Re: [PSES] Technical musings

[Ken Javor]

With a time domain receiver, the dwell time is pegged to the EUT cycle period, 
and that’s it.  That dwell time is for the “slice” size.  About ten years ago, 
it was close to but under 100 MHz.  The latest R&S machine of which I am aware 
now does 970 MHz at a slice, meaning the entire 30 – 1000 MHz spectrum is 
sampled simultaneously.  And the dwell time for that entire 970 MHz would be 
whatever was deemed necessary for the EUT to complete a full cycle of whatever 
it does – independent of the type of detector selected.

 

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Gert Gremmen F4LDP 
Organization: ce-test, qualified testing bv
Reply-To: Gert Gremmen F4LDP 
Date: Saturday, October 12, 2024 at 1:50 AM
To: 
Subject: Re: [PSES] Technical musings

 

But you need a continuous sweep  with the duration of the EUT cycling time, 
think of washing machines, or chemical analysers.
In that way the old hat solutions had te same problem, but for each frequency . 
That can be  quite an amount of data, te be sampled with 2x the highest 
frequency of interest.
And what Karen states, you need to execute the pre-scan in peak mode with a 
dwell time >equal to the UT cycling time, otherwise
you will miss those peaks that cannot be detected in the usual 100 mS.

Gert
 

On 11-10-2024 23:54, Ken Javor wrote:

Using the physical circuit, absolutely, which is why the traditional technique 
sweeps in peak and then QP detects only the signals above the QP limit. But 
with the final IF digitized, and then a software QP detector transfer function 
applied, it happens as fast t as the data processing runs. Which is very fast 
these days.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Karen Burnham 
Reply-To: Karen Burnham 
Date: Friday, October 11, 2024 at 2:56 PM
To: 
Subject: Re: [PSES] Technical musings

 

Ken, isn't there a longer dwell time required for QP detection? I know most of 
the standards recommend sweeping in Peak first, then doing QP only for 
frequencies of exceedance, just because of the dwell time per frequency value. 
I'd be happy to find out I'm wrong about this.  


Best,

-=-Karen Burnham

President and Chief Engineer, NCE

EMC United, Inc.

www.emcunited.com

 

 

On Fri, Oct 11, 2024 at 1:28 PM Ken Javor  wrote:

My understanding is that all present-day EMI receivers – and for quite some 
time now – have simulated the detectors in software, as opposed to applying the 
final IF signal to an actual circuit.  The point being, it takes no more time 
to do a QP sweep than a peak sweep. Even an averages sweep takes no longer than 
a peak sweep.  Seems to me one could run a single sweep, and show the results 
using all three detectors, which would help immensely in identifying the type 
of signal. And it could facilitate different limits for all three kinds of 
detectors, again from a single sweep. Many of these receivers also have the 
capability to show how often such signals occur, which can also assist in 
determining how problematic they are.

 

As Gert says, lots to fix, and I agree with many of his suggestions.

 

But we also have equipment that can help make more useful, and more timely 
measurements.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Gert Gremmen F4LDP 
Organization: ce-test, qualified testing bv
Reply-To: Gert Gremmen F4LDP 
Date: Friday, October 11, 2024 at 1:48 PM
To: 
Subject: Re: [PSES] Technical musings

 

Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using number assumes a 
defined and known uncertainty.

All this experiences calls out for a more strict measurement set-up, with 
extensive cable lay-out description, EUT set-up
a uniform test site (5 meter FAR ?) , standard antennas, regular calibration 
and verification ahead on each test ,
an intelligent site attenuation calculation per frequency range (such as 30-100 
100-300 and 300-1000 MHz) and more, if well done resulting
in a lower MU of the total measurement. Focus shall be on reproducibility, a 6 
dB offset is not that of a problem als long as we are all 6 dB off.
Seen the fact that the current measurements do result in a (more or less) 
satisfactorily EMC situation in spite of excessive variations in results, we 
may assume that the current emission limits are on the safe side (= too low), 
and can be adjusted (say 5 dB) upwards, once a better overall MU is obtained, 
finally resulting in cheaper EMC testing, cheaper EUT production, and less 
excessive radiation = less interference.
As the determining value for compliance is a QP-value, additional attention 
shall be paid to the peak pre-scan dwell times (actually defining the 
frequencies to be measured) and EUT emission cycling times, in order to find 
all qualifying frequencies for QP-evaluation, an aspect that is too often 
overlooked.
It won't be easy to catch up for all these, but didn't we get to Mars too ?

Gert Gremmen

On 11-10-2024 20:23, John Woodgate wrote:

Yes, there's not only the 

Re: [PSES] Technical musings

[Gert Gremmen F4LDP]

But you need a continuous sweep  with the duration of the EUT cycling 
time, think of washing machines, or chemical analysers.
In that way the old hat solutions had te same problem, but for each 
frequency . That can be  quite an amount of data, te be sampled with 2x 
the highest frequency of interest.
And what Karen states, you need to execute the pre-scan in peak mode 
with a dwell time >equal to the UT cycling time, otherwise

you will miss those peaks that cannot be detected in the usual 100 mS.

Gert


On 11-10-2024 23:54, Ken Javor wrote:


Using the physical circuit, absolutely, which is why the traditional 
technique sweeps in peak and then QP detects only the signals above 
the QP limit. But with the final IF digitized, and then a software QP 
detector transfer function applied, it happens as fast t as the data 
processing runs. Which is very fast these days.


--

Ken Javor

Ph: (256) 650-5261

*From: *Karen Burnham 
*Reply-To: *Karen Burnham 
*Date: *Friday, October 11, 2024 at 2:56 PM
*To: *
*Subject: *Re: [PSES] Technical musings

Ken, isn't there a longer dwell time required for QP detection? I know 
most of the standards recommend sweeping in Peak first, then doing QP 
only for frequencies of exceedance, just because of the dwell time per 
frequency value. I'd be happy to find out I'm wrong about this.



Best,

-=-Karen Burnham

President and Chief Engineer, NCE

EMC United, Inc.

www.emcunited.com <http://www.emcunited.com>

On Fri, Oct 11, 2024 at 1:28 PM Ken Javor 
 wrote:


My understanding is that all present-day EMI receivers – and for
quite some time now – have simulated the detectors in software, as
opposed to applying the final IF signal to an actual circuit.  The
point being, it takes no more time to do a QP sweep than a peak
sweep. Even an averages sweep takes no longer than a peak sweep. 
Seems to me one could run a single sweep, and show the results
using all three detectors, which would help immensely in
identifying the type of signal. And it could facilitate different
limits for all three kinds of detectors, again from a single
sweep. Many of these receivers also have the capability to show
how often such signals occur, which can also assist in determining
how problematic they are.

As Gert says, lots to fix, and I agree with many of his suggestions.

But we also have equipment that can help make more useful, and
more timely measurements.

-- 


Ken Javor

Ph: (256) 650-5261

*From: *Gert Gremmen F4LDP 
*Organization: *ce-test, qualified testing bv
*Reply-To: *Gert Gremmen F4LDP 
*Date: *Friday, October 11, 2024 at 1:48 PM
    *To: *
    *Subject: *Re: [PSES] Technical musings

Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using
number assumes a defined and known uncertainty.

All this experiences calls out for a more strict measurement
set-up, with extensive cable lay-out description, EUT set-up
a uniform test site (5 meter FAR ?) , standard antennas, regular
calibration and verification ahead on each test ,
an intelligent site attenuation calculation per frequency range
(such as 30-100 100-300 and 300-1000 MHz) and more, if well done
resulting
in a lower MU of the total measurement. Focus shall be on
reproducibility, a 6 dB offset is not that of a problem als long
as we are all 6 dB off.
Seen the fact that the current measurements do result in a (more
or less) satisfactorily EMC situation in spite of excessive
variations in results, we may assume that the current emission
limits are on the safe side (= too low), and can be adjusted (say
5 dB) upwards, once a better overall MU is obtained, finally
resulting in cheaper EMC testing, cheaper EUT production, and less
excessive radiation = less interference.
As the determining value for compliance is a QP-value, additional
attention shall be paid to the peak pre-scan dwell times (actually
defining the frequencies to be measured) and EUT emission cycling
times, in order to find all qualifying frequencies for
QP-evaluation, an aspect that is too often overlooked.
It won't be easy to catch up for all these, but didn't we get to
Mars too ?

Gert Gremmen

On 11-10-2024 20:23, John Woodgate wrote:

Yes, there's not only the intractable near-field issue, but
all the EM influences between the various pieces of equipment.
This all adds to the uncertainty and irrepeatable results.

On 2024-10-11 18:08, doug emcesd.com <http://emcesd.com> wrote:

A criteria I have seen and agree with is that the distance
from the EUT to the antenna be 10x the size of the EUT to
insure the antenna is seeing a uniform field so it’s
calibration is valid. This is not the same as being in the
far field. This is

Re: [PSES] Technical musings

[Ken Javor]

No.  That is a separate thing. The implementation of a digitized final IF is 
old hat now. It does not require the very wide bandwidth of digitizing the 
first IF.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: "Larry K. Stillings" 
Reply-To: "Larry K. Stillings" 
Date: Friday, October 11, 2024 at 3:04 PM
To: 
Subject: Re: [PSES] Technical musings

 

Karen,

 

Ken is referring to the manufacturers that have implemented wide bandwidth FFT 
technology into their EMI Receivers. Wide bandwidth being around 1 GHz.

 

R&S ESW series is an example of one.

TDEMI is another manufacturer of them.

 

There could be others at this point.

 

Larry K. Stillings
Compliance Worldwide, Inc. 
Test Locally, Sell Globally and Launch Your Products Around the World! 
FCC - Wireless - Telecom - CE Marking - International Approvals - Product 
Safety 
357 Main Street
Sandown, NH 03873
(603) 887 3903 Fax 887-6445
complianceworldwide.com


Privileged/Confidential Information may be contained in this message. If you 
are not the addressee indicated in this message (or responsible for delivery of 
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consent to Internet email for messages of this kind. Opinions, conclusions and 
other information in this message that do not relate to the official business 
of my firm shall be understood as neither given nor endorsed by it.

 

From: Karen Burnham 
Sent: Friday, October 11, 2024 3:56 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Technical musings

 

Ken, isn't there a longer dwell time required for QP detection? I know most of 
the standards recommend sweeping in Peak first, then doing QP only for 
frequencies of exceedance, just because of the dwell time per frequency value. 
I'd be happy to find out I'm wrong about this.  


Best,

-=-Karen Burnham

President and Chief Engineer, NCE

EMC United, Inc.

www.emcunited.com

 

 

On Fri, Oct 11, 2024 at 1:28 PM Ken Javor  wrote:

My understanding is that all present-day EMI receivers – and for quite some 
time now – have simulated the detectors in software, as opposed to applying the 
final IF signal to an actual circuit.  The point being, it takes no more time 
to do a QP sweep than a peak sweep. Even an averages sweep takes no longer than 
a peak sweep.  Seems to me one could run a single sweep, and show the results 
using all three detectors, which would help immensely in identifying the type 
of signal. And it could facilitate different limits for all three kinds of 
detectors, again from a single sweep. Many of these receivers also have the 
capability to show how often such signals occur, which can also assist in 
determining how problematic they are.

 

As Gert says, lots to fix, and I agree with many of his suggestions.

 

But we also have equipment that can help make more useful, and more timely 
measurements.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Gert Gremmen F4LDP 
Organization: ce-test, qualified testing bv
Reply-To: Gert Gremmen F4LDP 
Date: Friday, October 11, 2024 at 1:48 PM
To: 
Subject: Re: [PSES] Technical musings

 

Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using number assumes a 
defined and known uncertainty.

All this experiences calls out for a more strict measurement set-up, with 
extensive cable lay-out description, EUT set-up
a uniform test site (5 meter FAR ?) , standard antennas, regular calibration 
and verification ahead on each test ,
an intelligent site attenuation calculation per frequency range (such as 30-100 
100-300 and 300-1000 MHz) and more, if well done resulting
in a lower MU of the total measurement. Focus shall be on reproducibility, a 6 
dB offset is not that of a problem als long as we are all 6 dB off.
Seen the fact that the current measurements do result in a (more or less) 
satisfactorily EMC situation in spite of excessive variations in results, we 
may assume that the current emission limits are on the safe side (= too low), 
and can be adjusted (say 5 dB) upwards, once a better overall MU is obtained, 
finally resulting in cheaper EMC testing, cheaper EUT production, and less 
excessive radiation = less interference.
As the determining value for compliance is a QP-value, additional attention 
shall be paid to the peak pre-scan dwell times (actually defining the 
frequencies to be measured) and EUT emission cycling times, in order to find 
all qualifying frequencies for QP-evaluation, an aspect that is too often 
overlooked.
It won't be easy to catch up for all these, but didn't we get to Mars too ?

Gert Gremmen

On 11-10-2024 20:23, John Woodgate wrote:

Yes, there's not only the intractable near-field issue, but all the EM 
influences between the various pieces of equipment. This all adds to the 
unce

Re: [PSES] Technical musings

[Ken Javor]

Using the physical circuit, absolutely, which is why the traditional technique 
sweeps in peak and then QP detects only the signals above the QP limit. But 
with the final IF digitized, and then a software QP detector transfer function 
applied, it happens as fast t as the data processing runs. Which is very fast 
these days.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Karen Burnham 
Reply-To: Karen Burnham 
Date: Friday, October 11, 2024 at 2:56 PM
To: 
Subject: Re: [PSES] Technical musings

 

Ken, isn't there a longer dwell time required for QP detection? I know most of 
the standards recommend sweeping in Peak first, then doing QP only for 
frequencies of exceedance, just because of the dwell time per frequency value. 
I'd be happy to find out I'm wrong about this.  


Best,

-=-Karen Burnham

President and Chief Engineer, NCE

EMC United, Inc.

www.emcunited.com

 

 

On Fri, Oct 11, 2024 at 1:28 PM Ken Javor  wrote:

My understanding is that all present-day EMI receivers – and for quite some 
time now – have simulated the detectors in software, as opposed to applying the 
final IF signal to an actual circuit.  The point being, it takes no more time 
to do a QP sweep than a peak sweep. Even an averages sweep takes no longer than 
a peak sweep.  Seems to me one could run a single sweep, and show the results 
using all three detectors, which would help immensely in identifying the type 
of signal. And it could facilitate different limits for all three kinds of 
detectors, again from a single sweep. Many of these receivers also have the 
capability to show how often such signals occur, which can also assist in 
determining how problematic they are.

 

As Gert says, lots to fix, and I agree with many of his suggestions.

 

But we also have equipment that can help make more useful, and more timely 
measurements.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Gert Gremmen F4LDP 
Organization: ce-test, qualified testing bv
Reply-To: Gert Gremmen F4LDP 
Date: Friday, October 11, 2024 at 1:48 PM
To: 
Subject: Re: [PSES] Technical musings

 

Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using number assumes a 
defined and known uncertainty.

All this experiences calls out for a more strict measurement set-up, with 
extensive cable lay-out description, EUT set-up
a uniform test site (5 meter FAR ?) , standard antennas, regular calibration 
and verification ahead on each test ,
an intelligent site attenuation calculation per frequency range (such as 30-100 
100-300 and 300-1000 MHz) and more, if well done resulting
in a lower MU of the total measurement. Focus shall be on reproducibility, a 6 
dB offset is not that of a problem als long as we are all 6 dB off.
Seen the fact that the current measurements do result in a (more or less) 
satisfactorily EMC situation in spite of excessive variations in results, we 
may assume that the current emission limits are on the safe side (= too low), 
and can be adjusted (say 5 dB) upwards, once a better overall MU is obtained, 
finally resulting in cheaper EMC testing, cheaper EUT production, and less 
excessive radiation = less interference.
As the determining value for compliance is a QP-value, additional attention 
shall be paid to the peak pre-scan dwell times (actually defining the 
frequencies to be measured) and EUT emission cycling times, in order to find 
all qualifying frequencies for QP-evaluation, an aspect that is too often 
overlooked.
It won't be easy to catch up for all these, but didn't we get to Mars too ?

Gert Gremmen

On 11-10-2024 20:23, John Woodgate wrote:

Yes, there's not only the intractable near-field issue, but all the EM 
influences between the various pieces of equipment. This all adds to the 
uncertainty and irrepeatable results.

On 2024-10-11 18:08, doug emcesd.com wrote:

A criteria I have seen and agree with is that the distance from the EUT to the 
antenna be 10x the size of the EUT to insure the antenna is seeing a uniform 
field so it’s calibration is valid. This is not the same as being in the far 
field. This is a big issue at 3 meters.

 

I have significant issues with many, if not most standards I have read. For 
instance, the people who wrote IEC 61000-4-4 did not understand the way the 
"capacitive" clamp works. It is also an "inductive" clamp and as a result it is 
directive and more energy is sent to the auxiliary equipment than to the EUT, 
there is no excuse for this. the clamp is positioned backwards in the 
standard I have been pointing this out for 30 years now to my clients and 
others. Here is a link to a paper I wrote on this almost 30 years ago:

 

https://emcesd.com/pdf/esd96-w.pdf

 

In my opinion, neither the clamp nor the standard accurately describe actual 
EFT although in later years some progress has been made, not nearly enough 
though.

 

I see problems like this in many standards I read.

 

Another problem that is much 

Re: [PSES] Technical musings

[Karen Burnham]

Ken, isn't there a longer dwell time required for QP detection? I know most
of the standards recommend sweeping in Peak first, then doing QP only for
frequencies of exceedance, just because of the dwell time per frequency
value. I'd be happy to find out I'm wrong about this.

Best,

-=-Karen Burnham
President and Chief Engineer, NCE
EMC United, Inc.
www.emcunited.com


On Fri, Oct 11, 2024 at 1:28 PM Ken Javor 
wrote:

> My understanding is that all present-day EMI receivers – and for quite
> some time now – have simulated the detectors in software, as opposed to
> applying the final IF signal to an actual circuit.  The point being, it
> takes no more time to do a QP sweep than a peak sweep. Even an averages
> sweep takes no longer than a peak sweep.  Seems to me one could run a
> single sweep, and show the results using all three detectors, which would
> help immensely in identifying the type of signal. And it could facilitate
> different limits for all three kinds of detectors, again from a single
> sweep. Many of these receivers also have the capability to show how often
> such signals occur, which can also assist in determining how problematic
> they are.
>
>
>
> As Gert says, lots to fix, and I agree with many of his suggestions.
>
>
>
> But we also have equipment that can help make more useful, and more timely
> measurements.
>
>
>
> --
>
>
>
> Ken Javor
>
> Ph: (256) 650-5261
>
>
>
>
>
> *From: *Gert Gremmen F4LDP 
> *Organization: *ce-test, qualified testing bv
> *Reply-To: *Gert Gremmen F4LDP 
> *Date: *Friday, October 11, 2024 at 1:48 PM
> *To: *
> *Subject: *Re: [PSES] Technical musings
>
>
>
> Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using number
> assumes a defined and known uncertainty.
>
> All this experiences calls out for a more strict measurement set-up, with
> extensive cable lay-out description, EUT set-up
> a uniform test site (5 meter FAR ?) , standard antennas, regular
> calibration and verification ahead on each test ,
> an intelligent site attenuation calculation per frequency range (such as
> 30-100 100-300 and 300-1000 MHz) and more, if well done resulting
> in a lower MU of the total measurement. Focus shall be on reproducibility,
> a 6 dB offset is not that of a problem als long as we are all 6 dB off.
> Seen the fact that the current measurements do result in a (more or less)
> satisfactorily EMC situation in spite of excessive variations in results,
> we may assume that the current emission limits are on the safe side (= too
> low), and can be adjusted (say 5 dB) upwards, once a better overall MU is
> obtained, finally resulting in cheaper EMC testing, cheaper EUT production,
> and less excessive radiation = less interference.
> As the determining value for compliance is a QP-value, additional
> attention shall be paid to the peak pre-scan dwell times (actually defining
> the frequencies to be measured) and EUT emission cycling times, in order to
> find all qualifying frequencies for QP-evaluation, an aspect that is too
> often overlooked.
> It won't be easy to catch up for all these, but didn't we get to Mars too ?
>
> Gert Gremmen
>
> On 11-10-2024 20:23, John Woodgate wrote:
>
> Yes, there's not only the intractable near-field issue, but all the EM
> influences between the various pieces of equipment. This all adds to the
> uncertainty and irrepeatable results.
>
> On 2024-10-11 18:08, doug emcesd.com wrote:
>
> A criteria I have seen and agree with is that the distance from the EUT to
> the antenna be 10x the size of the EUT to insure the antenna is seeing a
> uniform field so it’s calibration is valid. This is not the same as being
> in the far field. This is a big issue at 3 meters.
>
>
>
> I have significant issues with many, if not most standards I have read.
> For instance, the people who wrote IEC 61000-4-4 did not understand the way
> the "capacitive" clamp works. It is also an "inductive" clamp and as a
> result it is directive and more energy is sent to the auxiliary equipment
> than to the EUT, there is no excuse for this. the clamp is positioned
> backwards in the standard I have been pointing this out for 30 years
> now to my clients and others. Here is a link to a paper I wrote on this
> almost 30 years ago:
>
>
>
> https://emcesd.com/pdf/esd96-w.pdf
>
>
>
> In my opinion, neither the clamp nor the standard accurately describe
> actual EFT although in later years some progress has been made, not nearly
> enough though.
>
>
>
> I see problems like this in many standards I read.
>
>
>
> Another problem that is much harder to control happens over in the ESD
> side

Re: [PSES] Technical musings

[John Woodgate]

Yes, there are advantages of improving MU, but they do not outweigh the 
cost of a major improvement.


On 2024-10-11 19:48, Gert Gremmen F4LDP wrote:
Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using number 
assumes a defined and known uncertainty.


All this experiences calls out for a more strict measurement set-up, 
with extensive cable lay-out description, EUT set-up
a uniform test site (5 meter FAR ?) , standard antennas, regular 
calibration and verification ahead on each test ,
an intelligent site attenuation calculation per frequency range (such 
as 30-100 100-300 and 300-1000 MHz) and more, if well done resulting
in a lower MU of the total measurement. Focus shall be on 
reproducibility, a 6 dB offset is not that of a problem als long as we 
are all 6 dB off.
Seen the fact that the current measurements do result in a (more or 
less) satisfactorily EMC situation in spite of excessive variations in 
results, we may assume that the current emission limits are on the 
safe side (= too low), and can be adjusted (say 5 dB) upwards, once a 
better overall MU is obtained, finally resulting in cheaper EMC 
testing, cheaper EUT production, and less excessive radiation = less 
interference.
As the determining value for compliance is a QP-value, additional 
attention shall be paid to the peak pre-scan dwell times (actually 
defining the frequencies to be measured) and EUT emission cycling 
times, in order to find all qualifying frequencies for QP-evaluation, 
an aspect that is too often overlooked.
It won't be easy to catch up for all these, but didn't we get to Mars 
too ?


Gert Gremmen

On 11-10-2024 20:23, John Woodgate wrote:


Yes, there's not only the intractable near-field issue, but all the 
EM influences between the various pieces of equipment. This all adds 
to the uncertainty and irrepeatable results.


On 2024-10-11 18:08, doug emcesd.com wrote:
A criteria I have seen and agree with is that the distance from the 
EUT to the antenna be 10x the size of the EUT to insure the antenna 
is seeing a uniform field so it’s calibration is valid. This is not 
the same as being in the far field. This is a big issue at 3 meters.


I have significant issues with many, if not most standards I have 
read. For instance, the people who wrote IEC 61000-4-4 did not 
understand the way the "capacitive" clamp works. It is also an 
"inductive" clamp and as a result it is directive and more energy is 
sent to the auxiliary equipment than to the EUT, there is no excuse 
for this. the clamp is positioned backwards in the standard I 
have been pointing this out for 30 years now to my clients and 
others. Here is a link to a paper I wrote on this almost 30 years ago:


https://emcesd.com/pdf/esd96-w.pdf

In my opinion, neither the clamp nor the standard accurately 
describe actual EFT although in later years some progress has been 
made, not nearly enough though.


I see problems like this in many standards I read.

Another problem that is much harder to control happens over in the 
ESD side. My personal discharge at 4 kV holding a small piece of 
metal with a measurement chain with 5 GHz bandwidth has a peak 
current twice what the standard calls for but the follow-on "hump" 
is more of a straight line down to the horizontal axis much faster 
than the standard calls for containing a lot less energy. I think 
this is due to the fact I have less capacitance (surface area, I am 
about two meters tall but on the skinny side from running 3,000 
miles a year) that what was used for the standard which is probably 
closer to average than me. I have no idea how to account for 
variability between people and the actual environment they are in 
when an ESD event happens.


Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org

*From:* John Woodgate 
*Sent:* Friday, October 11, 2024 8:58:14 AM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG 
*Subject:* Re: [PSES] Technical musings

Thanks, Jim. I wondered whether there was anything other than the 
'near-field thicket' involved. Measurement results in the near field 
can be reliably reproduced only in absolutely identical test 
set-ups. This is not compatible with 'standardization'.


On 2024-10-11 16:48, Jim Bacher wrote:


John, you ask why the difference in levels measured between test 
distances of 3 meters and 10 meters. It’s fairly common for a 
device to fail at frequencies below 125 MHz at 3 Meter test 
distance and then pass at a 10 Meter test distance. Besides all the 
other possible factors (such as was a different chamber and test 
equipment used), the question becomes, was it a Near Field or Far 
Field RF signal that was being measured?  Near Field RF levels drop 
faster than Far Field RF Levels. The problem with a 3 Meter test 
distance is the frequency being

Re: [PSES] Technical musings

[Ralph McDiarmid]

And yet, while there is considerable uncertainty with EMC measured quantities 
this situation doesn’t appear to be causing a general problem.It’s the 
“nature of beast” and there is little motivation to do anything about it since 
the status quo appears to be acceptable.

 

Ralph

 

From: Jim Bacher, WB8VSU  
Sent: October 11, 2024 12:17 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] Technical musings

 

Gert, the FCC based their numbers on preventing interference to police and 
other emergency services along with not interfering with your neighbors radio 
or TV. I assume Europe picked their levels for the same reasons. At current 
levels I occasionally have had issues with near by RF emitting devices 
interfering with my ham radio activity. The same could be true for other 
services. 

 

What the standards do not take in consideration is what is happening to the 
noise floor. The noise floor rising makes weak signal detection more difficult. 
If it gets bad enough it could impact more than just weak signal detection. 
Raising the RF levels of the standard would raise the noise floor. 

 

Raising the levels would not be a good thing. Well designed devices can easily 
comply with the standards with reasonable margins. 

 

Jim Bacher, WB8VSU 

j.bac...@ieee.org <mailto:j.bac...@ieee.org>  or ja.bac...@outlook.com 
<mailto:ja.bac...@outlook.com> 

 

 

On October 11, 2024 2:49:00 PM Gert Gremmen F4LDP mailto:g.grem...@cetest.nl> > wrote:

Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using number assumes a 
defined and known uncertainty.

All this experiences calls out for a more strict measurement set-up, with 
extensive cable lay-out description, EUT set-up
a uniform test site (5 meter FAR ?) , standard antennas, regular calibration 
and verification ahead on each test ,
an intelligent site attenuation calculation per frequency range (such as 30-100 
100-300 and 300-1000 MHz) and more, if well done resulting
in a lower MU of the total measurement. Focus shall be on reproducibility, a 6 
dB offset is not that of a problem als long as we are all 6 dB off.
Seen the fact that the current measurements do result in a (more or less) 
satisfactorily EMC situation in spite of excessive variations in results, we 
may assume that the current emission limits are on the safe side (= too low), 
and can be adjusted (say 5 dB) upwards, once a better overall MU is obtained, 
finally resulting in cheaper EMC testing, cheaper EUT production, and less 
excessive radiation = less interference.
As the determining value for compliance is a QP-value, additional attention 
shall be paid to the peak pre-scan dwell times (actually defining the 
frequencies to be measured) and EUT emission cycling times, in order to find 
all qualifying frequencies for QP-evaluation, an aspect that is too often 
overlooked.
It won't be easy to catch up for all these, but didn't we get to Mars too ?

Gert Gremmen

On 11-10-2024 20:23, John Woodgate wrote:

Yes, there's not only the intractable near-field issue, but all the EM 
influences between the various pieces of equipment. This all adds to the 
uncertainty and irrepeatable results.

On 2024-10-11 18:08, doug emcesd.com wrote:

A criteria I have seen and agree with is that the distance from the EUT to the 
antenna be 10x the size of the EUT to insure the antenna is seeing a uniform 
field so it’s calibration is valid. This is not the same as being in the far 
field. This is a big issue at 3 meters.

 

I have significant issues with many, if not most standards I have read. For 
instance, the people who wrote IEC 61000-4-4 did not understand the way the 
"capacitive" clamp works. It is also an "inductive" clamp and as a result it is 
directive and more energy is sent to the auxiliary equipment than to the EUT, 
there is no excuse for this. the clamp is positioned backwards in the 
standard I have been pointing this out for 30 years now to my clients and 
others. Here is a link to a paper I wrote on this almost 30 years ago:

 

https://emcesd.com/pdf/esd96-w.pdf

 

In my opinion, neither the clamp nor the standard accurately describe actual 
EFT although in later years some progress has been made, not nearly enough 
though.

 

I see problems like this in many standards I read.

 

Another problem that is much harder to control happens over in the ESD side. My 
personal discharge at 4 kV holding a small piece of metal with a measurement 
chain with 5 GHz bandwidth has a peak current twice what the standard calls for 
but the follow-on "hump" is more of a straight line down to the horizontal axis 
much faster than the standard calls for containing a lot less energy. I think 
this is due to the fact I have less capacitance (surface area, I am about two 
meters tall but on the skinny side from running 3,000 miles a year) that what 
was used for the standard which is probably closer to average than me. I have

Re: [PSES] Technical musings

[Ken Javor]

My understanding is that all present-day EMI receivers – and for quite some 
time now – have simulated the detectors in software, as opposed to applying the 
final IF signal to an actual circuit.  The point being, it takes no more time 
to do a QP sweep than a peak sweep. Even an averages sweep takes no longer than 
a peak sweep.  Seems to me one could run a single sweep, and show the results 
using all three detectors, which would help immensely in identifying the type 
of signal. And it could facilitate different limits for all three kinds of 
detectors, again from a single sweep. Many of these receivers also have the 
capability to show how often such signals occur, which can also assist in 
determining how problematic they are.

 

As Gert says, lots to fix, and I agree with many of his suggestions.

 

But we also have equipment that can help make more useful, and more timely 
measurements.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Gert Gremmen F4LDP 
Organization: ce-test, qualified testing bv
Reply-To: Gert Gremmen F4LDP 
Date: Friday, October 11, 2024 at 1:48 PM
To: 
Subject: Re: [PSES] Technical musings

 

Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using number assumes a 
defined and known uncertainty.

All this experiences calls out for a more strict measurement set-up, with 
extensive cable lay-out description, EUT set-up
a uniform test site (5 meter FAR ?) , standard antennas, regular calibration 
and verification ahead on each test ,
an intelligent site attenuation calculation per frequency range (such as 30-100 
100-300 and 300-1000 MHz) and more, if well done resulting
in a lower MU of the total measurement. Focus shall be on reproducibility, a 6 
dB offset is not that of a problem als long as we are all 6 dB off.
Seen the fact that the current measurements do result in a (more or less) 
satisfactorily EMC situation in spite of excessive variations in results, we 
may assume that the current emission limits are on the safe side (= too low), 
and can be adjusted (say 5 dB) upwards, once a better overall MU is obtained, 
finally resulting in cheaper EMC testing, cheaper EUT production, and less 
excessive radiation = less interference.
As the determining value for compliance is a QP-value, additional attention 
shall be paid to the peak pre-scan dwell times (actually defining the 
frequencies to be measured) and EUT emission cycling times, in order to find 
all qualifying frequencies for QP-evaluation, an aspect that is too often 
overlooked.
It won't be easy to catch up for all these, but didn't we get to Mars too ?

Gert Gremmen

On 11-10-2024 20:23, John Woodgate wrote:

Yes, there's not only the intractable near-field issue, but all the EM 
influences between the various pieces of equipment. This all adds to the 
uncertainty and irrepeatable results.

On 2024-10-11 18:08, doug emcesd.com wrote:

A criteria I have seen and agree with is that the distance from the EUT to the 
antenna be 10x the size of the EUT to insure the antenna is seeing a uniform 
field so it’s calibration is valid. This is not the same as being in the far 
field. This is a big issue at 3 meters.

 

I have significant issues with many, if not most standards I have read. For 
instance, the people who wrote IEC 61000-4-4 did not understand the way the 
"capacitive" clamp works. It is also an "inductive" clamp and as a result it is 
directive and more energy is sent to the auxiliary equipment than to the EUT, 
there is no excuse for this. the clamp is positioned backwards in the 
standard I have been pointing this out for 30 years now to my clients and 
others. Here is a link to a paper I wrote on this almost 30 years ago:

 

https://emcesd.com/pdf/esd96-w.pdf

 

In my opinion, neither the clamp nor the standard accurately describe actual 
EFT although in later years some progress has been made, not nearly enough 
though.

 

I see problems like this in many standards I read.

 

Another problem that is much harder to control happens over in the ESD side. My 
personal discharge at 4 kV holding a small piece of metal with a measurement 
chain with 5 GHz bandwidth has a peak current twice what the standard calls for 
but the follow-on "hump" is more of a straight line down to the horizontal axis 
much faster than the standard calls for containing a lot less energy. I think 
this is due to the fact I have less capacitance (surface area, I am about two 
meters tall but on the skinny side from running 3,000 miles a year) that what 
was used for the standard which is probably closer to average than me. I have 
no idea how to account for variability between people and the actual 
environment they are in when an ESD event happens.

 

Doug Smith

Sent from my iPhone

IPhone: 408-858-4528

Office: 702-570-6108

Email: d...@dsmith.org

Website: http://dsmith.org

From: John Woodgate 
Sent: Friday, October 11, 2024 8:58:14 AM
To: EMC-PSTC@LISTSERV.IE

Re: [PSES] Technical musings

[Jim Bacher, WB8VSU]

Gert, the FCC based their numbers on preventing interference to police and 
other emergency services along with not interfering with your neighbors 
radio or TV. I assume Europe picked their levels for the same reasons. At 
current levels I occasionally have had issues with near by RF emitting 
devices interfering with my ham radio activity. The same could be true for 
other services.


What the standards do not take in consideration is what is happening to the 
noise floor. The noise floor rising makes weak signal detection more 
difficult. If it gets bad enough it could impact more than just weak signal 
detection. Raising the RF levels of the standard would raise the noise floor.


Raising the levels would not be a good thing. Well designed devices can 
easily comply with the standards with reasonable margins.


Jim Bacher, WB8VSU
j.bac...@ieee.org or ja.bac...@outlook.com

On October 11, 2024 2:49:00 PM Gert Gremmen F4LDP  wrote:
Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using number assumes 
a defined and known uncertainty.


All this experiences calls out for a more strict measurement set-up, with 
extensive cable lay-out description, EUT set-up
a uniform test site (5 meter FAR ?) , standard antennas, regular 
calibration and verification ahead on each test ,
an intelligent site attenuation calculation per frequency range (such as 
30-100 100-300 and 300-1000 MHz) and more, if well done resulting
in a lower MU of the total measurement. Focus shall be on reproducibility, 
a 6 dB offset is not that of a problem als long as we are all 6 dB off.
Seen the fact that the current measurements do result in a (more or less) 
satisfactorily EMC situation in spite of excessive variations in results, 
we may assume that the current emission limits are on the safe side (= too 
low), and can be adjusted (say 5 dB) upwards, once a better overall MU is 
obtained, finally resulting in cheaper EMC testing, cheaper EUT production, 
and less excessive radiation = less interference.
As the determining value for compliance is a QP-value, additional attention 
shall be paid to the peak pre-scan dwell times (actually defining the 
frequencies to be measured) and EUT emission cycling times, in order to 
find all qualifying frequencies for QP-evaluation, an aspect that is too 
often overlooked.

It won't be easy to catch up for all these, but didn't we get to Mars too ?

Gert Gremmen


On 11-10-2024 20:23, John Woodgate wrote:
Yes, there's not only the intractable near-field issue, but all the EM 
influences between the various pieces of equipment. This all adds to the 
uncertainty and irrepeatable results.

On 2024-10-11 18:08, doug emcesd.com wrote:
A criteria I have seen and agree with is that the distance from the EUT to 
the antenna be 10x the size of the EUT to insure the antenna is seeing a 
uniform field so it’s calibration is valid. This is not the same as being 
in the far field. This is a big issue at 3 meters.



I have significant issues with many, if not most standards I have read. For 
instance, the people who wrote IEC 61000-4-4 did not understand the way the 
"capacitive" clamp works. It is also an "inductive" clamp and as a result 
it is directive and more energy is sent to the auxiliary equipment than to 
the EUT, there is no excuse for this. the clamp is positioned backwards in 
the standard I have been pointing this out for 30 years now to my 
clients and others. Here is a link to a paper I wrote on this almost 30 
years ago:



https://emcesd.com/pdf/esd96-w.pdf



In my opinion, neither the clamp nor the standard accurately describe 
actual EFT although in later years some progress has been made, not nearly 
enough though.



I see problems like this in many standards I read.


Another problem that is much harder to control happens over in the ESD 
side. My personal discharge at 4 kV holding a small piece of metal with a 
measurement chain with 5 GHz bandwidth has a peak current twice what the 
standard calls for but the follow-on "hump" is more of a straight line down 
to the horizontal axis much faster than the standard calls for containing a 
lot less energy. I think this is due to the fact I have less capacitance 
(surface area, I am about two meters tall but on the skinny side from 
running 3,000 miles a year) that what was used for the standard which is 
probably closer to average than me. I have no idea how to account for 
variability between people and the actual environment they are in when an 
ESD event happens.



Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org
From: John Woodgate 
Sent: Friday, October 11, 2024 8:58:14 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG 
Subject: Re: [PSES] Technical musings
Thanks, Jim. I wondered whether there was anything other than the 
'near-field thicket' involved. Measurement results in the near field can be 
reliably reprod

Re: [PSES] Technical musings

[Gert Gremmen F4LDP]

Why using numbers (in dBuV/m) if the MU is 200-400 % ? Using number 
assumes a defined and known uncertainty.


All this experiences calls out for a more strict measurement set-up, 
with extensive cable lay-out description, EUT set-up
a uniform test site (5 meter FAR ?) , standard antennas, regular 
calibration and verification ahead on each test ,
an intelligent site attenuation calculation per frequency range (such as 
30-100 100-300 and 300-1000 MHz) and more, if well done resulting
in a lower MU of the total measurement. Focus shall be on 
reproducibility, a 6 dB offset is not that of a problem als long as we 
are all 6 dB off.
Seen the fact that the current measurements do result in a (more or 
less) satisfactorily EMC situation in spite of excessive variations in 
results, we may assume that the current emission limits are on the safe 
side (= too low), and can be adjusted (say 5 dB) upwards, once a better 
overall MU is obtained, finally resulting in cheaper EMC testing, 
cheaper EUT production, and less excessive radiation = less interference.
As the determining value for compliance is a QP-value, additional 
attention shall be paid to the peak pre-scan dwell times (actually 
defining the frequencies to be measured) and EUT emission cycling times, 
in order to find all qualifying frequencies for QP-evaluation, an aspect 
that is too often overlooked.

It won't be easy to catch up for all these, but didn't we get to Mars too ?

Gert Gremmen

On 11-10-2024 20:23, John Woodgate wrote:


Yes, there's not only the intractable near-field issue, but all the EM 
influences between the various pieces of equipment. This all adds to 
the uncertainty and irrepeatable results.


On 2024-10-11 18:08, doug emcesd.com wrote:
A criteria I have seen and agree with is that the distance from the 
EUT to the antenna be 10x the size of the EUT to insure the antenna 
is seeing a uniform field so it’s calibration is valid. This is not 
the same as being in the far field. This is a big issue at 3 meters.


I have significant issues with many, if not most standards I have 
read. For instance, the people who wrote IEC 61000-4-4 did not 
understand the way the "capacitive" clamp works. It is also an 
"inductive" clamp and as a result it is directive and more energy is 
sent to the auxiliary equipment than to the EUT, there is no excuse 
for this. the clamp is positioned backwards in the standard I 
have been pointing this out for 30 years now to my clients and 
others. Here is a link to a paper I wrote on this almost 30 years ago:


https://emcesd.com/pdf/esd96-w.pdf

In my opinion, neither the clamp nor the standard accurately describe 
actual EFT although in later years some progress has been made, not 
nearly enough though.


I see problems like this in many standards I read.

Another problem that is much harder to control happens over in the 
ESD side. My personal discharge at 4 kV holding a small piece of 
metal with a measurement chain with 5 GHz bandwidth has a peak 
current twice what the standard calls for but the follow-on "hump" is 
more of a straight line down to the horizontal axis much faster than 
the standard calls for containing a lot less energy. I think this is 
due to the fact I have less capacitance (surface area, I am about two 
meters tall but on the skinny side from running 3,000 miles a year) 
that what was used for the standard which is probably closer to 
average than me. I have no idea how to account for variability 
between people and the actual environment they are in when an ESD 
event happens.


Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org

*From:* John Woodgate 
*Sent:* Friday, October 11, 2024 8:58:14 AM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG 
*Subject:* Re: [PSES] Technical musings

Thanks, Jim. I wondered whether there was anything other than the 
'near-field thicket' involved. Measurement results in the near field 
can be reliably reproduced only in absolutely identical test set-ups. 
This is not compatible with 'standardization'.


On 2024-10-11 16:48, Jim Bacher wrote:


John, you ask why the difference in levels measured between test 
distances of 3 meters and 10 meters. It’s fairly common for a device 
to fail at frequencies below 125 MHz at 3 Meter test distance and 
then pass at a 10 Meter test distance. Besides all the other 
possible factors (such as was a different chamber and test equipment 
used), the question becomes, was it a Near Field or Far Field RF 
signal that was being measured? Near Field RF levels drop faster 
than Far Field RF Levels. The problem with a 3 Meter test distance 
is the frequency being measured might be impacted by Near Field, 
verses Far Field only measurement at 10 Meters.


I have read a number of papers that claim different wave lengths for

Re: [PSES] Technical musings

[John Woodgate]

Yes, there's not only the intractable near-field issue, but all the EM 
influences between the various pieces of equipment. This all adds to the 
uncertainty and irrepeatable results.


On 2024-10-11 18:08, doug emcesd.com wrote:
A criteria I have seen and agree with is that the distance from the 
EUT to the antenna be 10x the size of the EUT to insure the antenna is 
seeing a uniform field so it’s calibration is valid. This is not the 
same as being in the far field. This is a big issue at 3 meters.


I have significant issues with many, if not most standards I have 
read. For instance, the people who wrote IEC 61000-4-4 did not 
understand the way the "capacitive" clamp works. It is also an 
"inductive" clamp and as a result it is directive and more energy is 
sent to the auxiliary equipment than to the EUT, there is no excuse 
for this. the clamp is positioned backwards in the standard I have 
been pointing this out for 30 years now to my clients and others. Here 
is a link to a paper I wrote on this almost 30 years ago:


https://emcesd.com/pdf/esd96-w.pdf

In my opinion, neither the clamp nor the standard accurately describe 
actual EFT although in later years some progress has been made, not 
nearly enough though.


I see problems like this in many standards I read.

Another problem that is much harder to control happens over in the ESD 
side. My personal discharge at 4 kV holding a small piece of metal 
with a measurement chain with 5 GHz bandwidth has a peak current twice 
what the standard calls for but the follow-on "hump" is more of a 
straight line down to the horizontal axis much faster than the 
standard calls for containing a lot less energy. I think this is due 
to the fact I have less capacitance (surface area, I am about two 
meters tall but on the skinny side from running 3,000 miles a year) 
that what was used for the standard which is probably closer to 
average than me. I have no idea how to account for variability between 
people and the actual environment they are in when an ESD event happens.


Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org

*From:* John Woodgate 
*Sent:* Friday, October 11, 2024 8:58:14 AM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG 
*Subject:* Re: [PSES] Technical musings

Thanks, Jim. I wondered whether there was anything other than the 
'near-field thicket' involved. Measurement results in the near field 
can be reliably reproduced only in absolutely identical test set-ups. 
This is not compatible with 'standardization'.


On 2024-10-11 16:48, Jim Bacher wrote:


John, you ask why the difference in levels measured between test 
distances of 3 meters and 10 meters. It’s fairly common for a device 
to fail at frequencies below 125 MHz at 3 Meter test distance and 
then pass at a 10 Meter test distance. Besides all the other possible 
factors (such as was a different chamber and test equipment used), 
the question becomes, was it a Near Field or Far Field RF signal that 
was being measured?  Near Field RF levels drop faster than Far Field 
RF Levels. The problem with a 3 Meter test distance is the frequency 
being measured might be impacted by Near Field, verses Far Field only 
measurement at 10 Meters.


I have read a number of papers that claim different wave lengths for 
the Near Field effect. The values I have seen are between 1 and 3 
wave lengths (with RF think wave lengths). I suspect it is system 
dependent and typically 1 to 2 wavelengths and I suspect the primary 
reason for the effect between the two measurement distances.


Here are the approximate possible frequency ranges impacted by Near 
Field at a test distance of 3 Meters:


Three wavelength signal: RF levels up to 280 MHz

Two wavelength signal: RF levels up to 140 MHz

One wavelength signal: RF levels up to 70 MHz

As far as I am concerned 10 meters is the better test distance as it 
is in the Far Field for the frequencies between 30 MHz and 1 GHz. 
Although 30 Mhz is close to one wavelength at 10 Meters.


Jim Bacher, WB8VSU

ja.bac...@outlook.com <mailto:ja.bac...@outlook.com> or 
j.bac...@ieee.org <mailto:j.bac...@ieee.org>


*From:*John Woodgate  <mailto:j...@woodjohn.uk>
*Sent:* Wednesday, October 09, 2024 4:18 PM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
*Subject:* [PSES] Technical musings

Reply to Derek @ LF Research, because his post is labelled as SPAM.

Yes, adding OATS is always healthy.😉

Is there an accepted explanation for the '3 m excess'? The published 
results are consistent with the field being diffuse (that term is 
from acoustics: I'm not sure how widely it's used in EMC circles), 
i.e the resultant of a large number of direct, reflected and 
diffracted rays. It is hardly surprising: a cuboid space is '

Re: [PSES] Technical musings

[doug emcesd.com]

A criteria I have seen and agree with is that the distance from the EUT to the 
antenna be 10x the size of the EUT to insure the antenna is seeing a uniform 
field so it’s calibration is valid. This is not the same as being in the far 
field. This is a big issue at 3 meters.

I have significant issues with many, if not most standards I have read. For 
instance, the people who wrote IEC 61000-4-4 did not understand the way the 
"capacitive" clamp works. It is also an "inductive" clamp and as a result it is 
directive and more energy is sent to the auxiliary equipment than to the EUT, 
there is no excuse for this. the clamp is positioned backwards in the 
standard I have been pointing this out for 30 years now to my clients and 
others. Here is a link to a paper I wrote on this almost 30 years ago:

https://emcesd.com/pdf/esd96-w.pdf

In my opinion, neither the clamp nor the standard accurately describe actual 
EFT although in later years some progress has been made, not nearly enough 
though.

I see problems like this in many standards I read.

Another problem that is much harder to control happens over in the ESD side. My 
personal discharge at 4 kV holding a small piece of metal with a measurement 
chain with 5 GHz bandwidth has a peak current twice what the standard calls for 
but the follow-on "hump" is more of a straight line down to the horizontal axis 
much faster than the standard calls for containing a lot less energy. I think 
this is due to the fact I have less capacitance (surface area, I am about two 
meters tall but on the skinny side from running 3,000 miles a year) that what 
was used for the standard which is probably closer to average than me. I have 
no idea how to account for variability between people and the actual 
environment they are in when an ESD event happens.

Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org

From: John Woodgate 
Sent: Friday, October 11, 2024 8:58:14 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG 
Subject: Re: [PSES] Technical musings


Thanks, Jim. I wondered whether there was anything other than the 'near-field 
thicket' involved. Measurement results in the near field can be reliably 
reproduced only in absolutely identical test set-ups. This is not compatible 
with 'standardization'.

On 2024-10-11 16:48, Jim Bacher wrote:

John, you ask why the difference in levels measured between test distances of 3 
meters and 10 meters. It’s fairly common for a device to fail at frequencies 
below 125 MHz at 3 Meter test distance and then pass at a 10 Meter test 
distance. Besides all the other possible factors (such as was a different 
chamber and test equipment used), the question becomes, was it a Near Field or 
Far Field RF signal that was being measured?  Near Field RF levels drop faster 
than Far Field RF Levels. The problem with a 3 Meter test distance is the 
frequency being measured might be impacted by Near Field, verses Far Field only 
measurement at 10 Meters.



I have read a number of papers that claim different wave lengths for the Near 
Field effect. The values I have seen are between 1 and 3 wave lengths (with RF 
think wave lengths). I suspect it is system dependent and typically 1 to 2 
wavelengths and I suspect the primary reason for the effect between the two 
measurement distances.



Here are the approximate possible frequency ranges impacted by Near Field at a 
test distance of 3 Meters:



Three wavelength signal: RF levels up to 280 MHz

Two wavelength signal: RF levels up to 140 MHz

One wavelength signal: RF levels up to 70 MHz



As far as I am concerned 10 meters is the better test distance as it is in the 
Far Field for the frequencies between 30 MHz and 1 GHz. Although 30 Mhz is 
close to one wavelength at 10 Meters.





Jim Bacher, WB8VSU

ja.bac...@outlook.com<mailto:ja.bac...@outlook.com> or  
j.bac...@ieee.org<mailto:j.bac...@ieee.org>



From: John Woodgate <mailto:j...@woodjohn.uk>
Sent: Wednesday, October 09, 2024 4:18 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: [PSES] Technical musings



Reply to Derek @ LF Research, because his post is labelled as SPAM.

Yes, adding OATS is always healthy.😉

Is there an accepted explanation for the '3 m excess'? The published results 
are consistent with the field being diffuse (that term is from acoustics: I'm 
not sure how widely it's used in EMC circles), i.e the resultant of a large 
number of direct, reflected and diffracted rays. It is hardly surprising: a 
cuboid space is 'ideal' for producing a diffuse field above 'eigentone' 
wavelengths. This might create at least a 3 dB increase over 'inverse square' 
and maybe more. I suppose things get complicated at wavelengths that cannot be 
called 'short'.

Has anyone tried a 

Re: [PSES] Technical musings

[John Woodgate]

Thanks, Jim. I wondered whether there was anything other than the 
'near-field thicket' involved. Measurement results in the near field can 
be reliably reproduced only in absolutely identical test set-ups. This 
is not compatible with 'standardization'.


On 2024-10-11 16:48, Jim Bacher wrote:


John, you ask why the difference in levels measured between test 
distances of 3 meters and 10 meters. It’s fairly common for a device 
to fail at frequencies below 125 MHz at 3 Meter test distance and then 
pass at a 10 Meter test distance. Besides all the other possible 
factors (such as was a different chamber and test equipment used), the 
question becomes, was it a Near Field or Far Field RF signal that was 
being measured?  Near Field RF levels drop faster than Far Field RF 
Levels. The problem with a 3 Meter test distance is the frequency 
being measured might be impacted by Near Field, verses Far Field only 
measurement at 10 Meters.


I have read a number of papers that claim different wave lengths for 
the Near Field effect. The values I have seen are between 1 and 3 wave 
lengths (with RF think wave lengths). I suspect it is system dependent 
and typically 1 to 2 wavelengths and I suspect the primary reason for 
the effect between the two measurement distances.


Here are the approximate possible frequency ranges impacted by Near 
Field at a test distance of 3 Meters:


Three wavelength signal: RF levels up to 280 MHz

Two wavelength signal: RF levels up to 140 MHz

One wavelength signal: RF levels up to 70 MHz

As far as I am concerned 10 meters is the better test distance as it 
is in the Far Field for the frequencies between 30 MHz and 1 GHz. 
Although 30 Mhz is close to one wavelength at 10 Meters.


Jim Bacher, WB8VSU

ja.bac...@outlook.com or j.bac...@ieee.org

*From:*John Woodgate 
*Sent:* Wednesday, October 09, 2024 4:18 PM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG
*Subject:* [PSES] Technical musings

Reply to Derek @ LF Research, because his post is labelled as SPAM.

Yes, adding OATS is always healthy.😉

Is there an accepted explanation for the '3 m excess'? The published 
results are consistent with the field being diffuse (that term is from 
acoustics: I'm not sure how widely it's used in EMC circles), i.e the 
resultant of a large number of direct, reflected and diffracted rays. 
It is hardly surprising: a cuboid space is 'ideal' for producing a 
diffuse field above 'eigentone' wavelengths. This might create at 
least a 3 dB increase over 'inverse square' and maybe more. I suppose 
things get complicated at wavelengths that cannot be called 'short'.


Has anyone tried a spherical chamber? If that's too difficult, a 
'quartic sphere [(x,y,z)^4 = r^4, like a Swedish traffic circle] has 
noticeably rounded corners and edges, so might be close enough for a 
useful improvement.


--
OOO - Own Opinions Only
Best Wishes
John Woodgate
Keep trying





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Keep trying


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Re: [PSES] Technical musings

[Jim Bacher]

John, you ask why the difference in levels measured between test distances of 3 
meters and 10 meters. It’s fairly common for a device to fail at frequencies 
below 125 MHz at 3 Meter test distance and then pass at a 10 Meter test 
distance. Besides all the other possible factors (such as was a different 
chamber and test equipment used), the question becomes, was it a Near Field or 
Far Field RF signal that was being measured?  Near Field RF levels drop faster 
than Far Field RF Levels. The problem with a 3 Meter test distance is the 
frequency being measured might be impacted by Near Field, verses Far Field only 
measurement at 10 Meters. 

 

I have read a number of papers that claim different wave lengths for the Near 
Field effect. The values I have seen are between 1 and 3 wave lengths (with RF 
think wave lengths). I suspect it is system dependent and typically 1 to 2 
wavelengths and I suspect the primary reason for the effect between the two 
measurement distances. 

 

Here are the approximate possible frequency ranges impacted by Near Field at a 
test distance of 3 Meters: 

 

Three wavelength signal: RF levels up to 280 MHz 

Two wavelength signal: RF levels up to 140 MHz 

One wavelength signal: RF levels up to 70 MHz

 

As far as I am concerned 10 meters is the better test distance as it is in the 
Far Field for the frequencies between 30 MHz and 1 GHz. Although 30 Mhz is 
close to one wavelength at 10 Meters. 

 

 

Jim Bacher, WB8VSU

ja.bac...@outlook.com   or  j.bac...@ieee.org 
 

 

From: John Woodgate  
Sent: Wednesday, October 09, 2024 4:18 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Technical musings

 

Reply to Derek @ LF Research, because his post is labelled as SPAM.

Yes, adding OATS is always healthy.😉

Is there an accepted explanation for the '3 m excess'? The published results 
are consistent with the field being diffuse (that term is from acoustics: I'm 
not sure how widely it's used in EMC circles), i.e the resultant of a large 
number of direct, reflected and diffracted rays. It is hardly surprising: a 
cuboid space is 'ideal' for producing a diffuse field above 'eigentone' 
wavelengths. This might create at least a 3 dB increase over 'inverse square' 
and maybe more. I suppose things get complicated at wavelengths that cannot be 
called 'short'.

Has anyone tried a spherical chamber? If that's too difficult, a 'quartic 
sphere [(x,y,z)^4 = r^4, like a Swedish traffic circle] has noticeably rounded 
corners and edges, so might be close enough for a useful improvement.

-- 
OOO - Own Opinions Only
Best Wishes
John Woodgate
Keep trying

 


 

 

Virus-free. 

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Re: [PSES] technical musings

[Ken Javor]

This is a point I made (unsuccessfully) to the SAE ARP-958E drafting committee. 
 They now require separate horizontal and vertical polarization antenna 
factors, but measure them three meters above a ground plane, and purport to say 
this is value-added relative to a single polarization calibration as earlier, 
even though these antennas are all used one meter above a ground plane.

 

Since we are discussing Don White, he made the point in volume 4 of the 
handbook series clear back in 1971 that a biconical used with one end closer to 
the floor than two feet would capacitively load the antenna enough to change 
the antenna factor.  So a half-century before the -958 working group hosed this 
up, the issue was clearly understood.

 

This gets back to Doug Smith.  Not saying we should require 0.1 dB uncertainty, 
but the people running the show don’t even understand the issues.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Brent DeWitt 
Reply-To: Brent DeWitt 
Date: Wednesday, October 9, 2024 at 7:42 PM
To: 
Subject: Re: [PSES] technical musings

 

Good point Ralph. As with many here, I grew up with Don's books and found them 
a great resource back then. That said, what I meant to examine is not so much 
the environment, but the characteristics of a receiving antenna in close 
proximity (fractions of a wavelength) to a reflecting "ground" plane. Depending 
on dimensions/balun design/spacing and who knows how many other variables, it 
gets quite messy! This is probably a point where our antenna design experts, 
rather the I, can chip in.

On 10/9/2024 4:13 PM, Ralph McDiarmid wrote:

Hi Brent,

 

The handbook series from Don White Consultants, “Electromagnetic Interference 
and Compatibility, Vol 4” does a nice job of describing the effect of 
resonances in a bounded space, like a shielded chamber with and without RF 
absorbing material.

 

Ralph

 

From: Brent DeWitt  
Sent: October 9, 2024 12:20 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] technical musings

 

Hi Ken,

I find it interesting that the data "settles" somewhat above 300 MHz, which is 
where many "hybrid" biconical/LP antennas transition effective elements. 
Shortened, fat dipoles are rather notorious for varying AF and VSWR, while LP 
arrays are relatively well behaved. The source antenna is well described and 
known, not so with the receive antenna.  The first question that comes to my 
mind is whether the same receive antenna was used in both measurement cases. In 
my past roles, I have put a great deal of "faith" in the AF calibrations done 
by high quality laboratories such as Liberty Labs, but that data doesn't always 
tell the whole story.

What I'm basically saying is that measurements made in the near-field are 
difficult to reproduce.

Brent


On 10/9/2024 2:42 PM, Lfresearch wrote:

Hi Ken, 

 

Nice article. I would love to have seen you add in an OATS to your measurements.

 

What you publish correlates with what we have found on our 10m OATS, 5m chamber 
and 3m compact chamber. Namely that below 100 MHz, 3m test distances emissions 
tend to read high. I hadn’t planned to publish our results, but in light of 
this series of posts, maybe I should.

 

Take care,

 

Derek.




On Oct 9, 2024, at 12:40 PM, Ken Wyatt  wrote:

 

Hi All,

 

I had a chance to make some comb generator measurements at a lab with two 10m 
chambers. I used the AET USDS spherical comb generator designed by Dr. Bruce 
Archambeault (no longer available, unfortunately). There was an age difference 
between the two chambers, with the older ferrite tile lined and the newer, 
ferrite tiles with absorber cones. One of the charts shows the difference 
between 3m and 10m test distance.

 

Use of comb generator to compare 3m and 10m measurements: 
https://www.edn.com/review-the-aet-usds-spherical-harmonic-comb-generator/

 

One outcome was the linked article, but what was missing in that was the 
comparison between the two chambers (horizon polarization, only). See second 
link to the table.  In every case, the comb generator was positioned on a 
tripod 1m above the reflecting floor. There was as much as 15 dB difference 
between the two. I’ve not published this last chart, but did leave it with the 
test lab management.

 

Chamber 1 and 2 comparison: 
https://www.dropbox.com/scl/fi/yln8697jufl7xl8kvybol/Delta-Chamber-1-Versus-2.png?rlkey=n9s1wvzgfe8wybwxfig8jangp&dl=0

 

Cheers, Ken
___

I'm here to help you succeed! Feel free to call or email with any questions 
related to EMC or EMI troubleshooting - at no obligation. I'm always happy to 
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Wyatt Technical Services LLC
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On Oct 9, 2024, at 1:07 AM, doug emcesd.com  wrote:

 

I agree and was involved wi

Re: [PSES] Technical musings

[Ken Javor]

I have seen similar values elsewhere, but always in the context of a one-meter 
separation measurement. One would expect much worse with antennas farther apart.

 

Not coincidentally, the original use of unlined chambers for radiated work was 
with antennas one-foot from the test sample.  Obviously even less effect there, 
making unlined chambers practical and useful in their original application.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Ralph McDiarmid 
Reply-To: 
Date: Wednesday, October 9, 2024 at 5:37 PM
To: 
Subject: Re: [PSES] Technical musings

 

I was hoping John would join the discussion at some point. 😊  I recall 
eigenvalue and eigenvector, but the term eigentone is a new one for me.

 

Don White Consultants wrote, “Pragmatically, it develops that the worst-case 
situations are likely to result in no more than about 20 dB peak-to-peak 
variation”   That was in the context of a metal box with no RF absorbers.

 

Ralph

 

From: John Woodgate  
Sent: October 9, 2024 1:18 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Technical musings

 

Reply to Derek @ LF Research, because his post is labelled as SPAM.

Yes, adding OATS is always healthy.😉

Is there an accepted explanation for the '3 m excess'? The published results 
are consistent with the field being diffuse (that term is from acoustics: I'm 
not sure how widely it's used in EMC circles), i.e the resultant of a large 
number of direct, reflected and diffracted rays. It is hardly surprising: a 
cuboid space is 'ideal' for producing a diffuse field above 'eigentone' 
wavelengths. This might create at least a 3 dB increase over 'inverse square' 
and maybe more. I suppose things get complicated at wavelengths that cannot be 
called 'short'.

Has anyone tried a spherical chamber? If that's too difficult, a 'quartic 
sphere [(x,y,z)^4 = r^4, like a Swedish traffic circle] has noticeably rounded 
corners and edges, so might be close enough for a useful improvement.
-- 
OOO - Own Opinions Only
Best Wishes
John Woodgate
Keep trying
 

Virus-free.www.avg.com
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Re: [PSES] Technical musings

[Ralph McDiarmid]

I was hoping John would join the discussion at some point. 😊  I recall 
eigenvalue and eigenvector, but the term eigentone is a new one for me.

 

Don White Consultants wrote, “Pragmatically, it develops that the worst-case 
situations are likely to result in no more than about 20 dB peak-to-peak 
variation”   That was in the context of a metal box with no RF absorbers.

 

Ralph

 

From: John Woodgate  
Sent: October 9, 2024 1:18 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] Technical musings

 

Reply to Derek @ LF Research, because his post is labelled as SPAM.

Yes, adding OATS is always healthy.😉

Is there an accepted explanation for the '3 m excess'? The published results 
are consistent with the field being diffuse (that term is from acoustics: I'm 
not sure how widely it's used in EMC circles), i.e the resultant of a large 
number of direct, reflected and diffracted rays. It is hardly surprising: a 
cuboid space is 'ideal' for producing a diffuse field above 'eigentone' 
wavelengths. This might create at least a 3 dB increase over 'inverse square' 
and maybe more. I suppose things get complicated at wavelengths that cannot be 
called 'short'.

Has anyone tried a spherical chamber? If that's too difficult, a 'quartic 
sphere [(x,y,z)^4 = r^4, like a Swedish traffic circle] has noticeably rounded 
corners and edges, so might be close enough for a useful improvement.

-- 
OOO - Own Opinions Only
Best Wishes
John Woodgate
Keep trying

 


 

 

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Re: [PSES] Technical musings

[Lfresearch]

Hi John,

Thanks, not sure this post deserved to be called spam, lol. Ironically, the 
list server rejected Derek@lfresearch, because I registered so long ago with my 
aol address. These days aol.com  is automatically assumed to 
be spam. Oh well.

So, to your point, Frankonia ( I believe ) make a chamber with a Gambrel roof. 
They claim it’s better than the usual rectangular box, but I haven’t seen the 
data.

On my travels I have seen coffin shaped chambers too, they met NSA so that was 
as deep as I looked.

I wish we could just agree to use reverb chambers.

Cheers,

Derek.


> On Oct 9, 2024, at 3:17 PM, John Woodgate  wrote:
> 
> Reply to Derek @ LF Research, because his post is labelled as SPAM.
> 
> Yes, adding OATS is always healthy.😉
> 
> Is there an accepted explanation for the '3 m excess'? The published results 
> are consistent with the field being diffuse (that term is from acoustics: I'm 
> not sure how widely it's used in EMC circles), i.e the resultant of a large 
> number of direct, reflected and diffracted rays. It is hardly surprising: a 
> cuboid space is 'ideal' for producing a diffuse field above 'eigentone' 
> wavelengths. This might create at least a 3 dB increase over 'inverse square' 
> and maybe more. I suppose things get complicated at wavelengths that cannot 
> be called 'short'.
> 
> Has anyone tried a spherical chamber? If that's too difficult, a 'quartic 
> sphere [(x,y,z)^4 = r^4, like a Swedish traffic circle] has noticeably 
> rounded corners and edges, so might be close enough for a useful improvement.
> 
> 
> -- 
> OOO - Own Opinions Only
> Best Wishes
> John Woodgate
> Keep trying
> 
>  
> 
>  Virus-free.www.avg.com 
> 
>  
> This message is from the IEEE Product Safety Engineering Society emc-pstc 
> discussion list. To post a message to the list, send your e-mail to 
> EMC-PSTC@LISTSERV.IEEE.ORG
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Re: [PSES] technical musings

[Ralph McDiarmid]

Hi Brent,

 

The handbook series from Don White Consultants, “Electromagnetic Interference 
and Compatibility, Vol 4” does a nice job of describing the effect of 
resonances in a bounded space, like a shielded chamber with and without RF 
absorbing material.

 

Ralph

 

From: Brent DeWitt  
Sent: October 9, 2024 12:20 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] technical musings

 

Hi Ken,

I find it interesting that the data "settles" somewhat above 300 MHz, which is 
where many "hybrid" biconical/LP antennas transition effective elements. 
Shortened, fat dipoles are rather notorious for varying AF and VSWR, while LP 
arrays are relatively well behaved. The source antenna is well described and 
known, not so with the receive antenna.  The first question that comes to my 
mind is whether the same receive antenna was used in both measurement cases. In 
my past roles, I have put a great deal of "faith" in the AF calibrations done 
by high quality laboratories such as Liberty Labs, but that data doesn't always 
tell the whole story.

What I'm basically saying is that measurements made in the near-field are 
difficult to reproduce.

Brent



On 10/9/2024 2:42 PM, Lfresearch wrote:

Hi Ken, 

 

Nice article. I would love to have seen you add in an OATS to your measurements.

 

What you publish correlates with what we have found on our 10m OATS, 5m chamber 
and 3m compact chamber. Namely that below 100 MHz, 3m test distances emissions 
tend to read high. I hadn’t planned to publish our results, but in light of 
this series of posts, maybe I should.

 

Take care,

 

Derek.





On Oct 9, 2024, at 12:40 PM, Ken Wyatt  <mailto:k...@emc-seminars.com> 
 wrote:

 

Hi All,

 

I had a chance to make some comb generator measurements at a lab with two 10m 
chambers. I used the AET USDS spherical comb generator designed by Dr. Bruce 
Archambeault (no longer available, unfortunately). There was an age difference 
between the two chambers, with the older ferrite tile lined and the newer, 
ferrite tiles with absorber cones. One of the charts shows the difference 
between 3m and 10m test distance.

 

Use of comb generator to compare 3m and 10m measurements: 
https://www.edn.com/review-the-aet-usds-spherical-harmonic-comb-generator/

 

One outcome was the linked article, but what was missing in that was the 
comparison between the two chambers (horizon polarization, only). See second 
link to the table.  In every case, the comb generator was positioned on a 
tripod 1m above the reflecting floor. There was as much as 15 dB difference 
between the two. I’ve not published this last chart, but did leave it with the 
test lab management.

 

Chamber 1 and 2 comparison: 
https://www.dropbox.com/scl/fi/yln8697jufl7xl8kvybol/Delta-Chamber-1-Versus-2.png?rlkey=n9s1wvzgfe8wybwxfig8jangp
 
<https://www.dropbox.com/scl/fi/yln8697jufl7xl8kvybol/Delta-Chamber-1-Versus-2.png?rlkey=n9s1wvzgfe8wybwxfig8jangp&dl=0>
 &dl=0

 

Cheers, Ken
___

I'm here to help you succeed! Feel free to call or email with any questions 
related to EMC or EMI troubleshooting - at no obligation. I'm always happy to 
help!

Kenneth Wyatt
Wyatt Technical Services LLC
8201 Lighthouse Lane Ct 

Windsor, CO 80528

Contact Me!New Books!





  

Web Site | Blog
The EMC Blog (EDN)
Subscribe to Newsletter
Connect with me on LinkedIn  





On Oct 9, 2024, at 1:07 AM, doug emcesd.com <http://emcesd.com/>  
mailto:d...@emcesd.com> > wrote:

 

I agree and was involved with the early development of emission standards with 
with Don Heirman. But still, other areas of engineering are much more 
accurate/have very low uncertainty than EMC.

 

It is sad that most everyone I knew from the early days of EMC are gone now. 
Many of them, Heirman and Ott, for example, were friends. I hope to continue to 
help engineers in the wider field of engineering and physics, including EMC for 
another 25-30 years.

 

By the way, another of my interests is medicine, which I have studied on my own 
for 50 years now and have successfully slowed the aging process and 
successfully treated my spouse’s ovarian cancer (after the surgery to remove 
two very large tumors) without an oncologist. Just another part of science as 
EMC is.

 

Doug Smith

Sent from my iPhone

IPhone: 408-858-4528

Office: 702-570-6108

Email: d...@dsmith.org <mailto:d...@dsmith.org> 

Website: http://dsmith.org <http://dsmith.org/> 


  _  


From: Brent DeWitt mailto:bdew...@ix.netcom.com> >
Sent: Tuesday, October 8, 2024 5:57:46 PM
To: doug emcesd.com <http://emcesd.com/>  mailto:d...@emcesd.com> >; EMC-PSTC@LISTSERV.IEEE.ORG 
<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>  mailto:EMC-PSTC@LISTSERV.IEEE.ORG> >
Subject: Re: [PSES] technical musings 

 

Doug,

Respectfully, I would not agree. I'm not sure what "other areas of engineering" 
yo

Re: [PSES] technical musings

[Jim Bacher, WB8VSU]

Hey Ken and Derek, please consider doing a presentation of your results in 
the EMC and Wireless Track at one of the IEEE PSES Symposiums.



Jim Bacher, WB8VSU
j.bac...@ieee.org or ja.bac...@outlook.com
EMC and Wireless Track Chair for ISPCE AND SPCE

On October 9, 2024 2:43:56 PM Lfresearch 
<00734758d943-dmarc-requ...@listserv.ieee.org> wrote:

Hi Ken,

Nice article. I would love to have seen you add in an OATS to your 
measurements.


What you publish correlates with what we have found on our 10m OATS, 5m 
chamber and 3m compact chamber. Namely that below 100 MHz, 3m test 
distances emissions tend to read high. I hadn’t planned to publish our 
results, but in light of this series of posts, maybe I should.


Take care,

Derek.



On Oct 9, 2024, at 12:40 PM, Ken Wyatt  wrote:

Hi All,

I had a chance to make some comb generator measurements at a lab with two 
10m chambers. I used the AET USDS spherical comb generator designed by Dr. 
Bruce Archambeault (no longer available, unfortunately). There was an age 
difference between the two chambers, with the older ferrite tile lined and 
the newer, ferrite tiles with absorber cones. One of the charts shows the 
difference between 3m and 10m test distance.


Use of comb generator to compare 3m and 10m measurements: 
https://www.edn.com/review-the-aet-usds-spherical-harmonic-comb-generator/


One outcome was the linked article, but what was missing in that was the 
comparison between the two chambers (horizon polarization, only). See 
second link to the table.  In every case, the comb generator was positioned 
on a tripod 1m above the reflecting floor. There was as much as 15 dB 
difference between the two. I’ve not published this last chart, but did 
leave it with the test lab management.


Chamber 1 and 2 comparison: 
https://www.dropbox.com/scl/fi/yln8697jufl7xl8kvybol/Delta-Chamber-1-Versus-2.png?rlkey=n9s1wvzgfe8wybwxfig8jangp&dl=0


Cheers, Ken
___

I'm here to help you succeed! Feel free to call or email with any questions 
related to EMC or EMI troubleshooting - at no obligation. I'm always happy 
to help!


Kenneth Wyatt
Wyatt Technical Services LLC
8201 Lighthouse Lane Ct
Windsor, CO 80528

Contact Me!New Books!



  

Web Site | Blog
The EMC Blog (EDN)
Subscribe to Newsletter
Connect with me on LinkedIn


On Oct 9, 2024, at 1:07 AM, doug emcesd.com  wrote:

I agree and was involved with the early development of emission standards 
with with Don Heirman. But still, other areas of engineering are much more 
accurate/have very low uncertainty than EMC.


It is sad that most everyone I knew from the early days of EMC are gone 
now. Many of them, Heirman and Ott, for example, were friends. I hope to 
continue to help engineers in the wider field of engineering and physics, 
including EMC for another 25-30 years.


By the way, another of my interests is medicine, which I have studied on my 
own for 50 years now and have successfully slowed the aging process and 
successfully treated my spouse’s ovarian cancer (after the surgery to 
remove two very large tumors) without an oncologist. Just another part of 
science as EMC is.


Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.orgFrom: Brent DeWitt 
Sent: Tuesday, October 8, 2024 5:57:46 PM
To: doug emcesd.com ; EMC-PSTC@LISTSERV.IEEE.ORG 


Subject: Re: [PSES] technical musings
Doug,

Respectfully, I would not agree. I'm not sure what "other areas of 
engineering" you're referring to. 🙂


First, if we are discussing commercial emissions standards, they are 
ancient and date back to the days when Apple 2 PCs were interfering with 
"rabbit ear" TV reception (1979) when Part 47 was drafted. The levels were 
largely drawn from the VDE 0871 standard. I doubt anyone with knowledge of 
the methodology has suggested that the overall process is deterministic.


The question of measurement uncertainty was championed by Don Heirman for 
years and continues to be debated.


Regulations and standards have done a very good, if somewhat painful, job 
of quantifying the uncertainty of the measurement process. The most 
competent and well executed test laboratory cannot fully control a 
customer's EUT or even have total control over the configuration. That is 
an advantage for a manufacturer having their own in-house test facility.


All that said, I feel that the "state of EMC testing" has evolved to 
produce very respectable results, given the real world constraints.


Best to all and 73 Jim!

Brent DeWitt, AB1LF
IEEE EMC Society Senior Life Member
Milford, MA



On 10/8/2024 7:07 PM, doug emcesd.com wrote:
Seems like the state of EMC testing is not good compared to other areas of 
engineering!


Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org
From: Jim Bacher, WB8VSU 
Sent: T

Re: [PSES] technical musings

[Lfresearch]

Hi Ken,

Nice article. I would love to have seen you add in an OATS to your measurements.

What you publish correlates with what we have found on our 10m OATS, 5m chamber 
and 3m compact chamber. Namely that below 100 MHz, 3m test distances emissions 
tend to read high. I hadn’t planned to publish our results, but in light of 
this series of posts, maybe I should.

Take care,

Derek.

> On Oct 9, 2024, at 12:40 PM, Ken Wyatt  wrote:
> 
> Hi All,
> 
> I had a chance to make some comb generator measurements at a lab with two 10m 
> chambers. I used the AET USDS spherical comb generator designed by Dr. Bruce 
> Archambeault (no longer available, unfortunately). There was an age 
> difference between the two chambers, with the older ferrite tile lined and 
> the newer, ferrite tiles with absorber cones. One of the charts shows the 
> difference between 3m and 10m test distance.
> 
> Use of comb generator to compare 3m and 10m measurements: 
> https://www.edn.com/review-the-aet-usds-spherical-harmonic-comb-generator/
> 
> One outcome was the linked article, but what was missing in that was the 
> comparison between the two chambers (horizon polarization, only). See second 
> link to the table.  In every case, the comb generator was positioned on a 
> tripod 1m above the reflecting floor. There was as much as 15 dB difference 
> between the two. I’ve not published this last chart, but did leave it with 
> the test lab management.
> 
> Chamber 1 and 2 comparison: 
> https://www.dropbox.com/scl/fi/yln8697jufl7xl8kvybol/Delta-Chamber-1-Versus-2.png?rlkey=n9s1wvzgfe8wybwxfig8jangp&dl=0
> 
> Cheers, Ken
> ___
> 
> I'm here to help you succeed! Feel free to call or email with any questions 
> related to EMC or EMI troubleshooting - at no obligation. I'm always happy to 
> help!
> 
> Kenneth Wyatt
> Wyatt Technical Services LLC
> 8201 Lighthouse Lane Ct
> Windsor, CO 80528
> 
> Contact Me!New Books!
> 
> 
>   
> 
> Web Site | Blog
> The EMC Blog (EDN)
> Subscribe to Newsletter
> Connect with me on LinkedIn 
> 
>> On Oct 9, 2024, at 1:07 AM, doug emcesd.com <http://emcesd.com/> 
>> mailto:d...@emcesd.com>> wrote:
>> 
>> I agree and was involved with the early development of emission standards 
>> with with Don Heirman. But still, other areas of engineering are much more 
>> accurate/have very low uncertainty than EMC.
>> 
>> It is sad that most everyone I knew from the early days of EMC are gone now. 
>> Many of them, Heirman and Ott, for example, were friends. I hope to continue 
>> to help engineers in the wider field of engineering and physics, including 
>> EMC for another 25-30 years.
>> 
>> By the way, another of my interests is medicine, which I have studied on my 
>> own for 50 years now and have successfully slowed the aging process and 
>> successfully treated my spouse’s ovarian cancer (after the surgery to remove 
>> two very large tumors) without an oncologist. Just another part of science 
>> as EMC is.
>> 
>> Doug Smith
>> Sent from my iPhone
>> IPhone: 408-858-4528
>> Office: 702-570-6108
>> Email: d...@dsmith.org <mailto:d...@dsmith.org>
>> Website: http://dsmith.org <http://dsmith.org/>
>> From: Brent DeWitt mailto:bdew...@ix.netcom.com>>
>> Sent: Tuesday, October 8, 2024 5:57:46 PM
>> To: doug emcesd.com <http://emcesd.com/> > <mailto:d...@emcesd.com>>; EMC-PSTC@LISTSERV.IEEE.ORG 
>> <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> > <mailto:EMC-PSTC@LISTSERV.IEEE.ORG>>
>> Subject: Re: [PSES] technical musings
>>  
>> Doug,
>> 
>> Respectfully, I would not agree. I'm not sure what "other areas of 
>> engineering" you're referring to. 🙂
>> 
>> First, if we are discussing commercial emissions standards, they are ancient 
>> and date back to the days when Apple 2 PCs were interfering with "rabbit 
>> ear" TV reception (1979) when Part 47 was drafted. The levels were largely 
>> drawn from the VDE 0871 standard. I doubt anyone with knowledge of the 
>> methodology has suggested that the overall process is deterministic.
>> 
>> The question of measurement uncertainty was championed by Don Heirman for 
>> years and continues to be debated.
>> 
>> Regulations and standards have done a very good, if somewhat painful, job of 
>> quantifying the uncertainty of the measurement process. The most competent 
>> and well executed test laboratory cannot fully control a customer's EUT or 
>> even have total control over the configuration. That is an advantage for a 
>

Re: [PSES] technical musings

[doug emcesd.com]

I agree and was involved with the early development of emission standards with 
with Don Heirman. But still, other areas of engineering are much more 
accurate/have very low uncertainty than EMC.

It is sad that most everyone I knew from the early days of EMC are gone now. 
Many of them, Heirman and Ott, for example, were friends. I hope to continue to 
help engineers in the wider field of engineering and physics, including EMC for 
another 25-30 years.

By the way, another of my interests is medicine, which I have studied on my own 
for 50 years now and have successfully slowed the aging process and 
successfully treated my spouse’s ovarian cancer (after the surgery to remove 
two very large tumors) without an oncologist. Just another part of science as 
EMC is.

Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org

From: Brent DeWitt 
Sent: Tuesday, October 8, 2024 5:57:46 PM
To: doug emcesd.com ; EMC-PSTC@LISTSERV.IEEE.ORG 

Subject: Re: [PSES] technical musings

Doug,

Respectfully, I would not agree. I'm not sure what "other areas of engineering" 
you're referring to. 🙂

First, if we are discussing commercial emissions standards, they are ancient 
and date back to the days when Apple 2 PCs were interfering with "rabbit ear" 
TV reception (1979) when Part 47 was drafted. The levels were largely drawn 
from the VDE 0871 standard. I doubt anyone with knowledge of the methodology 
has suggested that the overall process is deterministic.

The question of measurement uncertainty was championed by Don Heirman for years 
and continues to be debated.

Regulations and standards have done a very good, if somewhat painful, job of 
quantifying the uncertainty of the measurement process. The most competent and 
well executed test laboratory cannot fully control a customer's EUT or even 
have total control over the configuration. That is an advantage for a 
manufacturer having their own in-house test facility.

All that said, I feel that the "state of EMC testing" has evolved to produce 
very respectable results, given the real world constraints.

Best to all and 73 Jim!

Brent DeWitt, AB1LF
IEEE EMC Society Senior Life Member
Milford, MA


On 10/8/2024 7:07 PM, doug emcesd.com wrote:
Seems like the state of EMC testing is not good compared to other areas of 
engineering!

Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org<mailto:d...@dsmith.org>
Website: 
http://dsmith.org<https://urldefense.proofpoint.com/v2/url?u=http-3A__dsmith.org&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=jCRzTaNQorPZq38xZ6lIGQ&m=PO8Xq-rf40J5GT-pnX65HnCPIlbJsadMVgQOBFB_G2_quXYk7CiKX5YgIgmvdwb9&s=kpNzJt0YWej3BUidKRv3bPPdHy9hltqIOUPrcw765Vg&e=>

From: Jim Bacher, WB8VSU <mailto:j.bac...@ieee.org>
Sent: Tuesday, October 8, 2024 8:50:49 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: Re: [PSES] technical musings

Back in the 1980s I had a variation in system measurements between labs. 
Management decided the lab I used wasn't any good. In the process of trying to 
convince management variations were normal, I came to the conclusion that 
measuring systems at different labs would likely have a +5 to -7 dB variations.

None of our test equipment is perfectly flat. No one calibrates every Hz to 
account for those imperfections. The frequency being measured is typically not 
on any of the calibrated frequencies.

For testing a system, equipment and cable variations can impact their emmisions 
significantly. I have seen over 20 dB of variation due to the variations. How 
much effort was made to peak signals?

Then is the test equipment measurement operator an avid Ham DXer (chases weak 
signals to talk to far away stations)? Reason is a Ham will likely do a more 
accurate peaking of rotation and height of the search antennas.

I have had one government lab fail to compensate for a preamp when reporting 
levels and said the product failed. I had the agent pull it back for a few 
days, then take it back and it passed with no changes. So some errors can be to 
using the wrong calibration factors when calculating the levels.


Jim Bacher, WB8VSU
j.bac...@ieee.org<mailto:j.bac...@ieee.org> or 
ja.bac...@outlook.com<mailto:ja.bac...@outlook.com>
JBRC Consulting LLC
Product EMC & Regulatory Consultant
https://www.trc.guru/<https://urldefense.proofpoint.com/v2/url?u=https-3A__trc.guru_&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=c6nhOLO-gj8oBRPLqcRVVpB0b-ty2YpxMuPsVxNFhzVvK9nhFk_fDyBnXHNW3JKZ&s=g1_EVtpoDllNYD7LkeKyb79aTJlbmsmq8mEaNwLSZ4I&e=>
 email:j...@trc.guru<mailto:email:j...@trc.guru>
IEEE Life Senior Member

Re: [PSES] technical musings

[Brent DeWitt]

Doug,

Respectfully, I would not agree. I'm not sure what "other areas of 
engineering" you're referring to. 🙂


First, if we are discussing commercial emissions standards, they are 
ancient and date back to the days when Apple 2 PCs were interfering with 
"rabbit ear" TV reception (1979) when Part 47 was drafted. The levels 
were largely drawn from the VDE 0871 standard. I doubt anyone with 
knowledge of the methodology has suggested that the overall process is 
deterministic.


The question of measurement uncertainty was championed by Don Heirman 
for years and continues to be debated.


Regulations and standards have done a very good, if somewhat painful, 
job of quantifying the uncertainty of the measurement process. The most 
competent and well executed test laboratory cannot fully control a 
customer's EUT or even have total control over the configuration. That 
is an advantage for a manufacturer having their own in-house test facility.


All that said, I feel that the "state of EMC testing" has evolved to 
produce very respectable results, given the real world constraints.


Best to all and 73 Jim!

Brent DeWitt, AB1LF
IEEE EMC Society Senior Life Member
Milford, MA


On 10/8/2024 7:07 PM, doug emcesd.com wrote:
Seems like the state of EMC testing is not good compared to other 
areas of engineering!


Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org

*From:* Jim Bacher, WB8VSU 
*Sent:* Tuesday, October 8, 2024 8:50:49 AM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG 
*Subject:* Re: [PSES] technical musings
Back in the 1980s I had a variation in system measurements between 
labs. Management decided the lab I used wasn't any good. In the 
process of trying to convince management variations were normal, I 
came to the conclusion that measuring systems at different labs would 
likely have a +5 to -7 dB variations.


None of our test equipment is perfectly flat. No one calibrates every 
Hz to account for those imperfections. The frequency being measured is 
typically not on any of the calibrated frequencies.


For testing a system, equipment and cable variations can impact their 
emmisions significantly. I have seen over 20 dB of variation due to 
the variations. How much effort was made to peak signals?


Then is the test equipment measurement operator an avid Ham DXer 
(chases weak signals to talk to far away stations)? Reason is a Ham 
will likely do a more accurate peaking of rotation and height of the 
search antennas.


I have had one government lab fail to compensate for a preamp when 
reporting levels and said the product failed. I had the agent pull it 
back for a few days, then take it back and it passed with no changes. 
So some errors can be to using the wrong calibration factors when 
calculating the levels.



Jim Bacher, WB8VSU
j.bac...@ieee.org or ja.bac...@outlook.com
JBRC Consulting LLC
Product EMC & Regulatory Consultant
https://www.trc.guru/ 
<https://urldefense.proofpoint.com/v2/url?u=https-3A__trc.guru_&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=c6nhOLO-gj8oBRPLqcRVVpB0b-ty2YpxMuPsVxNFhzVvK9nhFk_fDyBnXHNW3JKZ&s=g1_EVtpoDllNYD7LkeKyb79aTJlbmsmq8mEaNwLSZ4I&e=> 
email:j...@trc.guru

IEEE Life Senior Member

On October 8, 2024 11:14:28 AM David Schaefer 
<12867effceb4-dmarc-requ...@listserv.ieee.org> wrote:


Harry Hodes gave a presentation at the C63 meetings last week on 
proficiency testing. He runs the ACIL PT program, and the data he 
shared showed a ton of variance. Many labs were in I think +/-3-4 dB 
range, but there were outliers – the worst cases being one lab 
reading 30-40 dB high, another 30-40 dB low. If I recall correctly 
for one PT program 95 labs participated and around 10 were outside 
the expected tolerance.


Doing a check of the measurement system prior to testing is critical. 
A comb gen scan takes only a few minutes but should catch these 
egregious errors.


David Schaefer

Technical Manager

Element Materials Technology

9349 W Broadway Ave

Brooklyn Park


,


MN


55445


,


United States

O +1 612 638 5136 


ext. 10461

david.schae...@element.com <mailto:david.schae...@element.com>

www.element.com 
<https://urldefense.proofpoint.com/v2/url?u=https-3A__us.content.exclaimer.net_-3Furl-3Dhttps-253A-252F-252Fwww.element.com-252F-26tenantid-3DixvYNdAGEeqbBQANOhMLNA-26templateid-3Daabe0990b90beb1196f5000d3a130b34-26excomponentid-3Dbvr0O264AGzU1lp7QuELkdlEOzfI2OKH9ixGcRY-2DRKU-26excomponenttype-3DLink-26signature-3DcZ5egsqVcuTJwdSIK2EbV6p7Tgro9jT7-5FTkg-2DFb3YiB23cBOgCoUmOEqeUjNn3Wb1utJh-5FtCAps2nMvNa74FEJYf-2DWrOczTU6zFlHw54Kkx7YpXyoM-2DCTV1wYsG6Kp67xdorBRMa5LiebYSyV1KLNeSLvlAMyCdpGXdRt4PdyKih9tRDbM50s0p-5F22b-5Fgp9LG

Re: [PSES] technical musings

[doug emcesd.com]

Seems like the state of EMC testing is not good compared to other areas of 
engineering!

Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org

From: Jim Bacher, WB8VSU 
Sent: Tuesday, October 8, 2024 8:50:49 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG 
Subject: Re: [PSES] technical musings

Back in the 1980s I had a variation in system measurements between labs. 
Management decided the lab I used wasn't any good. In the process of trying to 
convince management variations were normal, I came to the conclusion that 
measuring systems at different labs would likely have a +5 to -7 dB variations.

None of our test equipment is perfectly flat. No one calibrates every Hz to 
account for those imperfections. The frequency being measured is typically not 
on any of the calibrated frequencies.

For testing a system, equipment and cable variations can impact their emmisions 
significantly. I have seen over 20 dB of variation due to the variations. How 
much effort was made to peak signals?

Then is the test equipment measurement operator an avid Ham DXer (chases weak 
signals to talk to far away stations)? Reason is a Ham will likely do a more 
accurate peaking of rotation and height of the search antennas.

I have had one government lab fail to compensate for a preamp when reporting 
levels and said the product failed. I had the agent pull it back for a few 
days, then take it back and it passed with no changes. So some errors can be to 
using the wrong calibration factors when calculating the levels.


Jim Bacher, WB8VSU
j.bac...@ieee.org or ja.bac...@outlook.com
JBRC Consulting LLC
Product EMC & Regulatory Consultant
https://www.trc.guru/<https://urldefense.proofpoint.com/v2/url?u=https-3A__trc.guru_&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=c6nhOLO-gj8oBRPLqcRVVpB0b-ty2YpxMuPsVxNFhzVvK9nhFk_fDyBnXHNW3JKZ&s=g1_EVtpoDllNYD7LkeKyb79aTJlbmsmq8mEaNwLSZ4I&e=>
 email:j...@trc.guru
IEEE Life Senior Member


On October 8, 2024 11:14:28 AM David Schaefer 
<12867effceb4-dmarc-requ...@listserv.ieee.org> wrote:

Harry Hodes gave a presentation at the C63 meetings last week on proficiency 
testing. He runs the ACIL PT program, and the data he shared showed a ton of 
variance. Many labs were in I think +/-3-4 dB range, but there were outliers – 
the worst cases being one lab reading 30-40 dB high, another 30-40 dB low. If I 
recall correctly for one PT program 95 labs participated and around 10 were 
outside the expected tolerance.



Doing a check of the measurement system prior to testing is critical. A comb 
gen scan takes only a few minutes but should catch these egregious errors.







[cid:part22664.1926cd36fa8.2881.5f19857d35c46c9714e7a4cd8a13b995@ieee.org]
David Schaefer
Technical Manager
Element Materials Technology
9349 W Broadway Ave
Brooklyn Park
,
MN
55445
,
United States
O +1 612 638 5136
ext. 10461
david.schae...@element.com<mailto:david.schae...@element.com>
www.element.com<https://urldefense.proofpoint.com/v2/url?u=https-3A__us.content.exclaimer.net_-3Furl-3Dhttps-253A-252F-252Fwww.element.com-252F-26tenantid-3DixvYNdAGEeqbBQANOhMLNA-26templateid-3Daabe0990b90beb1196f5000d3a130b34-26excomponentid-3Dbvr0O264AGzU1lp7QuELkdlEOzfI2OKH9ixGcRY-2DRKU-26excomponenttype-3DLink-26signature-3DcZ5egsqVcuTJwdSIK2EbV6p7Tgro9jT7-5FTkg-2DFb3YiB23cBOgCoUmOEqeUjNn3Wb1utJh-5FtCAps2nMvNa74FEJYf-2DWrOczTU6zFlHw54Kkx7YpXyoM-2DCTV1wYsG6Kp67xdorBRMa5LiebYSyV1KLNeSLvlAMyCdpGXdRt4PdyKih9tRDbM50s0p-5F22b-5Fgp9LGtkISjiEDnV76ZvXKmVbUxVVd0tqHec9MBwk-5FT418oc5ZZWOclsIYRqkwfQqf0Wqj5isA4xlnhmt49FZz-2D5XoxKuiGArsymw-5FY4qtO9TEOwjITToveVj6b1-5FZkHWiMlIWuUr1cjhpNrAxmzAv6LY8g-26v-3D1-26imprintMessageId-3Daf671dc5-2D2f27-2D4e6c-2D8522-2Db4326c125f66&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&r=c9NR2mGfldry-2pM9Bbuww&m=c6nhOLO-gj8oBRPLqcRVVpB0b-ty2YpxMuPsVxNFhzVvK9nhFk_fDyBnXHNW3JKZ&s=xjPbbnT7r9JzjJRQocs1tboth_-n-izdjcIZPOOZ7Vc&e=>
[cid:part22665.1926cd36fa8.2881.5f19857d35c46c9714e7a4cd8a13b995@ieee.org]<https://urldefense.proofpoint.com/v2/url?u=https-3A__us.content.exclaimer.net_-3Furl-3Dhttps-253A-252F-252Ftwitter.com-252FElementTesting-252F-26tenantid-3DixvYNdAGEeqbBQANOhMLNA-26templateid-3Daabe0990b90beb1196f5000d3a130b34-26excomponenttype-3DSocialMediaIcon-26signature-3DACovrZvJeYWsDyyKT0zvYAsZsidrWJylGQABf2bJhKNtCg10KfO2BYNiEUfocR4zw1YzoxFMvQi8ibysZnq3cNZQ2enJrElHRFhuRkcKd45P1AH6s8ee-2D4IsaM0qk-5FDybvwO5i12-2D-5FP-5FXaBFh2-5F9xOmCWZdsBiX-2Dt-5F6d3mt1nvVR8gKtz-2D8s3FLwTT0uFlbk4MqGLEBOJRREfG-5FZRdBPMRb4PKgkhNDQ4QWsEBPZxwChBoMJQyoQTTD6h1cgGbuyr7tQO6Qs9Y36o1lT7tgQY1FpJ7t8IzelvDE7pnzJ7HW6Izwq6FoBil54k2vQh9lhHva6dgfz-5Fzh9TdhlHUeFOw-26v-3D1-26imprintMessageId-3Daf671dc5-2D2f27-2D4e6c-2D8522-2Db4326c125f66&d=DwMFaQ&c=euGZstcaTDllvimEN8b7jXrwqOf-v5A_CdpgnVfiiMM&a

Re: [PSES] technical musings

[Ken Javor]

These days Harry is supporting NASA at the Johnson Space Flight Center. He is 
no longer running a commercial test facility.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: Ralph McDiarmid 
Reply-To: 
Date: Tuesday, October 8, 2024 at 11:06 AM
To: 
Subject: Re: [PSES] technical musings

 

Happy to hear that Harry is still working in the industry.  I met with him many 
times, long ago when he ran Acme Testing in Acme, WA.

 

Ralph

 

From: David Schaefer <12867effceb4-dmarc-requ...@listserv.ieee.org> 
Sent: October 8, 2024 8:14 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] technical musings

 

Harry Hodes gave a presentation at the C63 meetings last week on proficiency 
testing. He runs the ACIL PT program, and the data he shared showed a ton of 
variance. Many labs were in I think +/-3-4 dB range, but there were outliers – 
the worst cases being one lab reading 30-40 dB high, another 30-40 dB low. If I 
recall correctly for one PT program 95 labs participated and around 10 were 
outside the expected tolerance. 

 

Doing a check of the measurement system prior to testing is critical. A comb 
gen scan takes only a few minutes but should catch these egregious errors. 

 

 

 

David Schaefer
Technical Manager
Element Materials Technology
9349 W Broadway Ave
Brooklyn Park
, 
MN
55445
, 
United States
O +1 612 638 5136
ext. 10461
david.schae...@element.com
www.element.com
From: doug emcesd.com  
Sent: Monday, October 7, 2024 6:08 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] technical musings

 

CAUTION:This email originated from outside of Element Materials Technology. DO 
NOT click links or open attachments unless you recognize the sender and know 
the content is safe. Please contact the TOC if you are in any doubt about this 
email.

I have seen differences of 9 dB on the same measurement on an EUT and comb 
generator by different accredited labs!

 

Doug

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
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Re: [PSES] technical musings

[Ken Javor]

I don’t believe human errors such as described by Bacher (not accounting for a 
preamp’s gain) and Gremmen (i.e., the 30 – 40 dB he mentioned) should figure in 
the mix.

 

-- 

 

Ken Javor

Ph: (256) 650-5261

 

 

From: "Jim Bacher, WB8VSU" 
Reply-To: "Jim Bacher, WB8VSU" 
Date: Tuesday, October 8, 2024 at 10:50 AM
To: 
Subject: Re: [PSES] technical musings

 

Back in the 1980s I had a variation in system measurements between labs. 
Management decided the lab I used wasn't any good. In the process of trying to 
convince management variations were normal, I came to the conclusion that 
measuring systems at different labs would likely have a +5 to -7 dB variations. 

 

None of our test equipment is perfectly flat. No one calibrates every Hz to 
account for those imperfections. The frequency being measured is typically not 
on any of the calibrated frequencies. 

 

For testing a system, equipment and cable variations can impact their emmisions 
significantly. I have seen over 20 dB of variation due to the variations. How 
much effort was made to peak signals? 

 

Then is the test equipment measurement operator an avid Ham DXer (chases weak 
signals to talk to far away stations)? Reason is a Ham will likely do a more 
accurate peaking of rotation and height of the search antennas. 

 

I have had one government lab fail to compensate for a preamp when reporting 
levels and said the product failed. I had the agent pull it back for a few 
days, then take it back and it passed with no changes. So some errors can be to 
using the wrong calibration factors when calculating the levels. 

 

 

Jim Bacher, WB8VSU 

j.bac...@ieee.org or ja.bac...@outlook.com

JBRC Consulting LLC 

Product EMC & Regulatory Consultant

https://www.trc.guru/ email:j...@trc.guru

IEEE Life Senior Member

 

On October 8, 2024 11:14:28 AM David Schaefer 
<12867effceb4-dmarc-requ...@listserv.ieee.org> wrote:

Harry Hodes gave a presentation at the C63 meetings last week on proficiency 
testing. He runs the ACIL PT program, and the data he shared showed a ton of 
variance. Many labs were in I think +/-3-4 dB range, but there were outliers – 
the worst cases being one lab reading 30-40 dB high, another 30-40 dB low. If I 
recall correctly for one PT program 95 labs participated and around 10 were 
outside the expected tolerance. 

 

Doing a check of the measurement system prior to testing is critical. A comb 
gen scan takes only a few minutes but should catch these egregious errors. 

 

 

 

David Schaefer
Technical Manager
Element Materials Technology
9349 W Broadway Ave
Brooklyn Park
, 
MN
55445
, 
United States
O +1 612 638 5136
ext. 10461
david.schae...@element.com
www.element.com
From: doug emcesd.com  
Sent: Monday, October 7, 2024 6:08 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] technical musings

 

CAUTION:This email originated from outside of Element Materials Technology. DO 
NOT click links or open attachments unless you recognize the sender and know 
the content is safe. Please contact the TOC if you are in any doubt about this 
email.

I have seen differences of 9 dB on the same measurement on an EUT and comb 
generator by different accredited labs!

 

Doug

This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to 
EMC-PSTC@LISTSERV.IEEE.ORG 

All emc-pstc postings are archived and searchable on the web at: 
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Disclaimer

This email is sent on behalf of Element Materials Technology Group Limited or 
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Element Materials Technology Group Limited is a limited company registered in 
England and Wales with registered number 09915743. Its registered office and 
its principal place of business is at 3rd Floor, Davidson Building, 5 
Southampton Street, London, United Kingdom, WC2E 7HA.

Element cannot accept responsibility for any loss or damage sustained as a 
result of viruses or malware and the recipient must ensure that the email and 
attachments are virus and malware free. Emails and attachments are opened at 
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The information transferred is intended only for the person or entity to which 
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Transmission of this email is not intended to waive confidentiality and/or 
pri

Re: [PSES] technical musings

[Ralph McDiarmid]

Happy to hear that Harry is still working in the industry.  I met with him many 
times, long ago when he ran Acme Testing in Acme, WA.

 

Ralph

 

From: David Schaefer <12867effceb4-dmarc-requ...@listserv.ieee.org> 
Sent: October 8, 2024 8:14 AM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: Re: [PSES] technical musings

 

Harry Hodes gave a presentation at the C63 meetings last week on proficiency 
testing. He runs the ACIL PT program, and the data he shared showed a ton of 
variance. Many labs were in I think +/-3-4 dB range, but there were outliers – 
the worst cases being one lab reading 30-40 dB high, another 30-40 dB low. If I 
recall correctly for one PT program 95 labs participated and around 10 were 
outside the expected tolerance. 

 

Doing a check of the measurement system prior to testing is critical. A comb 
gen scan takes only a few minutes but should catch these egregious errors. 

 

 

 














David Schaefer



Technical Manager




Element Materials Technology



9349 W Broadway Ave




Brooklyn Park


, 



MN


55445


, 


United States






O   +1 612 638 5136


ext. 10461



 <mailto:david.schae...@element.com> david.schae...@element.com



www.element.com















From: doug emcesd.com mailto:d...@emcesd.com> > 
Sent: Monday, October 7, 2024 6:08 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG <mailto:EMC-PSTC@LISTSERV.IEEE.ORG> 
Subject: [PSES] technical musings

 

CAUTION:This email originated from outside of Element Materials Technology. DO 
NOT click links or open attachments unless you recognize the sender and know 
the content is safe. Please contact the TOC if you are in any doubt about this 
email.

I have seen differences of 9 dB on the same measurement on an EUT and comb 
generator by different accredited labs!

 

Doug

  
<https://lh4.googleusercontent.com/_HuR3Ky2TF_XhFHyxnYRmiq7nHQldnMsPNYFaLG6kb5T4y8MeCe-BDC_BscJtSFgszSSjssihHS-pjM3-jwNP8S0CwE-gN8fsRsPkojiAlmpBwb20vIVizS-siCUywW_jqrefbVr>
 

  _  

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Disclaimer

This email is sent on behalf of Element Materials Technology Group Limited or 
the relevant group company with which you are dealing (together, Element). 
Element Materials Technology Group Limited is a limited company registered in 
England and Wales with registered number 09915743. Its registered office and 
its principal place of business is at 3rd Floor, Davidson Building, 5 
Southampton Street, London, United Kingdom, WC2E 7HA.

Element cannot accept responsibility for any loss or damage sustained as a 
result of viruses or malware and the recipient must ensure that the email and 
attachments are virus and malware free. Emails and attachments are opened at 
your own risk.

The information transferred is intended only for the person or entity to which 
it is addressed and may contain confidential and/or privileged material. 
Transmission of this email is not intended to waive confidentiality and/or 
privilege.

The contents of this email are subject to contract and do not contain an offer 
that is capable of acceptance. Unless otherwise agreed in writing with you, the 
Element Standard Terms of Business for the relevant group company apply in 
respect of any services provided to you, including advice given to you by 
email. The Standard Terms of Business are available on request and can be found 
at https://www.element.com/terms/terms-and-conditions

For information about how we process data and monitor communications please see 
our Privacy statement at https://www.element.com/terms/privacy-statement 

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All emc-pst

Re: [PSES] technical musings

[Jim Bacher, WB8VSU]

Back in the 1980s I had a variation in system measurements between labs. 
Management decided the lab I used wasn't any good. In the process of trying 
to convince management variations were normal, I came to the conclusion 
that measuring systems at different labs would likely have a +5 to -7 dB 
variations.


None of our test equipment is perfectly flat. No one calibrates every Hz to 
account for those imperfections. The frequency being measured is typically 
not on any of the calibrated frequencies.


For testing a system, equipment and cable variations can impact their 
emmisions significantly. I have seen over 20 dB of variation due to the 
variations. How much effort was made to peak signals?


Then is the test equipment measurement operator an avid Ham DXer (chases 
weak signals to talk to far away stations)? Reason is a Ham will likely do 
a more accurate peaking of rotation and height of the search antennas.


I have had one government lab fail to compensate for a preamp when 
reporting levels and said the product failed. I had the agent pull it back 
for a few days, then take it back and it passed with no changes. So some 
errors can be to using the wrong calibration factors when calculating the 
levels.



Jim Bacher, WB8VSU
j.bac...@ieee.org or ja.bac...@outlook.com
JBRC Consulting LLC
Product EMC & Regulatory Consultant
https://www.trc.guru/ email:j...@trc.guru
IEEE Life Senior Member
On October 8, 2024 11:14:28 AM David Schaefer 
<12867effceb4-dmarc-requ...@listserv.ieee.org> wrote:
Harry Hodes gave a presentation at the C63 meetings last week on 
proficiency testing. He runs the ACIL PT program, and the data he shared 
showed a ton of variance. Many labs were in I think +/-3-4 dB range, but 
there were outliers – the worst cases being one lab reading 30-40 dB high, 
another 30-40 dB low. If I recall correctly for one PT program 95 labs 
participated and around 10 were outside the expected tolerance.



Doing a check of the measurement system prior to testing is critical. A 
comb gen scan takes only a few minutes but should catch these egregious errors.










David Schaefer








Technical Manager


Element Materials Technology




9349 W Broadway Ave


Brooklyn Park

,

MN



55445

,

United States






O +1 612 638 5136



ext. 10461




david.schae...@element.com


www.element.com




















From: doug emcesd.com 
Sent: Monday, October 7, 2024 6:08 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] technical musings

CAUTION:This email originated from outside of Element Materials Technology. 
DO NOT click links or open attachments unless you recognize the sender and 
know the content is safe. Please contact the TOC if you are in any doubt 
about this email.
I have seen differences of 9 dB on the same measurement on an EUT and comb 
generator by different accredited labs!


Doug


This message is from the IEEE Product Safety Engineering Society emc-pstc 
discussion list. To post a message to the list, send your e-mail to

EMC-PSTC@LISTSERV.IEEE.ORG
All emc-pstc postings are archived and searchable on the web at:
https://www.mail-archive.com/emc-pstc@listserv.ieee.org/

Website: https://ewh.ieee.org/soc/pses/

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Disclaimer

This email is sent on behalf of Element Materials Technology Group Limited 
or the relevant group company with which you are dealing (together,
Element). Element Materials Technology Group Limited is a limited company 
registered in England and Wales with registered number 09915743. Its 
registered office and its principal place of business is at 3rd Floor, 
Davidson Building, 5 Southampton Street, London, United Kingdom, WC2E 7HA.


Element cannot accept responsibility for any loss or damage sustained as a 
result of viruses or malware and the recipient must ensure that the email 
and attachments are virus and malware free. Emails and attachments are 
opened at your own risk.


The information transferred is intended only for the person or entity to 
which it is addressed and may contain confidential and/or privileged 
material. Transmission of this email is not intended to waive 
confidentiality and/or privilege.


The contents of this email are subject to contract and do not contain an 
offer that is capable of acceptance. Unless otherwise agreed in writing 
with you, the Element Standard Terms of Business for the relevant group 
company apply in respect of any services provided to you, including advice 
given to you by email. The Standard Terms of Business are available on 
request and can be fou

Re: [PSES] technical musings

[Gert Gremmen F4LDP]

To the group:
What are your ideas on improving measurement uncertainty:

1. For a defined subject (such as a golden EUT)  in proficiency testing
   (most often a radiating noise source with integral antenna)  Most
   type A errors
2. For a real life EUT (configuration unknown) (additional type B
   uncertainties , see GUM)
3. Is there a justification to use metrological  methods in EMC ? Will
   The current type "simple acceptance" of limit without guard band  be
   sufficient for the wireless future  (see ILAC-G8) with increasing
   need for legal certainty due to exponential increase of use of the
   spectrum ?

Anyone has experiences to share in improving for example radiated site 
attenuation uncertainties (the famous +/- 4 dB), the largest uncertainty 
factor in radiated emissions testing uncertainty calculations by 
frequency range division ?


Any ideas views /objections are welcome to discuss


Gert Gremmen


On 8-10-2024 17:13, David Schaefer wrote:


Harry Hodes gave a presentation at the C63 meetings last week on 
proficiency testing. He runs the ACIL PT program, and the data he 
shared showed a ton of variance. Many labs were in I think +/-3-4 dB 
range, but there were outliers – the worst cases being one lab reading 
30-40 dB high, another 30-40 dB low. If I recall correctly for one PT 
program 95 labs participated and around 10 were outside the expected 
tolerance.


Doing a check of the measurement system prior to testing is critical. 
A comb gen scan takes only a few minutes but should catch these 
egregious errors.


David Schaefer

Technical Manager

Element Materials Technology

9349 W Broadway Ave

Brooklyn Park


,


MN


55445


,


United States

O +1 612 638 5136 


ext. 10461

david.schae...@element.com 

www.element.com 
 



 




 




 

Re: [PSES] technical musings

[David Schaefer]

Harry Hodes gave a presentation at the C63 meetings last week on proficiency 
testing. He runs the ACIL PT program, and the data he shared showed a ton of 
variance. Many labs were in I think +/-3-4 dB range, but there were outliers – 
the worst cases being one lab reading 30-40 dB high, another 30-40 dB low. If I 
recall correctly for one PT program 95 labs participated and around 10 were 
outside the expected tolerance.

Doing a check of the measurement system prior to testing is critical. A comb 
gen scan takes only a few minutes but should catch these egregious errors.



[cid:image404476.jpg@2001647C.0D532BB8]
David Schaefer
Technical Manager
Element Materials Technology
9349 W Broadway Ave
Brooklyn Park
,
MN
55445
,
United States
O +1 612 638 5136
ext. 10461
david.schae...@element.com
www.element.com
[cid:image627505.png@50A3C332.5BAB9734]
[cid:image882535.png@7239732F.B79C8E60]
[cid:image798446.png@DBDB480F.C616CF9B]
[cid:image979275.jpg@2EEB73C0.31EB461E]
From: doug emcesd.com 
Sent: Monday, October 7, 2024 6:08 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] technical musings


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I have seen differences of 9 dB on the same measurement on an EUT and comb 
generator by different accredited labs!

Doug
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Re: [PSES] technical musings

[doug emcesd.com]

That’s what I meant, EMC is very imprecise compared to some other areas of 
engineering.

Because of that I would not hesitate to test at a second lab if I needed a few 
more dB, although that may not help much in Silicon Valley where labs agree 
closely.

Doug Smith
Sent from my iPhone
IPhone: 408-858-4528
Office: 702-570-6108
Email: d...@dsmith.org
Website: http://dsmith.org

From: Brent DeWitt 
Sent: Monday, October 7, 2024 5:49:12 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG 
Subject: Re: [PSES] technical musings

Well said Ralph! On 10/7/2024 8:12 PM, Ralph McDiarmid wrote: “I have seen 
differences of 9 dB on the same measurement on an EUT and comb generator by 
different accredited labs! “ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ 
‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍ ‍
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Well said Ralph!


On 10/7/2024 8:12 PM, Ralph McDiarmid wrote:

“I have seen differences of 9 dB on the same measurement on an EUT and comb 
generator by different accredited labs! “



Doug, I recall this has been the case for decades. There are a lot of variables 
to consider, and some are hard to assign a value.  The equipment has been 
refined somewhat over those same decades, but the physics remains unchanged and 
still produce the same challenges with measurement uncertainty.



It’s only a problem if that uncertainly creates, well… a problem.  Otherwise, 
EMC measurement is an approximate science, all but impossible to model 
accurately, and yet universally accepted as fit for purpose.



Ralph



From: doug emcesd.com <mailto:d...@emcesd.com>
Sent: October 7, 2024 4:08 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG<mailto:EMC-PSTC@LISTSERV.IEEE.ORG>
Subject: [PSES] technical musings



Hi All,



When I was a young engineer at AT&T Bell Labs, about 50 years ago, my designs 
had to have an amplitude tolerance of +/- 1/10th dB to meet requirements (even 
without computer simulation). So when I came across EMC topics later on I was 
initially surprised to see tolerances like +/-2 dB or more. To me this means 
either the engineers do not understand the designs, or (and I think this is the 
case) there are too many uncontrolled variables to allow a narrower tolerance. 
I have seen differences of 9 dB on the same measurement on an EUT and comb 
generator by different accredited labs!



I personally think that Silicon Valley is the best place to do EMC testing 
because there are so many labs, very close to each other, there that they are 
driven to be very close to each other in measurement results (otherwise the 
outliers would go out of business, quickly). Given a choice, I would test in 
Silicon Valley.



On a separate topic, I am 77 years old but have the physical and mental 
capabilities of a 30 year old from my 50 year experiment to slow the aging 
process, which has proven to be a success for me. We often unofficially discus 
this after my seminars are finished for the day. On a recent seminar, the 
attendees kept me over for two hours after the seminar, questioning me and 
taking notes. This is not part of the seminar, but a significant freebie 
available to the attendees.



I run 3,000+ miles per year, even on 120°F days in the Southern Nevada desert. 
Such heat does not even feel stressful to me!  I design my own hydration. I 
designed my own nutrition and supplement plans as well. I never get sick, and 
am immune from sunburn from one of my supplements, astaxanthin. This comes from 
applying science and engineering to my mind and body. I have read many, many 
thousands of pages of medical research in my life and make use of it!



Another topic, my classe

Re: [PSES] technical musings

[Brent DeWitt]

Well said Ralph!


On 10/7/2024 8:12 PM, Ralph McDiarmid wrote:


“I have seen differences of 9 dB on the same measurement on an EUT and 
comb generator by different accredited labs! “


Doug, I recall this has been the case for decades. There are a lot of 
variables to consider, and some are hard to assign a value.  The 
equipment has been refined somewhat over those same decades, but the 
physics remains unchanged and still produce the same challenges with 
measurement uncertainty.


It’s only a problem if that uncertainly creates, well… a problem.  
Otherwise, EMC measurement is an approximate science, all but 
impossible to model accurately, and yet universally accepted as fit 
for purpose.


Ralph

*From:*doug emcesd.com 
*Sent:* October 7, 2024 4:08 PM
*To:* EMC-PSTC@LISTSERV.IEEE.ORG
*Subject:* [PSES] technical musings

Hi All,

When I was a young engineer at AT&T Bell Labs, about 50 years ago, my 
designs had to have an amplitude tolerance of +/- 1/10^th dB to meet 
requirements (even without computer simulation). So when I came across 
EMC topics later on I was initially surprised to see tolerances like 
+/-2 dB or more. To me this means either the engineers do not 
understand the designs, or (and I think this is the case) there are 
too many uncontrolled variables to allow a narrower tolerance. I have 
seen differences of 9 dB on the same measurement on an EUT and comb 
generator by different accredited labs!


I personally think that Silicon Valley is the best place to do EMC 
testing because there are so many labs, very close to each other, 
there that they are driven to be very close to each other in 
measurement results (otherwise the outliers would go out of business, 
quickly). Given a choice, I would test in Silicon Valley.


On a separate topic, I am 77 years old but have the physical and 
mental capabilities of a 30 year old from my 50 year experiment to 
slow the aging process, which has proven to be a success for me. We 
often unofficially discus this after my seminars are finished for the 
day. On a recent seminar, the attendees kept me over for two hours 
after the seminar, questioning me and taking notes. This is not part 
of the seminar, but a significant freebie available to the attendees.


I run 3,000+ miles per year, even on 120°F days in the Southern Nevada 
desert. Such heat does not even feel stressful to me!  I design my own 
hydration. I designed my own nutrition and supplement plans as well. I 
never get sick, and am immune from sunburn from one of my supplements, 
astaxanthin. This comes from applying science and engineering to my 
mind and body. I have read many, many thousands of pages of medical 
research in my life and make use of it!


Another topic, my classes are focused on finding hidden design flaws 
in designs that can cause a manufacturing or field disaster, 
especially flaws that result in a problem once in a week or month of 
significant consequence that cannot be found by normal engineering 
methods. Next one is in a few weeks, mid-October. Contact me if 
interested.


Doug



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---

Re: [PSES] technical musings

[Brent DeWitt]

Your statement: "there are too many uncontrolled variables to allow a 
narrower tolerance." is, in my opinion, exactly the issue.


Accredited labs are required to calculate and express their measurement 
uncertainty. This is generally near plus or minus 4-5 dB. I expect that 
many of the folks on this forum will have noticed that the uncertainty 
with respect to EUT setup is far greater. I was the benefactor of a free 
trip to South Korea, only to find the measurement delta was caused by 
the length of a DC power feed from one site to another.


I had many folks tell me "EMC is Black Magic". It only seems that way 
when we can't wrap our arms around all the variables!


Respectfully,

Brent DeWitt, AB1LF
Milford, MA



On 10/7/2024 7:08 PM, doug emcesd.com wrote:

there are too many uncontrolled variables to allow a narrower tolerance.


-

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Re: [PSES] technical musings

[Ralph McDiarmid]

“I have seen differences of 9 dB on the same measurement on an EUT and comb
generator by different accredited labs! “

 

Doug, I recall this has been the case for decades. There are a lot of
variables to consider, and some are hard to assign a value.  The equipment
has been refined somewhat over those same decades, but the physics remains
unchanged and still produce the same challenges with measurement
uncertainty.

 

It’s only a problem if that uncertainly creates, well… a problem.
Otherwise, EMC measurement is an approximate science, all but impossible to
model accurately, and yet universally accepted as fit for purpose.

 

Ralph

 

From: doug emcesd.com  
Sent: October 7, 2024 4:08 PM
To: EMC-PSTC@LISTSERV.IEEE.ORG
Subject: [PSES] technical musings

 

Hi All,

 

When I was a young engineer at AT&T Bell Labs, about 50 years ago, my
designs had to have an amplitude tolerance of +/- 1/10th dB to meet
requirements (even without computer simulation). So when I came across EMC
topics later on I was initially surprised to see tolerances like +/-2 dB or
more. To me this means either the engineers do not understand the designs,
or (and I think this is the case) there are too many uncontrolled variables
to allow a narrower tolerance. I have seen differences of 9 dB on the same
measurement on an EUT and comb generator by different accredited labs!

 

I personally think that Silicon Valley is the best place to do EMC testing
because there are so many labs, very close to each other, there that they
are driven to be very close to each other in measurement results (otherwise
the outliers would go out of business, quickly). Given a choice, I would
test in Silicon Valley.

 

On a separate topic, I am 77 years old but have the physical and mental
capabilities of a 30 year old from my 50 year experiment to slow the aging
process, which has proven to be a success for me. We often unofficially
discus this after my seminars are finished for the day. On a recent seminar,
the attendees kept me over for two hours after the seminar, questioning me
and taking notes. This is not part of the seminar, but a significant freebie
available to the attendees.

 

I run 3,000+ miles per year, even on 120°F days in the Southern Nevada
desert. Such heat does not even feel stressful to me!  I design my own
hydration. I designed my own nutrition and supplement plans as well. I never
get sick, and am immune from sunburn from one of my supplements,
astaxanthin. This comes from applying science and engineering to my mind and
body. I have read many, many thousands of pages of medical research in my
life and make use of it!

 

Another topic, my classes are focused on finding hidden design flaws in
designs that can cause a manufacturing or field disaster, especially flaws
that result in a problem once in a week or month of significant consequence
that cannot be found by normal engineering methods. Next one is in a few
weeks, mid-October. Contact me if interested.

 

Doug

 
 

  _  

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