Measurement

This may be outdated. Someone help me understand the zeros

What a joke, .0005 by a tower. I drove by 1 at  850.

http://www.who.int/peh-emf/meetings/base_stations_june05/en/index.html



Microwave oven RF leakage 5 mW/cm 2


2Ghz cell phone public guideline 1


850 Mhz public guideline 
½ or .005 mW/cm 2


Typical RF at bottom of base station  tower .0005

Kathy





[Non-text portions of this message have been removed]

Hi Kathy,

> This may be outdated. Someone help me understand the zeros
>  
Not outdated, and I'll try.


> What a joke, .0005 by a tower. I drove by 1 at  850.
>  
Which unit of measure?

I see 850 uW/m2 in town all the time, and higher even closer to urban
towers.
The other possibile units that fit your sentence would be mV/m.
850 mV/m = 0.85 V/m = 1.92 mW/m2 = 1916 uW/m2 = 0.00019 mW/cm2

Those 5 units are:
milli Volts per meter, Volts per meter, milli Watts per square meter,
micro watts per sq. meter, and milli watts per sq. centimeter.

To understand the zeros:
1000 micro = 1 milli, and 1000 milli = 1 unit. It is the way the metric
system works, to keep the number of zeros down to a readable level. But
without the units the message gets lost.
This is also why I prefer to only work in a logrythmic unit of measure,
like V/m or dBm (decibal milli-watts) , so that the range from minimum
to maximum is reduced to only a few digits.

I can't stress enough the need to include the units of measure. This is
the same reason NASA lost a probe that went to Mars, because they used
Miles and Kilometers in the same trajectory program, but did not convert
to a common unit of measure.


For the 0.0005
Assuming this is in milli-Watts per cm2 I would agree, it is normal to
only measure
0.0005 mW/cm2 = 5 mW/m2 = 1.37 V/m
at the base of a tower. Very normal and correct.

Still in the red zone for biological effects.
http://seahorseCorral.org/images/meter/power-density-chart.png


> Microwave oven RF leakage 5 mW/cm 2
>  
Yes, that is off the top of my chart, and is equivilant to 50 W/m2 or
137. V/m

With numbers, and power density that high, you can see why food cooks.


> 850 Mhz public guideline
> ½ or .005 mW/cm 2
>
>  
Those 2 numbers are different by a factor of 100. Will have to pick one.
0.5 > 0.005


> Typical RF at bottom of base station  tower .0005
>  
must be milli-watts per sq. centimeter to be typical, as discussed above.

I hope I explained that well?
Stewart

Stweartt,

I am trying to understand, with so many conversions.

I assume my meter was giving 850 mW/m 2  I have to read your website to help.

Kathy

<[hidden email] wrote:
Subject: Re: [eSens] Measurement
















 



 


   
     
     
      Hi Kathy,



> This may be outdated. Someone help me understand the zeros

>  

Not outdated, and I'll try.



> What a joke, .0005 by a tower. I drove by 1 at  850.

>  

Which unit of measure?



I see 850 uW/m2 in town all the time, and higher even closer to urban

towers.

The other possibile units that fit your sentence would be mV/m.

850 mV/m = 0.85 V/m = 1.92 mW/m2 = 1916 uW/m2 = 0.00019 mW/cm2



Those 5 units are:

milli Volts per meter, Volts per meter, milli Watts per square meter,

micro watts per sq. meter, and milli watts per sq. centimeter.



To understand the zeros:

1000 micro = 1 milli, and 1000 milli = 1 unit. It is the way the metric

system works, to keep the number of zeros down to a readable level. But

without the units the message gets lost.

This is also why I prefer to only work in a logrythmic unit of measure,

like V/m or dBm (decibal milli-watts) , so that the range from minimum

to maximum is reduced to only a few digits.



I can't stress enough the need to include the units of measure. This is

the same reason NASA lost a probe that went to Mars, because they used

Miles and Kilometers in the same trajectory program, but did not convert

to a common unit of measure.



For the 0.0005

Assuming this is in milli-Watts per cm2 I would agree, it is normal to

only measure

0.0005 mW/cm2 = 5 mW/m2 = 1.37 V/m

at the base of a tower. Very normal and correct.



Still in the red zone for biological effects.

http://seahorseCorral.org/images/meter/power-density-chart.png



> Microwave oven RF leakage 5 mW/cm 2

>  

Yes, that is off the top of my chart, and is equivilant to 50 W/m2 or

137. V/m



With numbers, and power density that high, you can see why food cooks.



> 850 Mhz public guideline

> ½ or .005 mW/cm 2

>

>  

Those 2 numbers are different by a factor of 100. Will have to pick one.

0.5 > 0.005



> Typical RF at bottom of base station  tower .0005

>  

must be milli-watts per sq. centimeter to be typical, as discussed above.



I hope I explained that well?

Stewart





   
     

   
   






 










[Non-text portions of this message have been removed]

Hi Kathy,

> I am trying to understand, with so many conversions.
>  
I agree too many units.
I have made a conversion table in javascript, and added it to my page.
Now you can convert any unit to the others quickly using actual formulas
instead of a lookup table.

http://seahorseCorral.org/ehs1.html#conv


> I assume my meter was giving 850 mW/m 2  I have to read your website to help.
>  
I actually doubt you measured that high in that unit, That is why I
listed the other units combinations for that value of 850 that are
within my experience as normal.

If it WAS that high, then you were awfully close to the transmitter antenna.

Stewart

Where did you get the dBm values from?
I thought dBm refered to dB relative to 1 mW at the receiver.
Therefore it would depend on the antenna in use.

Bill

On Fri, Nov 4, 2011 at 3:53 PM, S Andreason <[hidden email]> wrote:


[Non-text portions of this message have been removed]



------------------------------------

Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/eSens/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/eSens/join
    (Yahoo! ID required)

<*> To change settings via email:
    [hidden email]
    [hidden email]

<*> To unsubscribe from this group, send an email to:
    [hidden email]

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/

Bill Bruno wrote:
> Where did you get the dBm values from?
>  
The calculation spreadsheet I have built up was originally made to
measure the Cornet results, and grew from that. And for some strange
reason it is similar to how the Spectran v4 shows dBm

Also there is a conversion chart and formula list at
www.*geopathfinder*.com
that seems to have an offset of 40dB. I ignored that column, and thought
it interesting their formula page didn't even try to convert to dBm or
dBW. The spectran manual does show it right.


> I thought dBm refered to dB relative to 1 mW at the receiver.
>  
It does. ... DOH

Good catch Bill ! thank you...


> Therefore it would depend on the antenna in use.
>  
Yes, that is why I find dBm a frustrating unit, that can not be compared
between different meters.
Fortunately few meters have it as the primary readout.
I have been avoiding it whenever possible, probably due to this exact
problem.

So the antenna factor for the Cornet is -27.55 dB.
That is less believable than the +2.45 I had been using.

I'll have to look into this more.

Stewart

Hi Bill and Charles and others technical enough about antennas,

I improved my "calculator" on my page, so that now I can enter readings
on one meter,
like -39.7 dBm
then uncheck the antenna factor anchor,
enter 61 in the uW/m2 field, and find out the antenna factor.
-27.55 dB
What does that say about the meter or the antenna?
Yes, this is the Cornet.

At least my frustration with dBm measurements on the Spectran over the
last few years has finally been shown a new light.

Stewart

Bill Bruno wrote:
> Where did you get the dBm values from?
> I thought dBm refered to dB relative to 1 mW at the receiver.
> Therefore it would depend on the antenna in use.
>  

Aaronia has an Excel formula.
In it you must give;
Measured value in dBm
Antenefactor in dBi
Cablefactor in dB
and the exact measured frequency.

Then all values come popping out.

If you use the latest LCS or better MCS software, all values come popping out, without you calculating anything.
uW/m2 or V/m or whatever.

Greetings,
Charles Claessens
member Verband Baubiologie
www.milieuziektes.nl
www.milieuziektes.be
www.hetbitje.nl
checked by Norton



  ----- Original Message -----
  From: S Andreason
  To: [hidden email]
  Sent: Monday, November 07, 2011 7:29 PM
  Subject: Antenna factors calculating dB Was: Re: [eSens] Measurement


  Hi Bill and Charles and others technical enough about antennas,

  I improved my "calculator" on my page, so that now I can enter readings
  on one meter,
  like -39.7 dBm
  then uncheck the antenna factor anchor,
  enter 61 in the uW/m2 field, and find out the antenna factor.
  -27.55 dB
  What does that say about the meter or the antenna?
  Yes, this is the Cornet.

  At least my frustration with dBm measurements on the Spectran over the
  last few years has finally been shown a new light.

  Stewart

  Bill Bruno wrote:
  > Where did you get the dBm values from?
  > I thought dBm refered to dB relative to 1 mW at the receiver.
  > Therefore it would depend on the antenna in use.
  >  





  ------------------------------------

  Yahoo! Groups Links





[Non-text portions of this message have been removed]

That tower sits next to an elementary school!

I was driving by maybe 20-40 ft away.

Kathy

<[hidden email] wrote:
Re: [eSens] Measurement

















 



 


   
     
     
      Hi Kathy,



> I am trying to understand, with so many conversions.

>  

I agree too many units.

I have made a conversion table in javascript, and added it to my page.

Now you can convert any unit to the others quickly using actual formulas

instead of a lookup table.



http://seahorseCorral.org/ehs1.html#conv



> I assume my meter was giving 850 mW/m 2  I have to read your website to help.

>  

I actually doubt you measured that high in that unit, That is why I

listed the other units combinations for that value of 850 that are

within my experience as normal.



If it WAS that high, then you were awfully close to the transmitter antenna.



Stewart





   
     

   
   






 










[Non-text portions of this message have been removed]

I think the reason they offer dBm is in case you connect a cable to
something like a signal generator and just want to know the voltage.
Or if you're using an antenna and don't know it's gain you can figure it
out later.

On Mon, Nov 7, 2011 at 11:29 AM, S Andreason <[hidden email]> wrote:


[Non-text portions of this message have been removed]



------------------------------------

Yahoo! Groups Links

<*> To visit your group on the web, go to:
    http://groups.yahoo.com/group/eSens/

<*> Your email settings:
    Individual Email | Traditional

<*> To change settings online go to:
    http://groups.yahoo.com/group/eSens/join
    (Yahoo! ID required)

<*> To change settings via email:
    [hidden email]
    [hidden email]

<*> To unsubscribe from this group, send an email to:
    [hidden email]

<*> Your use of Yahoo! Groups is subject to:
    http://docs.yahoo.com/info/terms/