Can I use a 2.4 GHz rated parabolic MIMO antenna for 700 MHz Verizon 4G LTE data?

Question

Can I use a 2.4 GHz rated parabolic MIMO antenna for 700 MHz Verizon 4G LTE data?

It seems 700 MHz are a long ways from the range of a 2.4 GHz antenna, but I have seen people marketing similar looking parabolic antennas that claim they are wide spectrum and go down to 600 Mhz and up to 5GHz... I'm just not sure at what attenuation though?

Will the same Verizon tower switch me from 700 MHz to one of their higher frequencies with better reception?

Verizon Wireless appears to utilize multiple 4G LTE frequencies like 2.1 GHz, 1.9 GHz, 1.7 GHz, 850 MHz, and 700 MHz. I don't know if they would they would responsively switch me from 700 MHz to a higher frequency if my signal improves though as some people report??? This would be important if I need an antenna that capable of working from 700 MHz to 2.1 GHz.

How I know the band I'm using: I used my iPhone to figure out I'm using band 13 for communication with my local Verizon tower, which is 700 Mhz by following these direction. I have LTE data miles away from the tower but it's not a good connection so I'm looking to get a highly directional antenna for my JetPack 7730L.

Specific use case

Here's the 900mm-wide (about 3 feet) parabolic antenna I'm looking at so you can have a specific example to pick on.

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Added 2020-01-28: I did my own test to see if Verizon switches bands based on signal quality. You can see the video here.

Answer 1

Can I use a 2.4 GHz rated parabolic MIMO antenna for 700 MHz Verizon 4G LTE data?

The gain of an antenna, that is, how much it focuses in one direction, is pretty much proportional to its size divided by the wavelength.

Generally, antennas don't work (well) for frequencies they're not designed for, but you can consider a parabolic dish more of a reflector than an actual antenna – the feed (which is mounted in the focal point) is what actually converts the electromagnetic wave from free space to a coax waveguide (or vice versa).

So, replace the feed with something that works for 700 MHz and you got a directive antenna that's roughly only 700/2400 = 7/24 ~= 1/3 as directive as it would've been for a signal at 2.4 GHz.

Now comes the problem: you don't seem to have such a feed (and you're right, you need a multi-band antenna as feed).

In this situation, you'd just buy a cellular-optimized multi-band antenna that has some gain in itself: it typically will have less gain than what you'd get from a well-matched dish, but considering this is all a bit impossible to calibrate and do right, it'll probably work much better than trying to attach a low-gain multi-band feed to your dish.

Generally, what you want to do is quite possible illegal: in many legislations the power times the gain is limited, and if your phone is legal with the little gain its antenna has, it's probably illegal with the gain of a highly directive antenna.

Will the same Verizon tower switch me from 700 MHz to one of their higher frequencies with better reception?

Only the base station configuration of Verizon's cellular infrastructure can answer that. But, generally, the lower the frequency, the better your reception is over a long-distance link: so, 700 MHz is pretty much the best you can get.

"as some people report": Um. "some people" are a terrible source.

Answer 2

The gain and directivity of a parabolic dish is inversely related to the wavelength of the signal and directly related to the size (diameter) of the dish. The wavelength at 700 MHz is approximately 3.5 times greater than 2.4 GHz. Hence keeping the dish size constant and lowering the frequency (increasing the wavelength) by 3.5 will result in a drop in gain and directivity (that is, the beamwidth increases.)

There are formulas for computing the gain of a parabolic dish as a function of it's size and the operating frequency out there on-line. Here's one I've used:

GAIN \$=10\log[0.5(\frac{\pi D}\lambda)^2]\$

Answer 3

I am going to simplify this for you. No, you cannot use the 2.4 GHz antenna for 700 MHz. The parabolic part of the antenna may still provide a little bit of gain, but it won't work nearly as well as it did at 2.4 GHz. More importantly, the antenna is probably not passive. I base this on the fact that the band specified is very narrow if it were a purely passive antenna. There is (or may be) a low-noise amplifier (LNA) at the focus of the reflector that won't work at 700 MHz. Even if there is not an amplifier, there is no guarantee that the radiating structure at the focus will perform well at 700 MHz.