connecting to public Access Point

hi All,

our ISP has installed a hotspot with a 7dbi omni antenna. my location is
about 400m LoS away.

Question:
Can i install a yagi antenna (14dbi) and connect to the ISP hotspot, which
is using the omni antenna?

if so, i do have a dlink AP2000+, which i use as wireless client. this
device has a external antenna. do i need a amplifier to connect a external
14 dbi 50watt antenna on this device, or can i just connect an external
antenna?

any help is very appreciated!

THANK YOU!

On Sat, 12 Nov 2005 12:36:41 -1000, "matt" <(E-Mail Removed)> wrote:

>our ISP has installed a hotspot with a 7dbi omni antenna. my location is
>about 400m LoS away.

Any clue what type of hardware he's using and how much coax between
his access point and the 7dBi omni.

>Can i install a yagi antenna (14dbi) and connect to the ISP hotspot, which
>is using the omni antenna?

Probably. I've only done the fade margin calculations about 20 times
in this newsgroup, but once more can't hurt too much. Sigh.

>if so, i do have a dlink AP2000+, which i use as wireless client. this
>device has a external antenna. do i need a amplifier to connect a external
>14 dbi 50watt antenna on this device, or can i just connect an external
>antenna?

50 watt antenna? That's the maximum power handling capeability of the
antenna before it melts.

Ok, let's work the numbers. Due to lack of detail, I'll make some
assumptions. Please juggle the numbers to correspond to your reality.

I'll assume your ISP is using a non-amplified access point located
fairly close to the omni antenna. That would be about +17dBi xmit
power and about 4dB coax and connector loss.

I don't have receive sensitivity numbers for the AP2000+ but do for
the DI-624.
* 54Mbps OFDM, 10% PER, -68dBm
* 48Mbps OFDM, 10% PER, -68dBm
* 36Mbps OFDM, 10% PER, -75dBm
* 24Mbps OFDM, 10% PER, -79dBm
* 18Mbps OFDM, 10% PER, -82dBm
* 12Mbps OFDM, 10% PER, -84dBm
* 11Mbps CCK, 8% PER, -82dBm
* 9Mbps OFDM, 10% PER, -87dBm
* 6Mbps OFDM, 10% PER, -88dBm
* 5.5Mbps CCK, 8% PER, -85dBm
* 2Mbps QPSK, 8% PER, -86dBm
* 1Mbps BPSK, 8% PER, -89dBm
I can't guess at what speed your ISP has his access point set but my
guess is 5.5Mbits/sec 802.11b in order to deal with the largest number
of possible clients without undue hassles. That's a receive
sensitivity of -85dBm.

I'll assume that in order to get Line-o-Sight, you're willing to
install your AP2000+ on the roof near the antenna and power it from
PoE. That means fairly low coax cable and connector losses similar to
those at the WISP end.

Pluging the quesswork into
http://www.terabeam.com/support/calculations/som.php
and starting at the WISP end:
TX power = +15dBm
TX coax loss = 4dB (3ft LMR-240 plus a mess of connectors)
TX ant gain = +7dBi (omni)
Distance = 0.25 miles (400 meters)
RX ant gain = +14dBi
RX coax loss = 4dB (same at other end)
RX sens = -85dBm (at 5.5Mbits/sec)
The resultant fade margin is 20dB which means it will work. Fade
margin is the increase in signal required to communicate above a
reference level at wherever the receiver sensitivity is measured with
a BER (bit error rate) of about 1 part in 10^5. It can also be
translated directly into link reliability.

Reliability Fade Margin
90% 8 dB
99% 18 dB
99.9% 28 dB
99.99% 38 dB
99.999% 48 dB

Note that this assumes no interference, no reflections, clearance in
the Fresnel zone, line of sight, and that everything meets
specifications. Basic conspiracy theory suggests otherwise. I would
be tempted to get just a bit more gain than 14dBi at your end. Pacific
Wireless dish antennas come in 15dBi, 19dBi, and 24dBi with prices
varying from $30 to $70. I suggest one of these to improve the fade
margin, but also to reduce interference pickup from the sides of the
pattern.

Good luck.

--
Jeff Liebermann (E-Mail Removed)
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

"matt" <(E-Mail Removed)> wrote in message
news:dl5qq0$9d9$(E-Mail Removed)...
> hi All,
>
> our ISP has installed a hotspot with a 7dbi omni antenna. my location is
> about 400m LoS away.
>
> Question:
> Can i install a yagi antenna (14dbi) and connect to the ISP hotspot, which
> is using the omni antenna?
>
> if so, i do have a dlink AP2000+, which i use as wireless client. this
> device has a external antenna. do i need a amplifier to connect a external
> 14 dbi 50watt antenna on this device, or can i just connect an external
> antenna?
>
> any help is very appreciated!
>
> THANK YOU!
>
Depending on the ISPs AP's type and configuration, it is most likely that
you will be able to access it with an even lower gain antenna on your
AP2000+. Use of a 14dbi yagi will only give you a better margin to work with
remembering that the higher the gain of the antenna, the more accurate you
need to be in pointing it correctly.

There is no need to add any amplifier at all over that distance considering
that you do have LoS. You may not get the full speed that WiFi often runs
but coming from an ISP, he probably has some sort of connection speed
limiting in place. A good reliable connection at 2Mbs or better should be
readily attainable with the equipment you have.
Peter
>
>
>
>

In article <(E-Mail Removed)>, Jeff Liebermann <(E-Mail Removed)> wrote:
>On Sat, 12 Nov 2005 12:36:41 -1000, "matt" <(E-Mail Removed)> wrote:
>
>>our ISP has installed a hotspot with a 7dbi omni antenna. my location is
>>about 400m LoS away.
>
>Any clue what type of hardware he's using and how much coax between
>his access point and the 7dBi omni.
>
>>Can i install a yagi antenna (14dbi) and connect to the ISP hotspot, which
>>is using the omni antenna?
>
>Probably. I've only done the fade margin calculations about 20 times
>in this newsgroup, but once more can't hurt too much. Sigh.

Ever consider putting this on your website (a directory off the main site)
and just post the link? Save you a lot of typing this way... just a thought
>
>>if so, i do have a dlink AP2000+, which i use as wireless client. this
>>device has a external antenna. do i need a amplifier to connect a external
>>14 dbi 50watt antenna on this device, or can i just connect an external
>>antenna?
>
>50 watt antenna? That's the maximum power handling capeability of the
>antenna before it melts.
>
>Ok, let's work the numbers. Due to lack of detail, I'll make some
>assumptions. Please juggle the numbers to correspond to your reality.
>
>I'll assume your ISP is using a non-amplified access point located
>fairly close to the omni antenna. That would be about +17dBi xmit
>power and about 4dB coax and connector loss.
>
>I don't have receive sensitivity numbers for the AP2000+ but do for
>the DI-624.
> * 54Mbps OFDM, 10% PER, -68dBm
> * 48Mbps OFDM, 10% PER, -68dBm
> * 36Mbps OFDM, 10% PER, -75dBm
> * 24Mbps OFDM, 10% PER, -79dBm
> * 18Mbps OFDM, 10% PER, -82dBm
> * 12Mbps OFDM, 10% PER, -84dBm
> * 11Mbps CCK, 8% PER, -82dBm
> * 9Mbps OFDM, 10% PER, -87dBm
> * 6Mbps OFDM, 10% PER, -88dBm
> * 5.5Mbps CCK, 8% PER, -85dBm
> * 2Mbps QPSK, 8% PER, -86dBm
> * 1Mbps BPSK, 8% PER, -89dBm
>I can't guess at what speed your ISP has his access point set but my
>guess is 5.5Mbits/sec 802.11b in order to deal with the largest number
>of possible clients without undue hassles. That's a receive
>sensitivity of -85dBm.
>
>I'll assume that in order to get Line-o-Sight, you're willing to
>install your AP2000+ on the roof near the antenna and power it from
>PoE. That means fairly low coax cable and connector losses similar to
>those at the WISP end.
>
>Pluging the quesswork into
> http://www.terabeam.com/support/calculations/som.php
>and starting at the WISP end:
> TX power = +15dBm
> TX coax loss = 4dB (3ft LMR-240 plus a mess of connectors)
> TX ant gain = +7dBi (omni)
> Distance = 0.25 miles (400 meters)
> RX ant gain = +14dBi
> RX coax loss = 4dB (same at other end)
> RX sens = -85dBm (at 5.5Mbits/sec)
>The resultant fade margin is 20dB which means it will work. Fade
>margin is the increase in signal required to communicate above a
>reference level at wherever the receiver sensitivity is measured with
>a BER (bit error rate) of about 1 part in 10^5. It can also be
>translated directly into link reliability.
>
> Reliability Fade Margin
> 90% 8 dB
> 99% 18 dB
> 99.9% 28 dB
> 99.99% 38 dB
> 99.999% 48 dB
>
>Note that this assumes no interference, no reflections, clearance in
>the Fresnel zone, line of sight, and that everything meets
>specifications. Basic conspiracy theory suggests otherwise. I would
>be tempted to get just a bit more gain than 14dBi at your end. Pacific
>Wireless dish antennas come in 15dBi, 19dBi, and 24dBi with prices
>varying from $30 to $70. I suggest one of these to improve the fade
>margin, but also to reduce interference pickup from the sides of the
>pattern.
>
>Good luck.
>

fundamentalism, fundamentally wrong.