How to calculate increase of home wireless router range?

Can you help me roughly CALCULATE how to increase the range of my home
Internet wireless WiFi setup to a shed 300 feet away from my house?

Presently, I can walk about half the way through the wooded area to the
shed with my laptop in hand before I lose the connection to the PCMCIA
802.11b,g Linksys card. Basically I need to gain 150 feet in "range".

But how?

At the store, I immediately become confused as I try to compare $30 USD
omnidirectional antennas (D-Link ANT24-070) that boost "power" by a claimed
7 db; $50 USD directional corner antennas (Hawking HAI15SC) that claim 15
dbi (whatever a dBi is); and $150 USD 802.11N routers that claim to boost
omnidirectional "range" by 4x (Linksys WRT300N).

How does an omnidirectional 7 db or directional 15 dBi boost in "power"
equate to range?

Approximately how many decibels of (omnidirectional or directional) power
do I really need to boost my WiFi range from about 150 feet to the 300 feet
I need?

Looking up what a decibel is
(http://en.wikipedia.org/wiki/Decibel#Definition), I
calculate the D-Link ANT24-070 omnidirectional antenna gives me about 5
times the power (assuming 7 db = 10^7/10 ~= 5); but does this get me the
additional 150 feet of range to my shed?

Spending almost twice as much money on the Hawking HAI15SC directional
antenna gets me roughly 30 times the power (assuming 15 db = 10^15/10 ~=
32); but is that enough power to get me the range to my shed?

Indeed, is there some way to add a Hawking 15db antenna on the receiving
end to get 1,000 times the power (15 db + 15 db = 30 db = 10^30/10 ~=
1,000); but what would I hook the wire output from this receiving antenna
to in the shed (I can't hook it to the pcmcia card, can I)?

Given those db calculations, how do I compare the antenna options with
replacing my home 802.11b,g router with the 4X range $150 USD Linksys
802.11n WRT300N router and the required $120 USD Linksys WPC300N PCMCIA
card (assuming 6 db = 10^6/10)?Will this three-antenna 802.11n router be
forced to drop down to 1X speeds because inside my house my kid's laptops
will all be using 802.11b or 802.11g? Or can the router work on both
802.11g to one computer and on 802.11n to the other computer at the same
time?

I'm so confused!

All I want is to make a well-informed buying decision to increase my WiFi
range reliably to 300 feet to a known point.

Can you help me sort out all these very confusing variable (to me anyway)?
I have no training in electrical engineering; but I can google.

Thank you,
Beverly

In article <2hqacpnj1nwj$.1683sqqzgbbo2$.(E-Mail Removed)>,
Beverly Erlebacher <(E-Mail Removed)> wrote:

>Can you help me roughly CALCULATE how to increase the range of my home
>Internet wireless WiFi setup to a shed 300 feet away from my house?
>
>Presently, I can walk about half the way through the wooded area to the
>shed with my laptop in hand before I lose the connection to the PCMCIA
>802.11b,g Linksys card. Basically I need to gain 150 feet in "range".

Doubling the range requires 6 dB of additional gain from the antennas
at one end or the other. You'd probably want more additional gain
than that, so that your connection is solid and reliable rather than
hanging right on the edge of failure.

>But how?
>
>At the store, I immediately become confused as I try to compare $30 USD
>omnidirectional antennas (D-Link ANT24-070) that boost "power" by a claimed
>7 db; $50 USD directional corner antennas (Hawking HAI15SC) that claim 15
>dbi (whatever a dBi is);

dB numbers are a ratio. When you see a figure given in dB, you have
to ask "dB relative to *what*, precisely?".

There are two common standards in use. dBi refers to gain relative to
an "isotropic" antenna - an imaginary antenna which radiates power
equally in all directions. dBd refers to gain relative to a half-wave
dipole - a common and well-studied type of antenna.

dBi numbers are approximately 2 dB higher than dBd numbers, for the
same actual amount of gain.

> and $150 USD 802.11N routers that claim to boost
>omnidirectional "range" by 4x (Linksys WRT300N).
>
>How does an omnidirectional 7 db or directional 15 dBi boost in "power"
>equate to range?

3 dB of additional gain equates to twice the delivered power at a
specific range. Because power falls off in proportion to the square
of the distance, twice the power yields sqrt(2) or about 1.4 times the
range, all else being equal (which it often isn't).

6 dB of additional gain is four times the delivered power at a given
distance, or twice the range for the same amount of power.

>Approximately how many decibels of (omnidirectional or directional) power
>do I really need to boost my WiFi range from about 150 feet to the 300 feet
>I need?

The _minimum_ you appear to need is 6 dB of additional gain. I'd
recommend trying for 10 dB or more in order to ensure a reliable
connection.

>Looking up what a decibel is
>(http://en.wikipedia.org/wiki/Decibel#Definition), I
>calculate the D-Link ANT24-070 omnidirectional antenna gives me about 5
>times the power (assuming 7 db = 10^7/10 ~= 5); but does this get me the
>additional 150 feet of range to my shed?

I think that it might, but without a lot of safety margin.

>Spending almost twice as much money on the Hawking HAI15SC directional
>antenna gets me roughly 30 times the power (assuming 15 db = 10^15/10 ~=
>32); but is that enough power to get me the range to my shed?

Yes, probably so. That's well over the 10 dB I guesstimate you would
need.

>Indeed, is there some way to add a Hawking 15db antenna on the receiving
>end to get 1,000 times the power (15 db + 15 db = 30 db = 10^30/10 ~=
>1,000); but what would I hook the wire output from this receiving antenna
>to in the shed (I can't hook it to the pcmcia card, can I)?

That depends on the PCMCIA card. Some have antenna jacks, many do not.

There may be a cheaper way for you to get the gain you need, from your
existing equipment, without spending any money at all. It's possible
to fabricate a corner reflector, or (even better) a parabolic
reflector, out of material as inexpensive as cardboard (or posterboard
or something like that) lined with aluminum foil. Simply make one,
and then set it behind your existing router's vertical antenna... aim
the parabola in the direction of your shed and place the router's
antenna at the focal point of the parabola. Aim carefully, and it
wouldn't be surprising for you to get 8 - 10 dB of additional gain.

For even more gain you could buy one of the D-Link omnidirectional
gain antennas, and then use the same trick of putting a parabolic or
corner reflector behind it.

See http://www.freeantennas.com/projects/template/
and http://www.freeantennas.com/projects...te2/index.html

The latter states an achievable gain of around 11 dB just from the
homemade reflector.

--
Dave Platt <(E-Mail Removed)> AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

On Tue, 04 Jul 2006 06:28:16 -0000, Dave Platt wrote:
>>Can you help me roughly CALCULATE how to increase the range of my home
>>Internet wireless WiFi setup from 150 feet to a shed 300 feet away?

> Doubling the range requires 6 dB of additional gain from the antennas
> at one end or the other.

Hi Dave,

First thank you for taking the time to help me and anyone who read this.
Second, I'm going to have to go slowly with you so I'll respond one by one.

Third, does your statement that 6 dB of gain equates to 2 times the range
mean that the "square root" of the power difference is my key to
calculating the range?

That is, is this range calculation from dB power roughly true (based on
what you said)?

6 dB = 10^(6/10) ~= 4X the power, where the square root of 4X equals a
doubling the range (assuming an omnidirectional antenna)?

Beverly

> 6 dB = 10^(6/10) ~= 4X the power, where the square root of 4X equals a
> doubling the range (assuming an omnidirectional antenna)?

I'm hoping I can extrapolate from the above statement to calculate the dB
gain for the $150 Linksys WRT300N router which claims a 4X range
improvement (so I can compare the $50 antenna's effect with that of the
802.11n router).

Following your lead, the power improvement necessary for a 4X range
improvement is 4^2 = 16X power gain.

This 16X power gain then equates to about 12 dB (since 12 dB = 10^[12/10]
~= 16X power).

So, is it safe to calculate that the claimed 4X range improvement of the
Linksys WRT300N wireless broadband router can be compared to that of a 12
dB gain omnidirectional antenna?

Beverly

On Tue, 04 Jul 2006 06:28:16 -0000, Dave Platt wrote:
>>Can you help me roughly CALCULATE how to increase the range of my home
>>Internet wireless WiFi setup to a shed 300 feet away from my house?
>
> dBi refers to gain relative to an "isotropic" antenna
> dBd refers to gain relative to a half-wave dipole
> dBi numbers are approximately 2 dB higher than dBd numbers,
> for the same actual amount of gain.

Hi Dave,

Oh my. I guess the Hawking marketing folks were trying to trick me by
quoting a decibel number that was higher those I compared with.
15 dBi ~= 15 -2 ~= 13 dBd

That makes the $50 USD 15 dBi Hawking HAI15SC Hi_Gain Antenna drop down
from a gain of 32X power to only 20X power which gives me about a 4X range.

13 dBd = 10^(13/10) power ~= 20x power

Assuming the square of the power is the range, I get 4X range.
20^(1/2) ~= 4X range

Assuming my reliable range is 100 feet, that equates to 400 feet of range.
100 feet * 4 = 400 feet range

Interestingly, for comparison purposes, that is the SAME RANGE that the
much more expensive Linksys (Cisco) WRT300N router claims.

Do these calculations make sense?
Beverly

On Tue, 04 Jul 2006 06:28:16 -0000, Dave Platt wrote:
>>Can you help me roughly CALCULATE how to increase the range of my home
>>Internet wireless WiFi setup to a shed 300 feet away from my house?

> 3 dB of additional gain equates to twice the delivered power at a
> specific range. Because power falls off in proportion to the square
> of the distance, twice the power yields sqrt(2) or about 1.4 times the
> range, all else being equal (which it often isn't).
>
> 6 dB of additional gain is four times the delivered power at a given
> distance, or twice the range for the same amount of power.

So that I may compare the different options available at the store to me
for increasing my range, are these simplified calculations below correct?

a. 3 dBd additional gain = 10^(3/10) ~= 2x the delivered power
b. 2x power = 2^(1/2) effective range ~= 1.4X the range

b. 6 dBd additional gain = 10^(6/10) ~= 4x the delivered power
b. 4x power = 4^(1/2) effective range ~= 2X the range

Can someone let me know if these calculations are correct because that
helps me equate the different antennas and routers to the one measure I
desire, which is effective range in the area of 400 feet.

Beverly

On Tue, 04 Jul 2006 06:28:16 -0000, Dave Platt wrote:
>> Approximately how many decibels of (omnidirectional or directional)
>> power do I really need to boost my WiFi range from about 150 feet
>> to the 300 feet I need?
>
> The _minimum_ you appear to need is 6 dB of additional gain. I'd
> recommend trying for 10 dB or more in order to ensure a reliable
> connection.

May I ask WHERE that 6 dBd of gain is coming from?

Is it ONLY from the "better" antenna?

If that additional 6 dBd is coming from a "better" antenna, then why didn't
they put that better antenna on my router in the first place?

Since the antenna isn't "powerered", there is no external amplifier .... so
I am a bit confused as to WHERE that power is coming from?

Can you unconfusify me here?
Beverly

On Tue, 04 Jul 2006 06:28:16 -0000, Dave Platt wrote:
> There may be a cheaper way for you to get the gain you need, from your
> existing equipment, without spending any money at all. It's possible
> to fabricate a corner reflector, or (even better) a parabolic
> reflector, out of material as inexpensive as cardboard (or posterboard
> or something like that) lined with aluminum foil. Simply make one,
> and then set it behind your existing router's vertical antenna... aim
> the parabola in the direction of your shed and place the router's
> antenna at the focal point of the parabola. Aim carefully, and it
> wouldn't be surprising for you to get 8 - 10 dB of additional gain.

Hmm. I wonder. This is too good to be true. So, I will be a bit critical
with you (i.e., the scientific method) just to "test" the assumption so
that I can be sure I understand your position.

Assuming a 9 dBd increase in the directional gain from putting a pie tin
behind one of my existing router antennas, that equates to either 280 or
380 feet of range based on the calculations below.

a) 9 dBd = 10^(9/10) power gain ~= 8x power gain
b) 8x power gain = sqrt(8) range gain ~= 2.8X range gain
c) 100 foot range * 2.8 ~= 280 foot range

I'm a bit confused about the "range gain". May I ask if thta 280 foot range
is the total range or the range improvement?

That is, is my range with a pie tin behind the antenna 280 feet in toto; or
is the range now the 100 original feet + 280 additional feet which equals
380 feet in toto?

Beverly

On Tue, 04 Jul 2006 06:28:16 -0000, Dave Platt wrote:
>>Can you help me roughly CALCULATE how to increase the range of my home
>>Internet wireless WiFi setup to a shed 300 feet away from my house?

> See http://www.freeantennas.com/projects/template/
> and http://www.freeantennas.com/projects...te2/index.html
> The latter states an achievable gain of around 11 dB just from the
> homemade reflector.

The skeptic in me wonders "if it's this easy to get 3.5X the 802.11b,g WiFi
range, then why don't the router manufacturers add this cheap parabola as
standard equipment on all their antennas?"

a) 11 dBd = 10^(11/10) power gain ~= 12.5 power gain
b) 12.5 power gain ~= sqrt(12.5) range gain ~= 3.5X range gain
c) 100 feet range * 3.5X range gain = 350 feet range

Being a firm believer in "you don't get nothin' for nothin'", I must ask:

What am I losing by putting a parabola behind one of the two antennas on my
home router so that it increases the directional range from approximately
100 feet to about 300 feet?

Beverly

On Tue, 04 Jul 2006 06:28:16 -0000, Dave Platt wrote:
> It's possible to fabricate a corner reflector, or (even better) a
> parabolic reflector, out of material as inexpensive as cardboard
> (or posterboard or something like that) lined with aluminum foil.

Hmm. At first, I thought you were pulling my leg; but a simple google for
more details gave me more homemade WiFi antenna reading than I can handle
in a month. Whew. Here, for others to share, are the Yagi pringles can
antennas (aka cantenna) which purport to "refocus" the WiFi signal from my
router in my house to my shed 300 feet away.

http://en.wikipedia.org/wiki/Cantenna
http://www.oreillynet.com/cs/weblog/view/wlg/448
http://www.seattlewireless.net/index...inglesCantenna
http://www.wi-fiplanet.com/reviews/article.php/3401501
http://www.turnpoint.net/wireless/has.html
http://www.binarywolf.com/249/pringles_cantenna.htm
http://verma.sfsu.edu/users/wireless/pringles.php
http://www.seattlewireless.net/index.cgi/CookieCantenna
http://webserver.computoredge.com/ed...2339/cover.htm
http://www.signonsandiego.com/news/c...b13canned.html
http://www.overclock.net/faqs/17669-...l-booster.html
http://www.g4tv.com/screensavers/fea...i_Antenna.html
http://www.netscum.com/~clapp/wireless.html
http://www.flickr.com/photos/binarywolf/sets/837698/
http://linuxathome.com/files_images/cantenna.pdf

Given that there are two fundamental design styles:
a) Parabola
b) Tube

Do folks here recommend the pringles cantenna or the pie tin antenna for my
2-antenna router 802.11b,g directional application where I need to also
feed the computers within the house in addition to the shed 300 feet away?

Beverly