Orinoco gold PC card power unit

NetFox · 06-28-2004

I used two Orinoco gold 802.11b cards (one transmits, one receives) to meassure the received power strength at a fixed distance, i.e, 2.5m. The indicated power strengh and noise at 2.5 m are 106 and 55. What are the units of these two values?

Thorn · 06-28-2004

dBm, just like is says on the RSSI graph. By the way, those two numbers are reversed or you got them out of the text listing. dB values are usually negative numbers.

If you looked at the text output, then subtract 149. in which case the Signal would be -43dBm and the Noise would be -94dBm.

"dBm" stands for "deciBels microvolts". For more information on dB and how to understand them, look at the Antenna FAQ.

NetFox · 06-28-2004

Thanks, Thorn.

I have another question. From the data I got at distances from 2.5m to 50m, the average received data match the the log-distance path loss model perfectly with a path loss exponent of 1.44. However, the data was meassured outdoor, so I guess this path loss exponent might be too small.

Is it possible that the indications given by the card are just signal amplitude but power? So when calculating the power, I need to square the amplitude, in this way, the path loss exponent will become 2.88, which might make more sense.

Thorn · 06-28-2004

Quote:

Originally Posted by NetFox

Thanks, Thorn.

I have another question. From the data I got at distances from 2.5m to 50m, the average received data match the the log-distance path loss model perfectly with a path loss exponent of 1.44. However, the data was meassured outdoor, so I guess this path loss exponent might be too small.

Is it possible that the indications given by the card are just signal strengh but power? So when calculating the power, I need to square the strength, in this way, the path loss exponent will become 2.88, which might make more sense.

I'm not exactly clear on what you are asking. The signal strength is the received power.

Many a newbe has been annoyed here by me because I've asked them if they've done the math/ It gives you a good idea if something is possible or not. (You can't argue with physics.) However, don't get so hung up on the math that you miss the point of whether something will work or not.

One thing to keep in mind about the log-distance path loss model (or any math model with radios) is that the model is usually derived from ideal lab conditions using tuned test gear to remove all possible variables. The exact power level is known. The exact receive sensitivity is known. The exact loss of the cable and connectors are all known. No interfering RF sources are nearby. Etc, etc.

Out in the real world we have to deal with some (a lot of) unknowns. The antennae aren't perfect. The transmit level may be off slightly, as may the RX sensitivity. The lobes of the antennea on these cards have funny shapes. All of these things mean that doing the math just puts you in a ballpark and is probably never going to work out exactly the same as on paper.

That's why we have fudge factors of 10dBm on signal paths rather than 1 or 2dBm.

NetFox · 06-28-2004

Sorry, when i said strength, i meant amplitude.

Thorn · 06-28-2004

I don't believe the amplitude would have any effect, at least nothing to do with the RSSI.

NetFox · 07-01-2004

What is the RSSI range and how to convert it to dBm or mW?

Thanks!

Thorn · 07-01-2004

Threads merged

It is in dBm; as stated in my first reply.

NetFox · 07-02-2004

Is received signal level the same thing as received signal strength? If not, what is the difference. Thanks.

The Others · 07-02-2004

Quote:

Originally Posted by NetFox

Is received signal level the same thing as received signal strength? If not, what is the difference. Thanks.

This type of thing seems to be occupying your mind a lot lately. Maybe a helpful book is in order?

Thorn · 07-02-2004

Quote:

Originally Posted by NetFox

Is received signal level the same thing as received signal strength? If not, what is the difference. Thanks.

Yes.

Please stick with one thread for the same issues.

NetFox · 07-02-2004

appreciate !!!

06-28-2004	#1 (permalink)
NetFox Registered Member Join Date: Jun 2004 Posts: 6	Orinoco gold PC card power unit I used two Orinoco gold 802.11b cards (one transmits, one receives) to meassure the received power strength at a fixed distance, i.e, 2.5m. The indicated power strengh and noise at 2.5 m are 106 and 55. What are the units of these two values?

06-28-2004	#3 (permalink)
NetFox Registered Member Join Date: Jun 2004 Posts: 6	Thanks, Thorn. I have another question. From the data I got at distances from 2.5m to 50m, the average received data match the the log-distance path loss model perfectly with a path loss exponent of 1.44. However, the data was meassured outdoor, so I guess this path loss exponent might be too small. Is it possible that the indications given by the card are just signal amplitude but power? So when calculating the power, I need to square the amplitude, in this way, the path loss exponent will become 2.88, which might make more sense. Last edited by NetFox : 06-28-2004 at 07:12 PM.

06-28-2004	#6 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,039	I don't believe the amplitude would have any effect, at least nothing to do with the RSSI. __________________ Thorn "Lawyers should never marry lawyers. This is called inbreeding. It produces idiot children and more lawyers."

07-01-2004	#7 (permalink)
NetFox Registered Member Join Date: Jun 2004 Posts: 6	One problem about Orinoco classical gold What is the RSSI range and how to convert it to dBm or mW? Thanks!

07-01-2004	#8 (permalink)
Thorn Did you do the math? Join Date: Apr 2002 Location: Villa Straylight Posts: 10,039	Threads merged It is in dBm; as stated in my first reply. __________________ Thorn "Lawyers should never marry lawyers. This is called inbreeding. It produces idiot children and more lawyers."

06-28-2004	#5 (permalink)
NetFox Registered Member Join Date: Jun 2004 Posts: 6	Sorry, when i said strength, i meant amplitude.

07-02-2004	#9 (permalink)
NetFox Registered Member Join Date: Jun 2004 Posts: 6	strength vs. level Is received signal level the same thing as received signal strength? If not, what is the difference. Thanks.

07-02-2004	#12 (permalink)
NetFox Registered Member Join Date: Jun 2004 Posts: 6	appreciate !!!

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