-/171340780546?pt=LH_DefaultDomain_0hash=item27
e4b4d402

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Re: [time-nuts] Measuring the accurcy of a wrist watch

[David C. Partridge]

I too tried that and equally failed even with 52dB gain.  I suspect that
part of the trick is how the piezo is mounted: Quite possibly if mounted in
a circular form held only at the edges, with the watch crown touching the
centre it might be more sensitive than if the centre is clamped to the watch
with the edges free?

Regards,
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Robert Darlington
Sent: 18 April 2014 19:49
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Measuring the accurcy of a wrist watch

Commercially they use piezo transducers (bender disks) in direct contact
with the watch to hear them tick.  I did my best to build one up several
weeks ago.  I could hear ants walking but my cheap swiss movement was just
too quiet.  It was amazingly quiet, even going through a preamp and dialing
the vertical amp to 11 on the scope.  They must have them sized for
resonance a little closer to the spectrum given off by the movement.

-Bob

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[time-nuts] Serial port splitter s/w

[David C. Partridge]

I'm running Meinberg NTP on the Windows 7 x64 machine to which my Thunderbolt 
is attached.

I'd like to be able to share the serial port between LH and NTP so that I can 
run the machine as an NTP Stratum 1 server locked to the TB, and also be able 
to use LH to check things.

I looked around the with Google, and saw *numerous serial port splitters.  
Which is recommended?

Also what's the best way how to configure NTP to lock the the TB on a serial 
port?  Do I need to modify the TB to deliver the PPS down one of the serial 
data lines or will NTP work well by parsing the NMEA time messages?

Many thanks
David Partridge 

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Re: [time-nuts] Serial port splitter s/w

[David C. Partridge]

You guys have me persuaded - I'll get a Raspberry Pi ... 

Regards,
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of David J Taylor
Sent: 26 February 2014 19:15
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Serial port splitter s/w


The Raspberry Pi with GPS/PPS certainly beats any internet connection I've
ever had delivered to this house, though:

  http://www.satsignal.eu/ntp/Raspberry-Pi-NTP.html
  http://www.satsignal.eu/mrtg/performance_ntp.php

Cheers,
David
--
SatSignal Software - Quality software written to your requirements
Web: http://www.satsignal.eu
Email: david-tay...@blueyonder.co.uk 

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[time-nuts] Lecture at Warwick University tomorrow

[David C. Partridge]

Time nuts in the UK will be interested in the Institute of Physics lecture at 
Warwick University tomorrow by Helen Margolis from NPL.  Title Keeping time 
with a single atom.

http://www2.warwick.ac.uk/fac/sci/physics/news/iop/


Regards,
David Partridge 

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Re: [time-nuts] 5370 processor boards available

[David C. Partridge]

Kudos! I applaud your effort, wish I had a 5370.

Regards,
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of John Seamons
Sent: 24 February 2014 03:57
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] 5370 processor boards available

Please excuse this commercial announcement (although it is a near-zero
profit endeavor).
I am now accepting general orders for the hp 5370 processor replacement
board.
More info and ordering information at: www.jks.com/5370/5370.html

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Re: [time-nuts] strange behavior of 53230A or is the light on, but nobody in?

[David C. Partridge]

Did you disconnect the external reference from the 53230A before doing the
test?

If no, I'll bet that the external reference being connected overrides the
internal reference 

Regards,
David Partridge 

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Re: [time-nuts] Z3816A Control and Cleaning

[David C. Partridge]

Is Calgonite just a brand name for regular dish-washer powder? (Not being a
US denizen, the name passes me by).

Thx
Dave
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Howard Davidson
Sent: 24 January 2014 08:12
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Z3816A Control and Cleaning

trip through a regular home dishwasher with tap water and Calgonite.

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Re: [time-nuts] fast edge, rise time.

[David C. Partridge]

Look at the Jim Williams application note
http://cds.linear.com/docs/en/application-note/an47fa.pdf


Regards,
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of ct1dmk
Sent: 26 December 2013 16:08
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] fast edge, rise time.

Hello,

I'm willing to generate a pulse (of some few hundred volts) by discharging a
capacitor into a pulse transformer I'm solely interested is the active edge
(call it either rise or fall depending on the wiring of the output of the
transformer).

The target is 4ns, while ideas seemed to be clear at some point, now I'm
having doubts if better to use a MOSFET or a bipolar transistor as the
switch element. Experiments with MOSFETs presented me some difficulties
charging the gate capacitance having some trouble to achieve something in
the 4ns region. Well 4ns seems hard whatever device anyway.

I would be happy to receive some comments/ideas that may pop out of your
heads.
Thanks.

hope that my quest for fast rise time is not too off topic on this time
list...
but... there are so many experts on this list that I could not resist ;-)

Luis Cupido
ct1dmk.


p.s. ( I switch a capacitor to GND with a transistor (fet or bipolar). 
that capacitor has a charging resistor to 48V, transformer has a 9:1 voltage
ratio. Pulse average power is quite low a few watt only. At the primary side
some 20A of peak current for less than 100ns... and very low duty cycle. )
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Re: [time-nuts] DTS-2077 Very Cool Toy!

[David C. Partridge]

Wow, where do I get one and how spendy are they? 

Cheers
David Partridge 
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On
Behalf Of Ed Palmer
Sent: 10 September 2013 05:34
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] DTS-2077 Very Cool Toy!

I fed a 1 GHz sine wave @ 0 dBm into the DTS-2077.  I told the DTS to sample
the voltage every 10 ps and dump the data to a file.  The attached graph
shows the result.  The horizontal axis is samples (i.e. 
increments of 10 ps).  The vertical axis is units of 100 uv. I've got a
digital scope with a sampling rate of 100 GS/s!  Very cool!

Ed


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Re: [time-nuts] Spectracom 8170 Time of Day grief...

[David C. Partridge]

I thought the Junghans Mega clock used DCF-77 rather than WWVB? 

Regards,
David Partridge
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of ewkeh...@aol.com
Sent: 13 June 2013 22:27
To: time-nuts@febo.com
Subject: Re: [time-nuts] Spectracom 8170 Time of Day grief...

I have four 15 year old Junghans Mega clocks through out the house. Ten days 
ago I noticed one of them dead. Battery, and by the look of the battery dead at 
least a month. I inserted a new battery and it did set. I did not watch  it but 
today I went with one of them through the house and all are exact within  a 
second. Even advance the second as close as I am able to observe. I am  
confident they synch daily.
Bert Kehren
 

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Re: [time-nuts] Dave Partridge Version 2 Full Board available

[David C. Partridge]

While on this subject, if anyone should want me to, I am quite happy to put the 
Gerbers for the PCB on my website. 


Regards,
David Partridge
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of James Robbins
Sent: 05 June 2013 13:06
To: time-nuts@febo.com
Subject: [time-nuts] Dave Partridge Version 2 Full Board available

I have a spare new unused, fully populated, Version 2 Frequency Divider board 
by Dave Partridge for sale.  Price is $80 plus $5.85 shipping (my cost was 
$98).  Offering it here before placing on Ebay.  Jim Robbins, N1JR 
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Re: [time-nuts] Found at a surplus store

[David C. Partridge]

Hi Pete 

How many did you buy? 

Where did you find 'em?

Dave
-Original Message-
From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf 
Of Pete Lancashire
Sent: 05 March 2013 04:53
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] Found at a surplus store

https://plus.google.com/u/0/photos/111617808980322733757/albums/5851716840178315361

$5 each

worth the $5 ?

-pete
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[time-nuts] Thunderbolt firmware to E-level ?

[David C. Partridge]

Something I saw in John Miles recent post on the TB thread leads me to ask if a 
regular TB can be upgraded to TB-E level firmaware, and if so is sensible to do 
so?

Thanks
Dave

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Re: [time-nuts] Low noise power supplies?

[David C. Partridge]

PTAT == Proportional To Absolute Temperature 

Dave

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[time-nuts] Racal MA-259 Crystal frequency standard on UK eBay

[David C. Partridge]

http://cgi.ebay.co.uk/230912316345

Dave

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