Low signal quality

Archived from groups: alt.internet.wireless (More info?)

On Thu, 07 Oct 2004 04:05:40 -0500, Tomas Pedersen <tp@yahoo.com>
wrote:

>On occasions I terminate end user DSL with WLAN bundling. The clients
>usually get's the cheapest wireless devices they can find and around these
>parts that is Topcom. I'm experiening that the signal strenght is extremely
>low in scenarios where the AP is only a few meters away from
>the client NIC. This is somethimes occuring on Dlink equipment aswell. All
>the while I have excellent signal strengt from the same location with
>my Linksys PCMCIA NIC.
>
>Does anyone have an idea why this is occuring? Is there some hardware I can
>use to test wireless connections?

Which Topcom product(s)? Are both the wireless router and client
radios made by Topcom?

http://www.topcom.net/products/ind [...] 20PRODUCTS
Which DLink equipment? Wireless router or client radio?

Topcom does NOT show up on the FCC ID search page. I'm trying to
determine who made the products, what chipset is used, and at what
power level they qualified for type certification. If you have the
FCC ID number from the serial number tag, it would be a big help.

I don't have an instant answer to why a particular brand has signal
strength problems. However, I've seen a wide variety of designed in
ways to screw up signal strength. Grossly inefficient antennas, long
lossy circuit board traces, poor quality circuit boards, dirty boards,
high VSWR board to antenna interfaces, variations on voltage
regulators, and defective firmware settings.

There are some Xmit signal strength testers available. Note that
measureing the TX signal strength is only half the equation. You also
need to measure the receive sensitivity, which is also capable of
limiting the range. Without a big budget pile of test equipment, this
is a non-trivial test. I'll limit my suggestions to TX power. I
assume that you want something other than an RSSI indication from a
"known good" wireless card.

1. Dedicated 802.11 tester $1500:
http://www.bvsystems.com/Products/ [...] hopper.htm

2. Cheapo WLAN tester made from a Symbol FHSS DPA. $150. I just
ordered one. (I couldn't resist)
http://cgi.ebay.com/ws/eBayISAPI.d [...] 5724414084

3. Spectrum analyzer test card. I can't find it, but it uses a
Proxim RangeLAN2 7400 series FHSS card. $25-30.

http://www.e3.com.au/modules.php?o [...] cle&sid=22

4. Digital microwave oven leakage detector. $35.
http://www.comforthouse.com/comfort/micleakdetwi.html
I butchered one by replacing the detector diode and adding an external
dipole antenna to the detector:

http://www.LearnByDestroying.com/p [...] index.html
Oops. I don't have the butchered version posted. Anyway, I can
measure 2.4GHz field stength about 3 meters away.

5. Real spectrum analyzer. Avcom is about as cheap as it gets:
http://www.avcomofva.com
There's no upper limit on what you can spend on a spectrum analyzer.

Customers ringing....gone.

--
Jeff Liebermann jeffl@comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 AE6KS 831-336-2558