Re: Emulating a wireless access point

From: David Ford (david@eRiskSecurity.com)
Date: 08/16/01


Message-ID: <3B7AF5F1.2060207@eRiskSecurity.com>
Date: Wed, 15 Aug 2001 18:21:37 -0400
From: David Ford <david@eRiskSecurity.com>
To: pen-test@securityfocus.com
Subject: Re: Emulating a wireless access point

This is perfectly true with the caveat that for every harmonic that you
step away from the prime, the power of the transmission drops
proportionately. This is all considering there is no harmonic
filtering, also known as a bandpass filter.

Here is where you truely get what you pay for. Inexpensive equipment
tends to skim on features such as noise suppression and filtering. Such
manufacturers don't care very much if they are splattering noise across
the spectrum.

David

bparis@sorrentolactalis.com wrote:

> You are correct Meredith.
>
> I live near a cell tower (100m away) and can clearly hear cell
>conversations on my scanner at the 1st lower harmonic, app 450-460Mhz.
>
> Getting back the the original question, cordless 2.4Ghz phones are
>notorious for creating interference with other devices using the same freq
>band. I recommend not operating 2.4Ghz phones in a wireless environment.
>
>William S. Paris
>Telecommunication/Network Analyst
>Sorrento Lactalis Inc.
>bparis@sorrentolactalis.com
>
>
> Actually, it probably has to do w/ the frequency / harmonic
>resonance of
>the phone interfearing w/the AP ... not the proximity. Even if the phone
>operates on a different frequency, it can interfere w/ the AP via harmonic
>resonance.
> Harmonic Resonance occurs when one of the frequencies is a multiple
>of the
>other. Say your AP operates at 2 hz ( for simplicity sake) and your phone
>operates at 4 hz, then every other cycle of the phones frequency will be in
>phase w/ the access points.
>
>ASCII Diagra:
>| x -- sine peak As you can see, the sine
>waves are prefectly
>| | | | | Phone in-phase at 2 and 4 w/
>respect to the phone.
>| | | | | | | | |
>| | | | |
>|_________________________________ T = 1 sec
>|
>| x -- sine peak
>| | |
>| ....| |.....| |. Access Point
>| | |
>| |
>__________________________________ T = 1 sec
>
> Are there any Ham operators out there that can confirm or deny this?
>
> -- Meredith Shaebanyan
>
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