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Marco2G

External smartphone antenna

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Posted · Original PosterOP

Hi there!

 

Just watched this video:

 

It shows a few options about boosting signal transmission in a fixed area.

 

The video always alludes to an external antenna having better reception than an internal one.

 

So I've been googling and I came up short... so perhaps someone around here can tell me why people don't hack their smartphones and rig up an external antenna.

 

Wouldn't it be possible to glue a wire coil, much like for NFC, to the back of your case and solder the leads to the antenna connections inside the phone? If it's not that easy, could someone enlighten me as to why?

 

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5 hours ago, Marco2G said:

Wouldn't it be possible to glue a wire coil, much like for NFC, to the back of your case and solder the leads to the antenna connections inside the phone? If it's not that easy, could someone enlighten me as to why?

 

Attaching a "wire coil" seems to come from the naive idea most people hold that "the bigger the antenna, the better", which is simply not true. The antenna size needs to match the wavelength of the signal to be received (or 1/2, 1/4th, depending on the antenna design), which is why extending or shortening your FM radio's antenna depending on the channel you're listening too can help get better reception.

 

For the high frequencies for cell phone signals the wavelengths get shorter and with some tricks they manage to embed a pretty good antenna inside the device. You can bet the properly engineered antenna inside the phone will vastly outperform a "wire coil".

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Posted · Original PosterOP
12 hours ago, Unimportant said:

Attaching a "wire coil" seems to come from the naive idea most people hold that "the bigger the antenna, the better", which is simply not true. The antenna size needs to match the wavelength of the signal to be received (or 1/2, 1/4th, depending on the antenna design), which is why extending or shortening your FM radio's antenna depending on the channel you're listening too can help get better reception.

 

For the high frequencies for cell phone signals the wavelengths get shorter and with some tricks they manage to embed a pretty good antenna inside the device. You can bet the properly engineered antenna inside the phone will vastly outperform a "wire coil".

I am more considering the fact that the antenna would be outside the phone. At this point I expect we have antenna design down pat so where else does the variance in reception quality between different smartphones come from?

 

I mean there are variances between different models from the same vendor as well.

 

Not to mention I carry my credit card in the phone case and I have it in an aluminum sleeve... so I expect that might shield the phone a bit as well or at least create interference.

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Cell phones use something called a microstrip patch antenna.  Designing antennas is not as trivial as it seems.  To make an omnidirectional high gain antenna and make it efficient with high gain requires a pretty complex understanding of E&M and often some pretty exotic materials.  Also, anything you place around the antenna changes its response.  You can design something on paper that works well, but then you need a full computer simulation to estimate its response.  Even then, you may go build the thing and it still doesn't perform how you designed it.

As others have mentioned, a wire coil is a very poor antenna and the antenna in your phone is vastly superior.

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