You may want to consider doing it the way cheaper way (using any of the N ((actually pre-n cuz there are no N standards yet)) is IMO the hard and expensive way)... I Had a linksys WRT54G in the house attached to my sat, and used one of the 4 router outputs to daisy chain one to the wan input of another WRT54G (same ssid) and a semi-directional antenna pointed towards the garage about 500ft away, (and another to the guest house (about 800 FT away) out back on my 5 acres).. The Linksys WRT54G (not the GS) are available at wal-mart for under $50 each... Cat 5 cables a few bucks, and the semi-directional antennas (not highly directional, just semi) where a few bucks each for the 2nd and 3rd wap/routers.. Am even thinking about adding a 4th wap/router so I can use my PDA (with wifi) out by the horse corral.
Think increased range by using multiple wap/routers and multiple antennas, rather than trying to get one that is more powerful and does it all..
Not really. Most routers are set to use the antenna with the most signal strength. Therefore if you are using a directional antenna on on and a omni antenna for the other. The directional will win out, since it will have more available signal. This is part of that antenna diversity thing.
The reason for the two antennas was so one could change the antenna to different planes to receive a better signal due to phase shifting of the signal that occurs when a given signal hit an object and bounces off that said object. The signal is no longer in phase, with that which was originally transmitted.
A hi gain dish or flat panel here would actually be better. A "range extender" or as it is commonly known as a"repeater" will actually cut the given speed of the signal in half. Since these items are "half duplex".
Since she also mentioned that there were some trees between the house and the shed. She most likely will need to have a directional antenna on both ends.
Yes. See the alt.internet.wireless FAQ section on link calcs at:
The trees are going to be a problem. The water in the leaves attenuate the signal and they impinge on the Fresnel zone. Calculating foliage attenuation is difficult as it varies with season, weather, type of foliage, etc.
The Fresnel Zone may also be a problem. You need at least 0.8 times the zone radius of clearance at midpoint to avoid edge diffraction and other nasty effects. At 300 ft, the Fresnel zone radius at midpoint is about 5.5ft. You'll need to be at least 4.4ft clear of any objects at midpoint including the ground. The problem is usually that the antennas on each end are at desk level which is not high enough to clear the ground.
Start with something simple:
can get substantial directional gain with a simple reflector at little cost.
Muddle. Antennas do not boost the "power". That's what an amplifier does. Antennas only redirect the available RF power. That means that for an increase in signal in one direction, the signal must decrease in another. This is also known as the Free Lunch axiom.
Be VERY careful of specifications from antenna vendors that supply pigtails with their antennas. The published specifications never seem to mention the coax cable and connector losses. Figure on 0.5dB per connector pair.
dBi is the gain over a theoretical isotropic radiator. This is commonly used as a reference point for antenna calculations.
When comparing different types of routers, it's common to claim that some have better range. For example, the range difference between MIMO routers and beam switching routers was tested in: |
has much better range than beam switching. The problem is that neither technology is useful for point to point which is apparently what you're doing. That's because it's impossible to attach external antennas.
That depends on what you're comparing them to. Let's say we start with the stock rubber ducky antenna supplied with most access points. It has a gain of about 2dBi. The 7dBi antenna has 5dB more gain. The
15dBi antenna has 13dB more gain. The relative range improvement is: range improvement = 10^(dB/20) or 1.8 times for the 7dBi antenna and 4.5 times for the 15dBi antenna.
The range improvement is the same for a given gain no matter what type of antenna. However, there is a big difference in the radiation angles. An 8dBi omni antenna will have a -3dB vertical radiation angle of perhaps 13 degrees. Tilt this antenna 7 degrees in any direction and the signal is gone. An 8dBi panel or biquad will have a radiation angle of about 60 degrees. It can be tilted 30 degrees vertically or horizontally before the signal is lost.
Want me to do the calculations? I need to know what you are going to use for hardware and how long are the coax cable runs. It's quite easy once you have the numbers. See:
Range and power are related by the inverse square law, which roughly states that you need 4 times the power to double your range. An increase of 5 times in power will only yield a 2.2 times increase in range.
One of the fun calculations is to work out the cost per decibel gain for each type of antenna. Using prices from:
Type Gain Cost Cost/dB dBi dish 15 $35 $2.3 yagi 15 $65 $4.3 panel 19 $68 $3.8 omni 12 $70 $5.8
So, from my random assortment of typical antennas, it seems that the dish is the cheapest way to get lots of gain, while the omni is the most expensive. Obviously, the cost/dB is going to vary depending on vendor, discounts, shipping, taxes, selection, and such. However, the numbers should be considered before buying.
No, you can't connect it to your PCMCIA card. You can butcher you card to add an external antenna pigtail. Other options are to purchase a PCMCIA wireless card with an antenna connector, or use an ethernet client bridge radio such as a WAP54G. Also a "game adapter".
No clue. There's not enough info to make a proper comparison. You can't attach an external antenna to a MIMO router anyway so that's out.
What's missing is:
What equipment do you currently have to work with?
What are the exact distances involved?
How long a coax cable run? Can the radio be mounted next to the antenna?
What obstructions are in the line of sight? Is the Fresnel zone clear? Are you going through any walls or windows? Trees and bushes?
Any limitations to antenna selection and placement (i.e. CC&R)?
Any performance expectations? What's the minimum thruput speed you're willing to tolerate? Thruput is about 50% of wireless connection speed.
Any local sources of interference? Any other wireless networks including municipal networks?
Yes. You need four times the power (radiated in the direction of interest) to double the range, nine times the ERP (effective radiated power) to triple the range, etc., all else being equal.
Yes, assuming the correct interpretation of "omnidirectional".
The only _truly_ omnidirectional antenna is an isotropic antenna... and these don't actually exist. All other antennas have stronger radiation in some directions than in others. The more power they radiate in some directions (that is, the higher the gain in those directions) the less power they radiate in other directions.
The usual meaning of "omnidirectional antenna", in the context of wireless networking, is a vertical antenna which emits a pattern of RF which resembles a donut. It's "omnidirectional" in the sense that it emits the same amount of power in each horizontal direction. At angles above and below the horizontal, the antenna radiates less power. Directly above and below the antenna, there's a deep "null" in the radiation - in fact a theoretically-perfect vertical dipole would radiate no power at all in those directions.
An "omnidirectional antenna with gain" achieves its gain by "squashing" the donut shape of the radiation pattern, in effect "squeezing" the pattern vertically. It radiates more power out towards the horizon, at the expense of radiating less pattern at angles above and below the horizon.
It's not hard to get a few dB of gain by this sort of squeezing of the vertical pattern. It's usually difficult and expensive and tricky to get a _lot_ of gain this way - it requires a relatively tall antenna (roughly doubling the length for each additional 3 dB of gain) and the antenna's positioning and design becomes fairly critical.
To get higher amounts of gain, it's usually necessary to use a directional antenna, with some form of reflector... in effect, taking power away from some "slices" of the "donut" and redistributing it in the slice towards which you really want to send the power.
As you can see, any antenna which gives you a positive gain in some direction, is going to have other directions in which the gain is negative - in which the signal is weaker than if you used an omnidirectional (or isotropic) antenna. It can't be otherwise, due to the principle of conservation of energy. Antennas don't create energy or power - they simply convey it.
Oh my! Is "wireless" daisy chaining workable? Is it that easy?
I did not think I could just daisy chain multiple routers! Are you sure? (My shed has no power but I think I could run an extension cord into it if that would make things workable.)
Would I just set the second Linksys router (which, amazingly, has it's own wikipedia entry at
in the shed on the same channel (SSID=12, name = default) as the first router in the house?
That is, could I put one linksys WRT54G in the house (perhaps with one antenna replaced with a 7 dBd higher-gain directional antenna); and then put the other Linksys WRT54G in the shed 300 feet away (perhaps with one of it's antennas replaced with a similar 7 dBd directional antenna)?
Or, is it best to hardwire with cat5 the first router downstairs in the house to the second router, say upstairs in the attic window pointing the antenna toward the shed? I didn't even know that two routers could be daisy chained. That might solve my dilemma.
Can someone confirm that two routers could be daisy chained either by wire cat5 cable or by wireless signals as long as they use the same SSID channel and network name? That solution seems to easy to be true ...
Possibly, _if_ the claimed range improvement is meaningful.
_If_ the WRT300N can actually sustain a connection over 4x the distance of your current router, then this could come from higher transmit power or receiver sensitivity (which would be independent of the antenna's pattern), or a higher-gain antenna, or the use of an RF modulation scheme which is less vulnerable to interference. The 4x figure could also be optimistic marketing puffery. The only way to be sure would be to try it in your environment, and see if it helps.
Quoting dBi rather than dBd is a very common marketing practice... many vendors do it, because it gives their antennas an apparent competitive advantage. Sorta like quoting EPA gas mileage on a car rather than real-world mileage. The buyer just has to be aware of what's being done.
I think you've got the idea!
Remember that antenna gain isn't the whole story. The other factors are the router/AP's actual transmitter power output (which is usually measured in dBm - that is, decibels referred to 1 millwatt of power) and receiver sensitivity. Different manufacturers' transmitters may vary by several dB of power - typical models seem to run between 15 dBm and 20 dBm. Higher transmitter power, and a more sensitive receiver in one model of router might give you more advantage than a high-gain antenna on another router which has a wimpier transmitter and a less-sensitive receiver.
In practice, the best way to figure out what's going to work well in your situation is to actually buy/borrow the equipment in question and test it. You can get some idea of what's likely to work by doing calculations, but there's enough variation in actual performance that you'll have to test the equipment to see what truly works and what doesn't.
Wow. I've never "modified" a router before but that is interesting that one can increase the $75 Linksys WRT54G router
RF output from 28 millwatts up to 251 milliwatts
Being true to the original intent of this thread, how do I CALCULATE what that does to my range?
Is this 9 dBd calculation of the modification roughly correct? a) Power gain = Power2/Power1 = 251/28 milliwatts = 9x power gain b) Range gain = sqrt(Power gain) = sqrt(9) = 3X range gain c) Range = original range * range gain = 100 feet * 3 = 300 feet
Well, that's close. Saying "6 dBd of additional gain" isn't quite right, though... you'd need 6 dB of additional gain compared to whatever your antenna's current gain is. If your current antenna is a
0 dBd antenna (that is, it's a dipole), then your new antenna would be
6 dB above that, or 6 dBb.
On the other hand, if your existing antenna already has some amount of gain... if it's a 3 dBd stacked dipole for example, then you'd need 6 dB more than that to double the range - you'd need 9 dBd in your new antenna.
I see there are multiple solutions. Probably on the end of my list is adding a wire to the laptop because then it wouldn't be wireless. Still, it's an intriguing idea (I never knew laptops could have fixed antenna's connected to them by wire).
If I do use two antennas, does that "add" the gain?
a) Antenna 1 transmits with a directional gain of, say 7 dBd b) Antenna 2 receives with a directional gain of, say 7 dBd c) Does that get me a 14 dBd overall gain?
Say "9 dB of additional gain", not "9 dBd of additional gain".
It's 280 feet. Try redoing the above calculations with 0 dB of additional gain:
a) 0 dB = 10^(0/10) = 1x power gain b) 1x power gain -> sqrt(1) = 1X range gain c) 100 foot range * 1 = 100 foot range
As you can see, the final figure is the total, not an amount which is added to the original. Otherwise, you'd be able to double the range of the system by adding no gain at all (0 dB) and that clearly doesn't work.
With respect to reflectors and so forth... there are a lot of ways to boost the range of WiFi systems using simple, easy-to-make antenna systems. Corner reflectors, parabolics, Pringles-can waveguides, and so forth. What I've read (and heard) is that "the first 8 to 10 dB of gain is easy. Beyond that is hard." Getting more than about 10 dB of additional gain from a signel antenna generally requires the use of a commercially-made antenna - usually a parabolic wire dish or something like that.
Oh... there's another possibility you might want to consider. So far we've talked about improving the directional gain of your router / access point, because it isn't all that easy to improve your laptop's antenna system (PCMCIA card with no antenna jack).
Another option is to use a different sort of wireless network interface to hook up to the laptop. If you're going to be using the laptop in only one location (e.g. your shed), then you could buy an outboard wireless network interface and hook it to your PC, and then use some sort of improved antenna at the laptop interface.
Two possibilities for the laptop: an Ethernet-to-802.11 bridge (often called a "game adapter" - e.g. a Netgear WGE111), or a USB-to-802.11 dongle.
If you were to stick a parabolic cardboard-and-aluminum-foil reflector behind the antenna of your router in your house, and were to use a game adapter or USB dongle in your shed with a second parabolic reflector behind it, and aim the two parabolas towards one another through a couple of clear windows, you'd end up with somewhere between
15 dB and 20 dB of total antenna gain. This would certainly give you a solid connection, and would probably be a lot less trouble and expense than trying to get extremely high gain from just one end of the connection (the router).
I've heard of people getting ranges of a mile or more, over clear terrain, with setups no more complex than this.
I had come across the concept of wireless "repeaters" in my initial googling before I went to the store, e.g., in this Microsoft "how to increase range" article
and in this "Extending WLAN Range" article
The repeater most often recommended was the "Linksys Wireless-G Range Expander WRE54G".
However, I can't find that 802.11b,g WiFi repeater (aka range expander or extender) anywhere in the local stores. The salesperson who sold me the $300 USD 802.11n router and PCMCIA card combination said they didn't work so they dropped it.
This solution seems to be the most elegant of all (but someone else suggested just using a second router).
Can someone unconfusify the situation?
Is placing a repeater (on the same SSID) in the shed really the same as adding a second router instead?
Beverly - i will leave the radio complications to the experts.
but - you mentioned you could run power out to your shed. Why not plumb it in for power and networking?
then you can add a separate access point there and avoid antennae, gain, loss through leaves and the rest.
If you run a power line, then there are homeplug devices which can provide network links through the mains feed - or you could just run some Cat 5 cable with the mains link (not forgetting earthing, safety and all those other details) - 300 ft is within the standard 100 m run for 100 Base-T.
Repeaters normally need to be placed somewhere around halfway between the existing router / access point and the location of use. In your case, that'd probably put the repeater smack-dab in the middle of the woods - probably not the best location for it?
Hi Stephen, I'm confused about this "access point" thing.
Is that the same as a "router"?
Is it as simple as buying a second router (routers are familiar to me) and just hooking that second router to the first router by cable and that would extend my range by the distance of the cable connecting the two routers?