# How to calculate increase of home wireless router range?

• posted

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

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

• posted

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.

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.

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.

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.

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

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

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

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

• posted

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

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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

• posted

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

• posted

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

• posted

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

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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

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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

• posted

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.

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

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Beverly Erlebacher wrote

Because most dont want something that directional.

That approach is quite directional.

No big deal in your situation because the location of each end doesnt move around much.

• posted

I'd personally buy a couple of antennas which have been designed for that specific use instead.

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I use panel antennas almost exclusively, exceptions being some 24dbi mesh antennas for backhaul. Unless you are pretty skilled at constructing electronic items, I'd just buy one on eBay. The panels I use are inexpensive, waterproof and work great. Different sizes for different uses. Might want to look at

some helpful info, and they're good people to deal with.

• posted

Hi Rôgêr,

After reading all the articles posted, I now understand that:

a) The pringles can is hip; but it's the worst performer

(it's not even metal foil lined and it's too small in diameter)

b) The coffee cantenna is more effective than the pringles cantenna

c) The dish antenna is the simplest of all and almost as good
I also see, as Rod Speed so kindly noted, that the give and take is that we lose range in some directions in favor of range in the desired direction. Fair enough.

My one question is a practical one.

Why are there two antennas on my router anyway? Is one transmit and the other receive? Or are they both transmit and receive?

Given I have TWO omnidirectional antennas on my wireless router, if I put the parabolic dish antenna on one to direct it to my shed, does that allow the OTHER antenna to radiate around the house to handle the other computers roving around the house?

Beverly

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This may seem confusing, but it's really simple. The two antennas are sampled to see which has the best signal many times a second. It's called diversity, not really a big deal when the antennas are 4 inches apart. Both are not used at the same time. Hook up a directional antenna to where you removed one of the omni antennas and it will have the best signal almost all the time. Given the info you've posted, I'd go with one of the 6dbi panel antennas. It concentrates the signal enough to aim it to your shed, but has enough of a wide spread spill to let other items work. High powered omni's are a pain in the ass. they radiate 360° but in a narrow horizontal notch. They have to be aimed carefully. Most of the time not a good idea.

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==================================================== Having followed today's postings on this topic , I see that there is a wooded area between your house and shed, hence there seems to be no free line of sight between the house and the shed. That's why it is difficult to calculate/predict the Gain you need to penetrate the wooded area with a 2.4 GHz signal.

If you wish to use the laptop inside the shed at a fixed location it MIGHT be good enough if you install a corner reflector yagi (High Gain)antenna at both the house AND the shed. However then your laptop needs a plug-in PCMCIA WiFi tansceiver with a connection for an external antenna. One of such units is the Make: Buffalo - Air Station Turbo G ,High Power

-unit which also has a built-in antenna. Note : The coaxial cable between the 2 devices and their associated antenna should be limited to only a few metres because of the high frequency being 2.4GHz

Communication here is 2 way . Your laptop might receive the ( antenna amplified) signal from your router located in the house ,but that does not mean the router will receive the signal from the laptop without additional facilities at the laptop.

Again , because of the probably partly obstructed path (wooded area) it is difficult making any sensible calculations.

Frank GM0CSZ / KN6WH

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Both I'd guess, for "diversity antenna gain."

Nick

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On Tue, 04 Jul 2006 05:57:12 GMT, Beverly Erlebacher wrote: [snip]

[snip a whole bunch of stuff]

AN antenna passive divice. It does not increase power. Gain is achieved by focusing more radial tion in one direction by reducing it in another direction.

Now more to the point (extending the range of your wireless LAN) . If you goal is to increase your range then add an extender (hams would prefer to call them repeaters).

You mentioned using D-Link. They make a good extender for around \$70 USD. I have one installed up on the second floor (I have a two story home) and am able to have good connections at distances over 500 FT.

Check it out.

73, Danny, K6MHE
• posted

The pringles antenna works great for me and some low-income neighbors I know in Seattle.

Also, here is an easy way to hack your \$60 wireless router into a \$600 router (they use Linksys as the example):