Strange 2.4Ghz antenna

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Strange 2.4Ghz antenna

Postby Tranworld » Sun Nov 06, 2011 5:23 am

Can someone knowledgeable enlighten me on this antenna design? They are the internal antenna of a Linksys WRT160n V3 wireless router. I can see that the antenna is a mere stamped piece of metal and in fact the core and the outer of the coax is joined, electrically, as they are soldered to the same piece of metal? What propagation pattern do these antenna provide? They are said to be of 1.5dbi ? Is that so?
Internal antenna 001.jpg
Internal antenna 001.jpg (94.24 KiB) Viewed 3311 times
Internal antenna 004.jpg
Internal antenna 004.jpg (102.44 KiB) Viewed 3311 times
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Re: Strange 2.4Ghz antenna

Postby Shotglass » Sun Nov 06, 2011 5:49 am

by the looks of it id guess the idea behind it is an inverted f antenna with some meandering to make it smaller
pattern wise its probably best described as a roughly omnidirectional mess
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Re: Strange 2.4Ghz antenna

Postby Tranworld » Sun Nov 06, 2011 6:26 am

Yes but how does it work when it is essentially shorted? The inner core soldered on top and the shield, soldered at the large plate is simply part of the same piece of metal, therefore electrically joined? That's the part I don't understand. Even though you said it's a mess, it actually works very well and the signal reaches quite far.

The writing on the stamped metal is Pat. Pending to Galtronics, if you searched Galtronics they are a specialist in antenna so I guess the design is quite novel from them and Linksys would not adopt it if it doesn't work
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Re: Strange 2.4Ghz antenna

Postby Shotglass » Sun Nov 06, 2011 6:48 am

because its rf and things arent that simple at higher frequencies
that short in particular will wrk as some sort of reactance depending on its length and distance from the feed point

and the farfield from folded antennas is generall a bit of a mess theres no way around it
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Re: Strange 2.4Ghz antenna

Postby Tranworld » Sun Nov 06, 2011 7:01 am

I am no expert in antenna of course, but Linksys need not "fold" the antenna that way, they have plenty of space inside the router to have the long one, should they wanted to, the item is like that I guess by design rather than construction restriction, there must be some advantage for them to do it that way
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Re: Strange 2.4Ghz antenna

Postby Tranworld » Sun Nov 06, 2011 7:05 am

Actually I would have thought that a "sleeved 1/4 wave" would be cheaper to implement, if cost was the reason, at about the same performance of the external antennas supplier to most of these router and, without the necessary connector, would be even more efficient, so my guess is that this design is somehow more performant than the normal antenna, perhaps in terms of being omidirectional (more so that a rubber duck type
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Re: Strange 2.4Ghz antenna

Postby Tranworld » Sun Nov 06, 2011 7:57 am

What I am driving at is that ... may be it was designed to overcome the known shortcoming of the standard cheapie short stick antenna? We know that such antenna has a "doughnut" radiation pattern, thus radiation is weak at the tip and bottom, this antenna being horizontal MAY have a different radiation pattern that is more omni? Saying that it is a mess doesn't tell me too much, what kind of mess are we talking about?

What I was thinking is to fit this inside my 9X transmitter, some has resorted to fitting a stripped short antenna inside, what about this design? will it be better? The Futaba 6J has an internal PCB style antenna, I can't buy that antenna but has this in hand, does anyone has a view on that?
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Re: Strange 2.4Ghz antenna

Postby Shotglass » Sun Nov 06, 2011 4:44 pm

Tranworld wrote:there must be some advantage for them to do it that way


yes its a 3rd party supplied antenna that can be easily fixed into a chassis with 2 screws thats the main advantage there

Tranworld wrote:my guess is that this design is somehow more performant than the normal antenna, perhaps in terms of being omidirectional (more so that a rubber duck type


a monopole is perfectly omnidirectional

also once you put any antenna that close to a pcb you end up with a rather ugly farfield
the reason it works well is that with modern protocols the antennas hardly matter anymore

Tranworld wrote:What I am driving at is that ... may be it was designed to overcome the known shortcoming of the standard cheapie short stick antenna?


nah by the looks of it it was desinged to be small and easy to integrate

We know that such antenna has a "doughnut" radiation pattern, thus radiation is weak at the tip and bottom, this antenna being horizontal MAY have a different radiation pattern that is more omni?


again a monopole is perfectly omnidirectional

Saying that it is a mess doesn't tell me too much, what kind of mess are we talking about?


dunno i havent simulated it

What I was thinking is to fit this inside my 9X transmitter, some has resorted to fitting a stripped short antenna inside, what about this design? will it be better? The Futaba 6J has an internal PCB style antenna, I can't buy that antenna but has this in hand, does anyone has a view on that?


any antenna you fix within the clutter of pcbs metal strips and cables that is the inside of a transmitter will perform a lot worse
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Re: Strange 2.4Ghz antenna

Postby Tranworld » Mon Nov 07, 2011 1:13 am

yes its a 3rd party supplied antenna that can be easily fixed into a chassis with 2 screws thats the main advantage there


nah by the looks of it it was desinged to be small and easy to integrate


You seems to think that this design was meant to be easy and save cost, but I would have thought that if that was the sole objective this antenna in the attached photo should be simpler and even lest costly, not having to buy a patented design from Galtronics. Our stock antenna is nothing more than a length of coax with the tip stripped bare and a length of copper tube added on to form the sleeve dipole design, noone own the patent on that and it should be dirt cheap to produce, all they need to do is form a small hole/clip on the case to clip the tube on et voila, I am sure it is cheaper than this stamped piece of metal, in fact newer PCB now even have the antenna etched in. To me this is an expensive way to do it.

Antenna 003.jpg
Antenna 003.jpg (57.24 KiB) Viewed 3267 times


any antenna you fix within the clutter of pcbs metal strips and cables that is the inside of a transmitter will perform a lot worse


This person modded his TX with an internal PCB antenna from Futaba and found that he has better range!!

http://www.rcgroups.com/forums/showthread.php?t=1519967
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Re: Strange 2.4Ghz antenna

Postby Shotglass » Mon Nov 07, 2011 2:49 am

Tranworld wrote:in fact newer PCB now even have the antenna etched in. To me this is an expensive way to do it.


integrating the antenna on the pcb is by far the cheapest solution there is
look i design antennas for a living and there is no free lunch in antenna design and the sum of all evils is always constant
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