wifi modem modifing antenna

[madhan_2005]

I have been lately involved in the process of modifying my wifi modem to increase its functionality. So i thought of extending its range. I have decided to make a yagi uda antenna, and if successful add an other patch antenna with required amplifiers.

my first obstacle is that my modem the D link 2750 U does not have a external connector. instead it i think has a u.fl connector inside its body and the wire comes outside to form a simple whip surrounded by a rubber ducky. not much of a range

So i am asking whether i can just pry the external insulation of the whip. and solder that to the driving element of the yagi uda. will that work?

.

 

[sky_123]

I'm not super-convinced it is likely to improve things much.
Plus, you'd need to ensure the PC also can transmit to the same range, so will the PC also have a yagi attached?

 

[E Kafeman]

Yes you can do so if your Yagi-Uda balanced feeding is converted to unbalanced with correct impedance, as the whip you have seems to be unbalanced.

Plus, you'd need to ensure the PC also can transmit to the same range

No.
If it result in antenna directional gain is this gain equal affecting both TX and RX, so it is no special need to improve PC antenna.
This router, is it a 802.11n router? Then it need to have similar antenna design for the remaining antennas, which dynamically can change which antenna that act as RX or TX.
It is often wiser to let the router antennas radiate omnidirectional if several PC's in different directions should reach the router. Better to place a directional antenna at the computer that have weakest signal.

 

[madhan_2005]

ya it is a 802.11n router.

And why are you saying similar design for remaining antenna. I am going to use it with my galaxy s2 alone. and also the galaxy s2 signal might not be as powerful but the yagi uda rx would be sensitive enough to track that weak signal(i think). I am not even getting the wifi at a range of 40-50 metres. so thinking of increasing the range by changing antenna and then if this does not work i will add a 2.4 ghz signal amplifier.


@E Kafeman:
how can u tell that the whip is unbalanced. I cant understand the first line that u are trying to say>>>

 

[E Kafeman]

Is it this type of antenna you have? It is unbalanced. Advantage is that it can be feed with a coaxial cable and no need for a balun.
A Yagi-Uda antenna is a balanced type of antenna. It need some kind of balun if it should be feeded with a unbalanced coaxial cable.

If you only modify one of the antennas, it will cause that 11n will be rather useless both in near field and at distance. If only one antenna have enough coverage, is it better then to accept a bit slower connection in 11g mode.
Here are some information

Same type of problem if you add a signal amplifier. A signal amplifier that should handle 11n costs 3x what a amplifier for 11g costs as it must be able to handle three antennas (one amplifier/LNA for each antenna).
Indoor coverage in 11g is only half compared to a similar unit in 11n mode due to the MIMO effect so a single directive antenna in 11g mode can have shorter coverage then three omnidirectional antennas in 11n mode.
If you use a single directive antenna will probably your router automatically step down to 11g-mode which can reduce you coverage!

Besides that, some routers have less sensitive receivers and weak transmitters. Poor location of the router can also reduce coverage. Existing antennas is in most cases good enough for indoor use. If it not is optical sight between your units, does not a directive antenna improve much as most of its power is lost when trying to burn a small hole in a wall. A less directive antenna may find the door hole or window and reach longer due to reflections.

If you still want to do antenna experiments do I recommend you to buy an old 11b or 11g router with single external antenna, and connect it as a wireless access point, bridge, behind your existing router. That way can you do long distance tests on this router without reducing local coverage or speed in 11n mode.
Beware of some cheap Ebay junk, a good amplifier is not cheap, a LNA with better performance then what you already have in the router do also cost. Besides poor performance can they cause interference with other radios and is most likely illegal to use.

 

[vedagarbhamsandeep]

If it is a low power router (65mW or so), it will not drive your 12-14dBi Yagi or any other bigger antennas which require bigger power to drive the antennas. check on your router specs before connecting any external antenna.

As a manufacturer of AP and CPE, we usually have a 14 / 16dBi patch antenna alongwith outdoor 200mW / 400mW routers which give a range of about 2kms in open space.
For higher power routers such as 800mW and 1W, we use upto 30dBi parabola dish for longer coverage upto almost 8-10Km in open space.