Re: [time-nuts] Thunderbolt Harmonics

[jimlux]

On 1/18/17 6:25 PM, Tom Holmes wrote:

Jim Lux...

Note that the Keysight 33622 is basically an ARB, and not really intended to
be an RF signal generator.


Yes, but it has performance that is as good as the run of the mill 
signal generator.


The big defect in the 33600 series is that it cannot be phase locked to 
an external reference.  If you feed it a 10 MHz ref, it has a frequency 
locked loop that pushes the internal oscillator around to match the 
external reference.



 It's output is DAC based, not oscillator based.

Hence it will tend to have higher distortion products than a good RF
generator.


As good as, if not better, than an inexpensive generator (e.g. the low 
end Keysight sig gens)


phase noise at non-harmonic frequencies is not as good.



 As you point out, a suitable filter for the intended frequency

certainly can clean that up, of course.

Tom Holmes, N8ZM


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Re: [time-nuts] 10MHz to 25MHz

[Richard (Rick) Karlquist]

On 1/18/2017 6:34 PM, David wrote:


An alternative very simple design I might try is a variation of the
active frequency multiplier where the 5th harmonic is filtered
directly from the output of the digital divide by two stage.


That's a useful trick to reduce the filtering burden.  Having said
that, if you need good spectral purity, the filtering is still
going to be very non-trivial.  The original poster is obviously
not an expert in filters and will not be successful trying that
approach, except for very low performance design.  Even if
you are a filter expert, components are hard to get.

Rick N6RK
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Re: [time-nuts] Thunderbolt Harmonics

[jimlux]

Yeah, but it's easier (cheaper if you're paying for labor) just to buy a box of 
10 filters at $30/each and stack them


Be *very* careful cascading those Min-Circuits filters without putting some 
sort of isolation between them. You can get all
sorts of wonky results as the reactances in one mis-terminates the reactances 
in another.


that's what a VNA is for.

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Re: [time-nuts] Thunderbolt Harmonics

[Gerhard Hoffmann]

Am 18.01.2017 um 22:12 schrieb Bob Camp:

Yeah, but it's easier (cheaper if you're paying for labor) just to buy a box of 
10 filters at $30/each and stack them

Be *very* careful cascading those Min-Circuits filters without putting some 
sort of isolation between them. You can get all
sorts of wonky results as the reactances in one mis-terminates the reactances 
in another.

Bob

But you can be quite lucky:

1 SLP15+ filter (15 MHz Low pass):
< 
https://www.flickr.com/photos/137684711@N07/31554251684/in/album-72157662535945536/ 
>


3 filters cascaded
< 
https://www.flickr.com/photos/137684711@N07/32019253490/in/album-72157662535945536/ 
>

Not bad.

73, Gerhard
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Re: [time-nuts] 10MHz to 25MHz

[Neil Smith G4DBN]

That is exactly what I have just done, using an HMC1031 to lock a good 100MHz 
OCXO to my GPSDO, using a very narrow filter bandwidth with decent 22uF ceramic 
caps in the loop filter. I’ve also made a second version using an XOR gate and 
an MC12080 prescaler and flipflops and fast comparators, but the HMC1031 
version is way simpler and has a wider lock-in range. Hard to measure the 
performance as the noise appears lower than my E4406A can resolve, but with one 
100MHz OCXO locked to the GPSDO and the other to my 10MHz Rb standard, and 
monitoring the relative phases using an AD8302, I see none of the (slight) 
glitchiness of the GPSDO reflected in the 100MHz locked output.

Neil 

> On 19 Jan 2017, at 02:08, Bob Camp  wrote:
> 
> Hi
> 
> What are you going to use the 25 MHz for? Will it drive any sort of radio? If 
> so, cleaning up the phase
> noise of the GPSDO is a *very* good idea. With a PLL, you can *subtract* 
> noise. With a multiplier you 
> can only *add* noise. The narrow bandwidth PLL combined with a low nose VCXO 
> is your friend in this case. 
> 
> I would take the process one step further. I’d lock up a 100 MHz VCXO to the 
> 10 MHz. Then you can get
> 100, 50, 25, and 20 MHz outputs. The 100 MHz is the key if you want to head 
> up into the microwave 
> region. 
> 
> Bob
> 
>> On Jan 18, 2017, at 8:40 PM, Loren Moline WA7SKT  wrote:
>> 
>> Are you talking about locking the 50MHz VCXO to my 10 MH. Standard? I want 
>> the 25MHz to be from my 10MHz OCXO which is my station standard which will 
>> locked to GPS eventually.
>> 
>> Loren WA7SKT
>> 
>> 
>> 
>> 
>> On Wed, Jan 18, 2017 at 4:01 PM -0800, "Richard (Rick) Karlquist" 
>> mailto:rich...@karlquist.com>> wrote:
>> 
>> 
>> A better and easier way is to phase lock a crystal oscillator.
>> I would use a 50 MHz VCXO and divide the output by 2 to get a
>> 25 MHz square wave.
>> 
>> Rick N6RK
>> 
>> On 1/18/2017 10:28 AM, Loren Moline WA7SKT wrote:
>>> Hello,
>>> 
>>> I am looking for a good X5 multiplier to use to generate a 25MHz signal 
>>> from my 10MHz OCXO. I want to divide by 2 and multiply by 5 with a bandpass 
>>> filter in the output and then a 3.3 volt 25MHz signal out.
>>> 
>>> 
>>> Maybe someone has better ways?
>>> 
>>> 
>>> Loren Moline  WA7SKT
>>> 
>>> Member: Pacific Northwest VHF Society and ARRL
>>> Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
>>> Member: CVARS-Chehalis Valley Amateur Radio Society
>>> Starchat IRC: Channel = #hearsat
>>> RF Electronics: Starchat IRC: Channel = #rfelectronics
>>> Grid: CN86mr
>>> ___
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>>> 
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Re: [time-nuts] Thunderbolt Harmonics

[Tom Holmes]

Jim Lux...

Note that the Keysight 33622 is basically an ARB, and not really intended to 
be an RF signal generator. It's output is DAC based, not oscillator based. 
Hence it will tend to have higher distortion products than a good RF 
generator. As you point out, a suitable filter for the intended frequency 
certainly can clean that up, of course.

Tom Holmes, N8ZM

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of jimlux
Sent: Wednesday, January 18, 2017 9:45 AM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Thunderbolt Harmonics

On 1/18/17 4:33 AM, Artek Manuals wrote:
> R
>
> Is what your seeing a harmonic (2nd? 3rd?) or a spur i.e what frequency
> is the "harmonic" ?
>
> How are you measuring this ? (Spectrum analyzer ? make/model?)
>
> More importantly and at the risk of displaying my naivety, what is the
> application that you are using the 10MHz source to feed and why if this
> harmonic is 60db down (or even only 40db down, the quoted spec) why
> would one care? What is the predicted error you will get in your
> application as a result?
>

One application that needs low harmonic content is where you are
measuring the harmonic generating (or lack thereof) of a downstream
component.

I have an application where we're measuring the performance of a RF
chain followed by a digitizer.  An easy test is to feed in a nice sine
wave (at a frequency that is NOT a submultiple of the samplerate) and
look for harmonics in the power spectrum of the sampled data stream.

the first time we ran the test (using a Keysight 33622 signal generator)
we saw significant 2nd and 3rd harmonics (50-60 dB down, but easily
detectable).  A quick review of the data sheet.. Oh, the signal
generator spec is only -43 dBc for frequencies above 10 MHz.

Another case where low harmonic content is when doing two tone IMD tests
- if the sources have significant harmonic content, you might be seeing
intermod between the harmonics of the source, rather than intermods
between the fundamental of the source.

For 10 MHz, you can get minicircuits filters for 10.7 MHz that are
fairly wideband and work pretty well... about 20-30 dB of harmonic
suppression per filter I'd use the low pass flavor

SBP-10.7
loss at 20MHz is 26.84
loss at 40MHz is 41.22
loss at 50MHz is 46
est loss at 30 is 35?

SLP-10.7
loss at 10 is 0.65 spec
loss at 20 is 31.35 specmeasured -33
loss at 30 measured -60
loss at 34 is 47.26 spec
loss at 40 measured -77
loss at 67.5 is 69.85 spec



Yeah, they might have a significant tempco, but you're running all this
stuff in an underground lair with small temperature variations, right?
It only looks like a small volcano from the outside.

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Re: [time-nuts] 10MHz to 25MHz

[Chris Albertson]

On Wed, Jan 18, 2017 at 5:40 PM, Loren Moline WA7SKT 
wrote:

> Are you talking about locking the 50MHz VCXO to my 10 MH. Standard? I want
> the 25MHz to be from my 10MHz OCXO which is my station standard which will
> locked to GPS eventually.
>

The 25MHz WOULD be locked to your 10MHz GPSDO if you first locked a 100MHz
or 50MHz to the 10MHz then divided down.   Dividers work really well, they
can improve the phase noise, Multipliers always add phase noise.Because
of this I have always wondered why we build our "standard" with such a low
frequency.   Why not a 100MHz GPSDO?   Why 10MHz


> Loren WA7SKT
>
>
>
>
> On Wed, Jan 18, 2017 at 4:01 PM -0800, "Richard (Rick) Karlquist" <
> rich...@karlquist.com> wrote:
>
>
> A better and easier way is to phase lock a crystal oscillator.
> I would use a 50 MHz VCXO and divide the output by 2 to get a
> 25 MHz square wave.
>
> Rick N6RK
>
> On 1/18/2017 10:28 AM, Loren Moline WA7SKT wrote:
> > Hello,
> >
> > I am looking for a good X5 multiplier to use to generate a 25MHz signal
> from my 10MHz OCXO. I want to divide by 2 and multiply by 5 with a bandpass
> filter in the output and then a 3.3 volt 25MHz signal out.
> >
> >
> > Maybe someone has better ways?
> >
> >
> > Loren Moline  WA7SKT
> >
> > Member: Pacific Northwest VHF Society and ARRL
> > Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
> > Member: CVARS-Chehalis Valley Amateur Radio Society
> > Starchat IRC: Channel = #hearsat
> > RF Electronics: Starchat IRC: Channel = #rfelectronics
> > Grid: CN86mr
> > ___
> > 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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-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] 10MHz to 25MHz

[David]

This document covers various methods but I agree with Rick about phase
locking a separate crystal oscillator; harmonic frequency
multiplication is more useful at higher frequencies where other
methods are unavailable:

http://www.qsl.net/va3iul/Frequency_Multipliers/Frequency_Multipliers.pdf

An alternative very simple design I might try is a variation of the
active frequency multiplier where the 5th harmonic is filtered
directly from the output of the digital divide by two stage.

On Wed, 18 Jan 2017 18:28:32 +, you wrote:

>Hello,
>
>I am looking for a good X5 multiplier to use to generate a 25MHz signal from 
>my 10MHz OCXO. I want to divide by 2 and multiply by 5 with a bandpass filter 
>in the output and then a 3.3 volt 25MHz signal out.
>Maybe someone has better ways?
>
>Loren Moline  WA7SKT
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Re: [time-nuts] 10MHz to 25MHz

[Bob Camp]

Hi

What are you going to use the 25 MHz for? Will it drive any sort of radio? If 
so, cleaning up the phase
noise of the GPSDO is a *very* good idea. With a PLL, you can *subtract* noise. 
With a multiplier you 
can only *add* noise. The narrow bandwidth PLL combined with a low nose VCXO is 
your friend in this case. 

I would take the process one step further. I’d lock up a 100 MHz VCXO to the 10 
MHz. Then you can get
100, 50, 25, and 20 MHz outputs. The 100 MHz is the key if you want to head up 
into the microwave 
region. 

Bob

> On Jan 18, 2017, at 8:40 PM, Loren Moline WA7SKT  wrote:
> 
> Are you talking about locking the 50MHz VCXO to my 10 MH. Standard? I want 
> the 25MHz to be from my 10MHz OCXO which is my station standard which will 
> locked to GPS eventually.
> 
> Loren WA7SKT
> 
> 
> 
> 
> On Wed, Jan 18, 2017 at 4:01 PM -0800, "Richard (Rick) Karlquist" 
> mailto:rich...@karlquist.com>> wrote:
> 
> 
> A better and easier way is to phase lock a crystal oscillator.
> I would use a 50 MHz VCXO and divide the output by 2 to get a
> 25 MHz square wave.
> 
> Rick N6RK
> 
> On 1/18/2017 10:28 AM, Loren Moline WA7SKT wrote:
>> Hello,
>> 
>> I am looking for a good X5 multiplier to use to generate a 25MHz signal from 
>> my 10MHz OCXO. I want to divide by 2 and multiply by 5 with a bandpass 
>> filter in the output and then a 3.3 volt 25MHz signal out.
>> 
>> 
>> Maybe someone has better ways?
>> 
>> 
>> Loren Moline  WA7SKT
>> 
>> Member: Pacific Northwest VHF Society and ARRL
>> Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
>> Member: CVARS-Chehalis Valley Amateur Radio Society
>> Starchat IRC: Channel = #hearsat
>> RF Electronics: Starchat IRC: Channel = #rfelectronics
>> Grid: CN86mr
>> ___
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>> 
>> 
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Re: [time-nuts] 10MHz to 25MHz

[Loren Moline WA7SKT]

Are you talking about locking the 50MHz VCXO to my 10 MH. Standard? I want the 
25MHz to be from my 10MHz OCXO which is my station standard which will locked 
to GPS eventually.

Loren WA7SKT




On Wed, Jan 18, 2017 at 4:01 PM -0800, "Richard (Rick) Karlquist" 
mailto:rich...@karlquist.com>> wrote:


A better and easier way is to phase lock a crystal oscillator.
I would use a 50 MHz VCXO and divide the output by 2 to get a
25 MHz square wave.

Rick N6RK

On 1/18/2017 10:28 AM, Loren Moline WA7SKT wrote:
> Hello,
>
> I am looking for a good X5 multiplier to use to generate a 25MHz signal from 
> my 10MHz OCXO. I want to divide by 2 and multiply by 5 with a bandpass filter 
> in the output and then a 3.3 volt 25MHz signal out.
>
>
> Maybe someone has better ways?
>
>
> Loren Moline  WA7SKT
>
> Member: Pacific Northwest VHF Society and ARRL
> Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
> Member: CVARS-Chehalis Valley Amateur Radio Society
> Starchat IRC: Channel = #hearsat
> RF Electronics: Starchat IRC: Channel = #rfelectronics
> Grid: CN86mr
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>
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Re: [time-nuts] How to create a super Rb standard

[Chris Albertson]

On Tue, Jan 17, 2017 at 9:23 PM, Li Ang <379...@qq.com> wrote:

> Hi
> I am wondering if anyone tried to put a Rb unit into a vacuum container.
> And how much the performance is improved?


Vacuum is a VERY good thermal insulator.   If the electronics used even
just a few watts of power you'd need some way to cool it, other then
convection.Almost all electronics depends on air for cooling.  You'd
need to redesign it for conductive or radiative cooling.   That is not easy.

I did something very simple that works.   I placed the Rb unit in a metal
box and used a thermostatically controlled fan. The fan speed is controlled
by a PID controller.  It all runs on one 8-pin AVR chip,  I use two analog
inputs for two temperature sensors (one epoxied to a heat sink and one in
free air.  Another pin is analog output to control the fan speed.   In
improvement would be to use a three wire fan with a tachometer.

I tried before to make an analog fan controller but without using a dozen
op amps it is hard to implement any kind of decent algorithm.

But BEFORE you try and improve the Rb performance you need to have some way
to MEASURE its performance.  This is likely much harder.
-- 

Chris Albertson
Redondo Beach, California
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Re: [time-nuts] 10MHz to 25MHz

[Richard (Rick) Karlquist]

A better and easier way is to phase lock a crystal oscillator.
I would use a 50 MHz VCXO and divide the output by 2 to get a
25 MHz square wave.

Rick N6RK

On 1/18/2017 10:28 AM, Loren Moline WA7SKT wrote:

Hello,

I am looking for a good X5 multiplier to use to generate a 25MHz signal from my 
10MHz OCXO. I want to divide by 2 and multiply by 5 with a bandpass filter in 
the output and then a 3.3 volt 25MHz signal out.


Maybe someone has better ways?


Loren Moline  WA7SKT

Member: Pacific Northwest VHF Society and ARRL
Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
Member: CVARS-Chehalis Valley Amateur Radio Society
Starchat IRC: Channel = #hearsat
RF Electronics: Starchat IRC: Channel = #rfelectronics
Grid: CN86mr
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Re: [time-nuts] PN/AM and 1.5Hz spur from frequency doubling?

[Magnus Danielson]

Hi,

Considering that you have a diode and a tuned LC-tank, the tank will 
"ring" in it's own frequency, even if it is driven by the diode and 5 
MHz. This creates a single side-band tone which then shows up both as AM 
and PM. Well, that is my guess. 1.5 Hz is however very very close, which 
is quite impressive for 10 MHz, so there should be something more going 
on, I'm just speculating.


This gives some insight as one of many:
https://www.minicircuits.com/app/DOUB9-2.pdf
See the warning of over-power on last page.

MVH
Magnus

On 01/18/2017 06:01 PM, Bob Camp wrote:

Hi

Without seeing the circuit involved it’s a bit tough to guess all of the 
possible
things that might be happening. One branch leads off to things like the circuit
it’s self oscillating and creating the spur. Sub branches involve oscillation in
a regulator at low frequency vs RF oscillation somewhere else. Another branch
heads in the direction  of a loose cable running around the shop with a bunch
of 10 MHz on it. There are many branches ….

Bob


On Jan 18, 2017, at 11:13 AM, Anders Wallin  wrote:

I'm seeing +20-30 dBc/Hz of excess AM/PN, as well as a strong 1.5 Hz spur
created by frequency doubling from 5 MHz to 10 MHz.
https://goo.gl/photos/GFx9tQoxrSmyzUQo8
The input amplitude to the doubler should be just above the recommended 11
dBm.
What's going on??

thanks!
Anders
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Re: [time-nuts] Thunderbolt Harmonics

[Rhys D]

Thanks all for the extremely educational replies.

On 19 January 2017 at 07:08, jimlux  wrote:

> On 1/18/17 8:56 AM, Bob Camp wrote:
>
>> HI
>>
>>>
>>> the first time we ran the test (using a Keysight 33622 signal
>>> generator) we saw significant 2nd and 3rd harmonics (50-60 dB down,
>>> but easily detectable).  A quick review of the data sheet.. Oh, the
>>> signal generator spec is only -43 dBc for frequencies above 10
>>> MHz.
>>>
>>
>> So even a pretty expensive signal generator still has “loud”
>> harmonics if judged at the -60 dbc level ….
>>
>> that's actually an inexpensive ($7.4k) function generator (with good
> performance for a function generator that does a lot of stuff, except
> generate chirps at the right rate)..
>
> A $8k Keysight N9310 is -30dBc
>
> A R+S SMA100 specs -30dBc  (actually does better)
>
> A $23k Keysight 8663D specs -55dBc (at 1 GHz)
>
>
>
>
>
>>> Another case where low harmonic content is when doing two tone IMD
>>> tests - if the sources have significant harmonic content, you might
>>> be seeing intermod between the harmonics of the source, rather than
>>> intermods between the fundamental of the source.
>>>
>>
>> Which is one of the reasons a lot of IMD test setups have a variety
>> of filters in them.
>>
>>
>> These also are a pretty common item on eBay, at ham fest, and in your
>> typical RF junk box. 10.7 MHz IF filter cans can fairly easily be
>> tuned down to 10 MHz to custom roll bandpass filters.
>>
>
> Yeah, but it's easier (cheaper if you're paying for labor) just to buy a
> box of 10 filters at $30/each and stack them
>
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Re: [time-nuts] Thunderbolt Harmonics

[Bob Camp]

Hi

> On Jan 18, 2017, at 1:08 PM, jimlux  wrote:
> 
> On 1/18/17 8:56 AM, Bob Camp wrote:
>> HI
>>> 
>>> the first time we ran the test (using a Keysight 33622 signal
>>> generator) we saw significant 2nd and 3rd harmonics (50-60 dB down,
>>> but easily detectable).  A quick review of the data sheet.. Oh, the
>>> signal generator spec is only -43 dBc for frequencies above 10
>>> MHz.
>> 
>> So even a pretty expensive signal generator still has “loud”
>> harmonics if judged at the -60 dbc level ….
>> 
> that's actually an inexpensive ($7.4k) function generator (with good 
> performance for a function generator that does a lot of stuff, except 
> generate chirps at the right rate)..
> 
> A $8k Keysight N9310 is -30dBc
> 
> A R+S SMA100 specs -30dBc  (actually does better)
> 
> A $23k Keysight 8663D specs -55dBc (at 1 GHz)
> 
> 
> 
> 
>>> 
>>> Another case where low harmonic content is when doing two tone IMD
>>> tests - if the sources have significant harmonic content, you might
>>> be seeing intermod between the harmonics of the source, rather than
>>> intermods between the fundamental of the source.
>> 
>> Which is one of the reasons a lot of IMD test setups have a variety
>> of filters in them.
>> 
>> 
>> These also are a pretty common item on eBay, at ham fest, and in your
>> typical RF junk box. 10.7 MHz IF filter cans can fairly easily be
>> tuned down to 10 MHz to custom roll bandpass filters.
> 
> Yeah, but it's easier (cheaper if you're paying for labor) just to buy a box 
> of 10 filters at $30/each and stack them

Be *very* careful cascading those Min-Circuits filters without putting some 
sort of isolation between them. You can get all
sorts of wonky results as the reactances in one mis-terminates the reactances 
in another.

Bob


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[time-nuts] 10MHz to 25MHz

[Loren Moline WA7SKT]

Hello,

I am looking for a good X5 multiplier to use to generate a 25MHz signal from my 
10MHz OCXO. I want to divide by 2 and multiply by 5 with a bandpass filter in 
the output and then a 3.3 volt 25MHz signal out.


Maybe someone has better ways?


Loren Moline  WA7SKT

Member: Pacific Northwest VHF Society and ARRL
Member: Hearsat Satellite Monitoring Group.  www.uhf-satcom.com
Member: CVARS-Chehalis Valley Amateur Radio Society
Starchat IRC: Channel = #hearsat
RF Electronics: Starchat IRC: Channel = #rfelectronics
Grid: CN86mr
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Re: [time-nuts] Thunderbolt Harmonics

[jimlux]

On 1/18/17 8:56 AM, Bob Camp wrote:

HI


the first time we ran the test (using a Keysight 33622 signal
generator) we saw significant 2nd and 3rd harmonics (50-60 dB down,
but easily detectable).  A quick review of the data sheet.. Oh, the
signal generator spec is only -43 dBc for frequencies above 10
MHz.


So even a pretty expensive signal generator still has “loud”
harmonics if judged at the -60 dbc level ….

that's actually an inexpensive ($7.4k) function generator (with good 
performance for a function generator that does a lot of stuff, except 
generate chirps at the right rate)..


A $8k Keysight N9310 is -30dBc

A R+S SMA100 specs -30dBc  (actually does better)

A $23k Keysight 8663D specs -55dBc (at 1 GHz)






Another case where low harmonic content is when doing two tone IMD
tests - if the sources have significant harmonic content, you might
be seeing intermod between the harmonics of the source, rather than
intermods between the fundamental of the source.


Which is one of the reasons a lot of IMD test setups have a variety
of filters in them.


These also are a pretty common item on eBay, at ham fest, and in your
typical RF junk box. 10.7 MHz IF filter cans can fairly easily be
tuned down to 10 MHz to custom roll bandpass filters.


Yeah, but it's easier (cheaper if you're paying for labor) just to buy a 
box of 10 filters at $30/each and stack them

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Re: [time-nuts] PN/AM and 1.5Hz spur from frequency doubling?

[Bob Camp]

Hi

Without seeing the circuit involved it’s a bit tough to guess all of the 
possible
things that might be happening. One branch leads off to things like the circuit
it’s self oscillating and creating the spur. Sub branches involve oscillation 
in 
a regulator at low frequency vs RF oscillation somewhere else. Another branch 
heads in the direction  of a loose cable running around the shop with a bunch 
of 10 MHz on it. There are many branches ….

Bob

> On Jan 18, 2017, at 11:13 AM, Anders Wallin  
> wrote:
> 
> I'm seeing +20-30 dBc/Hz of excess AM/PN, as well as a strong 1.5 Hz spur
> created by frequency doubling from 5 MHz to 10 MHz.
> https://goo.gl/photos/GFx9tQoxrSmyzUQo8
> The input amplitude to the doubler should be just above the recommended 11
> dBm.
> What's going on??
> 
> thanks!
> Anders
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Re: [time-nuts] Thunderbolt Harmonics

[Scott Stobbe]

Harmonic traps are another avenue to explore since the frequency is "fixed"
at well below ppm. Which leaves the fundamental untouched.

On Wed, Jan 18, 2017 at 5:21 AM, Charles Steinmetz 
wrote:

> Rhys wrote:
>
> I was looking at the output of my Trimble Thunderbolt GPSDO and was rather
>> surprised to see really "loud" harmonics in there. ~ 60dB down from the
>> 10Mhz signal.
>>
>
> Welcome to the world of RF.  Loudest harmonic at ~ -60dBc (dB with respect
> to carrier) is actually pretty good for a commercial product. Very few
> distribution amplifiers do this well.  For that matter, many good
> laboratory RF generators are specified with harmonics only below -35 to -45
> dBc.  We do not generally expect RF sources or amplifiers to get down to
> the -80 to -90 dBc range (although amplifiers with harmonics < -80dBc at
> 10MHz/1Vrms/50 ohms are possible), and certainly not the -100 to -120dBc
> that we expect from high fidelity audio sources and amplifiers.
>
> Even harmonics (which make the carrier asymmetrical) can cause phase
> errors that are harmful in high-precision systems [1], so I am a vocal
> supporter of distribution amplifiers with harmonics < -80dBc.
>
> Note that cleaning up the Tbolt output to < -80dBc would probably require
> a crystal filter (a filter with a sharp corner very close to 10MHz, in any
> case), which means its phase response changes very rapidly with the filter
> frequency.  Sharp filters shift frequency with temperature, which causes
> temperature-dependent phase shifts.  Unless the filter is maintained in an
> isothermal environment (like a good oven), this can cause problems in
> sensitive applications.
>
> Best regards,
>
> Charles
>
>
> [1]   F.L. Walls (NIST), F.G. Ascarrunz (SpectraDynamics), The Effect of
> Harmonic Distortion on Phase Errors in Frequency Distribution and Synthesis
> (year unknown, probably late '90s).
>
>
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Re: [time-nuts] Thunderbolt Harmonics

[Charles Steinmetz]

Is what your seeing a harmonic (2nd? 3rd?) or a spur i.e what frequency
is the "harmonic" ?


The OP attached a spectrum analyzer screen shot to his initial post -- 
go back and have a look.


It shows the harmonic series from 1 to 7, with H6 close to the noise 
level.  Loudest harmonic is H2 at ~ -60dBc.


Charles


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Re: [time-nuts] How to create a super Rb standard

[Javier Herrero]

Hello,

And about temperature, in this article 
http://www.dtic.mil/dtic/tr/fulltext/u2/a495520.pdf there is an 
interesting point, in the last page: Riley answer to the question "You 
mentioned larger cells. Where there any other things done go get these 
fantastic results?


Regards,

Javier

On 18/01/2017 13:12, Bob Camp wrote:

Hi

You would need to redesign the Rb to work in a vacuum. There is a lot involved
in doing that. They depend on the air inside the package to properly operate the
heating in the physics package. Different parts of the package are at different
temperatures. Without the air cooling the temperature offsets could not be 
properly
maintained.

There are a *lot* of differences between the GPS Rb’s and the ones we buy on
eBay. The fact that they operate in pretty far down the list of significant 
differences.
The most simple answer to “why” the Rb is better is that the design requirements
on the two standards were different, as were the design teams. Coming up with
an Rb with better short term stability is the way that all worked out. That 
short
term stability is better than other large cell Rb designs, but not by a crazy 
amount.
How much better it is depends a lot on which large cell Rb design you compare 
to.
It also depends a bit on which specific unit you are looking at.

All that said, space benign is indeed a pretty quiet environment. It certainly 
does
help a bit if you operate there. There is also data on the GPS Rb’s that show 
them
doing quite well on the ground. So no, it’s not all space, but space does not 
hurt
their performance.

Bob


On Jan 18, 2017, at 12:23 AM, Li Ang <379...@qq.com> wrote:

Hi
I am wondering if anyone tried to put a Rb unit into a vacuum container. And 
how much the performance is improved? Someone told me that's why the Rb clocks 
are more stable than Cs clocks on the GPS satellites.

LiAng

---Original---
From: "Bob Camp"
Date: 2017/1/17 21:20:23
To: "Discussion of precise time and frequency measurement";"Perry 
Sandeen";
Subject: Re: [time-nuts] How to create a super Rb standard


Hi

Since the physics package in the small Rb’s is different than the stuff in the 
large units,
you have some basic limits on what you can do to improve them. The main things 
people
have done are to modify them to turn off the temperature compensation and 
replace it
with some sort of precision controlled thermal enclosure. Pressure compensation 
is a good
idea on any of these parts (large or small). How much your particular unit 
benefits is a
“that depends” sort of thing.

Bob


On Jan 16, 2017, at 10:24 PM, Perry Sandeen via time-nuts  
wrote:


List
It looks like their is as infinitely small chance of being able to get 5065.
So what can be done with the telco Rb's (mine are analog tuned) to wring the 
best possible performance from them? Sooper Duper power supplies, Peltier (sp) 
cooling modules?
Regards,
Perrier
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Re: [time-nuts] Thunderbolt Harmonics

[Bob Camp]

HI

> On Jan 18, 2017, at 9:44 AM, jimlux  wrote:
> 
> On 1/18/17 4:33 AM, Artek Manuals wrote:
>> R
>> 
>> Is what your seeing a harmonic (2nd? 3rd?) or a spur i.e what frequency
>> is the "harmonic" ?
>> 
>> How are you measuring this ? (Spectrum analyzer ? make/model?)
>> 
>> More importantly and at the risk of displaying my naivety, what is the
>> application that you are using the 10MHz source to feed and why if this
>> harmonic is 60db down (or even only 40db down, the quoted spec) why
>> would one care? What is the predicted error you will get in your
>> application as a result?
>> 
> 
> One application that needs low harmonic content is where you are measuring 
> the harmonic generating (or lack thereof) of a downstream component.
> 
> I have an application where we're measuring the performance of a RF chain 
> followed by a digitizer.  An easy test is to feed in a nice sine wave (at a 
> frequency that is NOT a submultiple of the samplerate) and look for harmonics 
> in the power spectrum of the sampled data stream.
> 
> the first time we ran the test (using a Keysight 33622 signal generator) we 
> saw significant 2nd and 3rd harmonics (50-60 dB down, but easily detectable). 
>  A quick review of the data sheet.. Oh, the signal generator spec is only -43 
> dBc for frequencies above 10 MHz.

So even a pretty expensive signal generator still has “loud” harmonics if 
judged at the -60 dbc level ….

> 
> Another case where low harmonic content is when doing two tone IMD tests - if 
> the sources have significant harmonic content, you might be seeing intermod 
> between the harmonics of the source, rather than intermods between the 
> fundamental of the source.

Which is one of the reasons a lot of IMD test setups have a variety of filters 
in them.

> 
> For 10 MHz, you can get minicircuits filters for 10.7 MHz that are fairly 
> wideband and work pretty well... about 20-30 dB of harmonic suppression per 
> filter I'd use the low pass flavor
> 
> SBP-10.7
> loss at 20MHz is 26.84
> loss at 40MHz is 41.22
> loss at 50MHz is 46
> est loss at 30 is 35?
> 
> SLP-10.7
> loss at 10 is 0.65 spec
> loss at 20 is 31.35 spec  measured -33
> loss at 30 measured -60
> loss at 34 is 47.26 spec
> loss at 40 measured -77
> loss at 67.5 is 69.85 spec

These also are a pretty common item on eBay, at ham fest, and in your typical 
RF junk box. 10.7 MHz IF filter cans can fairly
easily be tuned down to 10 MHz to custom roll bandpass filters. 

Bob


> 
> 
> 
> Yeah, they might have a significant tempco, but you're running all this stuff 
> in an underground lair with small temperature variations, right? It only 
> looks like a small volcano from the outside.
> 
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Re: [time-nuts] PN/AM and 1.5Hz spur from frequency doubling?

[Mattia Rizzi]

Hello,
can you share also the Phase Difference trace?

cheers,
Mattia

2017-01-18 17:13 GMT+01:00 Anders Wallin :

> I'm seeing +20-30 dBc/Hz of excess AM/PN, as well as a strong 1.5 Hz spur
> created by frequency doubling from 5 MHz to 10 MHz.
> https://goo.gl/photos/GFx9tQoxrSmyzUQo8
> The input amplitude to the doubler should be just above the recommended 11
> dBm.
> What's going on??
>
> thanks!
> Anders
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Re: [time-nuts] Looking for GPS module (Exactime ET6000/Datum 9390-6000)

[ziggy9+time-nuts]

I considered that. Unfortunately the Heol Designs units don’t emulate the 
SV6-CM3 and the Ace receivers were not a direct replacement. So it seems they 
have nothing to offer at this time.


> On Jan 18, 2017, at 1:24 AM, Gregory Beat  wrote:
> 
> Heol Designs offers replacement boards for Trimble GPS receivers.
> http://www.heoldesign.com/N01x-Trimble-Lassen-SK2-iQ-sQ-LP-ACE-replacements-boards
> 
> Heol Design's GPS receivers are based on the Copernicus II high performance 
> GPS chip set and mimic the legacy Trimble GPS receivers.  These OEM boards 
> are designed for use in embedded and industrial applications requiring high 
> accuracy positioning and timing information. They can also be used as a 
> replacement and upgrade for users of the Trimble Lassen iQ, SQ, LP, SK2 and 
> ACE (ACEII, ACEIII) receiver boards, which are now EOL (end of life).
> 
> Some time-nuts members are using the Heol Design N024 solution in their Datum 
> Tymserve 2100, which also corrects 2 additional firmware/hardware bugs.
> http://www.heoldesign.com/N024-GPS-receiver-board-for-Tymserve-2100
> 
> Sent from iPad Air
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[time-nuts] PN/AM and 1.5Hz spur from frequency doubling?

[Anders Wallin]

I'm seeing +20-30 dBc/Hz of excess AM/PN, as well as a strong 1.5 Hz spur
created by frequency doubling from 5 MHz to 10 MHz.
https://goo.gl/photos/GFx9tQoxrSmyzUQo8
The input amplitude to the doubler should be just above the recommended 11
dBm.
What's going on??

thanks!
Anders
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Re: [time-nuts] Thunderbolt Harmonics

[jimlux]

On 1/18/17 4:33 AM, Artek Manuals wrote:

R

Is what your seeing a harmonic (2nd? 3rd?) or a spur i.e what frequency
is the "harmonic" ?

How are you measuring this ? (Spectrum analyzer ? make/model?)

More importantly and at the risk of displaying my naivety, what is the
application that you are using the 10MHz source to feed and why if this
harmonic is 60db down (or even only 40db down, the quoted spec) why
would one care? What is the predicted error you will get in your
application as a result?



One application that needs low harmonic content is where you are 
measuring the harmonic generating (or lack thereof) of a downstream 
component.


I have an application where we're measuring the performance of a RF 
chain followed by a digitizer.  An easy test is to feed in a nice sine 
wave (at a frequency that is NOT a submultiple of the samplerate) and 
look for harmonics in the power spectrum of the sampled data stream.


the first time we ran the test (using a Keysight 33622 signal generator) 
we saw significant 2nd and 3rd harmonics (50-60 dB down, but easily 
detectable).  A quick review of the data sheet.. Oh, the signal 
generator spec is only -43 dBc for frequencies above 10 MHz.


Another case where low harmonic content is when doing two tone IMD tests 
- if the sources have significant harmonic content, you might be seeing 
intermod between the harmonics of the source, rather than intermods 
between the fundamental of the source.


For 10 MHz, you can get minicircuits filters for 10.7 MHz that are 
fairly wideband and work pretty well... about 20-30 dB of harmonic 
suppression per filter I'd use the low pass flavor


SBP-10.7
loss at 20MHz is 26.84
loss at 40MHz is 41.22
loss at 50MHz is 46
est loss at 30 is 35?

SLP-10.7
loss at 10 is 0.65 spec
loss at 20 is 31.35 specmeasured -33
loss at 30 measured -60
loss at 34 is 47.26 spec
loss at 40 measured -77
loss at 67.5 is 69.85 spec



Yeah, they might have a significant tempco, but you're running all this 
stuff in an underground lair with small temperature variations, right? 
It only looks like a small volcano from the outside.


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Re: [time-nuts] Thunderbolt Harmonics

[jimlux]

On 1/18/17 2:21 AM, Charles Steinmetz wrote:

Rhys wrote:




[1]   F.L. Walls (NIST), F.G. Ascarrunz (SpectraDynamics), The Effect of
Harmonic Distortion on Phase Errors in Frequency Distribution and
Synthesis (year unknown, probably late '90s).




9th Euro Freq & Time Forum
1995
Besancon


http://tf.nist.gov/general/pdf/1437.pdf
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Re: [time-nuts] Thunderbolt Harmonics

[Charles Steinmetz]

I suppose I should have said that Trimble specifies the Tbolt with 
harmonics -40dBc max, according to the User Guide v.5.0 (2003).


Best regards,

Charles


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[time-nuts] Galileo clock failure

[REEVES Paul]

It seems like the Rb and H-maser clocks on the Galileo satellites might be 
experiencing a problem
Here is a link to a BBC report:
http://www.bbc.co.uk/news/science-environment-38664225

"What do you mean, ' nobody told us they were meant to work in vacuum'  ?"
Paul Reeves
Senior Engineer

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Ocean House, Throop Road, Templecombe, Somerset,  BA8 0DH, UK
www.thalesgroup.com/uk

Tel: +44 (0)1963 372851.  Mob: +44 (0) 00.  Fax: +44 (0)  00.
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Re: [time-nuts] Thunderbolt Harmonics

[Artek Manuals]

R

Is what your seeing a harmonic (2nd? 3rd?) or a spur i.e what frequency 
is the "harmonic" ?


How are you measuring this ? (Spectrum analyzer ? make/model?)

More importantly and at the risk of displaying my naivety, what is the 
application that you are using the 10MHz source to feed and why if this 
harmonic is 60db down (or even only 40db down, the quoted spec) why 
would one care? What is the predicted error you will get in your 
application as a result?


Dave

manu...@artekmanuals.com



On Jan 17, 2017, at 9:40 PM, Rhys D  wrote:

Hi all,

Before I start, let me say I'm rather a newbie at this sort of stuff so
please be gentle.

I was looking at the output of my Trimble Thunderbolt GPSDO and was rather
surprised to see really "loud" harmonics in there. ~ 60dB down from the
10Mhz signal.

Can anyone here shed some light on what I am seeing here?
Surely this isn't what it is supposed to look like? Should I be trying to
filter these before going to my distribution amplifier?

Thanks for any light you can shed.

R


​
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--
Dave
manu...@artekmanuals.com
www.ArtekManuals.com


---
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Re: [time-nuts] Thunderbolt Harmonics

[Charles Steinmetz]

Rhys wrote:


I was looking at the output of my Trimble Thunderbolt GPSDO and was rather
surprised to see really "loud" harmonics in there. ~ 60dB down from the
10Mhz signal.


Welcome to the world of RF.  Loudest harmonic at ~ -60dBc (dB with 
respect to carrier) is actually pretty good for a commercial product. 
Very few distribution amplifiers do this well.  For that matter, many 
good laboratory RF generators are specified with harmonics only below 
-35 to -45 dBc.  We do not generally expect RF sources or amplifiers to 
get down to the -80 to -90 dBc range (although amplifiers with harmonics 
< -80dBc at 10MHz/1Vrms/50 ohms are possible), and certainly not the 
-100 to -120dBc that we expect from high fidelity audio sources and 
amplifiers.


Even harmonics (which make the carrier asymmetrical) can cause phase 
errors that are harmful in high-precision systems [1], so I am a vocal 
supporter of distribution amplifiers with harmonics < -80dBc.


Note that cleaning up the Tbolt output to < -80dBc would probably 
require a crystal filter (a filter with a sharp corner very close to 
10MHz, in any case), which means its phase response changes very rapidly 
with the filter frequency.  Sharp filters shift frequency with 
temperature, which causes temperature-dependent phase shifts.  Unless 
the filter is maintained in an isothermal environment (like a good 
oven), this can cause problems in sensitive applications.


Best regards,

Charles


[1]   F.L. Walls (NIST), F.G. Ascarrunz (SpectraDynamics), The Effect of 
Harmonic Distortion on Phase Errors in Frequency Distribution and 
Synthesis (year unknown, probably late '90s).



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Re: [time-nuts] How to create a super Rb standard

[Bob Camp]

Hi

You would need to redesign the Rb to work in a vacuum. There is a lot involved
in doing that. They depend on the air inside the package to properly operate the
heating in the physics package. Different parts of the package are at different 
temperatures. Without the air cooling the temperature offsets could not be 
properly 
maintained. 

There are a *lot* of differences between the GPS Rb’s and the ones we buy on
eBay. The fact that they operate in pretty far down the list of significant 
differences.
The most simple answer to “why” the Rb is better is that the design requirements
on the two standards were different, as were the design teams. Coming up with 
an Rb with better short term stability is the way that all worked out. That 
short 
term stability is better than other large cell Rb designs, but not by a crazy 
amount. 
How much better it is depends a lot on which large cell Rb design you compare 
to.
It also depends a bit on which specific unit you are looking at.

All that said, space benign is indeed a pretty quiet environment. It certainly 
does 
help a bit if you operate there. There is also data on the GPS Rb’s that show 
them
doing quite well on the ground. So no, it’s not all space, but space does not 
hurt
their performance. 

Bob

> On Jan 18, 2017, at 12:23 AM, Li Ang <379...@qq.com> wrote:
> 
> Hi
> I am wondering if anyone tried to put a Rb unit into a vacuum container. And 
> how much the performance is improved? Someone told me that's why the Rb 
> clocks are more stable than Cs clocks on the GPS satellites.
> 
> LiAng
> 
> ---Original---
> From: "Bob Camp"
> Date: 2017/1/17 21:20:23
> To: "Discussion of precise time and frequency 
> measurement";"Perry Sandeen";
> Subject: Re: [time-nuts] How to create a super Rb standard
> 
> 
> Hi
> 
> Since the physics package in the small Rb’s is different than the stuff in 
> the large units, 
> you have some basic limits on what you can do to improve them. The main 
> things people
> have done are to modify them to turn off the temperature compensation and 
> replace it
> with some sort of precision controlled thermal enclosure. Pressure 
> compensation is a good
> idea on any of these parts (large or small). How much your particular unit 
> benefits is a 
> “that depends” sort of thing.
> 
> Bob
> 
>> On Jan 16, 2017, at 10:24 PM, Perry Sandeen via time-nuts 
>>  wrote:
>> 
>> 
>> List
>> It looks like their is as infinitely small chance of being able to get 5065.
>> So what can be done with the telco Rb's (mine are analog tuned) to wring the 
>> best possible performance from them? Sooper Duper power supplies, Peltier 
>> (sp) cooling modules?
>> Regards,
>> Perrier
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> 
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Re: [time-nuts] Thunderbolt Harmonics

[Bob Camp]

Hi

If you look at the FCC transmitter regs, -60 dbc is “ok” for many transmitters. 

Bob

> On Jan 17, 2017, at 9:40 PM, Rhys D  wrote:
> 
> Hi all,
> 
> Before I start, let me say I'm rather a newbie at this sort of stuff so
> please be gentle.
> 
> I was looking at the output of my Trimble Thunderbolt GPSDO and was rather
> surprised to see really "loud" harmonics in there. ~ 60dB down from the
> 10Mhz signal.
> 
> Can anyone here shed some light on what I am seeing here?
> Surely this isn't what it is supposed to look like? Should I be trying to
> filter these before going to my distribution amplifier?
> 
> Thanks for any light you can shed.
> 
> R
> 
> 
> ​
> <10MhzRef.png>___
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Re: [time-nuts] Brass Screws

[John Ponsonby]

Re: Brass screws
Brass is not only to be avoided because of residual ferromagnetism but 
is also unsuitable for use in ultrahigh vacuum because zinc has a high vapour 
pressure. In an H-maser I used beryllium-copper BeCu for small screws and 
springs, aluminium-bronze for larger components and of course pure Al. BeCu 
requires special care when being cut as it is toxic, but finished items are 
safe to handle when all microscopic swarf and filing "dust" has been removed. I 
think magnetic instruments, such as steering compasses, magnetometers etc are 
traditionally made of bronze. I have an invaluable but very simple and 
sensitive astatic-magnetometer supplied by the Danish Meteorological Institute 
in Copenhagen.
John P
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Re: [time-nuts] Thunderbolt Harmonics

[Tom Curlee]

I'm not sure what the Thunderbolt specs state for harmonics, but -60 dB seems 
quite good to me.


  From: Rhys D 
 To: Discussion of precise time and frequency measurement  
 Sent: Tuesday, January 17, 2017 6:40 PM
 Subject: [time-nuts] Thunderbolt Harmonics
   
Hi all,

Before I start, let me say I'm rather a newbie at this sort of stuff so
please be gentle.

I was looking at the output of my Trimble Thunderbolt GPSDO and was rather
surprised to see really "loud" harmonics in there. ~ 60dB down from the
10Mhz signal.

Can anyone here shed some light on what I am seeing here?
Surely this isn't what it is supposed to look like? Should I be trying to
filter these before going to my distribution amplifier?

Thanks for any light you can shed.

R


​
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Re: [time-nuts] Looking for GPS module (Exactime ET6000/Datum 9390-6000)

[Gregory Beat]

Heol Designs offers replacement boards for Trimble GPS receivers.
http://www.heoldesign.com/N01x-Trimble-Lassen-SK2-iQ-sQ-LP-ACE-replacements-boards

Heol Design's GPS receivers are based on the Copernicus II high performance GPS 
chip set and mimic the legacy Trimble GPS receivers.  These OEM boards are 
designed for use in embedded and industrial applications requiring high 
accuracy positioning and timing information. They can also be used as a 
replacement and upgrade for users of the Trimble Lassen iQ, SQ, LP, SK2 and ACE 
(ACEII, ACEIII) receiver boards, which are now EOL (end of life).

Some time-nuts members are using the Heol Design N024 solution in their Datum 
Tymserve 2100, which also corrects 2 additional firmware/hardware bugs.
http://www.heoldesign.com/N024-GPS-receiver-board-for-Tymserve-2100

Sent from iPad Air
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