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From: miso on 19 Jan 2007 23:27

bi241(a)scn.org wrote:
> did you install the driver on the CD that comes with the card? the
> updated driver seems not working well with netstumbler
>
> i bought those airlink cards about a year ago and havent done any
> modification. i did pop the USB plastic case open and saw two antennas
> on this card. the external seems to be the TX and the one on PCB i
> think is the RX... it has different antenna configuration than its PCI
> counterpart, but the USB has a different chipset, the rt73 (vs rt61)
> which i suspect having better receive sensitivity
>
> so the perfect mod would be replacing the external antenna with a
> reverse polarity SMA connector and hook it up with
>
> a) yes, a very high gain omni or directional antenna
> b) or an external amp, like the popular and available hawking HSB2
> that can put out 500mW and comes with a 2dBi omni
>
> Frys is having HSB2 on sale for $69.... for antenna, i would look for
> one on eBay or other websites... i just can't stand the ridiculous
> prices that they set on those simple devices at local electronics
> retailers, even at Frys... despite the fact that i dont have enough
> skill and too lazy to build one
>
> i am not sure how this set up would work for MIMO design, as the
> AWLL5025 specification says that it has diversity antenna
> configuration... meaning it assigns TX to one antenna and RX to
> another. This mod would probably improve just the TX side and leave
> the RX side at the mercy of the chipset's RX sensitivity
>
> but the AWLH4030 is a different story. it has one single antenna for
> both TX and RX... so i removed the antenna and hooked it up to a
> hawking HSB1 (yeah i've got the version 1 of the HSB) set the amp to
> 500mW, snapped in a 9dbi omni and ran wildpackets omnipeek. From my 2nd
> floor apartment, i can see a wifi hotspot from a nearby scottish inn,
> which is about 1.5 miles away as the crow flies.... by the way, the
> setup is entirely indoor and done in my desk in the living room, and
> no, there's no clear line-of-sight to any of the networks i was able to
> "see" with this setup
>
> contrary to popular beliefs, and politics, an external wifi amplifiers
> does boost the receiving side of the radio it hooks up to, provided
> that one single antenna is being used..... from my experience, the
> Hawking HSB1 and HSB2 are bi-directional, output 500mW of TX power and
> provide a +12dB RX gain, are relatively inexpensive and work well with
> both OFDM and DSSS in half-duplex mode ...
>
> my next wifi adventure would be buying another HSB, hook them up in
> series, that would theoretically give me a +24dB boost in RX gain while
> maintaining the output TX power within legal limit... i cant wait to
> see how far my hotrod wifi toys can reach...
>
> cheers


<snip>
I am running X64, so I had to get the driver off the net. I haven't
tried the Airlink with netstumber on my notebook (win2kpro).

My understanding of diversity receive is there are multiple receive
antennas and one combination transmit/receive antenna. On my SMC card,
the combination TX/RX port is the one near the LED.

From: bi241 on 20 Jan 2007 00:25
easy mate, interpreting the FCC, the IRS and the US Constitution
shouldn't be that difficult

you see, a standard industrial spectrum analyzer, with proper input
attennuator settings, hooked up directly to the RF transmitter at the
connector will show exactly the TX power of the device. Simple as that!

now, suppose the measure of TX power is at the transmitting antenna,
then of course there's another setup and calculation for the spectrum
analyzer to do just that, but it begs the questions

1) how far away from the transmitter should the spectrum analyzer be
positioned? 0 feet? 1 feet? 3 feet? 10 feet? 10 miles?
2) what is the standard for the field-probing antenna? loop? yagi?
omni? what about its sensitivity?
3) if the probing antenna is to be right at the transmitting antenna,
then what part of the transmitting antenna should it touches? the head?
the tail? the middle? the center? the rim? at what angle?

sounds like the things only a clown would do in a circus, eh?

oh and why not buy at Fry's?..... like, the things you buy from the
store would fry themselves... or what?
just kidding


Jeff Liebermann wrote:
> bi241(a)scn.org hath wroth:
>
> >so the broadcom miniPCI driver says it's got 1300mW... but why 1300mW
> >and not 3100mW? well, i have another theory beside thinking garbage
> >values being returned..
>
> The garbage values theory was what the developers at Wi-Fi Hopper
> responded with when I bug reported the problem. I've seen the same
> bogus power report with other boards and drivers.
>
> >1300mW is about 31dBm!!! and i dont see why wifi cards cannot have
> >exactly that much of TX power. the FCC part 15 states that the limit
> >for 2.4GHz non-channel-hopping radios is 1000mW (or 30dBm) provided it
> >is attached to an antenna of 6dBi gain or less.... and for every 3dBi
> >increase in antenna gain, the TX power has to be reduced by 1dBm.
> >nothing further about the variations of radios+antennas
> >configuration...
>
> I don't want to get into interpreting FCC 15.247. The maximum power
> output is 1 watt. Unfortunatly, they don't say where they measure
> this 1 watt. It could be at the transmitter, or at the antenna. Hard
> to tell. The common interpretation is 1 watt maximum at the antenna
> with a 6dBi omni antenna. If you lower the gain of the antenna, you
> cannot increase the power output to compensate. It would have made
> much more sense for the FCC to specific EIRP (Effective isotropic
> reference radiated power).
>
> >but here comes the creative thinking.. from there, one may deductively
> >conclude that if the radio is permanently attached to a 3dbi antenna or
> >less, then its maximum TX power can be legally increased to 31dBi!!!
>
> No. Or at least no according to several testing labs that submit FCC
> Part 15 type certification reports. Nice try.
>
> Incidentally, if you really want high power in a laptop, see:
> <http://www.ubnt.com/products.php4>
>
> >i suspect that notebooks manufactures been doing this with their OEM
> >wifi cards, especially with those miniPCIs, to keep their customers
> >happy.... of course, those cards are not intended for desktop use,
> >obviously, never to be sold as a part of a "highpower wardriving kit",
> >or to be sold seperately at all, even if they are hard coded to a
> >specific channel within the 2.4GHz spectrum
>
> I like conspiracy theories but not this time. Linux utilities report
> the correct power output from the same cards that Windoze reports
> garbage.
>
> >the wireless networking section at Frys, compared to other sections,
> >has the most returned items from pissed off customer who bought
> >brand-name wifi devices that put out 30mW... lol
>
> That's one reason why I don't buy at Fry's.
>
> --
> Jeff Liebermann jeffl(a)comix.santa-cruz.ca.us
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558

From: Jeff Liebermann on 20 Jan 2007 01:13
bi241(a)scn.org hath wroth:

>easy mate, interpreting the FCC, the IRS and the US Constitution
>shouldn't be that difficult

True. It shouldn't, but it is. I've been dealing with the FCC on and
off since about 1968. These days, rules-n-regs are scribbled by
attorneys, not engineers. I'll spare you my list of horror stories
over the years.

>you see, a standard industrial spectrum analyzer, with proper input
>attennuator settings, hooked up directly to the RF transmitter at the
>connector will show exactly the TX power of the device. Simple as that!

Nope. Quiz time:

You have a spectrum analyzer that shows an 802.11g spread spectrum
signal that is approximately 25Mhz wide. Peak power on the scale is
0dBm to make the calculations easy. The spectrum analyzer IF
bandwidth is 500KHz. What is the "real" power (ignoring duty cycle)?

I'll supply the answer tomorrow. Note that this is not a trick
question and the numbers are quite real.

>now, suppose the measure of TX power is at the transmitting antenna,
>then of course there's another setup and calculation for the spectrum
>analyzer to do just that, but it begs the questions

What question? The FCC is usually very clear where to measure things.
They missed this time. However, I've learned from bitter experience
to NEVER ask the FCC for clarification, because I've always gotten the
answer I least expect, and often with unpredictable side effects.

>1) how far away from the transmitter should the spectrum analyzer be
>positioned? 0 feet? 1 feet? 3 feet? 10 feet? 10 miles?

You're measuring power output, not field strength. If you want to
measure RF field strength, there are some rather simple guidelines
intended to keep your spectrum analyzer out of the near field and only
pickup the far field. The only time the distance needs to be
specified for the test is when measuring incidentally radiation. For
field strength, anything resembling a calibrated antenna will work to
calculate the field strength.

>2) what is the standard for the field-probing antenna? loop? yagi?
>omni? what about its sensitivity?

The type certification, they're rather specific in what may be used.
Go to the FCC ID web pile and pick any likely FCC ID number for a
wireless device. The applicants are required to supply photographs of
their test setup, which includes the test antennas.

>3) if the probing antenna is to be right at the transmitting antenna,

It's not.

>then what part of the transmitting antenna should it touches? the head?
>the tail? the middle? the center? the rim? at what angle?

None. Look at the photos on the FCC ID web pile. They have to be far
enough from the unit under test to not be considered within the near
field.

>sounds like the things only a clown would do in a circus, eh?

Ummm.... I'm one of those clown. Thanks for sharing. Bye.

>oh and why not buy at Fry's?..... like, the things you buy from the
>store would fry themselves... or what?
>just kidding
--
Jeff Liebermann jeffl(a)comix.santa-cruz.ca.us
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
From: dold on 20 Jan 2007 12:24
miso(a)sushi.com wrote:

> Actually, what is returned at Fry's is handy to know. If there are lots
> of returns, try something else. I know those on this usenet group are
> Linksys fans, but most of what is returned to Fry's is Linksys.

I would say that's hard to judge. In the WiFi sections (more than one,
since there are some dedicated sections, including Linksys), there are
many empty shelf spaces, usually for the item you want, plenty of items in
the wrong shelf space, and some opened/returned/markdown units, with
markdowns of 12-15 cents, which fascinates me.

I would guess that they don't give Linksys their own dedicated space unless
they move lots of units, so the number of returns on the shelf would have
to be noted against the number sold.

Wifi is still an emerging market. Many of the units are purchased with
unreasonable hopes, like using Wifi while commuting on Caltrain... okay, so
that works now; or getting free access anywhere, or full coverage in a
home. Those units probably come back, maybe for refund, maybe to exchange
for a different brand.

The motherboard section is full of returns, often with no new units on the
shelf. For stores other than Sunnyvale, I don't know what that means, but
in Sunnyvale, I have overheard engineers selecting motherboards to take
back and test/certify against some product or another, after which it will
be returned to Fry's. But these are the same guys trying to make sure they
get one that is unopened.

> If I think there are going to be problems with something, I always go
> to Fry's because they will take back anything.

The home of the thirty day free trial for almost anything.
I have seen people return stereos with no packaging.

--
---
Clarence A Dold - Hidden Valley Lake, CA, USA GPS: 38.8,-122.5

From: bi241 on 20 Jan 2007 14:37
i played with the linksys WRT54G for a while and somehow got stuck in
DD-WRT concept of diversity antenna. and also i am skeptical about the
MIMO title that the Ralink chipset is advertised, after all, the
AWLL5025 is still within 802.11G specs, while MIMO seems to belong to
draft-N or whatever...

but yeah in true MIMO design, diversity mean multiple RX antennas, (and
mulltiple TX antennas too)
i often see draft-N wireless adpaters with three antennas, just like
the 802.11G AWLH5025 PCI adapter, but i was too lazy to learn about the
antenna configurations. let me give it a try. these are possible
configuration in a three-antenna setup

a) three TX/RX combos
b) one dedicated RX and two TX/RX combos
c) one dedicated TX and two TX/RX combos
d) two dedicated RX and one TX/RX combos
e) two dedicated TX and one TX/RX combos

i am still clueless about how many radios needed for one "draft-N"
adaptor. but i do hope that there's no final N. 802.11 B/G is good
enough for me, and for all, that's all we need for wireless
internet.... as for networking, i'd prefer and recommend the old
fashion way...

anyways, in the case of the AWLL5025 USB, the external antenna must be
the combo TX/RX. Thank you for pointing that out. it makes alot of
sense... and i think i am gonna hack the antenna after this... yes i am
serious!


cheers


miso(a)sushi.com wrote:
>
>
> <snip>
> I am running X64, so I had to get the driver off the net. I haven't
> tried the Airlink with netstumber on my notebook (win2kpro).
>
> My understanding of diversity receive is there are multiple receive
> antennas and one combination transmit/receive antenna. On my SMC card,
> the combination TX/RX port is the one near the LED.

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