RE: 2. 4 GHz cordless telephone, question of general interest

[Doug McKean]

22 GHz is the resonant frequency of water folks.  Not 2.45 GHz.
uwave ovens heat by way of dielectric heating.  Oils heat much
faster than water.  That's why your uwave food mfrs load up on
the oils and salts in the food.  Which by the way, hasn't been
looked into as far as a high fat diet contributing to cancer.
Or has it?

Also, the higher above 1GHz you go, the more surface heating of
a human body happens. Not deeper.  Deep tissue heating combined
with surface tissue heating happens below that.  Ionization of
atoms and molecules require much higher freqs which translates
to higher levels of eVs.

Typical eV's that occur during normal chemical reactions with STP
(standard temp and pressure) is about 15 eV.  The photo-electric work
function of say Tungsten = 4.58 eV = 2694 Angstroms = 0.27 cm.
Pretty damn small in my opinion.

And you have to get far above approx 10 mW/cm^2 to really start
being a problem.  1 mW/cm^2 I think is the limit.  I worked the
numbers out with one uwave oven which I thought had exceedingly
high emissions, and it turned out to be pretty benign in terms
of W/cm^2.  More like uW/cm^2.

Higher freqs are required to actually start perturbation at the
atomic level. At the low GHz range, you're only perturbing the
general molcular structure en masse.  You have to go much higher
to start doing the funky thing with an atom.

Trying to consider that *only* uwave ovens are even involved
with the whole cancer thing leaves out many many other factors
to the point of being ignored.

All the above of course, IMHO.

And opinions may vary at any speed.

Regards, Doug McKean


 -Original Message-
 From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf
 Of Ken Javor
 Sent: Friday, April 20, 2001 2:40 PM
 To: emc-p...@ieee.org
 Subject: 2. 4 GHz cordless telephone, question of general interest



 Someone on this forum likely knows the answer to this question...

 I was at Wal-Mart the other day and they had 2.4 GHz cordless phones on
 clearance.  My home cordless phones are 900 MHz.  One is multiple
 channels,
 the other is some kind of spread spectrum.  2.4 GHz is very close to 2450
 MHz, the microwave oven frequency that resonates with H2O
 molecules.  Is 2.4
 GHz close enough to 2450 MHz to cause significantly more heating than 900
 MHz (in the human head adjacent to the head/handset antenna)?  I realize
 this is very low power relative to a cell phone, but I wonder if the issue
 was ever addressed.  Another way of asking this question is, what
 is the Q
 of H20 resonance?  If it is much better than 50, the problem is not
 important.  If it is 50 or less, then 2.4 GHz would transfer more
 energy to
 head tissue than 900 MHz.  One way of measuring this effect would
 be to time
 how long it takes to raise the temperature of a beaker of water a
 set amount
 at 2450 MHz, and then time how long it takes at 2400 MHz...

 But this all must have been done already...

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RE: Job Description

[Doug McKean]

Oh, something like 

This person SHALL 

1. Address any compliance/agency issues during the 
   entire life cycle of a product starting with 
   product development, maintanence of approvals 
   through product release, and finally with product 
   obsolescence. 

2. This will require someone to be proactive in 
   both design and manfacturing phases of a product. 

3. Perform any prelimenary testing where possible. 

4. Manage product compliance testing with the appropriate 
   test labs and agencies. 

5. Maintain all documents of product approval. 

6. Manage sustaining compliance issues during the life 
   cycle of a product after manufacturing release. 

7. Be involved in the ECR/ECO process where changes 
   could compromise agnecy approvals of products. 

8. Will expected to work either independently or 
   within groups. 

9. Must have a working knowledge of the following: 
   the pertinent standards to which the product is 
   being tested,  EMC to include printed circuit 
   board design techniques, safety issues to include 
   any possible liability issues with said product, 
   any possible National Electrical Codes within 
   said country, bills of materials, ECR/ECO processes 
   used by this or any other company with which this 
   companies does OEM arrangements. 

10. BS expected.  
MS preferrred.  
PE desired. (any state license is sufficient but 
 all of them is desired ...) 

11. Multi-lingual in at least 5 languages. 

12. Be able to correct hardware design in a blink. 

13. Have enough brass to call a stop ship at any time. 

13. And then once hired, expect to be generally ignored ... 

14. Must be willing to work lots of overtime without 
being asked. 

15. Pay approx  $35K max ...  

Regards, Doug McKean 


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Re: ESD generators max Contact discharge level

[Douglas C. Smith]

Hi Glyn,

Here is one way to approach 30kV. First, slide out of your car seat, the
Ford Taurus is great for this effect. This puts a charge on your behind.
As you get out of the car (everything is plastic so you remain charged
with respect to the car) your voltage rises because Q=CV. Q stays the
same (charge on your behind) but since C to the car goes down, voltage
goes up. Then you go to close the metal door and a huge spark jumps
between your hand and the door. Usually this results in jumping into the
air muttering a few four letter words sometimes ending in (I am sure
this happens with other cars, I just happen to own Fords, which I like)
F O R D.

I wonder why the car companies don't make seat material out of
anti-static material

BTW, contact discharge has the same risetime at all reasonable voltages,
as opposed to air discharges, but still some equipment will fail at a
low voltage and pass at high voltages. I can imagine a few ways circuits
might do this. The effect is more pronunced with air discharge because
of the risetime dependence on voltage (really arc length and whatever
effects that, including speed of approach).

Doug

Glyn Garside(TUV) wrote:
 
 On the other hand very low voltage (and energy) events, such as jingling
 change have very high di/dt because of the tens of ps risetimes that
 occur at low voltage.
 
 I think this is why, as I recall, some (maybe all?) IEC standards require
 you to test not only to the ESD level indicated, but also the lower levels
 too. For example, if you are required to test at level 4, you are also
 required test at levels 3, 2 and 1.  This is counter-intuitive -- Surely
 the highest voltage is the worst case? -- but apparently grounded in good
 physics, which Doug explains better than I would.
 
 PS: As to testing at higher levels than typical IEC values, I have read
 that the human body can, rarely, gain a charge of up to about 30kV(??), in
 conditions of low RH. Others may have better insight into this. Also, some
 manufacturers may want to build some margin into their test results: if
 five samples pass at 8kV, how sure can you be that the next 995 production
 units would also pass?
 
 PPS: I have a question of my own, drifting off topic slightly: if the
 relative humidity was fairly high when you passed the ESD test, and you
 retest (esp. air discharge?, or indirect discharge?) some months later when
 humidity is lower, could the same EUT now fail? (I think the answer is,
 yes?)
 
 Best Regards, Glyn
 
 Glyn R. Garside   (mailto:ggars...@us.tuv.com)
 Senior Engineer, Industrial Machinery Division
 TUV Rheinland of North America, Inc.  (Chicago Office)
 1945 Techny Rd, Unit 4, NORTHBROOK, IL 60062-5357, USA
 http://www.us.tuv.com
 
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-- 
---
___  _   Doug Smith
 \  / )  P.O. Box 1457
  =  Los Gatos, CA 95031-1457
   _ / \ / \ _   TEL/FAX: 408-356-4186/358-3799
 /  /\  \ ] /  /\  \ Mobile:  408-858-4528
|  q-( )  |  o  |Email:   d...@dsmith.org
 \ _ /]\ _ / Website: http://www.dsmith.org
---

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Re: 2. 4 GHz cordless telephone, question of general interest

[John Cronin]

Two points regarding this question. I understand that 2.4 GHz is not a resonant frequency of the water molecule which resonates at a much higher frequency. 2.4 GHz is just the ISM frequency. 
Also the depth of penetration is only a few cm at 2.4 GHz and issomewhat higher at 900 MHz. 27 MHz diathermy gives a very good depth of penetration and more even heating through human joints.
Regards
John Cronin

From: "Ralph Cameron" 
Reply-To: "Ralph Cameron" 
To: "Ken Javor" , 
Subject: Re: 2. 4 GHz cordless telephone, question of general interest 
Date: Fri, 20 Apr 2001 22:39:29 -0400 
 
 
In terms of heating ( cooking ) 900Mhz is more efficient but its a question 
then of density of tissue , I understand that between 70-90Mhz the human 
body absorbs most energy and that first microwave ovens were designed around 
450Mhz but 2.4 Ghz was an I.S.M. band so permitted limitless power. 
 
The leakage in the average Microwave oven should be so small that you'd 
never hear it on a 2.4Ghz cell phone (i.e. 50Mhz off frequency) 
 
many offie type 2.4Ghz cordless phone use 900mw on the base unit and 200mw 
on the handset. I would suspect the field intensity that close to the head 
could be substantial. 
 
Ralph Cameron 
 
- Original Message - 
From: "Ken Javor" 
To: 
Sent: Friday, April 20, 2001 5:40 PM 
Subject: 2. 4 GHz cordless telephone, question of general interest 
 
 
  
  Someone on this forum likely knows the answer to this question... 
  
  I was at Wal-Mart the other day and they had 2.4 GHz cordless phones on 
  clearance. My home cordless phones are 900 MHz. One is multiple 
channels, 
  the other is some kind of spread spectrum. 2.4 GHz is very close to 2450 
  MHz, the microwave oven frequency that resonates with H2O molecules. Is 
2.4 
  GHz close enough to 2450 MHz to cause significantly more heating than 900 
  MHz (in the human head adjacent to the head/handset antenna)? I realize 
  this is very low power relative to a cell phone, but I wonder if the issue 
  was ever addressed. Another way of asking this question is, what is the 
"Q" 
  of H20 resonance? If it is much better than 50, the problem is not 
  important. If it is 50 or less, then 2.4 GHz would transfer more energy 
to 
  head tissue than 900 MHz. One way of measuring this effect would be to 
time 
  how long it takes to raise the temperature of a beaker of water a set 
amount 
  at 2450 MHz, and then time how long it takes at 2400 MHz... 
  
  But this all must have been done already... 
  
  --- 
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Job Description

[Luiz Claudio]

Dear Colleagues,

I have been asked to write a complete new job description for a Product
Safety / Codes Compliance Engineer. Although being familiar with this
activity (I'm on it for almost 10 years), I would like to avoid describing
my job, since this could lead to some kind of bias.
If any of you has a job description of a product safety engineer who is
responsible for getting compliance certifications of electrical products, I
would be very thankful for receiving it.
In order to avoid overflowing this list with attached files, I'd appreciate
receiving the responses through my personal email address.

Regards,

Luiz



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Re: ESD generators max Contact discharge level

[Glyn Garside(TUV)]

On the other hand very low voltage (and energy) events, such as jingling
change have very high di/dt because of the tens of ps risetimes that
occur at low voltage.

I think this is why, as I recall, some (maybe all?) IEC standards require
you to test not only to the ESD level indicated, but also the lower levels
too. For example, if you are required to test at level 4, you are also
required test at levels 3, 2 and 1.  This is counter-intuitive -- Surely
the highest voltage is the worst case? -- but apparently grounded in good
physics, which Doug explains better than I would.

PS: As to testing at higher levels than typical IEC values, I have read
that the human body can, rarely, gain a charge of up to about 30kV(??), in
conditions of low RH. Others may have better insight into this. Also, some
manufacturers may want to build some margin into their test results: if
five samples pass at 8kV, how sure can you be that the next 995 production
units would also pass?

PPS: I have a question of my own, drifting off topic slightly: if the
relative humidity was fairly high when you passed the ESD test, and you
retest (esp. air discharge?, or indirect discharge?) some months later when
humidity is lower, could the same EUT now fail? (I think the answer is,
yes?)

Best Regards, Glyn


Glyn R. Garside   (mailto:ggars...@us.tuv.com)
Senior Engineer, Industrial Machinery Division
TUV Rheinland of North America, Inc.  (Chicago Office)
1945 Techny Rd, Unit 4, NORTHBROOK, IL 60062-5357, USA
http://www.us.tuv.com


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Re: 2. 4 GHz cordless telephone, question of general interest

[Ralph Cameron]

In terms of heating ( cooking ) 900Mhz is more efficient but its a question
then of density of tissue , I understand that between 70-90Mhz the human
body absorbs most energy and that first microwave ovens were designed around
450Mhz  but 2.4 Ghz was an I.S.M. band so permitted limitless power.

The leakage in the average Microwave oven should be so small that you'd
never hear it on a 2.4Ghz cell phone (i.e. 50Mhz off frequency)

many offie type 2.4Ghz cordless phone use 900mw on the base unit and 200mw
on the handset. I would suspect the field intensity that close to the head
could be substantial.

Ralph Cameron

- Original Message -
From: Ken Javor ken.ja...@emccompliance.com
To: emc-p...@ieee.org
Sent: Friday, April 20, 2001 5:40 PM
Subject: 2. 4 GHz cordless telephone, question of general interest



 Someone on this forum likely knows the answer to this question...

 I was at Wal-Mart the other day and they had 2.4 GHz cordless phones on
 clearance.  My home cordless phones are 900 MHz.  One is multiple
channels,
 the other is some kind of spread spectrum.  2.4 GHz is very close to 2450
 MHz, the microwave oven frequency that resonates with H2O molecules.  Is
2.4
 GHz close enough to 2450 MHz to cause significantly more heating than 900
 MHz (in the human head adjacent to the head/handset antenna)?  I realize
 this is very low power relative to a cell phone, but I wonder if the issue
 was ever addressed.  Another way of asking this question is, what is the
Q
 of H20 resonance?  If it is much better than 50, the problem is not
 important.  If it is 50 or less, then 2.4 GHz would transfer more energy
to
 head tissue than 900 MHz.  One way of measuring this effect would be to
time
 how long it takes to raise the temperature of a beaker of water a set
amount
 at 2450 MHz, and then time how long it takes at 2400 MHz...

 But this all must have been done already...

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Re: ESD generators max Contact discharge level

[Douglas C. Smith]

Hi Dan,

Contact discharge is meant to be applied to conductive surfaces. If a
product has a plastic case, breakdown voltage (through seams and holes)
is the important parameter. This is best done with air discharge, the
object of which is not to have one.

Doug

Dan Kinney (A) wrote:
 
 While we're on the topic, I have a question (actually a couple) regarding
 air discharge.  Since contact discharge is the preferred method, as stated
 in an earlier message and in EN61000-4-2, Paragraph 5, why would one perform
 the Air Discharge method?  The same paragraph states Air discharges shall
 be used where contact discharge cannot be applied.  What conditions would
 make it such that contact discharge could not be applied?
 
 Thanks in advance.
 Dan Kinney
 Horner APG
 
  -Original Message-
  From: Douglas C. Smith [SMTP:d...@emcesd.com]
  Sent: Friday, April 20, 2001 2:54 PM
  To:   Terry Meck
  Cc:   emc-p...@ieee.org
  Subject:  Re: ESD generators max Contact discharge level
 
 
  Hi Terry and the group,
 
  Besides the question of finding a generator that can reach the level you
  mention, I am not aware of any natural ESD event that approaches the
  interference potential of even an 8 kV contact discharge. The problem
  comes in that high voltage air discharges have relatively slow
  risetimes, for 16 kV on the order of tens of ns, whereas contact
  discharges maintain a better than 1 ns risetime at all voltages. This
  makes for a much smaller dt to go along with the greater di to make a
  di/dt that is much higher, more than an order of magnitude, than you
  will see for these voltages in nature.
 
  Maybe if you were making atom bomb trigger mechanisms there would be a
  justification for this kind of testing, but not for real equipment.
 
  On the other hand very low voltage (and energy) events, such as jinjling
  change have very high di/dt because of the tens of ps risetimes that
  occur at low voltage. The combination of high voltage (and energy) with
  fast risetimes is too severe and meeting such a test is a waste of money
  for most equipment.
 
  Doug
 
  Terry Meck wrote:
  
   Hello again:
  
   Does anyone recall if there were any standard called for or ESD
  generator that simulated as the case may be =  +-10 kV CONTACT discharge.
  
   We have a customer that is specifying passing +-16 kV ESD without
  referring to AIR or Contact discharge.  I am inclined to ask what they
  have in mind since I have not seen any generators that go that high in the
  Contact mode.
   I suspect the writer of the SOW knows nothing and the engineering group
  only thinks Air Discharge.
  
   What do you all think?
  
   Terry J. Meck
   Accu-Sort Systems Inc.
  
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  --
  ---
  ___  _   Doug Smith
   \  / )  P.O. Box 1457
=  Los Gatos, CA 95031-1457
 _ / \ / \ _   TEL/FAX: 408-356-4186/358-3799
   /  /\  \ ] /  /\  \ Mobile:  408-858-4528
  |  q-( )  |  o  |Email:   d...@dsmith.org
   \ _ /]\ _ / Website: http://www.dsmith.org
  ---
 
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Re: 2. 4 GHz cordless telephone, question of general interest

[Ken Javor]

Just goes to show you can find anything on the net.  I have measured leakage
from microwave ovens and every one was at 2450 MHz.  And that IS a resonant
frequency for water and water alone.  That's why you can put waterless items
in and they won't heat up, and also why you should never run a microwave
oven without a water load: with no load you get high vswr and the magnetron
can be damaged by reflected energy.

--
From: Rich Nute ri...@sdd.hp.com
To: ken.ja...@emccompliance.com
Cc: emc-p...@ieee.org
Subject: Re: 2. 4 GHz cordless telephone, question of general interest
Date: Fri, Apr 20, 2001, 5:27 PM





 Hi Ken:


 Here are some quotes:

 http://www.eskimo.com/~billb/weird/microexp.html#demo:

 Q:  Aren't these ovens tuned to a special frequency so they only heat
 water?

 A:  No.  The usual operating frequency of a microwave oven is nowhere
 near the resonant frequency of water, and the RF energy will heat
 other substances.  For example, drops of grease on a plastic
 microwave dish can be heated far hotter than 100C, and this causes
 the mysterious scarring which frequently occurs on plastic utensils.
 Any molecule which is polar and has positive and negative ends
 will be rotated to align with the electric field of the radio waves
 in the oven.  The vibrating electric field rotates (vibrates) the
 water molecules (and any other polar molecules) within the food.

 Microwave ovens have difficulty melting ice, presumably because the
 water molecules are bound together and cannot be easily rotated by
 the e-fields.  If the oven was tuned to the water resonance
 frequency, then the water would become far more opaque to the wave
 energy.  The water in the food's thin surface would absorb all the
 energy, and only the outside surface of foods would be heated.  The
 thin outer surface of meat would become a blast of steam, and the
 inside would remain ice cold.  But because water does not resonate
 with the microwave frequency, the waves can travel an inch or so
 into the meat before being absorbed.

 See also:

 http://hypertextbook.com/facts/HowardCheung.shtml

 Here's another quote:

 http://rabi.phys.virginia.edu/HTW//microwave_ovens.html

 My science book said that a microwave oven uses a laser resonating
 at the natural frequency of water.  Does such a laser exist or was
 that a major typo?

 It's a common misconception that the microwaves in a microwave oven
 excite a natural resonance in water.  The frequency of a microwave
 oven is well below any natural resonance in an isolated water
 molecule, and in liquid water those resonances are so smeared out
 that they're barely noticeable anyway.  It's kind of like playing a
 violin under water--the strings won't emit well-defined tones in
 water because the water impedes their vibrations.  Similarly, water
 molecules don't emit (or absorb) well-defined tones in liquid water
 because their clinging neighbors impede their vibrations.

 Instead of trying to interact through a natural resonance in water,
 a microwave oven just exposes the water molecules to the intense
 electromagnetic fields in strong, non-resonant microwaves.  The
 frequency used in microwave ovens (2,450,000,000 cycles per second
 or 2.45 GHz) is a sensible but not unique choice.  Waves of that
 frequency penetrate well into foods of reasonable size so that the
 heating is relatively uniform throughout the foods.  Since leakage
 from these ovens makes the radio spectrum near 2.45 GHz unusable for
 communications, the frequency was chosen in part because it would
 not interfere with existing communication systems.

 As for there being a laser in a microwave oven, there isn't.  Lasers
 are not the answer to all problems and so the source for microwaves
 in a microwave oven is a magnetron.  This high-powered vacuum tube
 emits a beam of coherent microwaves while a laser emits a beam of
 coherent light waves.  While microwaves and light waves are both
 electromagnetic waves, they have quite different frequencies.  A
 laser produces much higher frequency waves than the magnetron.  And
 the techniques these devices use to create their electromagnetic
 waves are entirely different.  Both are wonderful inventions, but
 they work in very different ways.

 The fact that this misleading information appears in a science book,
 presumably used in schools, is a bit discouraging.  It just goes to
 show you that you shouldn't believe everything read in books or on
 the web (even this web site, because I make mistakes, too).

 On the other hand:

 http://www.sciencenet.org.uk/database/Physics/EMandLight/p00571b.html

 How does a microwave oven work?

 Everything has what is called a natural frequency.  When you hold a
 ruler over the edge of a table 

Transformer Question

[Matsuda, Ken]

Group,

I was wondering if you could help me with this one?  Currently, I have a
switching power supply, using custom transformers. Now I am looking at
submitting this product to a agency...

 Many transformer manufacturers claim they build to UL ...standards,
obviously, this is not considered approved, but are there

transformer houses that can manufacture transformers that are considered
recognized components under a program similar to a sign shop program, where
customers can request custom wound transformers that are covered under the
UL recognition ?


Thanks for any input,


Ken

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