On Tue, Dec 7, 2010 at 2:47 AM, Blaise Gassend <bla...@willowgarage.com> wrote: >> Which chipset are you using? On which cards? With the AR9280/AR9220, >> I see the output power is pretty close to what is being set through iw >> (measured with a spectrum analyzer). I've been selecting output >> levels between 5 and 17dBm. > > I agree that with my adapter 2, things behave well from 5 to 17dBm. > (Adapter 1 works well from 3 to 20, but with worse calibration.) > However, there the fact that it goes to a high power level from 0 to 5 > dBm is disturbing to me. At best it is very misleading, and at worst > it could cause regulatory violations. > > Adapter 1 is a PCI-E adapter from Sparklan > http://sparklan.com/product.php?func=view&prod_id=157 > http://sparklan.com/product.php?func=view&prod_id=63 > (I have one of each, and they behave identically.) > 03:00.0 Network controller: Atheros Communications Inc. AR928X > Wireless Network Adapter (PCI-Express) (rev 01) > Subsystem: Lite-On Communications Inc Device 6512 > Flags: bus master, fast devsel, latency 0, IRQ 16 > Memory at fbaf0000 (64-bit, non-prefetchable) [size=64K] > Capabilities: <access denied> > Kernel driver in use: ath9k > Kernel modules: ath9k > > Adapter 2 is an Ubiquiti SR71-A (http://ubnt.com/sr71a) > 02:02.0 Network controller: Atheros Communications Inc. AR9160 > 802.11abgn Wireless PCI Adapter (rev 01) > Subsystem: Device 0777:4082 > Flags: bus master, 66MHz, medium devsel, latency 168, IRQ 16 > Memory at fb9e0000 (32-bit, non-prefetchable) [size=64K] > Capabilities: <access denied> > Kernel driver in use: ath9k > Kernel modules: ath9k >
Ah, ok. I have noticed going all the way back to madwifi and AR500x-series chips that 0 is an especially low power setting. Not quite off, but often well below 0dBm. Anything positive tends to be within a couple dB of what is desired, until you get close to the max output of the card. Usually they don't really let you exceed what the card was designed for, so there's often a wide range near the top of what you may be dialing in that is all the same output power. The card's EEPROM specifies the maxes here, for each bitrate. Are you forcing a bitrate when you're trying to take measurements? Going from BPSK to 64-QAM, the output power can easily drop by 6dB. If I get time this week, I can plot the actual output power with R52n and R52Hn cards, across desired power settings of 0-25dBm. I have a WPEA-111N, but hooking it up to the spectrum analyzer is a bit too troublesome. _______________________________________________ ath9k-devel mailing list ath9k-devel@lists.ath9k.org https://lists.ath9k.org/mailman/listinfo/ath9k-devel
