On Aug 4, 2004, at 5:38 AM, Haudy Kazemi wrote:
There are also 300 mW (24.8 dBm) prism 2.5 cards from Demarctech. I
haven't tried them but the specs are here:
http://www.demarctech.com/products/reliawave-rwz/reliawave-rwz-300mw- prism2
-5-pcmcia-card.html
http://www.demarctech.com/techsupport/rw-wireless-cards-support/100mw- rx-te
st.htm
Their 100mw and 200mw models sensitivity was found to be, and the 300mw card is probably about the same: -91dBm 11mbps FER<8% -93dBm 5.5mbps FER<8% -95dBm 2mbps FER<8% -96dBm 1mbps FER<8%
Theoretical receive sensitivity can be calculated as:
Receive sensitivity = Nt + Ns + SNRmin
where Nt is the thermal noise floor, Ns is the system noise figure, and SNRmin is the minimum SNR required for a given bit-error rate.
802.11b's CCK requires a SNR of about 10dB to decode frames with a FER of 0.08. (We'll leave SIR and/or SINR out of the discussion unless someone insists.) We'll call this SNRmin.
All matter at temperatures above absolute zero (0K, about -460F) radiates electromagnetic energy. The amount of energy is related to temperature -- the hotter the matter, the more energy is radiated. This energy is described by Boltzmann's Constant, 'k' (k = -198.6dBm/degreesK-Hz). This constant, multiplied by the temperature of the matter a receiver views and the system bandwidth, yields an irreducible background noise against which a desired signal must compete. This is thermal noise.
For the purpose of this exercise, lets use 80F, or about 300K (T=300K). RF engineers typically use this number as a rule of thumb, and its roughly the year-round temp here in Hawaii. :-)
802.11b uses a channel 22Mhz wide.
Tn(dBm) = -198.6 + 10 * log10(300) + 10 * log10(22,000,000) = -100.4dBm.
Receive sensitivity = Nt + Ns + 10log(BW) + SNRmin
-91dBm = -100.4dBm + Ns + 10dBYou can see we're in-trouble already. (Or my math is out to lunch, and someone will correct me.)
The thermal noise floor is at -100.4dBm, we require 10dBm of SNR, and someone has promised us -91dBm rx sensitivity. Even with a noise-free (perfect) LNA and receiver chain, we're slightly short.
I'll leave it as an exercise to the reader to fill in the noise figure for the LNA and Prism-II receiver on the Zcom designs. They'll be listed on the datasheet(s) for the part(s).
That said, the extra power may or may not make a difference in your ability
to talk to an access point, depending on the AP's own sensitivity. (If you
have a powerful but insensitive AP, this card may help.)
Note: there was a way to overdrive the 200mw Senao cards to 249mw using one
of the linux drivers.
Its a huge mistake to do this, and not just for the obvious legal reason.
Maybe the 300mw cards can go even higher...or maybe
like when overclocking cpus, the higher spec chips are simply the higher
grade cut of the chip production line.
This is what Tony would like you to believe, but its not true.
3054 is 21dBm in 11b modes. (+/- 2dBm)
Aries info links:
review: http://ben.pfountz.com/~bpfountz/3054CB.html
http://www.netgate.com/3054CBARIES.html
http://www.netgate.com/New/NL_3054%20CB%20Aries.pdf
http://www.hautespot.net/products/datasheets/nl-3054%20cb%20plus- spec.pdf
Atheros AR5212 baseband, AR2112 radio
Typical TX Output power upto 21dBm / 126mW
On 4 Aug 2004, crispin wrote:greatThe Senao cards are some of the best, check out netgate.com for descriptions. They are available with or w/o buit-in antennas. Until recently they were among the highest powered "B" cards w/200mw of power(compared to an Orinoco or mant other at about 32mw), they havesensitivity as well. They also use a standard Prism chipset so they play"G"
well w/other gear. You should be able to pick one up for around $70(just
saw that they're on sale @ netgate for $65). That site also has a goodcard based upon the Atheros chipset, the Aries, which is 100mw(high for a
"G" card"). They also have the same cards available in a mini pci form,
enjoy. crispin
On 8/3/04 2:59 PM, "Philip J Robar" <[EMAIL PROTECTED]> wrote:
On Aug 3, 2004, at 1:36 PM, Randy S wrote:
I'm looking for an 802.1b, g is optional, ext. antenna jack is optional, pc card that has great reception with just the built in antenna.
Can anyone recommend a good card or a good site with some tests and reviews of hardware? I'd like to upgrade from my current Netgear MA401.
http://www.practicallynetworked.com
Phil
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