Totally unrelated, but..
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.vanhorn@backcountryaccess.commailto:david.vanhorn@backcountryaccess.com
In message <CY1PR04MB234753318BF0F8B94BD16BF4E0820@CY1PR04MB2347.namprd04.prod.
outlook.com>, "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
phk@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.
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 <CY1PR04MB234753318BF0F8B94BD16BF4E0820@CY1PR04MB2347.namprd04.prod.
outlook.com>, "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.
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
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:
- Something else is oscillating and it is simply interacting with the regulator in an odd way.
- The oscillation / noise is at a very low level and it’s below your test gear’s noise floor
- 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.vanhorn@backcountryaccess.commailto:david.vanhorn@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.
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 kb8tq@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:
- Something else is oscillating and it is simply interacting with the
regulator in an odd way. - The oscillation / noise is at a very low level and it’s below your test
gear’s noise floor - 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.vanhorn@backcountryaccess.com<mailto:david.vanhorn@
backcountryaccess.com>
mailman/listinfo/time-nuts
and follow the instructions there.
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.
The probes don't seem to affect anything.
-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces@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
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.
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-bounces@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:
- Something else is oscillating and it is simply interacting with the regulator in an odd way.
- The oscillation / noise is at a very low level and it’s below your test gear’s noise floor
- 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.vanhorn@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.
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.
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-bounces@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 kb8tq@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:
- Something else is oscillating and it is simply interacting with the
regulator in an odd way. - The oscillation / noise is at a very low level and it’s below your
test gear’s noise floor - 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.vanhorn@backcountryaccess.com<mailto:david.vanhorn@
backcountryaccess.com>
mailman/listinfo/time-nuts
and follow the instructions there.
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.
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.
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:
- Something else is oscillating and it is simply interacting with the regulator in an odd way.
- The oscillation / noise is at a very low level and it’s below your test gear’s noise floor
- 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.vanhorn@backcountryaccess.commailto:david.vanhorn@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.
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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