Is there any technique in which I can send 433MHz and 915 MHz with the same antenna?

Thread Starter

ashokraj

Joined Feb 1, 2018
124
Hi,
I am using LORA. Is there any multiband antenna that can support these two frequencies?
or
I would need an antenna with the same footprint for 915MHz and 433MHz. Technically, as the frequency reduces antenna length increases. I am wondering with advancements in technology if at all there is some component that can solve my problem.
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Thanks,
Ashok
 

Ya’akov

Joined Jan 27, 2019
6,856
Dual, tri, and even quad band antennas are common. There are a number of design strategies depending on the form factor of the antenna. You can find a lot of information by searching for “dual band antenna design” and adding the bands of interest will help, though in those IoT focused bands you will find a lot of microstrip and PCB antennas e which may not be what you are in interested in.

Mobile ham radio operators have a special interest in multiband antennas and particularly common are 2m/70cm (144MHz/440Mhz) models. You might find information about practical construction from that source. The will be of the monopole variety.

As @dendad points out, you will need diplexer circuitry at the end of the feedline to connect the two transceivers. At the low powers used in those bands, it can be on the PCB. His suggestion of a discone, which is an inherently wideband design is certainly reasonable but for the likely application you have in mind some collinear design is more likely to be the best choice.

So, yes, dual band antennas are certainly possible, and are quite widely used. The exact physical realization depends on the type of antenna you need.
 

UweX

Joined Sep 2, 2020
24
I recommend to take a look at https://www.diamondantenna.net . As a ham I am using an antenna for 144/43/1200 MHz (2m/70cm/23cm). That are only the frequencies, where operation (SWR) is specified. I attached a transceiver also able to receive FM-radio and the signal from the antenna was strong enough to generate intermodulation in the handheld transceiver. So besides frequency of operation the aspect of size, ruggedness and withstanding outside weather conditions maybe more important. So I recommend to try out a ham-band antenna covering 70 cm ( exactly 433 MHz) and 23 cm ( 1.2 GHz, but not too far away from 915 MHz). I expect the transmitter you are using low power, so getting some reflection from the antenna at 915 MHz may not burn the output.

In case you need some directivity look at a logarithmic periodic antenna (LPA). These cover usually a broad frequency range. Here 433 MHz maybe a little bit too large for a PCB-style antenna, but there are also a lot of different construction advice around.
 

Tim-MK

Joined Oct 29, 2019
7
I am using LORA. Is there any multiband antenna… with the same footprint for 915MHz and 433MHz.
I would assume you are shipping to different countries and their unlicensed bands differ?
… might be facing the same dilemma myself in the near future…. As RF manufacturing depends on critical tuning to get optimum performance I would approach it by using similar modules targeting each countries RF band.
as a licensed Ham (some years ago now) the antenna tuning is foremost in achieving the range.
 
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