Upgrading Antenna on Wireless D-Link DI-713P Router

[Dre]

I'm trying to buy a better antenna from D-Link that will increase the coverage of my Router. Here is a link to the one I was looking at:

Antenna

Is this better then the stock antenna that comes with the 713p? It never really tells you and I really don't understand the technical specification listed. If it is better, how much better is it?


D-Link has a bunch of antenna's, but they never really tell you much about them besides their specs. Here is a link to them, they are at the bottom:

D-Link Antennas



Can someone with a little knowledge help me out please?

 

[JackMDS]

The following info is put in very simple terms (the plumbers will pardon me).

Attaching auxiliary Antenna usually improves the distance of the Wireless unit.

dbi relates to the amount of gain in powwer. *

The major advantage of most auxiliary antennae is the capability to be connected through a cable to the Router (or WAP), thus giving the flexibility to put the antenna in a better position then the Router (higher and in the middle of the environment).

However you have to be careful about the directionality of the Antenna, some antenna gain power by making the transmission directly toward a certain point (very common in a bridging situation when one bridge is pointed toward the other bridge).

An antenna that transmits all around is called omni directional, otherwise the segment that is covered is defined in the specs. usually indicating vertical and horizontal converge.

As an example the antenna that you mentioned is not omni directional it covers 90 degrees vertically, but horizontally only 60 degrees i.e. this antenna covers only 1/6 of the surrounding circle.

If you need all around coverage this is what you looking for:

D-Link ANT24-0401 Indoor 4 dBi Omni-Directional Ceiling Antenna.


* Here is a quote from: http://www.zoom.com/zoomair/zaaops.shtml

1. Gain - Decibel (dBi or dBic for circular) expression for the ratio of the radiation intensity in a given direction relative to a theoretical isotropic (omni-directional) radiator.

2. Polarization: Linear - A pattern requiring antennas to be placed in the same orientation with close attention to polarization alignment angle (alignment should be within ± 5° for optimum performance).

3. Polarization: Right-hand circular - A pattern that reduces the effects of reflections in a typical indoor environment providing improved coverage for access point use.

4. Azimuth - The radiation intensity pattern located in the horizontal plane.

 

[astroview]

I thought that the 713p's antenna was not upgradeable. Practicallynetworked's review said you "Can't attach external 'booster' antennas" Is this the same as upgrading the main antenna.

The review also says it has

"Two moveable position, non-detachable monopole 'rabbit ears'" for antennas

 

[Dre]

The antenna's that come with the 713p are screw on. They come in a bag and you screw them in. Maybe you were looking at the older version which is the 713 without the "p"?

 

[Rkonster]

<< I thought that the 713p's antenna was not upgradeable. Practicallynetworked's review said you "Can't attach external 'booster' antennas" Is this the same as upgrading the main antenna.

The review also says it has

"Two moveable position, non-detachable monopole 'rabbit ears'" for antennas >>



DLink revamped their 713p, so the newer ones have the detachable antennas. When practicallynetworked did their review, the dlinks did not yet have the removeable antennas.

 

[astroview]

I just got my 713p and yes it has the removeable antennas

So does anyone know any other good omni directional antennas that have reverse SMA connectors and good dBi signal gain?

 

[Dre]

I called D-Link and spoke with someone there. If you are looking for an omni-directional antenna for inside use, they recommend the ANT24-0500 which has a 5DBi gain for upgrading the 713P wireless router. They said you would only need to buy 1 of the antenna and that it attaches right onto the 713P with no modifications. I found it online for $88.00 using yahoo price search and using Pricegrabber found it for $99.00.

D-Link explained that this was the better choice as opposed to the ANT24-0401 because the ANT24-0500 has a higher DBi gain and is only $2.00 more expensive. I checked the prices for both and confirmed what they told me.

 

[astroview]

My only problem with Dlink's recommendation is that Dlink told you to buy that antenna, and that a generic one might work just as well for less money. Thats what I'm ultimately looking for right now, though if need be I can spare the extra change.

 

[Dre]

<< My only problem with Dlink's recommendation is that Dlink told you to buy that antenna, and that a generic one might work just as well for less money. Thats what I'm ultimately looking for right now, though if need be I can spare the extra change. >>




I'd like to find a generic one as well, but it's too difficult unless you actually know about this stuff. That's why I was looking at D-Link's antennas. It'd be great if someone could give us a recommendation for a generic one.

 

[JackMDS]

http://www.hdcom.com/2.4ghzantennas.html

 

[ktwebb]

Antennas are pointed at each other, not bridges. The 90 degree beamwidth is the directed radiation pattern but you will still get reception beyond the 90 degrees. If you want 360 degree coverage, get yourself an omni although most omni dont do very well at steep vertical angles so if your trying to cover downstairs rooms as well as the ones on the same floor as the antenna you could have problems with reception. A squint omni works well if your placing the antenna at the top or bottom of a structure. Keep your transmission cable or pigtail short if your using something short like RG58.

 

[Dre]

<< http://www.hdcom.com/2.4ghzantennas.html >>




Some of those Antennas look like the ones D-Link sells for more money. So who wants to recommend an Antenna from this store for a D-Link 713p wireless router?

 

[Hossenfeffer]

I have a feeling I'll also be looking for an antenna. Buying the equipment this week for a medium/large house. The ap will be on the second floor with probably 75% of the wireless use on the ground floor.

 

[astroview]

I have the feeling that this is a relatively new technology at the normal consumer level that buying antennas and other addons for them is still a hassle. Its even annoying for me, and I'm a geek but now I have to learn a whole new set of networking standards and information.

I'm still not sure how this whole dBi works, because I'm just a casual computer user not a EE or physics type of guy.

 

[JustinLerner]

The link by JackMDS to zoom has good diagrams of the real patterns. Please note that these patterns are on log scales - not linear. These diagrams display more accurately the actual patterns of their particular antennas. This is a topic for the High Tech forum. Yes, EE people there can give you a better answer. Let me point out a few things though.

The reason there are two rabbit ears on these wireless units is to allow full use of each antenna at different frequencies for 1. transmit and 2. receive.
Wireless uses CSMA/CA, not CSMA/CD. Therefore no collisions, but only one remote device can transmit data at any time.

Using a single antenna would seem to defeat some of the purposes of having two independent antennas. Though it probably works with greater gain (only because of the physical design), the interference, crosstalk and other problems might increase. If only one antenn is upgraded, then you have mismatched strengths of transmit, but your transmit on your laptop NIC doesn't increase, so it still has the same power limitations and hopefully there is greater sensitivity on the receive side of the WAP to compensate. The wireless units are designed with two antennas for a reason, but I don't know where the 'weak' point is in these units (either WAP or NIC), so maybe you only need one antenna since the mfg might make the units with disparity from the begining.

I might buy one omnidirectional for transmit and one pole type for greater reception and mount them up at least at head height with cable extensions if available, which might look goofy, of course I wouldn't buy wireless at all. Had too much exposure to RF as it is.

 

[Dre]

<< The link by JackMDS to zoom has good diagrams of the real patterns. Please note that these patterns are on log scales - not linear. These diagrams display more accurately the actual patterns of their particular antennas. This is a topic for the High Tech forum. Yes, EE people there can give you a better answer. Let me point out a few things though.

The reason there are two rabbit ears on these wireless units is to allow full use of each antenna at different frequencies for 1. transmit and 2. receive.
Wireless uses CSMA/CA, not CSMA/CD. Therefore no collisions, but only one remote device can transmit data at any time.

Using a single antenna would seem to defeat some of the purposes of having two independent antennas. Though it probably works with greater gain (only because of the physical design), the interference, crosstalk and other problems might increase. If only one antenn is upgraded, then you have mismatched strengths of transmit, but your transmit on your laptop NIC doesn't increase, so it still has the same power limitations and hopefully there is greater sensitivity on the receive side of the WAP to compensate. The wireless units are designed with two antennas for a reason, but I don't know where the 'weak' point is in these units (either WAP or NIC), so maybe you only need one antenna since the mfg might make the units with disparity from the begining.

I might buy one omnidirectional for transmit and one pole type for greater reception and mount them up at least at head height with cable extensions if available, which might look goofy, of course I wouldn't buy wireless at all. Had too much exposure to RF as it is. >>





Yea, I found it strange that D-Link told me I only need to buy one upgrade antenna. I asked him if he was sure and he said yes. I guess I should have asked him why the router comes with 2 antenna's then.

 

[ktwebb]

802.11b AP's with two dipoles do not use Frequency diversity. They incorporate spatial diversity. It's the same frequency coming out of each antenna. The AP simply switches between each antenna to reduce multipath to the client. If you do buy one aftermarket antenna then you would want to turn diversity off. Basically the client picks the best signal but it's only one frequency coming out of the AP. When you use spatial diversity you want both antennas to be of equal gain. They also need to be within a couple of feet of each other to be effective reducing multipath. Couple of reasons he told you to buy just one antenna.

 

[JustinLerner]

A few years ago when 2.4 Ghz cordless phones hit the market, I looked at the specs on some of them, especially those having two antennas. It appeared from the manufacturer literature and specs that some of these early 2.4Ghz cordless phones were employing frequency diversity (different frequencies on each antenna for either xmit or rcv). I assumed that since 802.11b uses the same 2.4Ghz frequency, that operations were similar.

Many web sites say that 802.11b WAP's employ antenna diversity, but make no differentiation between spatial, frequency, polarization diversity.
If the 802.11b standard employed frequency diversity, this would seem to provide speed benefits over signal strength, thus allowing full duplex operations or simultaneous receive and transmit operations with two different clients or even a single client with disregard to the signal strengths (what significant difference will result with antenna separtion of 6"?). Certainly frequency diversity, though more expensive and complex, makes more sense from the benefits of speed switching and full duplex vs signal strength efficiency at a separation of 2" or 6", but unfortunately, frequency diversity is not part of the spec (only one frequency per channel). Eventually, wireless mfgs will probably make WAP's and wireless NIC's capable of using dual channels (say 1 and 6) and thus give them full duplex capabilities.

Correct me if I'm wrong, but spatial diversity only allows the selection of the stronger signal and only the point (or AP in this case) with at least two antennas makes the selection and responds from the antenna with the stronger received signal. Although 802.11b client NICs can employ IC antennas or microstrip antennas, the antenna separation is even smaller and efficiency of the diversity even less, so I would rather have a single microstrip or dipole antenna on the NIC (with twice the length) than dual diversity microstrips. I think this just makes much more sense.

Since I'm not an engineer but interested in the implementation standards, I find it hard to believe that there is any significant benefit in employing spatial diversity with the minimal separation of antennas at a few inches (2" or 6") and extremely unlikely that simulataneous transmission from both antennas occur from the WAP at the same frequecy, because wouldn't this cause transmission problems in certain locations by particular concentric geometric, overlapping patterns of transmitted signals? Certainly, the wirelss access points with two antennas transmit on one antenna (the one selected by the higher receive signal), but receive on both for the diversity differentiation. The benefits of spatial diversity or it's efficiency with small antenna separation should be small compared to wider antenna separation.

If the WAP employs spatial diversity for detection of the strongest signal for reception, what is the benefit or efficiency of a few inches of separation? After all, aren't obstructions that cause problems for one antenna likely to affect another antenna when their separation is only a few inches? Think of a person in a kitchen where a refrigerator or stove is between mobile NIC and WAP. What's the benefit of 2" or 6"? Now if the antennas were extended and separated by a few feet, wouldn't this provide greater effective diversity?

IF so, wouldn't it be better to install two antennas mounted at different points a few feet from each other (with approapriate matched transmission lines -- i.e. coax cable.)

Take a look at this before installing newer antenna(s).
http://www.ittc.ku.edu/wlan/
http://www.ittc.ku.edu/wlan/security.shtml

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Of course, if you use two antennas, they should be the same type with the same length and type of cable, the same types of connectors, etc. Everything for both should be identical except mounting locations on the wall(s). With two antennas mounted a few feet apart, diversity could remain enabled (I don't know if it's possible to disable on all or many WAP units.)
Last, I still think two antennas is better than one and would like to hear otherwise from anyone who has an EE background.