Re: [time-nuts] Crystal filters in test equipment

[Bernd Neubig]

>> Learned Gentlemen,
>> Both the HP 106 and 107 have a post oscillator crystal filter.  There 
>> is also a 10 MHz crystal filter used in my Tracor 527E FDM.
>> So the question I have is there anything to be gained by adding 10 
>> MHz crystal filters to the 10811 and similar OCXO's?  They are very 
>> inexpensive to purchase.
>> Regards,
>> Perrier

Some of the commercial ultra-low phase noise OCXO today are using crystals 
filters at (or just in front of) the output buffer stage. These filters are 
usually heavily overdriving the crystal into the non-linear region, therefore 
the long-term reliability of such a circuit is suspect.
The purpose is to improve the far-off noise floor, which works fine, but 
sometimes the close-in noise gets worse, as Rick said before.
Cheap monolithic filters (duals) are much more sensitive to high drive levels, 
and thus are not recommended at all.
Another effect of a crystal filter in the output is, that its output impedance 
outside the passband is far off from 50 Ohm. So it fools the power splitter at 
the input of cross-correlation based phase noise test equipment, and may 
display lower unrealistic phase noise "dBc/Hz" values at the noise floor, 
sometimes lower than the thermal noise floor of a 50 Ohm system.

Regards
Bernd



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Re: [time-nuts] Crystal filters in test equipment

[Taka Kamiya via time-nuts]

I don't have sophisticated instruments, so I did a basic test.  Feed 2MHz into 
a spectrum analyzer and place a 2MHz crystal in series.  I didn't concern 
myself with impedance matching or any other details.  Just a coax in and out.

It basically acts like a very sharp filter.  What it does to phase noise, etc, 
is beyond my ability to measure.  I'll have to remember this trick  It 
might come in handy!

--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Thursday, March 26, 2020, 7:32:24 PM EDT, Perry Sandeen via time-nuts 
 wrote:  
 
 Learned Gentlemen,
Both the HP 106 and 107 have a post oscillator crystal filter.  There is also a 
10 MHz crystal filter used in my Tracor 527E FDM.
So the question I have is there anything to be gained by adding 10 MHz crystal 
filters to the 10811 and similar OCXO's?  They are very inexpensive to purchase.
Regards,
Perrier
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Re: [time-nuts] Crystal filters in test equipment

[John Ackermann N8UR]

One of my Sulzers on an oddball frequency seems, from the phase noise
plot, to have a crystal filter about 1 kHz wide -- see attached.

John


On 3/26/20 8:04 PM, Richard (Rick) Karlquist wrote:
> On 3/26/2020 3:03 PM, Perry Sandeen via time-nuts wrote:
>> Learned Gentlemen,
>> Both the HP 106 and 107 have a post oscillator crystal filter.  There
>> is also a 10 MHz crystal filter used in my Tracor 527E FDM.
>> So the question I have is there anything to be gained by adding 10 MHz
>> crystal filters to the 10811 and similar OCXO's?  They are very
>> inexpensive to purchase.
>> Regards,
>> Perrier
>> ___
> 
> I never knew those oscillators had filters, even though
> I worked for HP.  My understanding is that the flicker
> noise of a crystal oscillator is established by the
> crystal, as opposed to the electronics.  A crystal
> filter using a similar crystal could not clean up
> flicker noise.  However, it could follow the buffer
> amplifier and clean up far out phase noise.  I am
> thinking that is why those models have filters.
> 
> The 10811 has an improved buffer that has very low
> far out phase noise, so I am thinking that there
> is no need for a post filter.  In all my time at HP,
> no one ever suggested a 10811 post filter.
> 
> "inexpensive to purchase" filters would probably not
> have good enough flicker noise and would degrade the
> close in noise.
> 
> The 8662 sig gen multiplies 10 MHz to 80 MHz and then
> has an 80 MHz crystal filter to clean up far out
> phase noise.  That makes more sense than a filter at
> the oscillator frequency.
> 
> If you really need lower far out phase noise than
> the 10811 offers, you can redesign the 2nd and 3rd
> buffer amplifier stages.  The 10811 designers knowingly
> degraded the phase noise in those stages because of
> requirements to be backward compatible with 10544
> sockets.  They made a one-off demonstration oscillator
> coded named "Barnabus" with ultra low noise.  It always
> seemed to be the proverbial "solution in search of a problem."
> 
> When I was designing the E1938A oscillator, I remember
> reading some papers about crystal oscillators that
> had a 2nd crystal that was installed in a Wheatstone
> bridge and used to servo the frequency of the oscillator
> to reduce temperature drift.  The breakthrough in the
> E19838A was to put the crystal in a bridge while
> simultaneously using it to make an oscillator.
> 
> Rick N6RK
> 
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Re: [time-nuts] Crystal filters in test equipment

[Bob kb8tq]

Hi

Narrowband filters have significant amounts of delay. Any change in that delay 
(like from
temperature or ……) will phase modulate the oscillator. Conventional wisdom 
these days
is that your ADEV will be better without the filter. 

Phase noise wise, you can only get just so close to the … errr …. noise floor. 
That moves 
you in the direction of a filter that can handle a bit of power. That takes you 
out of the “cheap 
filter” part of the world …. 

Bob

> On Mar 26, 2020, at 6:03 PM, Perry Sandeen via time-nuts 
>  wrote:
> 
> Learned Gentlemen,
> Both the HP 106 and 107 have a post oscillator crystal filter.  There is also 
> a 10 MHz crystal filter used in my Tracor 527E FDM.
> So the question I have is there anything to be gained by adding 10 MHz 
> crystal filters to the 10811 and similar OCXO's?  They are very inexpensive 
> to purchase.
> Regards,
> Perrier
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Re: [time-nuts] Crystal filters in test equipment

[Bruce Griffiths]

A constant temperature oven for the crystal filter may be required to minimise 
the crystal filter phase shift tempco contribution to the output phase 
stability. 

Bruce
> On 27 March 2020 at 11:03 Perry Sandeen via time-nuts 
>  wrote:
> 
> 
> Learned Gentlemen,
> Both the HP 106 and 107 have a post oscillator crystal filter.  There is also 
> a 10 MHz crystal filter used in my Tracor 527E FDM.
> So the question I have is there anything to be gained by adding 10 MHz 
> crystal filters to the 10811 and similar OCXO's?  They are very inexpensive 
> to purchase.
> Regards,
> Perrier
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Re: [time-nuts] Mains frequency data for Europe

[Detlef Schuecker via time-nuts]

Hi,

I uploaded european frequency data starting 2019 to ftp site 
'dschuecker.dyndns.org' name/pw 'mainsf'.

feel free to download

Cheers Detlef




Von:"Azelio Boriani" 
An: "Discussion of precise time and frequency measurement" 

Datum:  25.03.2020 02:30
Betreff:Re: [time-nuts] Mains frequency data for Europe
Gesendet von:   "time-nuts" 



The entsoe.eu site is full of 404... the only site I can find with
frequency data is this (for the Belgian grid):


What happened to the grid frequency in Europe in Jan 2019 and Apr 2019:
<
https://www.next-kraftwerke.com/energy-blog/who-is-disrupting-the-utility-frequency
>


On Wed, Mar 25, 2020 at 12:52 AM Pieter-Tjerk de Boer
 wrote:
>
> Hello Attila,
>
> In principle I have that data (I've been logging the grid's phase since 
2008),
> but I'll need to do a bit of work to extract it to a usable format.
> Please contact me off-list.
>
> Regards,
>   Pieter-Tjerk
>
>
> On Tue, Mar 24, 2020 at 04:30:25PM +0100, Attila Kinali wrote:
> > Hi,
> >
> > Does someone here have recordings of the mains frequency of the west
> > European Grid from the last weeks and from the same time last year?
> > There is something I've been told which I would like to fact-check.
> > I wasn't able to find anything online.
> >
> > Thanks in advance
> >
> >   Attila Kinali
> > --
> > Science is made up of so many things that appear obvious
> > after they are explained. -- Pardot Kynes
> >
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[time-nuts] Key to HP 106 Performance?

[Perry Sandeen via time-nuts]

Learned Gentlemen,
After TVB posted his HP 106 experience I became curios why it was so good after 
having a HP 107.
Both schematics look extremely similar but on closer examination the 106 uses a 
2.5 MHz oscillator crystal which is doubled and then fed through a 5 MHz 
crystal.  The 107 uses a 5 MHz crystal but it is also fed through a 5 MHz 
crystal.
Both are physically mammoth compared to the previous 100 series which allows 
for more circuitry which makes both far easier to service.  Lifting however is 
another issue... 

Another similarity for both are the number of *factory select* with nominal 
values shown.
It would be quite interesting to know how they did the process of *final 
tuning*.
Regards,
Perrier



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[time-nuts] Crystal filters in test equipment

[Perry Sandeen via time-nuts]

Learned Gentlemen,
Both the HP 106 and 107 have a post oscillator crystal filter.  There is also a 
10 MHz crystal filter used in my Tracor 527E FDM.
So the question I have is there anything to be gained by adding 10 MHz crystal 
filters to the 10811 and similar OCXO's?  They are very inexpensive to purchase.
Regards,
Perrier
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Re: [time-nuts] Noise Floor

[Taka Kamiya via time-nuts]

Yes.  The first page says that, along with several entries in the spec sheet.  
Then, on page 6 lists absolute maximum.  12.6V (I was .1V off).  To me, that's 
awfully close.  I chose not to go there, especially when 9V gave me what I 
wanted in the first place.

In many ways and places, I've learned not to get too close to the maximum 
rating of devices.
--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Thursday, March 26, 2020, 4:48:25 PM EDT, Charles Steinmetz 
 wrote:  
 
 Taka Kamiya wrote:

> According to the datasheet, AD8007's absolute max is 12.5V.  It's a bit scary 
> to go to 12V.

Not at all.  Look at the first page of the datasheet, which recommends 
supplies from 5v to 12v.  I've deployed thousands of them running at 12v 
(usually, +/- 6v) with superb reliability.

That said, today I use modern CFB amps with 36v supply ratings for these 
jobs, and if I had a Z1 I would certainly retrofit it with one 
without a second thought.  There is no substitute for headroom!

Best regards,

Charles



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Re: [time-nuts] Noise Floor

[Bruce Griffiths]

The PN floor is somewhat lower with a 15dBm rather than a 4dBm input

http://www.ko4bb.com/getsimple/index.php?id=phase-noise-and-other-measurements-with-a-timepod

Bruce

> On 27 March 2020 at 06:11 kb...@n1k.org mailto:kb...@n1k.org wrote:
> 
> 
> Hi
> 
> Ok so here's a "new" part as opposed to one that is many decades old. 
> Again
> this is a part that has been talked about
> more than once on the list. The demo board is an early one, but I assume 
> it
> is representative of how the CMOS output
> part you get today works.
> 
> There are two runs. The first pretty clearly shows the part warming up. 
> The
> second still shows temperature effects,
> they just are not as obvious. If you *really* need to hit < 1x10^-15 at 
> 100
> seconds with this part, drafts are not a good thing.
> 
> The part is being driven with 4 dbm at 5 MHz. Max input is rated as 10 dbm
> so that's not as nutty as it sounds. 5 MHz ( or
> even 10 MHz) is well below the design target for this part. There's not a
> lot on the datasheet to compare to. As with the previous
> part, ADEV is pretty good (out to 100 sec). Phase noise is not in the 
> 10811
> class wideband. If you need low wideband phase noise
> as a logic signal at 5 MHz, you need to do something different. For ADEV,
> this will do just fine.
> 
> Bob
> 
> -Original Message-
> From: time-nuts  mailto:time-nuts-boun...@lists.febo.com > On Behalf Of Charles
> Steinmetz
> Sent: Wednesday, March 25, 2020 5:23 PM
> To: time-nuts@lists.febo.com mailto:time-nuts@lists.febo.com
> Subject: Re: [time-nuts] Noise Floor
> 
> Taka Kamiya wrote:
> 
> > > I've been playing around with Clifton amplifier as well. Mine, 
> input is
> > 
> > > terminated with 50 ohm register, and rest is unmodified, so it has 
> > 6dB gain.
> I have a 10dB pad on input side. I, too, noticed there will be a severe
> clipping with driving it too hard. * * * I with there was a little
> more room there
> 
> Bob wrote:
> >> Maybe there's some noise in those resistors
> >> Well. maybe not so much.
> >>
> >> If you drive this board so it has a couple db more output, it goes into
> clipping. When that happens  yuck.
> >> Noise and ADEV both are massively impacted.
> >> You very much do *not* want to overdrive this board. * * *
> >> I would stick with 12 dbm or less
> 
> You can buy some headroom by raising the supply voltage. There is an
> on-card LM78L09 9v voltage regulator (U902) that can safely be raised to
> 12v (LM78L12). This will get you cleanly to and a bit past the
> traditional +13 dBm (1v rms) standard reference level. Of course, you
> will need to make sure the raw supply voltage is >15v.
> 
> As to noise, the 200 ohm resistor on the opamp's noninverting input
> (R901) accounts for nearly 6dB of the amplifier noise (assuming an
> effective source impedance of 50 ohms). Reducing this to, say, 33 ohms
> will lower the noise floor a few dB.
> 
> Finally, the state of CFB video amplifier development has advanced
> dramatically in the 20 years since the AD8007 was introduced. New
> amplifiers with supply voltage ratings up to 36v are available (allowing
> about 10dB greater headroom than the 8007), and many of the newer opamps
> clip much more gracefully than the 8007 when you do hit the limit (but
> you really want not to do that in any measurement application).
> 
> Many of these new CFB amplifiers have been discussed here on the list,
> and each has its own fans. One I like that doesn't get mentioned much
> is the LME49713. It is discontinued, but still available from Rochester
> Electronics and others. But there are lots of good choices.
> 
> Best regards,
> 
> Charles
> 
> 
> 
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Re: [time-nuts] Symmetricom analog network clocks.

[Peter Vince]

I have several Leitch clocks.  These are (were?) widely used in
broadcasting studios, and locked to SMPTE/EBU timecode (or mains frequency,
or their internal crystal).  Often available on our favourite auction site
- see, for example:  https://www.ebay.com/itm/123679630402
The second hand can be set to sweep or "step", but the latter is a fast
sweep between seconds, and then a pause, so is virtually silent (critical
for a broadcast studio!)  They come in various sizes: 8 inch, 12 inch, and
18 inch.  They were extremely reliable at work, and I've been delighted
with the couple I now have at home.

Peter
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Re: [time-nuts] Noise Floor

[Charles Steinmetz]

Taka Kamiya wrote:


According to the datasheet, AD8007's absolute max is 12.5V.  It's a bit scary 
to go to 12V.


Not at all.  Look at the first page of the datasheet, which recommends 
supplies from 5v to 12v.  I've deployed thousands of them running at 12v 
(usually, +/- 6v) with superb reliability.


That said, today I use modern CFB amps with 36v supply ratings for these 
jobs, and if I had a Z1 I would certainly retrofit it with one 
without a second thought.  There is no substitute for headroom!


Best regards,

Charles



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Re: [time-nuts] Symmetricom analog network clocks.

[Peter Reilley]

I didn't know that there was such a thing as an analog IP clock.
Now it is on my "gotta have" list.

Pete.

On 3/26/2020 3:22 AM, Bob Darlington wrote:

I ended up throwing all three of mine away.  None worked right.  Bought
two, did an RMA for one and the new one was broken and was told to keep it,
and they had no more stock.   It felt good to get rid of the junk that
didn't work.  It was a shame because they looked really nice.  They simply
did not work.

-Bob

On Tue, Mar 24, 2020 at 7:30 PM djl  wrote:


Some years ago, symmetricom sold out some analog network clocks. Last
winter, both of mine froze up and would not adjust. Being naturally
curious, I opened one up, and found the motor and wheels that drive the
hands. Knowing that this type of motor has problems, I simply unplugged
it and manually forced the going train and the motor on each clock to
turn in both directions(use your thumb.) After all, it was no good as
is. I guess the grease was redistributed, as both clocks now function
properly. They do have to be set using the software sort of often, but
sure look classy :-). No wonder we got them so cheap!
73, Don

--
Dr. Don Latham  AJ7LL
PO Box 404, Frenchtown, MT, 59834
VOX: 406-626-4304


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Re: [time-nuts] Symmetricom analog network clocks.

[Esa Heikkinen]

djl kirjoitti 25.3.2020 klo 2:46:

turn in both directions(use your thumb.) After all, it was no good as 
is. I guess the grease was redistributed, as both clocks now function 
properly. They do have to be set using the software sort of often, but 
sure look classy :-). No wonder we got them so cheap!


Root cause in my unit was that rotor was hitting stator and caused 
random "jams". The rotor was mounted off-center and got contact with 
stator. I was able to bend the motor frame so that rotor was properly 
centered.


No problems aftert that, now it has been running many years after that 
fix without any issues. At the same opening I also converted it to PoE 
powered, so only one cable now. It's 15V system but runs perfectly with 
12V also.


Very nice wallclock indeed!

--
73s!
Esa
OH4KJU

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Re: [time-nuts] Noise Floor

[Taka Kamiya via time-nuts]

According to the datasheet, AD8007's absolute max is 12.5V.  It's a bit scary 
to go to 12V.  I was able to reduce the gain to zero dB, and get a clean and 
respectable 11.5dBm output.  With this, I'm perfectly happy.  I would 
experiment with other changes if I had a meaningful way to measure its impact, 
but I do not.
Thanks for your advice!

--- 
(Mr.) Taka Kamiya
KB4EMF / ex JF2DKG
 

On Wednesday, March 25, 2020, 5:28:16 PM EDT, Charles Steinmetz 
 wrote:  
 
 Taka Kamiya wrote:
> I've been playing around with Clifton amplifier as well.  Mine, input is 
> terminated with 50 ohm register, and rest is unmodified, so it has 6dB gain.  
> I have a 10dB pad on input side.  I, too, noticed there will be a severe 
> clipping with driving it too hard.    *  *  *  I with there was a little more 
> room there

Bob wrote:
>> Maybe there's some noise in those resistors
>> Well. maybe not so much.
 >>
>> If you drive this board so it has a couple db more output, it goes into 
>> clipping. When that happens  yuck.
 >> Noise and ADEV both are massively impacted.
>> You very much do *not* want to overdrive this board.  *  *  *
>> I would stick with 12 dbm or less

You can buy some headroom by raising the supply voltage.  There is an 
on-card LM78L09 9v voltage regulator (U902) that can safely be raised to 
12v (LM78L12).  This will get you cleanly to and a bit past the 
traditional +13 dBm (1v rms) standard reference level.  Of course, you 
will need to make sure the raw supply voltage is >15v.

As to noise, the 200 ohm resistor on the opamp's noninverting input 
(R901) accounts for nearly 6dB of the amplifier noise (assuming an 
effective source impedance of 50 ohms).  Reducing this to, say, 33 ohms 
will lower the noise floor a few dB.

Finally, the state of CFB video amplifier development has advanced 
dramatically in the 20 years since the AD8007 was introduced.  New 
amplifiers with supply voltage ratings up to 36v are available (allowing 
about 10dB greater headroom than the 8007), and many of the newer opamps 
clip much more gracefully than the 8007 when you do hit the limit (but 
you really want not to do that in any measurement application).

Many of these new CFB amplifiers have been discussed here on the list, 
and each has its own fans.  One I like that doesn't get mentioned much 
is the LME49713.  It is discontinued, but still available from Rochester 
Electronics and others.  But there are lots of good choices.

Best regards,

Charles



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Re: [time-nuts] Symmetricom analog network clocks.

[Bob Darlington]

I ended up throwing all three of mine away.  None worked right.  Bought
two, did an RMA for one and the new one was broken and was told to keep it,
and they had no more stock.   It felt good to get rid of the junk that
didn't work.  It was a shame because they looked really nice.  They simply
did not work.

-Bob

On Tue, Mar 24, 2020 at 7:30 PM djl  wrote:

> Some years ago, symmetricom sold out some analog network clocks. Last
> winter, both of mine froze up and would not adjust. Being naturally
> curious, I opened one up, and found the motor and wheels that drive the
> hands. Knowing that this type of motor has problems, I simply unplugged
> it and manually forced the going train and the motor on each clock to
> turn in both directions(use your thumb.) After all, it was no good as
> is. I guess the grease was redistributed, as both clocks now function
> properly. They do have to be set using the software sort of often, but
> sure look classy :-). No wonder we got them so cheap!
> 73, Don
>
> --
> Dr. Don Latham  AJ7LL
> PO Box 404, Frenchtown, MT, 59834
> VOX: 406-626-4304
>
>
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