Re: [time-nuts] Totally unrelated, but..

[David G. McGaw]

One has to be very careful with LDOs.  As we say in applications, 
RTFDS.  :-)  The output capacitor often needs a finite ESR (effective 
series resistance).  A too-large ceramic cap WILL make them oscillate.  
I have noticed that they are used in some GPSDOs.


David


On 12/8/16 11:39 AM, Van Horn, David wrote:

Yes, I hit one of those. I forget the frequency other than around 1 MHz, but it 
was pretty warm when it shouldn't have been, and it was several volts amplitude.

This thing I'm chasing is much more subtle.

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chuck Harris
Sent: Wednesday, December 7, 2016 1:57 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Totally unrelated, but..

I don't think so.  I first ran into a batch of LM340-5's that were excellent 
oscillators back in the 1970's... long before counterfeiting was even remotely 
possible.

The symptom is the regulator puts out only 4.5 out of 5V.

LM309's were, however, totally immune.

Usually, I had to be really bad to make it happen, things like using clip leads 
between the power supply and load with the LM340-5 dangling in between.

The answer is as simple as a couple of 0.1uf ceramic caps soldered right at the 
input and ground, and the output and ground pins.

LDO (low dropout) regulators are very susceptible to oscillation.  They need to 
have a couple of hundred uf of good quality capacitance right on the input and 
output leads.  Where people usually get in trouble, is in not knowing that 
electrolytic capacitors lose most of their capacitance as the temperature 
starts hovering around 0C.

The circuit works great on the bench, but fails when out hanging on a light 
pole...

-Chuck Harris

Joe Leikhim wrote:

Could the low noise parts actually be counterfeit, relabeled as such?

Is the circuit the regulator feeds sensitive to a narrow band of
voltage that the "good regulator" is outside of?

Try replacing the regulator with a battery supply and resistor divider
to attain the working voltage. Move the voltage around. A good
potentiometer and stiff filter capacitors are recommended so as not to introduce 
"pot noise".

Is something corrupting your test procedure?  I had a circuit that
misbehaved due to floating logic pins reacting to static electricity
on the work bench. Another time a diode was photosensitive.




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Re: [time-nuts] Totally unrelated, but..

[David]

I am pretty sure that I ran across this once as well with the
7800/LM340 series in the early 1980s with parts from a major
manufacturer like Motorola, National, or Texas Instruments; the
regulators ran hot and the output voltages were slightly low no matter
what decoupling arrangements were made at the input and output.  The
stability was poor as if the parts were oscillating but no oscillation
was apparent.

There is some discussion here about different designs for these
regulators although the photographs are broken:

http://www.righto.com/2014/09/reverse-engineering-counterfeit-7805.html

On Wed, 7 Dec 2016 15:56:55 -0500, you wrote:

>I don't think so.  I first ran into a batch of LM340-5's
>that were excellent oscillators back in the 1970's... long
>before counterfeiting was even remotely possible.
>
>The symptom is the regulator puts out only 4.5 out of 5V.
>
>LM309's were, however, totally immune.
>
>Usually, I had to be really bad to make it happen, things
>like using clip leads between the power supply and load
>with the LM340-5 dangling in between.
>
>The answer is as simple as a couple of 0.1uf ceramic caps
>soldered right at the input and ground, and the output
>and ground pins.
>
>LDO (low dropout) regulators are very susceptible to
>oscillation.  They need to have a couple of hundred uf
>of good quality capacitance right on the input and output
>leads.  Where people usually get in trouble, is in not
>knowing that electrolytic capacitors lose most of their
>capacitance as the temperature starts hovering around 0C.
>
>The circuit works great on the bench, but fails when out
>hanging on a light pole...
>
>-Chuck Harris
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Re: [time-nuts] Totally unrelated, but..

[David]

On Thu, 8 Dec 2016 02:25:14 +0100, you wrote:

>Am 08.12.2016 um 01:20 schrieb Scott Stobbe:
>> Yes, the short hand I like to use is 4 nV*sqrt(R/1000).
>>
>> 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta
>> vbe gained up ~10x.
>
>Methinks the advantage comes from converting their reference (whatever 
>that may be)
>to a really high impedance current source where a few uF help 
>tremendously in cleaning things up.
>
>regards, Gerhard

The output stage of the LT3042 also operates with unity gain so the
reference noise is not multiplied by the gain set by the divider and
bandwidth of the error amplifier is maximized.  Some regulators
include an extra pin or the voltage divider is external so that point
can be bypassed but their reference is still in series with the error
amplifier so this does not suppress noise from the bandgap reference
itself.
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Re: [time-nuts] Totally unrelated, but..

[Van Horn, David]

Possible, but it should not need that, and the original design didn't include 
it.


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray
Sent: Wednesday, December 7, 2016 10:35 PM
To: Discussion of precise time and frequency measurement
Cc: hmur...@megapathdsl.net
Subject: Re: [time-nuts] Totally unrelated, but..


kb...@n1k.org said:
>> the cool thing about those parts is that their PSRR extends up to 
>> several MHz.  A lot of LDOs have good PSRR to kHz.
> Which to bring it back to noise in radios ….. could be the issue 
> there. The device isn’t oscillating, it’s just not blocking the crud from 
> upstream.

Would a simple L-C type filter on the input side solve that?

--
These are my opinions.  I hate spam.



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Re: [time-nuts] Totally unrelated, but..

[Bob Camp]

HI

Ok, so to fully evaluate the problem, you will need to de-encapsulate the 
parts. That *is* the next step
in this adventure. First pass would be to pull the plastic off of a couple of 
bad ones and get some pictures
of the die. After that, trace them back and see if they are Brand A or Brand B. 
Next, do the same for a good 
one (or two) and see if the die trace to the same manufacturer. 

Next after the die are traced down would be probing with something like a 
Cascade probe system. You can
get them that are alleged to be good into the > 20 GHz range. Team that up with 
some low noise test gear
and you will be able to rule in / rule out the regulator it’s self. Yes this is 
a bit expensive. If you want to troubleshoot
the issue, it is the next step. 

It’s a whole lot easier to swap out the regulator for a different one and just 
move on. 

Bob

> On Dec 8, 2016, at 11:37 AM, Van Horn, David 
> <david.vanh...@backcountryaccess.com> wrote:
> 
> I did check the circuit through the whole range that it should operate in, 
> based on component data sheets. No issues.
> I also carefully varied the voltage right around where the regulator output 
> is, to see if there was some very narrow band of sensitivity.
> Nothing.
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Joe Leikhim
> Sent: Wednesday, December 7, 2016 12:31 PM
> To: time-nuts@febo.com
> Subject: Re: [time-nuts] Totally unrelated, but..
> 
> Could the low noise parts actually be counterfeit, relabeled as such?
> 
> Is the circuit the regulator feeds sensitive to a narrow band of voltage that 
> the "good regulator" is outside of?
> 
> Try replacing the regulator with a battery supply and resistor divider to 
> attain the working voltage. Move the voltage around. A good potentiometer and 
> stiff filter capacitors are recommended so as not to introduce "pot noise".
> 
> Is something corrupting your test procedure?  I had a circuit that misbehaved 
> due to floating logic pins reacting to static electricity on the work bench. 
> Another time a diode was photosensitive.
> 
> 
> 
> --
> Joe Leikhim
> 
> 
> Leikhim and Associates
> 
> Communications Consultants
> 
> Oviedo, Florida
> 
> jleik...@leikhim.com
> 
> 407-982-0446
> 
> WWW.LEIKHIM.COM
> 
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Re: [time-nuts] Totally unrelated, but..

[Poul-Henning Kamp]

In message , "Van Horn, David" writes:

>I did check the circuit through the whole range that it should
>operate in, based on component data sheets. No issues.

How long are the wires supplying the regulator ?

The LC of the wires inductance and the shunt capacitor over the
regulators input has a resonance frequency...


-- 
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] Totally unrelated, but..

[Van Horn, David]

I did check the circuit through the whole range that it should operate in, 
based on component data sheets. No issues.
I also carefully varied the voltage right around where the regulator output is, 
to see if there was some very narrow band of sensitivity.
Nothing.

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Joe Leikhim
Sent: Wednesday, December 7, 2016 12:31 PM
To: time-nuts@febo.com
Subject: Re: [time-nuts] Totally unrelated, but..

Could the low noise parts actually be counterfeit, relabeled as such?

Is the circuit the regulator feeds sensitive to a narrow band of voltage that 
the "good regulator" is outside of?

Try replacing the regulator with a battery supply and resistor divider to 
attain the working voltage. Move the voltage around. A good potentiometer and 
stiff filter capacitors are recommended so as not to introduce "pot noise".

Is something corrupting your test procedure?  I had a circuit that misbehaved 
due to floating logic pins reacting to static electricity on the work bench. 
Another time a diode was photosensitive.



--
Joe Leikhim


Leikhim and Associates

Communications Consultants

Oviedo, Florida

jleik...@leikhim.com

407-982-0446

WWW.LEIKHIM.COM

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Re: [time-nuts] Totally unrelated, but..

[Charles Steinmetz]

Ed wrote:


It would be helpful to give some specific info about the circuit and
regulators used for these experiments, such as operating voltage,
load current, and regulator type.


I concur.  It would also be helpful to have more detail about the 
phenomenon you are observing (see below).


Also, consider the possibility that what you are hearing and concluding 
is RF interference may be noise generated elsewhere, for example in the 
audio section of the rx. If the audio section is quasi-stable, it could 
be sensitive to the absolute power supply voltage, or to the output 
impedance of the regulator. The same could happen in the AGC circuit, or 
the local oscillator.


Can you see the noise on the signal strength monitor or on the AGC line? 
 (If the rx doesn't have a SS monitor, you may need to add one for 
troubleshooting.)


Over what range of frequencies is the interference/noise produced? 
Listen for it on a wideband receiver (which has much greater sensitivity 
above noise than a S/A).  To do this, make a test antenna by stripping a 
couple of feet of shield off a length of coax and forming the insulated 
center conductor into a solenoid with several turns.  Feed this into the 
50 ohm receiver input, then "sniff around" the misbehaving circuit. 
Tune the wideband rx up and down to gauge the extent of the noise band.


Is there anything about the rx that could cause unusual behavior (for 
example, is it a direct-conversion rx, or is there something unusual 
about the LO)?


Best regards,

Charles


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Re: [time-nuts] Totally unrelated, but..

[Scott Stobbe]

That's a really nice part, like the old LM723 was bring your own pass
element, the 3042 is essentially bring your own reference, I hope that is a
trend that continues. And a 10uF capacitor is pretty quiet at 1KHz plus.

The other neat thing about the 3042 is the error amplifier is run unity
gain with a compensation network. For a typical 12V ldo you loose 20 dB
loopgain and 1 decade of loop bandwidth gaining up 1.2 VRef to 12 V on the
feedback divider. At 12 V I'm sure the 3042 would blow a typical LDO out of
the water in line/load regulation.

On Wed, Dec 7, 2016 at 11:36 PM, jimlux  wrote:

> On 12/7/16 4:20 PM, Scott Stobbe wrote:
>
>> Yes, the short hand I like to use is 4 nV*sqrt(R/1000).
>>
>> 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta
>> vbe gained up ~10x.
>>
>> On Wed, Dec 7, 2016 at 7:03 PM Bob Camp  wrote:
>>
>> H
>>>
>>
> the cool thing about those parts is that their PSRR extends up to several
> MHz.  A lot of LDOs have good PSRR to kHz.
>
> Someone at LT did a good job on that design.
>
>
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Re: [time-nuts] Totally unrelated, but..

[Van Horn, David]

Yes, I hit one of those. I forget the frequency other than around 1 MHz, but it 
was pretty warm when it shouldn't have been, and it was several volts amplitude.

This thing I'm chasing is much more subtle.

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Chuck Harris
Sent: Wednesday, December 7, 2016 1:57 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Totally unrelated, but..

I don't think so.  I first ran into a batch of LM340-5's that were excellent 
oscillators back in the 1970's... long before counterfeiting was even remotely 
possible.

The symptom is the regulator puts out only 4.5 out of 5V.

LM309's were, however, totally immune.

Usually, I had to be really bad to make it happen, things like using clip leads 
between the power supply and load with the LM340-5 dangling in between.

The answer is as simple as a couple of 0.1uf ceramic caps soldered right at the 
input and ground, and the output and ground pins.

LDO (low dropout) regulators are very susceptible to oscillation.  They need to 
have a couple of hundred uf of good quality capacitance right on the input and 
output leads.  Where people usually get in trouble, is in not knowing that 
electrolytic capacitors lose most of their capacitance as the temperature 
starts hovering around 0C.

The circuit works great on the bench, but fails when out hanging on a light 
pole...

-Chuck Harris

Joe Leikhim wrote:
> Could the low noise parts actually be counterfeit, relabeled as such?
> 
> Is the circuit the regulator feeds sensitive to a narrow band of 
> voltage that the "good regulator" is outside of?
> 
> Try replacing the regulator with a battery supply and resistor divider 
> to attain the working voltage. Move the voltage around. A good 
> potentiometer and stiff filter capacitors are recommended so as not to 
> introduce "pot noise".
> 
> Is something corrupting your test procedure?  I had a circuit that 
> misbehaved due to floating logic pins reacting to static electricity 
> on the work bench. Another time a diode was photosensitive.
> 
> 
> 
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Re: [time-nuts] Totally unrelated, but..

[jimlux]

On 12/7/16 9:34 PM, Hal Murray wrote:


kb...@n1k.org said:

the cool thing about those parts is that their PSRR extends
up to several MHz.  A lot of LDOs have good PSRR to kHz.

Which to bring it back to noise in radios ….. could be the issue there. The
device isn’t oscillating, it’s just not blocking the crud from upstream.


Would a simple L-C type filter on the input side solve that?

It would be difficult to get the kind of rejection the 3042 gives you 
with a *simple* LC, you're looking at 80 dB or better from DC to 3MHz
See the attached figure.   A multisection filter with carefully chosen 
components can do it.


The usual "solder in" bulkhead feethroughs (e.g. Spectrum Controls), for 
instance are ok at higher frequencies (70dB above 10 MHz), but pretty 
bad low down.  So you're looking at a discrete design.



they've even got an ap note on how to *measure* this, which is no easy feat
http://cds.linear.com/docs/en/application-note/an159fa.pdf
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Re: [time-nuts] Totally unrelated, but..

[ed breya]

It would be helpful to give some specific info about the circuit and 
regulators used for these experiments, such as operating voltage, load 
current, and regulator type. I may have missed some points in the 
discussion on this, but I think the following things are the case:


1. The circuit exhibits excessive internal interference only when using 
certain regulator ICs, but works fine with others of the same type.


2. No apparent oscillation or excessive output noise can be found with 
scopes and SAs to explain it.


3. Various battery voltages have been tried in place of the regulator to 
run the circuit and seem OK.


4. The receiver carrier is 467 kHz (not MHz?).

5. The regulators in question are LM78XX, which use a band-gap reference.

6. Changing or adding various filtering caps seem to have no effect on a 
"bad" regulator.


Without additional info, I would suspect that the bad parts have a 
low-level oscillation somewhere near (or harmonically near) the carrier, 
the LO, or the IF, that is too small to see above the PS noise floor, 
but big enough to cause problems. It is likely these frequencies are in 
the range of where a linear regulator could oscillate. I doubt that one 
could oscillate in the VHF or microwave region, out of reach of your 
SA's span and sensitivity (presumably, depending on what you have). If 
the regulator could oscillate up there, it could certainly leak through 
or around any typical near-band filtering and decoupling in the 
receiver, and cause problems. Looking in the time domain with a scope, 
there will be less sensitivity and dynamic range, so there could be 
something below the floor, and maybe below the SA's bottom frequency 
range too. The SA's low-end can be compromised by the need to safely 
AC-couple the PS voltage into the 50 ohm input. A reasonably-sized 
coupling cap may put it too far up to see a small but important signal 
in the kHz range.


If it's a low frequency or in-band oscillation, you may want to look at 
the receiver circuits for internal susceptibility and PSRR - you may 
have discovered an unanticipated weakness, separate from the regulator 
issue.


Another thing to consider is that there may be a specific supply voltage 
that causes the problem - like a marginal circuit in the receiver front 
or LO going unstable. The battery test, I presume, was at certain 
discrete voltages. It may be worth running it on a variable PS over a 
continuous range. It's possible that the bad regulators just happen to 
land at a "bad" voltage. With a fairly wide tolerance spec, they could 
be all over the place. One way to eliminate this is to measure as 
precisely as possible the output voltage of a bad regulator, then 
replicate it with a variable supply.


If the receiver circuit works fine throughout its supply range, then the 
regulator is again the prime suspect. Also consider what the load 
current is versus its max rating - if it's anywhere close, it could be 
on the verge of current-limiting, and all sorts of strange things can 
happen. If this is the case, adding a helper resistor from input to 
output should get it back into the normal range.


If you haven't already, before all kinds of experiments and analysis, 
try the good old heat and cool methods - blast a bad regulator with 
freeze spray or a heat gun and see what happens. And of course, do the 
same to a "good" one. And maybe also the LO.


This is an interesting case, and I think we all would like some more 
info on the particulars.


Ed




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Re: [time-nuts] Totally unrelated, but..

[Bob Camp]

Hi

The problem with a “simple” filter is that they rarely work as well as you 
might think
they do. Grounding and other layout issues generally get you sooner than you 
would
think. Coils and caps are often not as broadband as you would hope….

Bob

> On Dec 8, 2016, at 12:34 AM, Hal Murray  wrote:
> 
> 
> kb...@n1k.org said:
>>> the cool thing about those parts is that their PSRR extends
>>> up to several MHz.  A lot of LDOs have good PSRR to kHz. 
>> Which to bring it back to noise in radios ….. could be the issue there. The
>> device isn’t oscillating, it’s just not blocking the crud from upstream. 
> 
> Would a simple L-C type filter on the input side solve that?
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
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Re: [time-nuts] Totally unrelated, but..

[Hal Murray]

kb...@n1k.org said:
>> the cool thing about those parts is that their PSRR extends
>> up to several MHz.  A lot of LDOs have good PSRR to kHz. 
> Which to bring it back to noise in radios ….. could be the issue there. The
> device isn’t oscillating, it’s just not blocking the crud from upstream. 

Would a simple L-C type filter on the input side solve that?

-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Totally unrelated, but..

[Bob Camp]

Hi

> On Dec 7, 2016, at 11:36 PM, jimlux  wrote:
> 
> On 12/7/16 4:20 PM, Scott Stobbe wrote:
>> Yes, the short hand I like to use is 4 nV*sqrt(R/1000).
>> 
>> 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta
>> vbe gained up ~10x.
>> 
>> On Wed, Dec 7, 2016 at 7:03 PM Bob Camp  wrote:
>> 
>>> H
> 
> the cool thing about those parts is that their PSRR extends up to several 
> MHz.  A lot of LDOs have good PSRR to kHz.

Which to bring it back to noise in radios ….. could be the issue there. The 
device isn’t oscillating, it’s just not blocking
the crud from upstream.

Bob


> 
> Someone at LT did a good job on that design.
> 
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Re: [time-nuts] Totally unrelated, but..

[jimlux]

On 12/7/16 4:20 PM, Scott Stobbe wrote:

Yes, the short hand I like to use is 4 nV*sqrt(R/1000).

2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta
vbe gained up ~10x.

On Wed, Dec 7, 2016 at 7:03 PM Bob Camp  wrote:


H


the cool thing about those parts is that their PSRR extends up to 
several MHz.  A lot of LDOs have good PSRR to kHz.


Someone at LT did a good job on that design.

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Re: [time-nuts] Totally unrelated, but..

[Bruce Griffiths]

Yes, the very low frequency noise of these regulators isn't anywhere near as 
impressive as their high frequency noise.However for some RF circuits the low 
frequency power supply noise may not be as significant as other effects.
Bruce   

On Thursday, 8 December 2016 2:59 PM, Gerhard Hoffmann  
wrote:
 

 Am 08.12.2016 um 01:20 schrieb Scott Stobbe:
> Yes, the short hand I like to use is 4 nV*sqrt(R/1000).
>
> 2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta
> vbe gained up ~10x.
>
Methinks the advantage comes from converting their reference (whatever 
that may be)
to a really high impedance current source where a few uF help 
tremendously in cleaning things up.

regards, Gerhard
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Re: [time-nuts] Totally unrelated, but..

[Gerhard Hoffmann]

Am 08.12.2016 um 01:20 schrieb Scott Stobbe:

Yes, the short hand I like to use is 4 nV*sqrt(R/1000).

2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta
vbe gained up ~10x.

Methinks the advantage comes from converting their reference (whatever 
that may be)
to a really high impedance current source where a few uF help 
tremendously in cleaning things up.


regards, Gerhard
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Re: [time-nuts] Totally unrelated, but..

[Gerhard Hoffmann]

Am 08.12.2016 um 00:50 schrieb jimlux:

On 12/7/16 3:32 PM, Richard (Rick) Karlquist wrote:

On 12/7/2016 12:16 PM, Clint Jay wrote:

I was looking for a low noise regulator to power a log amp/detector
earlier
this year and was rather surprised to find the 78xx regulators were
considerably better than many of the "low noise" devices.



Are you kidding me?  Check out the Linear Technology LT3042 and
LT3045 with 2 (yes, TWO) NANOVOLTS/root-Hz spot noise.  Orders of
magnitude better than the 78XX introduced 45 years ago.



I'd second the recommendation for the LT3042 - I'm using them in a 
science instrument which is very noise sensitive.




I can only point again to my own measurements under comparable conditions:

< 
https://www.flickr.com/photos/137684711@N07/24070698809/in/album-72157662535945536/ 
>


The LT3042 outclasses the old crowd, whether they are called low noise 
or not.


Don't overdo it with the output capacitor, the 4.7uF from the data sheet 
is ideal.


Too much, and the response gets a peak. The pic was taken from a dead 
bug implementation


involving a Micro-SO with thermal pad on the belly, too horrible to show.

There is also a pic with an external D44VH10G power transistor to supply 
more current.


And remember, 0dB == 1nV/rtHz is the INPUT voltage noise of an LT1028 or 
AD797.


(give or take 10%...)

regards, Gerhard


p.s.

Ulrich, I seem to remember that you were in Ulm in a previous life.

Then you might recognize the Blau valley on the leftmost image. :-)

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Re: [time-nuts] Totally unrelated, but..

[Scott Stobbe]

Yes, the short hand I like to use is 4 nV*sqrt(R/1000).

2 nV/rthz off a bandgap is pretty darn impressive, that includes a delta
vbe gained up ~10x.

On Wed, Dec 7, 2016 at 7:03 PM Bob Camp <kb...@n1k.org> wrote:

> Hi
>
>
>
> Just for reference, KTB in 1 Hz at 50 ohms is roughly 0.9 nV at room
>
> temperature. The previously mentioned 2 nV is equivalent to about 250 ohms.
>
>
>
> Bob
>
>
>
> > On Dec 7, 2016, at 6:58 PM, Scott Stobbe <scott.j.sto...@gmail.com>
> wrote:
>
> >
>
> > You can buy opamps off the shelf with an input referred noise less than a
>
> > 50 ohm resistor to build up a preamp (of course you can build up
> something
>
> > even lower with discretes, but then it's a time commitment over a basic
>
> > opamp preamp)
>
> >
>
> > Even if your regulator is low noise if it's running with low phase margin
>
> > you can get noise peaking.
>
> >
>
> > On Wed, Dec 7, 2016 at 3:06 PM Van Horn, David <
>
> > david.vanh...@backcountryaccess.com> wrote:
>
> >
>
> >>
>
> >>
>
> >> I replaced the original caps, and I added caps, I substituted good
>
> >> Jonhansen RF caps, and Tanceram caps.
>
> >>
>
> >> No help at all.
>
> >>
>
> >>
>
> >>
>
> >> The layout and routing is as good as I could do, and the only
> improvement
>
> >> I could see possible would be to move one cap closer to the reg.
>
> >>
>
> >> The difference would be less than the tolerance of part placement on the
>
> >> existing pads.
>
> >>
>
> >>
>
> >>
>
> >> Fortunately this isn't a critical piece of equipment, but I want it
>
> >> working RIGHT before I put it back in service.
>
> >>
>
> >> It's a custom receiver for 457 kHz.
>
> >>
>
> >>
>
> >>
>
> >>
>
> >>
>
> >> -Original Message-
>
> >>
>
> >> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of
> Graham /
>
> >> KE9H
>
> >>
>
> >> Sent: Wednesday, December 7, 2016 10:41 AM
>
> >>
>
> >> To: Discussion of precise time and frequency measurement
>
> >>
>
> >> Subject: Re: [time-nuts] Totally unrelated, but..
>
> >>
>
> >>
>
> >>
>
> >> Remember that the internal Voltage reference in the original three
>
> >> terminal regulator designs is a Zener.
>
> >>
>
> >> (Zeners are also useful as RF white noise sources.) The regulator is
>
> >> generally an amplifier with DC feedback.
>
> >>
>
> >> If you look at the application notes on the early regulators, they
> require
>
> >> capacitors to ground on both the input and outputs.
>
> >>
>
> >> If these capacitors are missing, or too low in value, or not good
>
> >> capacitors at RF frequencies, then the Zener noise is amplified by the
>
> >> regulator amplifier and pushed out the output port.
>
> >>
>
> >> I would experiment by putting a good ceramic 0.1uF cap to ground, right
> at
>
> >> the regulator output port.
>
> >>
>
> >>
>
> >>
>
> >>
>
> >>
>
> >> --- Graham
>
> >>
>
> >>
>
> >>
>
> >> ==
>
> >>
>
> >>
>
> >>
>
> >>
>
> >>
>
> >> On Wed, Dec 7, 2016 at 10:43 AM, Bob Camp <kb...@n1k.org> wrote:
>
> >>
>
> >>
>
> >>
>
> >>> Hi
>
> >>
>
> >>>
>
> >>
>
> >>> You probably have proven one of the most basic design truths: Parts
>
> >>
>
> >>> will
>
> >>
>
> >>> *always* oscillate just
>
> >>
>
> >>> outside the bandwidth of your test gear” :). A few other possible
> issues:
>
> >>
>
> >>>
>
> >>
>
> >>> 1) Something else is oscillating and it is simply interacting with the
>
> >>
>
> >>> regulator in an odd way.
>
> >>
>
> >>> 2) The oscillation / noise is at a very low level and it’s below your
>
> >>
>
> >>> test gear’s noise floor
>
> >>
>
> >>> 3) Testing stops the oscillation
>
> >>
>
> >>>
>
> >>
&

Re: [time-nuts] Totally unrelated, but..

[Clint Jay]

I've no doubt there are many excellent low noise regulators out there that
are orders of magnitude better than the 78xx series,  but there are also
many that claim low noise as a headline feature and are actually worse
 when you dig into the specification.

On 7 Dec 2016 23:42, "Richard (Rick) Karlquist" 
wrote:

> On 12/7/2016 12:16 PM, Clint Jay wrote:
>
>> I was looking for a low noise regulator to power a log amp/detector
>> earlier
>> this year and was rather surprised to find the 78xx regulators were
>> considerably better than many of the "low noise" devices.
>>
>>
> Are you kidding me?  Check out the Linear Technology LT3042 and
> LT3045 with 2 (yes, TWO) NANOVOLTS/root-Hz spot noise.  Orders of
> magnitude better than the 78XX introduced 45 years ago.
>
> Rick N6RK
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Re: [time-nuts] Totally unrelated, but..

[Bob Camp]

Hi

Just for reference, KTB in 1 Hz at 50 ohms is roughly 0.9 nV at room 
temperature. The previously mentioned 2 nV is equivalent to about 250 ohms.

Bob

> On Dec 7, 2016, at 6:58 PM, Scott Stobbe <scott.j.sto...@gmail.com> wrote:
> 
> You can buy opamps off the shelf with an input referred noise less than a
> 50 ohm resistor to build up a preamp (of course you can build up something
> even lower with discretes, but then it's a time commitment over a basic
> opamp preamp)
> 
> Even if your regulator is low noise if it's running with low phase margin
> you can get noise peaking.
> 
> On Wed, Dec 7, 2016 at 3:06 PM Van Horn, David <
> david.vanh...@backcountryaccess.com> wrote:
> 
>> 
>> 
>> I replaced the original caps, and I added caps, I substituted good
>> Jonhansen RF caps, and Tanceram caps.
>> 
>> No help at all.
>> 
>> 
>> 
>> The layout and routing is as good as I could do, and the only improvement
>> I could see possible would be to move one cap closer to the reg.
>> 
>> The difference would be less than the tolerance of part placement on the
>> existing pads.
>> 
>> 
>> 
>> Fortunately this isn't a critical piece of equipment, but I want it
>> working RIGHT before I put it back in service.
>> 
>> It's a custom receiver for 457 kHz.
>> 
>> 
>> 
>> 
>> 
>> -Original Message-
>> 
>> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Graham /
>> KE9H
>> 
>> Sent: Wednesday, December 7, 2016 10:41 AM
>> 
>> To: Discussion of precise time and frequency measurement
>> 
>> Subject: Re: [time-nuts] Totally unrelated, but..
>> 
>> 
>> 
>> Remember that the internal Voltage reference in the original three
>> terminal regulator designs is a Zener.
>> 
>> (Zeners are also useful as RF white noise sources.) The regulator is
>> generally an amplifier with DC feedback.
>> 
>> If you look at the application notes on the early regulators, they require
>> capacitors to ground on both the input and outputs.
>> 
>> If these capacitors are missing, or too low in value, or not good
>> capacitors at RF frequencies, then the Zener noise is amplified by the
>> regulator amplifier and pushed out the output port.
>> 
>> I would experiment by putting a good ceramic 0.1uF cap to ground, right at
>> the regulator output port.
>> 
>> 
>> 
>> 
>> 
>> --- Graham
>> 
>> 
>> 
>> ==
>> 
>> 
>> 
>> 
>> 
>> On Wed, Dec 7, 2016 at 10:43 AM, Bob Camp <kb...@n1k.org> wrote:
>> 
>> 
>> 
>>> Hi
>> 
>>> 
>> 
>>> You probably have proven one of the most basic design truths: Parts
>> 
>>> will
>> 
>>> *always* oscillate just
>> 
>>> outside the bandwidth of your test gear” :). A few other possible issues:
>> 
>>> 
>> 
>>> 1) Something else is oscillating and it is simply interacting with the
>> 
>>> regulator in an odd way.
>> 
>>> 2) The oscillation / noise is at a very low level and it’s below your
>> 
>>> test gear’s noise floor
>> 
>>> 3) Testing stops the oscillation
>> 
>>> 
>> 
>>> Bob
>> 
>>> 
>> 
>>>> On Dec 6, 2016, at 4:24 PM, Van Horn, David <david.vanhorn@
>> 
>>> backcountryaccess.com> wrote:
>> 
>>>> 
>> 
>>>> Lots of discussion on here about low noise regulation so someone may
>> 
>>> know what to look for.
>> 
>>>> 
>> 
>>>> I have a receiver which is getting a lot of interference from
>> somewhere.
>> 
>>>> Antenna disconnected, interference still high.
>> 
>>>> After much poking around, we found that replacing a voltage
>> 
>>>> regulator
>> 
>>> with a slightly different part cures the problem.
>> 
>>>> Running that section on external battery is also fine, so it appears
>> 
>>>> the
>> 
>>> original regulator causes some problem.
>> 
>>>> We tried various batteries over a range of voltages within the chip
>> 
>>> spec, and couldn't make it have a problem.
>> 
>>>> 
>> 
>>>> I looked at the reg input and output with scope and spectrum
>> 
>>>> analyzer,
>> 
>>> and I don't see anything that indicates excessive noise or oscillation.
>> 
>

Re: [time-nuts] Totally unrelated, but..

[Scott Stobbe]

You can buy opamps off the shelf with an input referred noise less than a
50 ohm resistor to build up a preamp (of course you can build up something
even lower with discretes, but then it's a time commitment over a basic
opamp preamp)

Even if your regulator is low noise if it's running with low phase margin
you can get noise peaking.

On Wed, Dec 7, 2016 at 3:06 PM Van Horn, David <
david.vanh...@backcountryaccess.com> wrote:

>
>
> I replaced the original caps, and I added caps, I substituted good
> Jonhansen RF caps, and Tanceram caps.
>
> No help at all.
>
>
>
> The layout and routing is as good as I could do, and the only improvement
> I could see possible would be to move one cap closer to the reg.
>
> The difference would be less than the tolerance of part placement on the
> existing pads.
>
>
>
> Fortunately this isn't a critical piece of equipment, but I want it
> working RIGHT before I put it back in service.
>
> It's a custom receiver for 457 kHz.
>
>
>
>
>
> -Original Message-
>
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Graham /
> KE9H
>
> Sent: Wednesday, December 7, 2016 10:41 AM
>
> To: Discussion of precise time and frequency measurement
>
> Subject: Re: [time-nuts] Totally unrelated, but..
>
>
>
> Remember that the internal Voltage reference in the original three
> terminal regulator designs is a Zener.
>
> (Zeners are also useful as RF white noise sources.) The regulator is
> generally an amplifier with DC feedback.
>
> If you look at the application notes on the early regulators, they require
> capacitors to ground on both the input and outputs.
>
> If these capacitors are missing, or too low in value, or not good
> capacitors at RF frequencies, then the Zener noise is amplified by the
> regulator amplifier and pushed out the output port.
>
> I would experiment by putting a good ceramic 0.1uF cap to ground, right at
> the regulator output port.
>
>
>
>
>
> --- Graham
>
>
>
> ==
>
>
>
>
>
> On Wed, Dec 7, 2016 at 10:43 AM, Bob Camp <kb...@n1k.org> wrote:
>
>
>
> > Hi
>
> >
>
> > You probably have proven one of the most basic design truths: Parts
>
> > will
>
> > *always* oscillate just
>
> > outside the bandwidth of your test gear” :). A few other possible issues:
>
> >
>
> > 1) Something else is oscillating and it is simply interacting with the
>
> > regulator in an odd way.
>
> > 2) The oscillation / noise is at a very low level and it’s below your
>
> > test gear’s noise floor
>
> > 3) Testing stops the oscillation
>
> >
>
> > Bob
>
> >
>
> > > On Dec 6, 2016, at 4:24 PM, Van Horn, David <david.vanhorn@
>
> > backcountryaccess.com> wrote:
>
> > >
>
> > > Lots of discussion on here about low noise regulation so someone may
>
> > know what to look for.
>
> > >
>
> > > I have a receiver which is getting a lot of interference from
> somewhere.
>
> > > Antenna disconnected, interference still high.
>
> > > After much poking around, we found that replacing a voltage
>
> > > regulator
>
> > with a slightly different part cures the problem.
>
> > > Running that section on external battery is also fine, so it appears
>
> > > the
>
> > original regulator causes some problem.
>
> > > We tried various batteries over a range of voltages within the chip
>
> > spec, and couldn't make it have a problem.
>
> > >
>
> > > I looked at the reg input and output with scope and spectrum
>
> > > analyzer,
>
> > and I don't see anything that indicates excessive noise or oscillation.
>
> > > The PCB layout is as tight as you could ask for. Fat tracks, lots of
>
> > ground, I couldn't lay it out any better.
>
> > > Replacing the input and output caps didn't change anything.
>
> > > Replacing the input and output caps with parts that should be
>
> > > "better",
>
> > like Johanson Tancerams or tantalums has no effect.
>
> > >
>
> > > Just for laughs, we tried a number of different regulator chips, all
>
> > > new
>
> > from the reel.
>
> > > The parts with the quietest and with the most noisy specs caused
>
> > problems.
>
> > > One part, with a noise spec more or less in the middle of the spread
>
> > > is
>
> > the one that works.
>
> > >
>
> > > So what is it that a monolithic 

Re: [time-nuts] Totally unrelated, but..

[Bob Camp]

Hi

You can indeed find regulators with noise densities that work out to be 
uV/sqrt(Hz) advertised as
“low noise”. Who knows how marketing justified making the claim other than “not 
as totally rotten
as our older part”. 

Bob

> On Dec 7, 2016, at 6:32 PM, Richard (Rick) Karlquist  
> wrote:
> 
> On 12/7/2016 12:16 PM, Clint Jay wrote:
>> I was looking for a low noise regulator to power a log amp/detector earlier
>> this year and was rather surprised to find the 78xx regulators were
>> considerably better than many of the "low noise" devices.
>> 
> 
> Are you kidding me?  Check out the Linear Technology LT3042 and
> LT3045 with 2 (yes, TWO) NANOVOLTS/root-Hz spot noise.  Orders of magnitude 
> better than the 78XX introduced 45 years ago.
> 
> Rick N6RK
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Re: [time-nuts] Totally unrelated, but..

[jimlux]

On 12/7/16 3:32 PM, Richard (Rick) Karlquist wrote:

On 12/7/2016 12:16 PM, Clint Jay wrote:

I was looking for a low noise regulator to power a log amp/detector
earlier
this year and was rather surprised to find the 78xx regulators were
considerably better than many of the "low noise" devices.



Are you kidding me?  Check out the Linear Technology LT3042 and
LT3045 with 2 (yes, TWO) NANOVOLTS/root-Hz spot noise.  Orders of
magnitude better than the 78XX introduced 45 years ago.



I'd second the recommendation for the LT3042 - I'm using them in a 
science instrument which is very noise sensitive.




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Re: [time-nuts] Totally unrelated, but..

[Richard (Rick) Karlquist]

On 12/7/2016 12:16 PM, Clint Jay wrote:

I was looking for a low noise regulator to power a log amp/detector earlier
this year and was rather surprised to find the 78xx regulators were
considerably better than many of the "low noise" devices.



Are you kidding me?  Check out the Linear Technology LT3042 and
LT3045 with 2 (yes, TWO) NANOVOLTS/root-Hz spot noise.  Orders of 
magnitude better than the 78XX introduced 45 years ago.


Rick N6RK
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Re: [time-nuts] Totally unrelated, but..

[Chuck Harris]

I don't think so.  I first ran into a batch of LM340-5's
that were excellent oscillators back in the 1970's... long
before counterfeiting was even remotely possible.

The symptom is the regulator puts out only 4.5 out of 5V.

LM309's were, however, totally immune.

Usually, I had to be really bad to make it happen, things
like using clip leads between the power supply and load
with the LM340-5 dangling in between.

The answer is as simple as a couple of 0.1uf ceramic caps
soldered right at the input and ground, and the output
and ground pins.

LDO (low dropout) regulators are very susceptible to
oscillation.  They need to have a couple of hundred uf
of good quality capacitance right on the input and output
leads.  Where people usually get in trouble, is in not
knowing that electrolytic capacitors lose most of their
capacitance as the temperature starts hovering around 0C.

The circuit works great on the bench, but fails when out
hanging on a light pole...

-Chuck Harris

Joe Leikhim wrote:
> Could the low noise parts actually be counterfeit, relabeled as such?
> 
> Is the circuit the regulator feeds sensitive to a narrow band of voltage that 
> the
> "good regulator" is outside of?
> 
> Try replacing the regulator with a battery supply and resistor divider to 
> attain the
> working voltage. Move the voltage around. A good potentiometer and stiff 
> filter
> capacitors are recommended so as not to introduce "pot noise".
> 
> Is something corrupting your test procedure?  I had a circuit that misbehaved 
> due to
> floating logic pins reacting to static electricity on the work bench. Another 
> time a
> diode was photosensitive.
> 
> 
> 
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Re: [time-nuts] Totally unrelated, but..

[Bob Camp]

Hi

There are a *bunch* of people making stuff like 78xx regulators. Even 
20 years ago, there was a lot of difference between brand M, brand T, 
and brand F on these devices. Today the spread is even larger. Toss in 
outfits that sub contract the work to who knows where this week ….
What you get today may not be what you got yesterday or what you 
get tomorrow.  At least 20 years ago you got the same thing when you
re-ordered. 

Crazy stuff 

Bob


> On Dec 7, 2016, at 3:16 PM, Clint Jay  wrote:
> 
> I was looking for a low noise regulator to power a log amp/detector earlier
> this year and was rather surprised to find the 78xx regulators were
> considerably better than many of the "low noise" devices.
> 
> But!!
> 
> I've also had odd experiences with some brands of 78xx devices (and way
> before the 'net was anything more than SLIP dial up to a shell so I doubt
> they were Chinese fakes) ,  one was bad enough that it gave some very
> random voltage measurements on a digital meter,  turned out of the was
> creating all sorts of RF hash in the low VHF range up to and possible
> beyond the FM broadcast band.
> 
> On 7 Dec 2016 20:10, "Joe Leikhim"  wrote:
> 
>> Could the low noise parts actually be counterfeit, relabeled as such?
>> 
>> Is the circuit the regulator feeds sensitive to a narrow band of voltage
>> that the "good regulator" is outside of?
>> 
>> Try replacing the regulator with a battery supply and resistor divider to
>> attain the working voltage. Move the voltage around. A good potentiometer
>> and stiff filter capacitors are recommended so as not to introduce "pot
>> noise".
>> 
>> Is something corrupting your test procedure?  I had a circuit that
>> misbehaved due to floating logic pins reacting to static electricity on the
>> work bench. Another time a diode was photosensitive.
>> 
>> 
>> 
>> --
>> Joe Leikhim
>> 
>> 
>> Leikhim and Associates
>> 
>> Communications Consultants
>> 
>> Oviedo, Florida
>> 
>> jleik...@leikhim.com
>> 
>> 407-982-0446
>> 
>> WWW.LEIKHIM.COM
>> 
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
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>> ailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
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Re: [time-nuts] Totally unrelated, but..

[Clint Jay]

I was looking for a low noise regulator to power a log amp/detector earlier
this year and was rather surprised to find the 78xx regulators were
considerably better than many of the "low noise" devices.

But!!

I've also had odd experiences with some brands of 78xx devices (and way
before the 'net was anything more than SLIP dial up to a shell so I doubt
they were Chinese fakes) ,  one was bad enough that it gave some very
random voltage measurements on a digital meter,  turned out of the was
creating all sorts of RF hash in the low VHF range up to and possible
beyond the FM broadcast band.

On 7 Dec 2016 20:10, "Joe Leikhim"  wrote:

> Could the low noise parts actually be counterfeit, relabeled as such?
>
> Is the circuit the regulator feeds sensitive to a narrow band of voltage
> that the "good regulator" is outside of?
>
> Try replacing the regulator with a battery supply and resistor divider to
> attain the working voltage. Move the voltage around. A good potentiometer
> and stiff filter capacitors are recommended so as not to introduce "pot
> noise".
>
> Is something corrupting your test procedure?  I had a circuit that
> misbehaved due to floating logic pins reacting to static electricity on the
> work bench. Another time a diode was photosensitive.
>
>
>
> --
> Joe Leikhim
>
>
> Leikhim and Associates
>
> Communications Consultants
>
> Oviedo, Florida
>
> jleik...@leikhim.com
>
> 407-982-0446
>
> WWW.LEIKHIM.COM
>
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> ailman/listinfo/time-nuts
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>
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Re: [time-nuts] Totally unrelated, but..

[Joe Leikhim]

Could the low noise parts actually be counterfeit, relabeled as such?

Is the circuit the regulator feeds sensitive to a narrow band of voltage 
that the "good regulator" is outside of?


Try replacing the regulator with a battery supply and resistor divider 
to attain the working voltage. Move the voltage around. A good 
potentiometer and stiff filter capacitors are recommended so as not to 
introduce "pot noise".


Is something corrupting your test procedure?  I had a circuit that 
misbehaved due to floating logic pins reacting to static electricity on 
the work bench. Another time a diode was photosensitive.




--
Joe Leikhim


Leikhim and Associates

Communications Consultants

Oviedo, Florida

jleik...@leikhim.com

407-982-0446

WWW.LEIKHIM.COM

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Re: [time-nuts] Totally unrelated, but..

[Van Horn, David]

I replaced the original caps, and I added caps, I substituted good Jonhansen RF 
caps, and Tanceram caps. 
No help at all.

The layout and routing is as good as I could do, and the only improvement I 
could see possible would be to move one cap closer to the reg.
The difference would be less than the tolerance of part placement on the 
existing pads.

Fortunately this isn't a critical piece of equipment, but I want it working 
RIGHT before I put it back in service.
It's a custom receiver for 457 kHz.


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Graham / KE9H
Sent: Wednesday, December 7, 2016 10:41 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Totally unrelated, but..

Remember that the internal Voltage reference in the original three terminal 
regulator designs is a Zener.
(Zeners are also useful as RF white noise sources.) The regulator is generally 
an amplifier with DC feedback.
If you look at the application notes on the early regulators, they require 
capacitors to ground on both the input and outputs.
If these capacitors are missing, or too low in value, or not good capacitors at 
RF frequencies, then the Zener noise is amplified by the regulator amplifier 
and pushed out the output port.
I would experiment by putting a good ceramic 0.1uF cap to ground, right at the 
regulator output port.


--- Graham

==


On Wed, Dec 7, 2016 at 10:43 AM, Bob Camp <kb...@n1k.org> wrote:

> Hi
>
> You probably have proven one of the most basic design truths: Parts 
> will
> *always* oscillate just
> outside the bandwidth of your test gear” :). A few other possible issues:
>
> 1) Something else is oscillating and it is simply interacting with the 
> regulator in an odd way.
> 2) The oscillation / noise is at a very low level and it’s below your 
> test gear’s noise floor
> 3) Testing stops the oscillation
>
> Bob
>
> > On Dec 6, 2016, at 4:24 PM, Van Horn, David <david.vanhorn@
> backcountryaccess.com> wrote:
> >
> > Lots of discussion on here about low noise regulation so someone may
> know what to look for.
> >
> > I have a receiver which is getting a lot of interference from somewhere.
> > Antenna disconnected, interference still high.
> > After much poking around, we found that replacing a voltage 
> > regulator
> with a slightly different part cures the problem.
> > Running that section on external battery is also fine, so it appears 
> > the
> original regulator causes some problem.
> > We tried various batteries over a range of voltages within the chip
> spec, and couldn't make it have a problem.
> >
> > I looked at the reg input and output with scope and spectrum 
> > analyzer,
> and I don't see anything that indicates excessive noise or oscillation.
> > The PCB layout is as tight as you could ask for. Fat tracks, lots of
> ground, I couldn't lay it out any better.
> > Replacing the input and output caps didn't change anything.
> > Replacing the input and output caps with parts that should be 
> > "better",
> like Johanson Tancerams or tantalums has no effect.
> >
> > Just for laughs, we tried a number of different regulator chips, all 
> > new
> from the reel.
> > The parts with the quietest and with the most noisy specs caused
> problems.
> > One part, with a noise spec more or less in the middle of the spread 
> > is
> the one that works.
> >
> > So what is it that a monolithic regulator (linear) can do which is 
> > not
> observable on a scope or SA, which would cause a receiver to think 
> it's getting a signal or significant noise in band?
> > Everything else in the system is shut down, I am sure the regulator 
> > chip
> is the culprit, but so far I don't see how it's causing the problem.
> > I could just use the quiet chip and move on, but experience tells me
> that I'd just have problems again down the road.  That's voodoo, not 
> science.
> >
> >
> > Ideas?
> >
> >
> >
> > --
> > David VanHorn
> > Lead Hardware Engineer
> >
> > Backcountry Access, Inc.
> > 2820 Wilderness Pl, Unit H
> > Boulder, CO  80301 USA
> > phone: 303-417-1345 x110
> > email: david.vanh...@backcountryaccess.com<mailto:david.vanhorn@
> backcountryaccess.com>
> >
> > ___
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> > https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
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> 

Re: [time-nuts] Totally unrelated, but..

[Van Horn, David]

The probes don't seem to affect anything.

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Andy
Sent: Wednesday, December 7, 2016 7:56 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Totally unrelated, but..

>
> I looked at the reg input and output with scope and spectrum analyzer, 
> and I don't see anything that indicates excessive noise or oscillation.
>

Does the receiver's noise persist with the scope or spectrum analyzer attached? 
 Connecting their probes might temporarily "fix" the problem so that it can 
never be observed.

Andy
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Re: [time-nuts] Totally unrelated, but..

[Bob Camp]

Hi

Usually what happens is you have a broadband oscillation at 3.5 to 4 GHz (based 
on your 3 GHz 
upper limit). The “munge” mixes with this and that creating interference at RF.

Bob

> On Dec 7, 2016, at 1:28 PM, Van Horn, David 
> <david.vanh...@backcountryaccess.com> wrote:
> 
> Well so far at least #3 is not true.
> 
> It may be something happening below the noise floor or outside the bandwidth, 
> but I was looking from 0-5MHz.
> I have 3Ghz+ available, but I wouldn't expect these parts to be that fast.
> 
> It's a mystery, but I love solving mysteries.
> 
> -Original Message-
> From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
> Sent: Wednesday, December 7, 2016 9:43 AM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] Totally unrelated, but..
> 
> Hi
> 
> You probably have proven one of the most basic design truths: Parts will 
> *always* oscillate just outside the bandwidth of your test gear” :). A few 
> other possible issues:
> 
> 1) Something else is oscillating and it is simply interacting with the 
> regulator in an odd way.
> 2) The oscillation / noise is at a very low level and it’s below your test 
> gear’s noise floor
> 3) Testing stops the oscillation 
> 
> Bob
> 
>> On Dec 6, 2016, at 4:24 PM, Van Horn, David 
>> <david.vanh...@backcountryaccess.com> wrote:
>> 
>> Lots of discussion on here about low noise regulation so someone may know 
>> what to look for.
>> 
>> I have a receiver which is getting a lot of interference from somewhere.
>> Antenna disconnected, interference still high.
>> After much poking around, we found that replacing a voltage regulator with a 
>> slightly different part cures the problem.
>> Running that section on external battery is also fine, so it appears the 
>> original regulator causes some problem.
>> We tried various batteries over a range of voltages within the chip spec, 
>> and couldn't make it have a problem.
>> 
>> I looked at the reg input and output with scope and spectrum analyzer, and I 
>> don't see anything that indicates excessive noise or oscillation.
>> The PCB layout is as tight as you could ask for. Fat tracks, lots of ground, 
>> I couldn't lay it out any better.
>> Replacing the input and output caps didn't change anything.
>> Replacing the input and output caps with parts that should be "better", like 
>> Johanson Tancerams or tantalums has no effect.
>> 
>> Just for laughs, we tried a number of different regulator chips, all new 
>> from the reel.
>> The parts with the quietest and with the most noisy specs caused problems.
>> One part, with a noise spec more or less in the middle of the spread is the 
>> one that works.
>> 
>> So what is it that a monolithic regulator (linear) can do which is not 
>> observable on a scope or SA, which would cause a receiver to think it's 
>> getting a signal or significant noise in band?
>> Everything else in the system is shut down, I am sure the regulator chip is 
>> the culprit, but so far I don't see how it's causing the problem.
>> I could just use the quiet chip and move on, but experience tells me that 
>> I'd just have problems again down the road.  That's voodoo, not science.
>> 
>> 
>> Ideas?
>> 
>> 
>> 
>> --
>> David VanHorn
>> Lead Hardware Engineer
>> 
>> Backcountry Access, Inc.
>> 2820 Wilderness Pl, Unit H
>> Boulder, CO  80301 USA
>> phone: 303-417-1345  x110
>> email: 
>> david.vanh...@backcountryaccess.com<mailto:david.vanhorn@backcountryac
>> cess.com>
>> 
>> ___
>> 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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Re: [time-nuts] Totally unrelated, but..

[Alexander Pummer]

Once upon the time, there were some "three legged" voltage regulators, 
which were very sensitive to the ESR value of the capacitor which was 
connected to their output. With to low ESR values they oscillated, [the 
oscillation was "inside" of the regulator, which became warm, or 
sometimes hot, because of the high AC output current feeding into the 
output capacitor]  that is actually logical since the dominant pole of 
the control loop is determined with that output capacitor. For noise 
critical application use one resistor -- 0,5 to 2,00 ohms -- serial with 
the output capacitor,  and use an inductor -- 200uH to 1mH -- with very 
low  -- 20mili-ohm to 100mili-ohm  depend how much voltage drop could 
you tolerate with the actual current load -- ohmic resistance serial 
with the output, and a large capacitor--- it could be even10uF -- with 
very low ESR value -- as low as available, ceramic multi-layer 
capacitors are the best -- after the inductor, at the load site -- that 
way the second capacitor is isolated from the output of the regulator,  
and will be not part of the feedback loop. If you have the luxury, to 
design your own regulator, separate the DC feedback and the AC feedback, 
that way you could keep the output voltage more stabile without oscillation.


73

KJ6UHN

Alex


On 12/7/2016 8:43 AM, Bob Camp wrote:

Hi

You probably have proven one of the most basic design truths: Parts will 
*always* oscillate just
outside the bandwidth of your test gear” :). A few other possible issues:

1) Something else is oscillating and it is simply interacting with the 
regulator in an odd way.
2) The oscillation / noise is at a very low level and it’s below your test 
gear’s noise floor
3) Testing stops the oscillation

Bob


On Dec 6, 2016, at 4:24 PM, Van Horn, David 
 wrote:

Lots of discussion on here about low noise regulation so someone may know what 
to look for.

I have a receiver which is getting a lot of interference from somewhere.
Antenna disconnected, interference still high.
After much poking around, we found that replacing a voltage regulator with a 
slightly different part cures the problem.
Running that section on external battery is also fine, so it appears the 
original regulator causes some problem.
We tried various batteries over a range of voltages within the chip spec, and 
couldn't make it have a problem.

I looked at the reg input and output with scope and spectrum analyzer, and I 
don't see anything that indicates excessive noise or oscillation.
The PCB layout is as tight as you could ask for. Fat tracks, lots of ground, I 
couldn't lay it out any better.
Replacing the input and output caps didn't change anything.
Replacing the input and output caps with parts that should be "better", like 
Johanson Tancerams or tantalums has no effect.

Just for laughs, we tried a number of different regulator chips, all new from 
the reel.
The parts with the quietest and with the most noisy specs caused problems.
One part, with a noise spec more or less in the middle of the spread is the one 
that works.

So what is it that a monolithic regulator (linear) can do which is not 
observable on a scope or SA, which would cause a receiver to think it's getting 
a signal or significant noise in band?
Everything else in the system is shut down, I am sure the regulator chip is the 
culprit, but so far I don't see how it's causing the problem.
I could just use the quiet chip and move on, but experience tells me that I'd 
just have problems again down the road.  That's voodoo, not science.


Ideas?



--
David VanHorn
Lead Hardware Engineer

Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO  80301 USA
phone: 303-417-1345  x110
email: 
david.vanh...@backcountryaccess.com

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-
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2016.0.7924 / Virus Database: 4728/13549 - Release Date: 12/07/16


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Re: [time-nuts] Totally unrelated, but..

[Van Horn, David]

Well so far at least #3 is not true.

It may be something happening below the noise floor or outside the bandwidth, 
but I was looking from 0-5MHz.
I have 3Ghz+ available, but I wouldn't expect these parts to be that fast.

It's a mystery, but I love solving mysteries.

-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp
Sent: Wednesday, December 7, 2016 9:43 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Totally unrelated, but..

Hi

You probably have proven one of the most basic design truths: Parts will 
*always* oscillate just outside the bandwidth of your test gear” :). A few 
other possible issues:

1) Something else is oscillating and it is simply interacting with the 
regulator in an odd way.
2) The oscillation / noise is at a very low level and it’s below your test 
gear’s noise floor
3) Testing stops the oscillation 

Bob

> On Dec 6, 2016, at 4:24 PM, Van Horn, David 
> <david.vanh...@backcountryaccess.com> wrote:
> 
> Lots of discussion on here about low noise regulation so someone may know 
> what to look for.
> 
> I have a receiver which is getting a lot of interference from somewhere.
> Antenna disconnected, interference still high.
> After much poking around, we found that replacing a voltage regulator with a 
> slightly different part cures the problem.
> Running that section on external battery is also fine, so it appears the 
> original regulator causes some problem.
> We tried various batteries over a range of voltages within the chip spec, and 
> couldn't make it have a problem.
> 
> I looked at the reg input and output with scope and spectrum analyzer, and I 
> don't see anything that indicates excessive noise or oscillation.
> The PCB layout is as tight as you could ask for. Fat tracks, lots of ground, 
> I couldn't lay it out any better.
> Replacing the input and output caps didn't change anything.
> Replacing the input and output caps with parts that should be "better", like 
> Johanson Tancerams or tantalums has no effect.
> 
> Just for laughs, we tried a number of different regulator chips, all new from 
> the reel.
> The parts with the quietest and with the most noisy specs caused problems.
> One part, with a noise spec more or less in the middle of the spread is the 
> one that works.
> 
> So what is it that a monolithic regulator (linear) can do which is not 
> observable on a scope or SA, which would cause a receiver to think it's 
> getting a signal or significant noise in band?
> Everything else in the system is shut down, I am sure the regulator chip is 
> the culprit, but so far I don't see how it's causing the problem.
> I could just use the quiet chip and move on, but experience tells me that I'd 
> just have problems again down the road.  That's voodoo, not science.
> 
> 
> Ideas?
> 
> 
> 
> --
> David VanHorn
> Lead Hardware Engineer
> 
> Backcountry Access, Inc.
> 2820 Wilderness Pl, Unit H
> Boulder, CO  80301 USA
> phone: 303-417-1345  x110
> email: 
> david.vanh...@backcountryaccess.com<mailto:david.vanhorn@backcountryac
> cess.com>
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to 
> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Totally unrelated, but..

[Graham / KE9H]

Remember that the internal Voltage reference in the original three terminal
regulator designs is a Zener.
(Zeners are also useful as RF white noise sources.)
The regulator is generally an amplifier with DC feedback.
If you look at the application notes on the early regulators, they require
capacitors to ground on both the input and outputs.
If these capacitors are missing, or too low in value, or not good
capacitors at RF frequencies, then the Zener noise is amplified by the
regulator amplifier and pushed out the output port.
I would experiment by putting a good ceramic 0.1uF cap to ground, right at
the regulator output port.

--- Graham

==


On Wed, Dec 7, 2016 at 10:43 AM, Bob Camp  wrote:

> Hi
>
> You probably have proven one of the most basic design truths: Parts will
> *always* oscillate just
> outside the bandwidth of your test gear” :). A few other possible issues:
>
> 1) Something else is oscillating and it is simply interacting with the
> regulator in an odd way.
> 2) The oscillation / noise is at a very low level and it’s below your test
> gear’s noise floor
> 3) Testing stops the oscillation
>
> Bob
>
> > On Dec 6, 2016, at 4:24 PM, Van Horn, David  backcountryaccess.com> wrote:
> >
> > Lots of discussion on here about low noise regulation so someone may
> know what to look for.
> >
> > I have a receiver which is getting a lot of interference from somewhere.
> > Antenna disconnected, interference still high.
> > After much poking around, we found that replacing a voltage regulator
> with a slightly different part cures the problem.
> > Running that section on external battery is also fine, so it appears the
> original regulator causes some problem.
> > We tried various batteries over a range of voltages within the chip
> spec, and couldn't make it have a problem.
> >
> > I looked at the reg input and output with scope and spectrum analyzer,
> and I don't see anything that indicates excessive noise or oscillation.
> > The PCB layout is as tight as you could ask for. Fat tracks, lots of
> ground, I couldn't lay it out any better.
> > Replacing the input and output caps didn't change anything.
> > Replacing the input and output caps with parts that should be "better",
> like Johanson Tancerams or tantalums has no effect.
> >
> > Just for laughs, we tried a number of different regulator chips, all new
> from the reel.
> > The parts with the quietest and with the most noisy specs caused
> problems.
> > One part, with a noise spec more or less in the middle of the spread is
> the one that works.
> >
> > So what is it that a monolithic regulator (linear) can do which is not
> observable on a scope or SA, which would cause a receiver to think it's
> getting a signal or significant noise in band?
> > Everything else in the system is shut down, I am sure the regulator chip
> is the culprit, but so far I don't see how it's causing the problem.
> > I could just use the quiet chip and move on, but experience tells me
> that I'd just have problems again down the road.  That's voodoo, not
> science.
> >
> >
> > Ideas?
> >
> >
> >
> > --
> > David VanHorn
> > Lead Hardware Engineer
> >
> > Backcountry Access, Inc.
> > 2820 Wilderness Pl, Unit H
> > Boulder, CO  80301 USA
> > phone: 303-417-1345 x110
> > email: david.vanh...@backcountryaccess.com backcountryaccess.com>
> >
> > ___
> > 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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Re: [time-nuts] Totally unrelated, but..

[Bob Camp]

Hi

You probably have proven one of the most basic design truths: Parts will 
*always* oscillate just 
outside the bandwidth of your test gear” :). A few other possible issues:

1) Something else is oscillating and it is simply interacting with the 
regulator in an odd way.
2) The oscillation / noise is at a very low level and it’s below your test 
gear’s noise floor
3) Testing stops the oscillation 

Bob

> On Dec 6, 2016, at 4:24 PM, Van Horn, David 
>  wrote:
> 
> Lots of discussion on here about low noise regulation so someone may know 
> what to look for.
> 
> I have a receiver which is getting a lot of interference from somewhere.
> Antenna disconnected, interference still high.
> After much poking around, we found that replacing a voltage regulator with a 
> slightly different part cures the problem.
> Running that section on external battery is also fine, so it appears the 
> original regulator causes some problem.
> We tried various batteries over a range of voltages within the chip spec, and 
> couldn't make it have a problem.
> 
> I looked at the reg input and output with scope and spectrum analyzer, and I 
> don't see anything that indicates excessive noise or oscillation.
> The PCB layout is as tight as you could ask for. Fat tracks, lots of ground, 
> I couldn't lay it out any better.
> Replacing the input and output caps didn't change anything.
> Replacing the input and output caps with parts that should be "better", like 
> Johanson Tancerams or tantalums has no effect.
> 
> Just for laughs, we tried a number of different regulator chips, all new from 
> the reel.
> The parts with the quietest and with the most noisy specs caused problems.
> One part, with a noise spec more or less in the middle of the spread is the 
> one that works.
> 
> So what is it that a monolithic regulator (linear) can do which is not 
> observable on a scope or SA, which would cause a receiver to think it's 
> getting a signal or significant noise in band?
> Everything else in the system is shut down, I am sure the regulator chip is 
> the culprit, but so far I don't see how it's causing the problem.
> I could just use the quiet chip and move on, but experience tells me that I'd 
> just have problems again down the road.  That's voodoo, not science.
> 
> 
> Ideas?
> 
> 
> 
> --
> David VanHorn
> Lead Hardware Engineer
> 
> Backcountry Access, Inc.
> 2820 Wilderness Pl, Unit H
> Boulder, CO  80301 USA
> phone: 303-417-1345  x110
> email: 
> david.vanh...@backcountryaccess.com
> 
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Re: [time-nuts] Totally unrelated, but..

[Andy]

>
> I looked at the reg input and output with scope and spectrum analyzer, and
> I don't see anything that indicates excessive noise or oscillation.
>

Does the receiver's noise persist with the scope or spectrum analyzer
attached?  Connecting their probes might temporarily "fix" the problem so
that it can never be observed.

Andy
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Re: [time-nuts] Totally unrelated, but..

[Peter Reilley]

Is part of the problem that the level of noise that is of concern is
below what a scope can see anyway: PPB?   If the noise is not narrow
band it might also be not observable using a spectrum analyzer?

Pete.



On 12/7/2016 4:09 AM, Poul-Henning Kamp wrote:


In message , "Van Horn, David" writes:


So what is it that a monolithic regulator (linear) can do which
is not observable on a scope or SA, which would cause a receiver
to think it's getting a signal or significant noise in band?

You have to pay really good attention to specs on some linear regulators,
they are unstable in the weirdest places in the loadmap.

For instance, many regulators really want a specific minimum load, and
if you don't for just a nanosecond, they'll do a hissy fit.

A shunt resistor to ground often solves that, at the cost of 10-20mA.



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Re: [time-nuts] Totally unrelated, but..

[Poul-Henning Kamp]

In message , "Van Horn, David" writes:

>So what is it that a monolithic regulator (linear) can do which
>is not observable on a scope or SA, which would cause a receiver
>to think it's getting a signal or significant noise in band?

You have to pay really good attention to specs on some linear regulators,
they are unstable in the weirdest places in the loadmap.

For instance, many regulators really want a specific minimum load, and
if you don't for just a nanosecond, they'll do a hissy fit.

A shunt resistor to ground often solves that, at the cost of 10-20mA.

-- 
Poul-Henning Kamp   | UNIX since Zilog Zeus 3.20
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Never attribute to malice what can adequately be explained by incompetence.
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[time-nuts] Totally unrelated, but..

[Van Horn, David]

Lots of discussion on here about low noise regulation so someone may know what 
to look for.

I have a receiver which is getting a lot of interference from somewhere.
Antenna disconnected, interference still high.
After much poking around, we found that replacing a voltage regulator with a 
slightly different part cures the problem.
Running that section on external battery is also fine, so it appears the 
original regulator causes some problem.
We tried various batteries over a range of voltages within the chip spec, and 
couldn't make it have a problem.

I looked at the reg input and output with scope and spectrum analyzer, and I 
don't see anything that indicates excessive noise or oscillation.
The PCB layout is as tight as you could ask for. Fat tracks, lots of ground, I 
couldn't lay it out any better.
Replacing the input and output caps didn't change anything.
Replacing the input and output caps with parts that should be "better", like 
Johanson Tancerams or tantalums has no effect.

Just for laughs, we tried a number of different regulator chips, all new from 
the reel.
The parts with the quietest and with the most noisy specs caused problems.
One part, with a noise spec more or less in the middle of the spread is the one 
that works.

So what is it that a monolithic regulator (linear) can do which is not 
observable on a scope or SA, which would cause a receiver to think it's getting 
a signal or significant noise in band?
Everything else in the system is shut down, I am sure the regulator chip is the 
culprit, but so far I don't see how it's causing the problem.
I could just use the quiet chip and move on, but experience tells me that I'd 
just have problems again down the road.  That's voodoo, not science.


Ideas?



--
David VanHorn
Lead Hardware Engineer

Backcountry Access, Inc.
2820 Wilderness Pl, Unit H
Boulder, CO  80301 USA
phone: 303-417-1345  x110
email: 
david.vanh...@backcountryaccess.com

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