>From a previous mail of almost two years ago. :-)
From: Tim Pozar <[EMAIL PROTECTED]>
To: Walter Bruce <[EMAIL PROTECTED]>
Cc: Tom Farrow <[EMAIL PROTECTED]>, [EMAIL PROTECTED], [EMAIL PROTECTED], [EMAIL
PROTECTED]
Subject: Re: [BAWUG] Re: Passive repeater net gain
Message-ID: <[EMAIL PROTECTED]>
References: <[EMAIL PROTECTED]> <[EMAIL PROTECTED]> <[EMAIL PROTECTED]>
In-Reply-To: <[EMAIL PROTECTED]>; from [EMAIL PROTECTED] on Tue, Feb 12, 2002 at
01:23:21PM -0800
Date: Tue Feb 12 14:08:01 2002
X-Original-Date: Tue, 12 Feb 2002 14:07:48 -0800
On Tue, Feb 12, 2002 at 01:23:21PM -0800, Walter Bruce wrote:
> So, why did it work for Cringely?
Hmm... Let's calculate it...
He states in the article that he is using a WAP11 at his house
running at 100mW (too bad as a WAP11 splatters all up and down the
band in this mode and he is likely violating the FCC's spectrum
requirements) into a 21dBi dish. The mountain top is 1.5 miles
away. He is using some sort of yagis on the mountain top. The
second path is 5 miles. He doesn't state the gain of the yagis or
what the antenna is at the ISP. But we can make some assumptions...
Ignoring cable/connector losses at his home he is doing 41dBm EIRP
out of his antenna (20dBm + 21dBi). The free space loss at 1.5
miles is about 108 dB. Lets assume his yagis are 18dBi and there
is no loss on the cable connecting them together. The 5 mile path
will have a free space loss about 118dB and we will assume he has
a 24dBi gain antenna on the roof of the ISP. Lets add this up...
41 dBm EIRP (20dBm + 21dBi) at his house.
- 108 dB Free space loss - first link
+ 18 dBi antenna gain on the mountain.
+ 18 dBi antenna gain on the mountain.
- 118 dB Free space loss - second link.
+ 24 dBi antenna gain at ISP.
=========
- 125 dBm
Most cards will start to work about -90dBm so this is 35dB below
his receiver threshold. Unless my assumptions or interpretation
of his paths are are wrong, it doesn't look like the numbers hold
up his claim.
--
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