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I have a GSM Modem that works on 2300MHz Frequency (LTE), but it could only receive 3 bar of signal strength. I plan to make a DIY directional antenna that is made specifically for this Frequency spectrum. From the online search, I found that people can make antenna either for 2.4GHz or 5GHz using the same material, same shape, but with a different measurement. So, my understanding is that we could make an antenna to work on a specific frequency by changing the measurement of the element. -- I am thinking about DIY bi-quad antenna --. Will it work?

Another thing that is kind of related to my question is that, This modem not only works on 2300MHz but also work on other frequency as well. Just like a cell phone. This modem, depending on what network carrier I use, also changed its frequency based on the frequency used by that mobile provider or carrier. Let say that 5 mobile network operator/Carrier in my country work on 850MHz, 900 MHz, 1800MHz, 1950MHz and 2300MHz. How the internal antenna work on all of those frequencies, are they using 5 different antennae inside of the device or they can use one antenna that works on all of that frequency spectrum?

By making one specific antenna for each one of those frequencies spectra will it improve the signal quality received by the modem?

I assume that the manufacturer of such device makes it able to receive so much different frequency is so that the device can be compatible with every mobile carrier, not necessarily because that the internal antenna inside the device is able to work on that wide range of the spectrum. I think by making a specific antenna for one specific frequency could improve the performance of the device.

Please do correct me if there are a lot of mistake in my way of thinking and my understanding of the matter. I just wanted to learn. :)

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  • $\begingroup$ Good question. One thing the current answer doesn't fully address is the second half: making one specific antenna for each frequency. Do you mean connecting several different antennas at the same time? That's almost worth a separate question, because in that case you have an antenna array and the antennas could end up ± interacting with "each other" (as their signals get combined) in potentially complicated ways (e.g. destructive interference at some frequencies, modified directionality than the antennas had individually…). $\endgroup$ – natevw - AF7TB Oct 24 '18 at 17:49
  • $\begingroup$ How is this question ("GSM Modem") related to Amateur Radio? Off topic? $\endgroup$ – Baruch Atta Oct 24 '18 at 19:41
  • $\begingroup$ @natevw by "making one antenna for specific frequency" is that I I wanted to make one antenna when I use a SIM card that is working on the specific frequency let say 2300 and make another antenna for say Network carrier that is working on the another frequency let's say 1800 and swap the antenna according to the operator or network carrier that I am currently using. $\endgroup$ – user3791830 Oct 26 '18 at 15:53
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It is possible that the antenna designed for 2.4-GHz will work well enough on 2.3-GHz because the difference in wavelength is only about 4%. But, to make it work better, increase every dimension of every antenna component by a factor of 2.4/2.3. That is, increase not only the lengths of the conductors, but also any spaces between conductors and, ideally, the thicknesses of the conductors themselves.

There may, indeed, be several different antennas inside your device. Depending on the relationships between the bands served, a single antenna may work on more than one band, reducing the number of antennas required to serve all of the carriers. Passive "matching" circuits may be inserted between an antenna and the active circuitry to improve system performance on a given band.

There are many antenna geometries whose performance is independent of frequency over a wide range. You can find an example that may fit your requirements at Kent Electronics.

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