Re: [time-nuts] 3120A issues

[John Miles]

> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Knox
> Sent: Saturday, June 18, 2016 6:17 PM
> To: Time-Nuts
> Subject: [time-nuts] 3120A issues
> 
> Does anyone have any insight as to why Microsemi has stopped shipping 3120A
> Phase Noise test sets  beside that they are not to spec?
> 

It looks like they're still advertising the 3120A on their site.  I'm pretty 
far out of the loop at this point, but if they're having production-test 
problems, I haven't heard anything about them at all -- and I normally would, 
if they're having problems passing the factory tests.  Is that what you meant 
by "to spec?"

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] 3120A issues

[jimlux]

On 6/18/16 6:17 PM, Tom Knox wrote:

Does anyone have any insight as to why Microsemi has stopped shipping 3120A 
Phase Noise test sets  beside that they are not to spec?

They're shipping them.. I got quoted a 12 week delivery in April, $9k 
for the box, about $12k-15k for the software, although I find that the 
Microsemi site doesn't really explain what the various software options are.




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[time-nuts] 3120A issues

[Tom Knox]

Does anyone have any insight as to why Microsemi has stopped shipping 3120A 
Phase Noise test sets  beside that they are not to spec?

Thanks;

Thomas Knox

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

[Bob Camp]

HI

It sort of depends on what offset frequency you are looking at. If you are 
after very wide band stuff at very low levels, 
the notch filter / spectrum analyzer approach has always been a good one. You 
may or may not need a low noise 
amp after the notch depending on the analyzer. Your notch may need to be more 
deep with some analyzers. It’s 
been used since at least the 1960’s. I would not be surprised to find it goes 
back a bit further than that. 

One basic assumption with the notch approach:

You are measuring total noise. Both the AM noise and PM noise go past the notch 
and into the analyzer. The fundamental
assumption is that out there the noise is equally distributed between AM and 
PM. There would be a paper in it if you
can prove that’s not the case. 

Lots of fun !!

Bob

> On Jun 18, 2016, at 6:11 PM, jimlux  wrote:
> 
> On 6/18/16 12:05 PM, Bob Camp wrote:
>> Hi
>> 
>> The Symmetricom Time Pod is pretty much the lowest cost commercial / newl 
>> “low phase noise” measurement instrument. You can find all sorts
>> of older stuff on auction sites in who knows what shape. The HP 3048 is the 
>> granddaddy of them all.
>> 
> 
> the time pod is about 8-9k (I just got a quote on one).
> 
> I don't think the 4406 is inherently very quiet, if they're making close in 
> measurements, they may have another quiet source to drive it from, or they 
> are beating the unit under test against a quiet reference, and just using the 
> 4406 to look at the IF.
> 
> 
> 
> 
>> Bob
>> 
>>> On Jun 18, 2016, at 12:11 PM, Dr. David Kirkby (Kirkby Microwave Ltd) 
>>>  wrote:
>>> 
>>> I was looking at some high end commercial low noise oscillators and see
>>> they use instrument like the Agilent E5052B signal source analyzer for
>>> phase noise measurements. When I looked for them on eBay, it soon because
>>> apparently they were very expensive.
>>> 
>>> Then I see this oscillator that locks to GPS
>>> 
>>> http://www.leobodnar.com/shop/index.php?main_page=product_info=107_id=234
>>> 
>>> and looked at what was used to make the phase noise measurements. It was an
>>> Agilent E4406A. The noise floor is nowhere near as low as the more
>>> expensive instruments, but the E4406A is available for under $500, which is
>>> more than two orders of magnitudes cheaper than an E5052B.
>>> 
>>> I'm wondering if there are other more suitable commercial instruments
>>> around that don't cost a fortune, yet would allow lower levels of phase
>>> noise to be measured. I tend to preference HP/Agilent kit, as it is better
>>> supported, both by the manufacturer and places like the HP/Agilent Yahoo
>>> group.
>>> 
>>> Dave
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Re: [time-nuts] Phase noise measurements on the cheap with an Agilent E4406A VSA Transmitter Tester?

[John Miles]

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

The E4406A will let you measure all the way down to 1 Hz from the carrier, and 
is quieter past 100 kHz.  And it's faster, being FFT-based.  Overall, though, 
their LO noise floors aren't that different.  They both need a lot of help to 
perform serious PN measurements.

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

Thanks -- coincidentally, someone else just reported that one a few days ago.  
I've fixed it but haven't updated it on the server yet.  It's safe to say there 
are plenty of other broken links on my site, as some of those pages are over 10 
years old now.  

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

Sadly, there are few good answers there other than "build a quadrature PLL."

-- john, KE5FX
Miles Design LLC


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

[jimlux]

On 6/18/16 12:05 PM, Bob Camp wrote:

Hi

The Symmetricom Time Pod is pretty much the lowest cost commercial / newl “low 
phase noise” measurement instrument. You can find all sorts
of older stuff on auction sites in who knows what shape. The HP 3048 is the 
granddaddy of them all.



the time pod is about 8-9k (I just got a quote on one).

I don't think the 4406 is inherently very quiet, if they're making close 
in measurements, they may have another quiet source to drive it from, or 
they are beating the unit under test against a quiet reference, and just 
using the 4406 to look at the IF.






Bob


On Jun 18, 2016, at 12:11 PM, Dr. David Kirkby (Kirkby Microwave Ltd) 
 wrote:

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

Then I see this oscillator that locks to GPS

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

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

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

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

[Dr. David Kirkby (Kirkby Microwave Ltd)]

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

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

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

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

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



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

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

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


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


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

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

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

Cheers John.


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


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

[Bob Camp]

Hi

The Symmetricom Time Pod is pretty much the lowest cost commercial / newl “low 
phase noise” measurement instrument. You can find all sorts
of older stuff on auction sites in who knows what shape. The HP 3048 is the 
granddaddy of them all. 

Bob

> On Jun 18, 2016, at 12:11 PM, Dr. David Kirkby (Kirkby Microwave Ltd) 
>  wrote:
> 
> I was looking at some high end commercial low noise oscillators and see
> they use instrument like the Agilent E5052B signal source analyzer for
> phase noise measurements. When I looked for them on eBay, it soon because
> apparently they were very expensive.
> 
> Then I see this oscillator that locks to GPS
> 
> http://www.leobodnar.com/shop/index.php?main_page=product_info=107_id=234
> 
> and looked at what was used to make the phase noise measurements. It was an
> Agilent E4406A. The noise floor is nowhere near as low as the more
> expensive instruments, but the E4406A is available for under $500, which is
> more than two orders of magnitudes cheaper than an E5052B.
> 
> I'm wondering if there are other more suitable commercial instruments
> around that don't cost a fortune, yet would allow lower levels of phase
> noise to be measured. I tend to preference HP/Agilent kit, as it is better
> supported, both by the manufacturer and places like the HP/Agilent Yahoo
> group.
> 
> Dave
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Re: [time-nuts] Phase noise measurements on the cheap with an Agilent E4406A VSA Transmitter Tester?

[John Miles]

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

It appears that Leo's using a notch filter to remove the carrier before 
measuring it with the E4406A, so it's not quite a plug-and-play sort of 
measurement.  But yes, the E4406A is a really cool piece of gear given the 
prices they sell for.  It's not meant to be a general-purpose spectrum analyzer 
-- and Agilent went well out of their way to make sure of that -- but it can 
still handle many common SA measurement tasks including SSB noise.

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

I've also heard of people opening up the E4406A and feeding HF signals directly 
to the ADC, eliminating the LO noise contribution but not the ADC's white 
noise, 1/f noise, or clock jitter.
 
> I'm wondering if there are other more suitable commercial instruments
> around that don't cost a fortune, yet would allow lower levels of phase
> noise to be measured. I tend to preference HP/Agilent kit, as it is better
> supported, both by the manufacturer and places like the HP/Agilent Yahoo
> group.

The E5052A/B's most immediate predecessor was probably the HP 4352A/B.  They 
were made specifically for VCO and PLL transient analysis and noise 
measurement, and they've been selling in the $1K-$3K neighborhood for several 
years.  Their measurement floor is better than a conventional spectrum 
analyzer, but still not adequate for "time nuts"-class measurements on 10 MHz 
sources. 

-- john, KE5FX
Miles Design LLC


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Re: [time-nuts] Hydrogen maser spin exchange

[Bob Camp]

Hi

Far more than you *ever* wanted to know about state selectors:

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19820012652.pdf

Bob

> On Jun 17, 2016, at 3:33 PM, Ole Petter Ronningen  
> wrote:
> 
> Hi. Apologies for a long post.
> 
> I'm trying to read up on the "care and feeding of hydrogen masers". While
> they are conceptually simple from a distance, there's quite a bit going on
> in the quantum mechanics department when looked at up close. Somewhat
> frustratingly, I am not mentally equipped to really grasp the finer (or
> even coarser) points of that particular department. The topic of this post
> is the concept of spin exchange, and it's relation to cavity (auto) tuning.
> I've read papers on the subject, but I am having difficulties building a
> "workable intuition", so I turn to the group.
> 
> Here's what I think I understand, and I respectfully ask for corrections if
> I am way off base here..
> 
> Spin-exchange in a hydrogen maser happens when two atoms collide, and
> exchange spin, as it were.. (Hazy on the details here..) The number of
> spin-exchange collisions is directly proportional to the density of atoms
> in the cavity. These collisions *will* happen, but is a problem in hydrogen
> masers for two reasons: 1) it takes away energy from the cavity, resulting
> in lower signal output power, which degrades stability, and, 2) more
> significantly, it results in a frequency shift.
> 
> The frequency shift, as far as I can gather, is directly related to the
> cavity resonant frequency - there is no way to *stop* spin exchange taking
> place (apart from reducing the hydrogen density to a level where collisions
> are rare, in which case the density will be too low for oscillation to take
> place), but it is possible to reduce the impact the spin exchange has on
> the output frequency.
> 
> While the resonant frequency obviously influences the output power of the
> maser cavity, the "mistuning" of the cavity also increases the effect spin
> exchange has. In other words, in a perfectly tuned cavity, spin exchange
> does not result in a frequency shift. In a badly tuned cavity, increasing
> or decreasing the hydrogen flux (thereby increasing or decreasing the
> number of collisions taking place) results in a corresponding
> increase/decrease of the output frequency. Since the cavity ages, and the
> cavity resonant frequency follows that aging, the long term stability of
> the maser is degraded unless the aging can be compensated for. Which is
> what cavity auto-tuning is all about.
> 
> From my understanding, there are a few ways to implement cavity auto-tuning:
> 1. From the above, it follows that a modulation of the hydrogen flux into a
> mis-tuned cavity will result in a frequency shift following the modulation
> frequency. Using a stable reference, this shift can be measured, and
> corrections can be made to the cavity varactor voltage. Once the output
> frequency no longer shifts in response to the changes in hydrogen flux, the
> cavity is correctly tuned.
> 
> 2. It is also possible to modulate the cavity varactor voltage. By
> measuring the output power of the cavity, an error signal can be obtained
> and used to correct the average varactor voltage. A square wave of i.e.
> 100hz, centered on the approximate correct varactor voltate is put in the
> varactor, and cavity output power is measured. If the output power measured
> on the "low" of the square wave is lower than the signal measured when the
> "high", lower the offset by some mV, and vice versa. Suitable filtering
> would of course be required.
> 
> The idea is that this method should not result in appreciable degradation
> of the short/medium term stability of the maser, because the frequency of
> the atoms interacting with the electromagnetic field in the maser cavity
> takes time to respond to the changes in the resonant frequency, but the
> output power responds "instantly". (Hazy on those details as well..) By
> modulating the cavity varactor voltage (much) faster that the time constant
> of the maser cavity, the modulation is effectively filtered out.
> 
> I am very interested in this method, as it seems to me that it would be
> easy (feasible) to retrofit this to older masers never equipped with cavity
> auto tuning.
> 
> There is at least one more way, which involves injecting a signal into the
> maser cavity through a second coupling loop. At least one vendor I know of
> does this in their newest design. I do not understand even the basics of
> this method.
> 
> Any insights and/or corrections of my understanding is most welcome.
> 
> Thanks,
> Ole
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[time-nuts] Phase noise measurements on the cheap with an Agilent E4406A VSA Transmitter Tester?

[Dr. David Kirkby (Kirkby Microwave Ltd)]

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

Then I see this oscillator that locks to GPS

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

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

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

Dave
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