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max safe power for WRT54GS and exposure time

 
 
jamessmalljr@gmail.com
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      04-03-2006, 11:46 PM
I have two WRT54GS talking though a 800-900 foot distance through
trees. There's no other way. I have a 15 db Yagi on one end, and
will be purchasing something similar for the second end. Right now,
I'm seeing -91 (+-1 or 2 points) signal rhough the DD-WRT wireless
status, This is with the transmit power turned up from 28 mw to 200 mw
(yes two hundred).


Has anyone else had the power turned up this high? If so, how long can
I expect these boxes to last?

Can anyone recomend a nice flat 15-ish db antenna I can mount on the
second box. I'd prefer flat, as a yagi would be an eye sore.



----

ON a side note, what would be the minimum safe distance/time exposure
for 200 mw with a 15 db yagi on 2.4 ghz?


---
http://marriage.jamessmall.com

 
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Jeff Liebermann
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      04-04-2006, 01:34 AM
(E-Mail Removed) hath wroth:

>Has anyone else had the power turned up this high? If so, how long can
>I expect these boxes to last?


Yep. Two of my friends locally. Lasted about 2 weeks and blew. I
have one of these V4 routers but haven't had time (or inspiration) to
do an autopsy.

>Can anyone recomend a nice flat 15-ish db antenna I can mount on the
>second box. I'd prefer flat, as a yagi would be an eye sore.


Oh, any one of these will work:
http://www.fab-corp.com/home.php?cat=255

>ON a side note, what would be the minimum safe distance/time exposure
>for 200 mw with a 15 db yagi on 2.4 ghz?


http://n5xu.ae.utexas.edu/rfsafety/
At 1ft away from the antenna, the RF exposure is 0.5 mw/cm^2.
The maximum permissible exposure for an uncontrolled environment is
1.0 mw/cm^2. You're safe to about 0.8ft away from the antenna.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
 
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jamessmalljr@gmail.com
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      04-04-2006, 11:44 PM
So if I move from the standard antenna to a 14 db flat panel on the
remaining 'stock' linksys, will that give me more than a 10db
improvement? What's the rating of the stock antenna?

If so, then will I get equivallently the same 'reception/transmission'
quality if I reduce the transmission power from 200 mw on both ends to
just 20 (rather, 28 mw, the stock).

--Now, I'm still getting fade during the day. How high can I put the
transmitters for general use? 40 mw? 48 mw? 50 mw?



---
http://marriage.jamessmall.com

 
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John Navas
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      04-05-2006, 12:12 AM
[POSTED TO alt.internet.wireless - REPLY ON USENET PLEASE]

In <(E-Mail Removed) .com> on 4 Apr 2006
16:44:35 -0700, (E-Mail Removed) wrote:

>So if I move from the standard antenna to a 14 db flat panel on the
>remaining 'stock' linksys, will that give me more than a 10db
>improvement? What's the rating of the stock antenna?


It should -- the gain of a stock "rubber ducky" antenna is about 2 dBi.

As an alternative, see
<http://www.radiolabs.com/products/antennas/2.4gig/backfire.php>

--
Best regards, SEE THE FAQ FOR ALT.INTERNET.WIRELESS AT
John Navas <http://en.wikibooks.org/wiki/FAQ_for_alt.internet.wireless>
 
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Jeff Liebermann
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      04-05-2006, 02:51 AM
On 4 Apr 2006 16:44:35 -0700, (E-Mail Removed) wrote:

>So if I move from the standard antenna to a 14 db flat panel on the
>remaining 'stock' linksys, will that give me more than a 10db
>improvement? What's the rating of the stock antenna?


The stock antenna is essentially a coaxial vertical dipole antenna.
Gain is about 2dBi. A 14dBi flat panel will give a maximum of 12dB
gain over the stock antenna. However, don't forget to subtract coax
cable and connector losses from the 12dB.

>If so, then will I get equivallently the same 'reception/transmission'
>quality


Most non-reflector antennas have the same gain in transmit and
receive. 14dBi gain in transmit and receive. However, if you use a
dish, the gain is somewhat different betweeen transmit and receive
depending on how well the feed illuminates the dish surface. In
general, the transmit gain of a dish is slightly less than the receive
gain because the feed's tendency to "overspray" the dish.

>if I reduce the transmission power from 200 mw on both ends to
>just 20 (rather, 28 mw, the stock).


Going from 200mw to 20mw is a factor of 10. In dB, that's a change
of:
dB = 10 * log(10) = 10dB

>Now, I'm still getting fade during the day.


Are you sure it's fade and not inteference from other networks that
only operate during the day?

>How high can I put the
>transmitters for general use? 40 mw? 48 mw? 50 mw?


I really don't know. My guess is 50-100mw max. I know that 250mw
will eventually blow up the transmitter, but I don't know exactly what
power is safe. There's also the not so minor issue of FCC type
certification. I'll pass. Anyway, going from 35mw to 100mw is
wasted. It's only
dB = 10 * log (100/35) = 4.6dB
I suggest you work on the antenna part of the puzzle and leave the
power alone.


--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558 (E-Mail Removed)
# http://802.11junk.com (E-Mail Removed)
# http://www.LearnByDestroying.com AE6KS
 
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