Re: [time-nuts] HP5065a cfield issue

[Poul-Henning Kamp]

paul swed writes:

> Guessing far less than 3 ma. by adding up resistors.

More like typical 4 mA: there is a factory select resistor in
parallel with the current-setting resistor.


-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
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Never attribute to malice what can adequately be explained by incompetence.

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[time-nuts] HP5061 Cesium ion pump question

[paul swed]

During my HP 5061Cesium testing last week I was watching the ion pump
current and am curious.
What is the typical behavior people see on the tube after say 3 months of
being turned off.
With 3 units I see one that pumps doen from 8 to 2 in 40 minutes. Another
maybe at 25 and takes 28 hours to get to 18. Just seems to be all over the
place.
Regards
Paul
WB8TSL
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[time-nuts] HP5065a cfield issue

[paul swed]

Hello to the group.
Was time for the quarterly Cesium and RB checks in an effort to support our
local power company.
I discovered that there is an issue with the HP5065a Rubidium reference.

The frequency has slowed and the cfield pot can not make up for the jump.
Normally a few small tick marks are ever needed. I used 3 large marks and
ran out of pot. Its at 9.9. Was at 6.14. The frequency does increate with
the cfield adjustment. I am assuming perhaps something has happened in the
cfield regulator.
At least the front panel meter is indicating the +20V supply is normal.
But my question is this. The schematic indicate very little current travels
through the cfield coil. Guessing far less than 3 ma. by adding up
resistors. What I do not know yet is what is the resistance of the cfield
coil? I may find that I simply have dirty contacts on the A15 regulator
card.
Its possible there are other things wrong but all front panel meter
readings look the same as they have been for years.

Thoughts?
Thank you in advance.
Paul
WB8TSL
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Re: [time-nuts] EOL Motorola Oncore Remote Antenna

[jimlux]

On 11/30/20 1:22 PM, Art Sepin wrote:



To me it looks more like water ingress through micro-cracks in the
  plastic-dome, and the O-ring did its job and kept that water in.


Interesting. That's the first we've heard about micro-cracks in the Radome but that's 
certainly a likely possibility with such a long exposure to U/V. The more common failure 
mode reported was moisture ingress due to "breathing;" the uptake of moisture 
laden air past the O-Ring, due to a small pressure differential. But, once the moisture 
was inside, it was also trapped internally by the O-Ring. This condition was reported 
more often in geographic areas that experienced a wide variation in barometric pressures.

Art



I'll bet pressure changes inside the "sealed" radome due to temperature 
changes are bigger than those due to local barometer changes.


But an interesting thing - water vapor will go through cracks, porosity, 
that liquid water will not. The commercial success of GoreTex is an 
example of this, but cracks, o-rings that aren't quite right, etc. are 
also ways it can happen.


Making a truly hermetic box is hard.



-Original Message-
From: Poul-Henning Kamp 
Sent: Sunday, November 29, 2020 11:19 PM
To: Discussion of precise time and frequency measurement ; 
Art Sepin 
Subject: Re: [time-nuts] EOL Motorola Oncore Remote Antenna




It's obvious from the photo that the O-Ring seal failed its purpose
over its many years of service. Has the unit totally failed or does the 
electronic portion still function?


No, the electronics is stone dead.

To me it looks more like water ingress through micro-cracks in the 
plastic-dome, and the O-ring did its job and kept that water in.

The microcracks are uniform and seem to follow the molding flow, and that is 
probably to be expected in our climate:  We have a lot of humid freeze-thaw 
cycles.

I wonder if buffing the radomes with car-wax would help ?


I said lucky because I found some GSynQ parts here in an engineering
storage cabinet that we  can send to you at no charge to revive your unit.


Thanks for the offer, but dont bother: I had a spare on hand, and I may still 
have third one lying around somewhere.




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Re: [time-nuts] TWT's was: Re: Voyager space probe question

[paul swed]

Dave it looks like I can not respond to you directly.
I just wanted to say that I still appreciate TWTs and the magic in them. I
have a number that are operational. 180 W on 10GHz using a Varian/CPI TWT.
Anyhow would like to correspond offline since this is not Time-nuts.
Regards
Paul
WB8TSL

On Mon, Nov 30, 2020 at 4:08 PM Dave B via time-nuts <
time-nuts@lists.febo.com> wrote:

> The power supplies for them are interesting too.
>
> Especially when you get to the multi kW beasties with multiple
> collectors etc.  Floating high power HV supplies, referenced to the more
> negative Cathode potential.
>
> That's one of the things I do for the day job, fix TWTA's.   99% of the
> time, it's a PSU problem.   The tubes themselves are amazingly rugged,
> so long as you do not store too much energy in the PSU on the HV side in
> case there's an arc in the tube.
>
> The secret is the voltage regulation controls and protection circuits.
> Loops within loops etc.   Great if you like analogue control and power
> switching systems.
>
> Can make a mess when things go wrong though.
>
> Current task on the bench though, is refurbishing a pumped oil cooling
> system, not for a TWT, but for a broadband RF power amplifier.  Messy in
> another way.
>
> There are some things solid state can't do economically yet, but it's
> getting close.
>
> But even the high power low microwave solid state amps, much of the bulk
> and complexity again is in the power supply and cooling systems.
>
> Regards.
>
> Dave G8KBV
>
> On 30/11/2020 18:51, time-nuts-requ...@lists.febo.com wrote:
> > I wouldn't be so sure about the GaN revolution overtaking it. TWTAs are
> > a pretty simple device, easy to get 50-60 dB of gain in a fairly small,
> > robust package with incredibly wide bandwidth (octaves in some cases),
> > and DC to RF conversion efficiency >50%.
>
> --
> Created on and sent from a Unix like PC running and using free and open
> source software:
>
>
> ___
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Re: [time-nuts] EOL Motorola Oncore Remote Antenna

[Lester Veenstra via time-nuts]

This brings up a point I have made frequently, in my professional life.  
Do not try to seal in electronics (for me , satellite units mounted near or
on the feed system) instead warm the area with electronics and place a weep
hole at the low point. Short of true hermetic seals, any other gasketed box
will inhale water vapor, condense it on the cooler surface, and collect
inside as water over time.  Much better to let the enclosure breath a bit
and drain as needed. The hole should not  be subject to external rain
encouraged to come un, and of course, prevent insects from nesting.  Most
active electronics will naturally form a warmer area, discouraging
condensation.

Lester B Veenstra  K1YCM  MØYCM  W8YCM   6Y6Y
les...@veenstras.com

452 Stable Ln (HC84 RFD USPS Mail)
Keyser WV 26726

GPS: 39.336826 N  78.982287 W (Google)
GPS: 39.33682 N  78.9823741 W (GPSDO)


Telephones:
Home:     +1-304-289-6057
US cell    +1-304-790-9192 
Jamaica cell:   +1-876-456-8898 
 


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of Art
Sepin
Sent: Monday, November 30, 2020 4:23 PM
To: Poul-Henning Kamp; Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] EOL Motorola Oncore Remote Antenna


> To me it looks more like water ingress through micro-cracks in the
>  plastic-dome, and the O-ring did its job and kept that water in.

Interesting. That's the first we've heard about micro-cracks in the Radome
but that's certainly a likely possibility with such a long exposure to U/V.
The more common failure mode reported was moisture ingress due to
"breathing;" the uptake of moisture laden air past the O-Ring, due to a
small pressure differential. But, once the moisture was inside, it was also
trapped internally by the O-Ring. This condition was reported more often in
geographic areas that experienced a wide variation in barometric pressures.


Art

-Original Message-
From: Poul-Henning Kamp  
Sent: Sunday, November 29, 2020 11:19 PM
To: Discussion of precise time and frequency measurement
; Art Sepin 
Subject: Re: [time-nuts] EOL Motorola Oncore Remote Antenna



> It's obvious from the photo that the O-Ring seal failed its purpose 
> over its many years of service. Has the unit totally failed or does the
electronic portion still function?

No, the electronics is stone dead.

To me it looks more like water ingress through micro-cracks in the
plastic-dome, and the O-ring did its job and kept that water in.

The microcracks are uniform and seem to follow the molding flow, and that is
probably to be expected in our climate:  We have a lot of humid freeze-thaw
cycles.

I wonder if buffing the radomes with car-wax would help ?

> I said lucky because I found some GSynQ parts here in an engineering 
> storage cabinet that we  can send to you at no charge to revive your unit.

Thanks for the offer, but dont bother: I had a spare on hand, and I may
still have third one lying around somewhere.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] EOL Motorola Oncore Remote Antenna

[Poul-Henning Kamp]

Lester Veenstra writes:

> This brings up a point I have made frequently, in my professional life.  
> Do not try to seal in electronics (for me , satellite units mounted near or
> on the feed system) instead warm the area with electronics and place a weep
> hole at the low point.

How to protect sensitive kit against the elements depends on the
climate, what works in one climate will be disastrous in another.

The weep holes you mention are no-go in certain costal climates, because
they reliably breathe salt-mist in, everytime a low-pressure leaves
the area.

The only thing which is guaranteed to work globally is "helium-tight".

Anything else needs to be judged against the climate in question, including
what kind of aerosols and particulate the wind might bring.



-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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Re: [time-nuts] EOL Motorola Oncore Remote Antenna

[Art Sepin]

> To me it looks more like water ingress through micro-cracks in the
>  plastic-dome, and the O-ring did its job and kept that water in.

Interesting. That's the first we've heard about micro-cracks in the Radome but 
that's certainly a likely possibility with such a long exposure to U/V. The 
more common failure mode reported was moisture ingress due to "breathing;" the 
uptake of moisture laden air past the O-Ring, due to a small pressure 
differential. But, once the moisture was inside, it was also trapped internally 
by the O-Ring. This condition was reported more often in geographic areas that 
experienced a wide variation in barometric pressures.  

Art

-Original Message-
From: Poul-Henning Kamp  
Sent: Sunday, November 29, 2020 11:19 PM
To: Discussion of precise time and frequency measurement 
; Art Sepin 
Subject: Re: [time-nuts] EOL Motorola Oncore Remote Antenna



> It's obvious from the photo that the O-Ring seal failed its purpose 
> over its many years of service. Has the unit totally failed or does the 
> electronic portion still function?

No, the electronics is stone dead.

To me it looks more like water ingress through micro-cracks in the 
plastic-dome, and the O-ring did its job and kept that water in.

The microcracks are uniform and seem to follow the molding flow, and that is 
probably to be expected in our climate:  We have a lot of humid freeze-thaw 
cycles.

I wonder if buffing the radomes with car-wax would help ?

> I said lucky because I found some GSynQ parts here in an engineering 
> storage cabinet that we  can send to you at no charge to revive your unit.

Thanks for the offer, but dont bother: I had a spare on hand, and I may still 
have third one lying around somewhere.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
p...@freebsd.org | TCP/IP since RFC 956
FreeBSD committer   | BSD since 4.3-tahoe
Never attribute to malice what can adequately be explained by incompetence.

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[time-nuts] TWT's was: Re: Voyager space probe question

[Dave B via time-nuts]

The power supplies for them are interesting too.

Especially when you get to the multi kW beasties with multiple
collectors etc.  Floating high power HV supplies, referenced to the more
negative Cathode potential.

That's one of the things I do for the day job, fix TWTA's.   99% of the
time, it's a PSU problem.   The tubes themselves are amazingly rugged,
so long as you do not store too much energy in the PSU on the HV side in
case there's an arc in the tube.

The secret is the voltage regulation controls and protection circuits. 
Loops within loops etc.   Great if you like analogue control and power
switching systems.

Can make a mess when things go wrong though.

Current task on the bench though, is refurbishing a pumped oil cooling
system, not for a TWT, but for a broadband RF power amplifier.  Messy in
another way.

There are some things solid state can't do economically yet, but it's
getting close.

But even the high power low microwave solid state amps, much of the bulk
and complexity again is in the power supply and cooling systems.

Regards.

Dave G8KBV

On 30/11/2020 18:51, time-nuts-requ...@lists.febo.com wrote:
> I wouldn't be so sure about the GaN revolution overtaking it. TWTAs are 
> a pretty simple device, easy to get 50-60 dB of gain in a fairly small, 
> robust package with incredibly wide bandwidth (octaves in some cases), 
> and DC to RF conversion efficiency >50%.

-- 
Created on and sent from a Unix like PC running and using free and open source 
software:


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Re: [time-nuts] Early Christmas - DMTD up and running

[Bob kb8tq]

Hi

When doing DMTD “noise floor” with a common oscillator, you need to use a “line 
stretcher” between the inputs to the DMTD. In the case of a 5 MHz system, you
would need about 30 to 50’ of coax to get the job done. There is no need for 
infinitely
fine steps, a set of 3 cables at 20 / 10 / 5 feet (or anything near those 
numbers)
would do fine. This is very much a “use what you have” sort of setup ….

Bob

> On Nov 30, 2020, at 11:34 AM, Skip Withrow  wrote:
> 
> Hello Time-Nuts,
> Some time back Bert Kehren supplied me with a DMTD board that he and
> Jeurig (in Germany) did.  Bert was kind enough to include the
> transformers and mixers with the board that he sent.  This board is
> quite similar to the Bill Wriley (Hamilton Technical Services) system,
> and is just the dual mixer portion.  I have finally managed to acquire
> all the rest of the parts, a 4.90MHz oscillator, power supplies,
> and packaged everything is a 2U chassis (first attached picture).
> 
> The system drives my HP 5370B (second attachment), which is obviously
> overkill.  A TICC or modest counter with TI capability would be
> sufficient. First tests are quite encouraging.  Right now I only have
> 5MHz capability, and will add a doubler to the other port of the
> offset oscillator to give me 10MHz ability as well.  Even though
> running a 5MHz input with a 10Hz offset gives you a 500,000 increase
> in resolution, noise in the system will degrade performance.
> However, it does look like my noise floor has been lowered by over two
> orders of magnitude.  The 5370B can get you to about 1x10E-10 at 1sec,
> with the DMTD it looks like it is about 7x10E-13 at 1 sec.  I now also
> get data between .1 and 1 second with the DMTD.  The third attachment
> is a timeLab plot of several different noise floor runs (and a couple
> of other random tests).
> 
> This will bring the true performance of many systems out of the noise
> for lower taus, and is necessary for high-performance oscillators.
> I'm looking forward to having some fun.
> 
> Need to learn a lot more though.
> 1. I have a three-way comparison of three oscillators done on a
> borrowed TSC-5110.  Need to make sure that the DMTD gives me similar
> results.
> 2. Corby Dawson uses a very good crystal oscillator for short taus and
> a maser for longer taus as the reference.  Need to figure out my best
> reference for specific measurements.
> 3. I do have an HP 8660B synthesized generator.  I need to investigate
> whether it may be a good offset oscillator candidate.  This would
> allow different sample rates and measurement of oscillators at odd
> frequencies (which I do have).
> 
> Thanks for the bandwidth to show-and-tell.
> 
> Regards,
> Skip Withrow
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Re: [time-nuts] Voyager space probe question

[jimlux]

On 11/30/20 2:20 AM, Gerhard Hoffmann wrote:


Am 30.11.20 um 07:00 schrieb Mark Sims:
I once bought a spool of tungsten-rhenium alloy wire on ebay for dirt 
cheap. A few weeks later a guy contacted me and offered a lot of money 
for it. Turns out they used it to rebuild TWTs. 


1. I used to live in Ulm, Germany, where there was? Thales TWT production.
My neighbor and fellow ham worked there, so I got an invitation for their
family-open-house day. That was most interesting. One division looked so
much like a mechanical craft shop: glass blowing, milling, electrical
discharge machining, welding, all so ...retro. And then, the next room:
An array of the best and newest vector network analyzers, with ladies
moving magnets to collimate the beam and maximizing S21.
But I don't think they can survive the GaN revolution.


Yes - that's a fascinating place. It's been there forever under a 
succession of names, but I assume all the same people. It used to be a 
cavalry station of some sort 100 years ago, people on top floors, horses 
on lower floors, etc.


Making & tuning a TWT is a "art" - there's special sauce in the 
cathodes, there's special sauce or knack in the tuning - some people are 
good at it, others aren't. All the modeling in the world won't replace 
those ladies moving little permanent magnets along the tube body to 
focus the beam.


I wouldn't be so sure about the GaN revolution overtaking it. TWTAs are 
a pretty simple device, easy to get 50-60 dB of gain in a fairly small, 
robust package with incredibly wide bandwidth (octaves in some cases), 
and DC to RF conversion efficiency >50%.


As a paper in IEEE Proceedings said (in the 80s) - it's a fully mature 
technology, and the only reason you haven't seen a particular power and 
frequency combination isn't that it can't be done, it's that nobody has 
happened to order one like that before.





2. @ Jim:  Is there a canonical way to couple a varactor etc to the
DRO for locking without killing Q or without having any effect?
I have made some experiments with 3D-electromagnetics but did
not get very far. It's not for the casual user.



Not that we found - What we were trying to do is get a DRO that was 
tunable over a >50 MHz range (at 8.4 GHz) - we had two varactors - 
coarse and fine (respectively tightly and loosely coupled), so we'd put 
a voltage on the coarse to get it in the right general place, and use 
the fine in the PLL loop to lock it.



https://ipnpr.jpl.nasa.gov/progress_report/42-156/156C.pdf
https://ipnpr.jpl.nasa.gov/progress_report/42-166/166A.pdf


Cook, B., Dennis, M., Kayalar, S., Lux, J., Mysoor, N., "Development of 
the Advanced Deep Space Transponder", JPL IPN Progress Report 42-156, 15 
Feb 2004


Smith, S. , Mysoor, N., Lux, J., Cook, B., Shah, B., "Frequency Agile 
Multi-Channel X-Band Coherent Receiver/Transmitter for the Advanced Deep 
Space Transponder", JPL IPN Progress Report 42-166, 15 August 2006




Mechanical vibration is probably not an issue for our electron spin
DRO.   :-)   It weighs more than 3 Kg, most of it iron to support the
DC field magnets. Looks good. I'd like to get one for the mantlepiece.
Our puck has a borehole for a tiny glass pipe through it to apply
the solution with the free radicals.  Q takes a hit but there is
still enough left. We get quite a frequency shift when changing
the uMol concentration. Can't tell numbers.

Cheers, Gerhard




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Re: [time-nuts] Voyager space probe question

[jimlux]

On 11/30/20 2:20 AM, Gerhard Hoffmann wrote:


Am 30.11.20 um 07:00 schrieb Mark Sims:
I once bought a spool of tungsten-rhenium alloy wire on ebay for dirt 
cheap. A few weeks later a guy contacted me and offered a lot of money 
for it. Turns out they used it to rebuild TWTs. 


1. I used to live in Ulm, Germany, where there was? Thales TWT production.
My neighbor and fellow ham worked there, so I got an invitation for their
family-open-house day. That was most interesting. One division looked so
much like a mechanical craft shop: glass blowing, milling, electrical
discharge machining, welding, all so ...retro. And then, the next room:
An array of the best and newest vector network analyzers, with ladies
moving magnets to collimate the beam and maximizing S21.
But I don't think they can survive the GaN revolution.


Yes - that's a fascinating place. It's been there forever under a 
succession of names, but I assume all the same people. It used to be a 
cavalry station of some sort 100 years ago, people on top floors, horses 
on lower floors, etc.


Making & tuning a TWT is a "art" - there's special sauce in the 
cathodes, there's special sauce or knack in the tuning - some people are 
good at it, others aren't. All the modeling in the world won't replace 
those ladies moving little permanent magnets along the tube body to 
focus the beam.


I wouldn't be so sure about the GaN revolution overtaking it. TWTAs are 
a pretty simple device, easy to get 50-60 dB of gain in a fairly small, 
robust package with incredibly wide bandwidth (octaves in some cases), 
and DC to RF conversion efficiency >50%.


As a paper in IEEE Proceedings said (in the 80s) - it's a fully mature 
technology, and the only reason you haven't seen a particular power and 
frequency combination isn't that it can't be done, it's that nobody has 
happened to order one like that before.





2. @ Jim:  Is there a canonical way to couple a varactor etc to the
DRO for locking without killing Q or without having any effect?
I have made some experiments with 3D-electromagnetics but did
not get very far. It's not for the casual user.


Not that we found - What we were trying to do is get a DRO that was 
tunable over a >50 MHz range (at 8.4 GHz) - we had two varactors - 
coarse and fine (respectively tightly and loosely coupled), so we'd put 
a voltage on the coarse to get it in the right general place, and use 
the fine in the PLL loop to lock it.



https://ipnpr.jpl.nasa.gov/progress_report/42-156/156C.pdf
https://ipnpr.jpl.nasa.gov/progress_report/42-166/166A.pdf


Cook, B., Dennis, M., Kayalar, S., Lux, J., Mysoor, N., "Development of 
the Advanced Deep Space Transponder", JPL IPN Progress Report 42-156, 15 
Feb 2004


Smith, S. , Mysoor, N., Lux, J., Cook, B., Shah, B., "Frequency Agile 
Multi-Channel X-Band Coherent Receiver/Transmitter for the Advanced Deep 
Space Transponder", JPL IPN Progress Report 42-166, 15 August 2006




Mechanical vibration is probably not an issue for our electron spin
DRO.   :-)   It weighs more than 3 Kg, most of it iron to support the
DC field magnets. Looks good. I'd like to get one for the mantlepiece.
Our puck has a borehole for a tiny glass pipe through it to apply
the solution with the free radicals.  Q takes a hit but there is
still enough left. We get quite a frequency shift when changing
the uMol concentration. Can't tell numbers.

Cheers, Gerhard



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Re: [time-nuts] Voyager space probe question

[donald collie]

IIRC Tungsten Rhenium alloy is used for the rotating anode in X-ray tubes.
Extremely high melting point. Cheers..Don C.


Virus-free.
www.avast.com

<#DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2>

On Mon, Nov 30, 2020 at 7:43 PM Mark Sims  wrote:

> I once bought a spool of tungsten-rhenium alloy wire on ebay for dirt
> cheap.   A few weeks later a guy contacted me and offered a lot of money
> for it.  Turns out they used it to rebuild TWTs.
>
> 
>
> > I wonder what sort of cathode material they use?
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Re: [time-nuts] David Allan amusing notes on ADEV, MDEV, TDEV etc.

[dschuecker]

Hi,

I managed to obtain the Lighthill book 'Introduction to Fourier Analysis 
and Generalised Functions' and I scanned it. It provides a different 
look on Fourier Analysis. Feel free to download it from my private cloud:


ftp://dschuecker.dyndns.org/Lighthill_Introduction_to_Fourier_Analysis_and_generalised_functions.pdf 



name/pw guest1

have fun.

Cheers



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Re: [time-nuts] Voyager space probe question

[Gerhard Hoffmann]

Am 30.11.20 um 07:00 schrieb Mark Sims:
I once bought a spool of tungsten-rhenium alloy wire on ebay for dirt 
cheap. A few weeks later a guy contacted me and offered a lot of money 
for it. Turns out they used it to rebuild TWTs. 


1. I used to live in Ulm, Germany, where there was? Thales TWT production.
My neighbor and fellow ham worked there, so I got an invitation for their
family-open-house day. That was most interesting. One division looked so
much like a mechanical craft shop: glass blowing, milling, electrical
discharge machining, welding, all so ...retro. And then, the next room:
An array of the best and newest vector network analyzers, with ladies
moving magnets to collimate the beam and maximizing S21.
But I don't think they can survive the GaN revolution.

2. @ Jim:  Is there a canonical way to couple a varactor etc to the
DRO for locking without killing Q or without having any effect?
I have made some experiments with 3D-electromagnetics but did
not get very far. It's not for the casual user.

Mechanical vibration is probably not an issue for our electron spin
DRO.   :-)   It weighs more than 3 Kg, most of it iron to support the
DC field magnets. Looks good. I'd like to get one for the mantlepiece.
Our puck has a borehole for a tiny glass pipe through it to apply
the solution with the free radicals.  Q takes a hit but there is
still enough left. We get quite a frequency shift when changing
the uMol concentration. Can't tell numbers.

Cheers, Gerhard



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