Fluctuating wireless signal from router

My laptop has a built-in wireless adapter (Intel PRO 3945ABG), so no external antenna is
present. There are no nearby networks, at least they are not reported by Network
Stumbler.
Shall I buy a USB dongle ? If so, will I have to disable the wireless card ? Is it
convenient ?
Thanks,

Mike
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<> wrote in message news:...
>
> On 19-Apr-2007, "Mike" <> wrote:
>
>> I am using Network Stumbler to monitor the signal levels of my Netgear router.
>> While it is understandable that the level drops every time I position myself
>> between the
>> router and my laptop ( average signal value is -58dBm, at a distance of approx. 30
>> feet ), I cannot explain why, all conditions being equal, sometimes the level drops
>> down
>> by a good 10 o 15 dBm, with sudden dips and then recovers after 10 seconds or so.
>> Again,
>> the surrounding environment is the same, no microwave ovens kicking in, only a
>> cordless
>> phone which is always on, actually. Looks like the router is misbehaving.
>> Any clues ??
>> Thanks,
>

> You don't say what antenna at the PC end. Often with built in antennas
> the PC case can screen the antenna, which is also being subject
> to nearby networks, even if they are on a different channel.
> If these are strong the compete with the desired signal and affect
> the automatic gain control.
> I've found adding a simple foil reflector to my USB wireless adapter,
> and locating it for maximum pickup, helps to reduce fluctuations
> of level.
> By raising gain in one direction you reduce the level of signals
> from rear and side of the direct path, whilst increasing the
> desired signal. Which is of course the purpose of reflectors.
> As a result there can be an improvement of signal quality,
> and a rise in link rate.
> USB wireless adapters on the end of a lead can be
> positioned for best pickup, and most USB adapter utilities
> show signal strength and quality. Signal quality seems
> the most important measure, and signal quality falls
> with multipath propagation.

Mike