Re: [Aironet] Compaq Laptop and Speaker noise...

[<lo...@pe...>]

Most likely it is a problem with something in the audio chain; technicaly,
the circuit paths within the laptop should be either balanced (to reject
common mode interference) or shielded (to shunt noise to relative ground). 

What could be happening sound similar to what I experienced with a bad
cable to a set of speakers on my desktop computer @ home (using an ISA
655-900 card). It happened that the shielding for the left channel broke
just enough to allow Rf energy in. As this cable in question was carrying
a very low level signal, it terminated into an amplifier, and the input
impedence was quite high ( >1000 Ohms), so you can imaging how wonderfully
loud the clicks were when I would transfer things @ 344kbit ;)

What I could recomend trying is to move to using a detached antenna; it
may be the shieling is adequte for most incident RF. just the cards
proximity is sooo close. 

One thing I should allso mention is the possibilty that the clicks you're
hearing are coming from poor power regulation, to that devices pcmcia
slot. I've done live recording w/ various computer sound devices before
and at times have been able to hear 'burried in the noise floor' small
clicks and transients from PCI acitivity, IRQ lines firing, and Hard Disk
accuator (head) movements. I know how frustrating it is ;)

If you're not able to detach the antenna, I don't know what else there
would be to do, if you're not interested in maybe having to solder on a
bit of extra capacitance or inductace somewhere near the pcmcia slots.

Hope this helps!

-Tony


On Tue, 5 Dec 2000, Dave Hartzell wrote:

> Maybe this is an already covered topic, but I looked 
> into the archives, and didn't find anything...
> 
> I have a Compaq Presario 1200 Notebook.  I run Linux
> on it with an Aironet PCM 340 card.  I use Linux since
> the Windows 98 driver doesn't work.  It does with 
> Linux!  ;-)
> 
> Anyway, there is an annoying clicking coming from the
> speakers each and every time a packet is RX'd or TX'd
> from the wireless card.  Each packet gets a click, and
> lots of packets produce lots of clicks.  It is very
> annoying and it is quite loud.  
> 
> Is this a problem with the driver, or the sound card?
> I've change IRQs and memory mappings, with no luck.
> 
> Is this a problem with the speaker shielding and the
> wireless?
> 
> Thanks!
> 
> Dave
> 
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