Unfortunately, I haven't had the opportunity to tear open a senao card yet - I am considering repeating my tests on the senao because it looks so promising
on paper. Spec sheets don't always tell the whole story. No vendor talks
about the shape of their RF passband, nor which mixing products end up in their IF band. I've yet to see a vendor who honestly pointed out their product's shortcommings in print -
That is not too surprising.
The general results were that transmit power fell within -3 to +1 dB of the product's specifications,
Sure. The FCC can easily measure that.
but on testing the receivers against a known stable source, the cisco hardware showed a +6 to +7 dB better performance
than its "spec" (perhaps this is just manufacturing margin that was being "left on the plate" as it's called) - Most other vendors were quoting specs
from the chipset vendor and not taking into consideration their RF and IF stages, which reduced their (chipset theoretical) performance to -3 to -6 dB
below "spec" (which most customers wouldn't notice in a residential or light
commercial space). Several of these are being copied in china by shops that were making VCR remote controlls the week before. They didn't even match
the 50 ohm impedance of the antenna system. The difference between the "best" and "worst" tolerance from "spec" was > 12 dB - in additon, a few of the cards published a slightly worse "spec" so the absolute difference from absolute best to absolute worst was substantial (at the time, most all were 30mW
xmit cards except the cisco, which was 100mW with introduction of the 350 series. Cisco also improved their receive "spec" by 1 dB.)
Wow! I imagined things might be worse than spec'd but this is really surprising.
I also ran susceptibility tests to intentional interferance (something that isn't in the manufacturer's spec at all) by summing a calibrated signal source with an artificial noise floor that could be raised or lowered programatically.
This is where the chipsets either showed their strength or This test was developed from a site survey that I did for a customer who had a line of site view to over 4000 1W ricocet 2.4 Ghz transmitters. While each one was technically within FCC compliance rules for emission, the
"air" summation of all 4000 created a -85 dBm signal on a spectrum analyzer using a -5 dBi antenna system at 3000 feet MSL - the peak/valley structure showed a clear channelization which we tracked back to ricochet's division of the 2400-2483 Mhz band (they assigned a unique number of channels, which
matched the number of peaks we found within 2400-2483. At high altitudes,
Metricom had single handedly polluted the entire 2.4 Ghz band from edge to edge.
Susceptibility to co-channel interferance was a key factor in picking hardware
to be used in densly populated areas.
That is what I would expect to happen. That is what 802.11 is going to do to the 2.4GHz ISM band too not that Metricom is defunct.
With regards to senao, I have 2-3 of them inside my network talking to existing cisco hardware where they became direct replacements for the previous cisco client card, however on my longest links (over 14 miles LOS)
the cisco was the only product which would register and maintain its link without downtime. Most other manufacturers products placed at both ends couldn't even register, much less pass error free data. I have 2 senao's
that are only 7.x miles from a cisco access point and working fine.
That is promising. I am using them in my APs and I want to optimize receiver performance since most clients have +14dbm to +16dbm transmitters. I have the Senao cards which are +23dbm so I have at least a 6db advantage on that part of the link. I just want to make sure that the receive side is doing its best.
Disclosure - I do not, nor have I ever, worked for an 802.11 card manufacturer.
All of the facts stated are from personal experience and lab tests I have done. I have not thoroughly analyzed any senao product as of this time. I just use them and they work for most applications.
Sounds good to me. This is exactly the kind of information I was looking for. Thank you for sending it.
--
Brian Lloyd 6501 Red Hook Plaza, Suite 201 [EMAIL PROTECTED] St. Thomas, VI 00802 +1.340.998.9447 - voice +1.360.838.9669 - fax GMT-4
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