Questions regarding antennas, gain and their connection with Wifi Bands.

[DatGameh]

When I was searching for antennas for my PC's Wifi unit, I thought it would be straight forward.
Find an SMP wifi antenna, buy it, and you're done.
But then, I discovered new terms about wifi antennas.

Due to this, I need to know some stuff about antennas and whatnot first:
(Note: I am using a dual band TP-Link PCI-E Wifi Adapter)

1. I can't seem to find an antenna that's designed for 5GHz; all I can find are 2.4GHz antennas. Will this make a difference?
2. My wifi adapater seems to have two antennas... Why? Is one antenna for 2.4GHz and one for 5GHz signals, or do both of them combine to form a 5GHz antenna?
3. Are dBi numbers only from the antennas? I don't want to get a 9dBi antenna, only to know that it's bottlenecked by my wifi module.
4. Will having a desktop antenna make a difference versus an antenna hooked directly on the module (especially with 5GHz signals)?

That's about all the questions I have for now.
You may answer it completely or give me a short answer; I'm fine with either (as long as I can learn from it, of course).
Hope these questions can be answered quickly!

 

[Unolocogringo]

1 most people use 2.4ghz for long range connections. 5ghz does not penetrate walls etc... as well 2.4 does. It is a fast short range connection.
2 both antennae are most likely2.4/5ghz combo antennae. 2 antennae is twice the signal sent and received. also look up "Beam Forming" where 2 or more antennae are used to focus the signal in a certain direction.
3 the antennae rating is for the antennae, not the combined antennae/radio amp rating. By US law you can go as high as 25dbi combined. About 1 1/2 mile range with good line if sight and directional antennae aiming on 2.4ghz. 5ghz will never reach this range..
4That really depends on router /computer location, but usually helps as it gets the antennae above the steel case for better reception.

 

[DatGameh]

1 most people use 2.4ghz for long range connections. 5ghz does not penetrate walls etc... as well 2.4 does. It is a fast short range connection.
2 both antennae are most likely2.4/5ghz combo antennae. 2 antennae is twice the signal sent and received. also look up "Beam Forming" where 2 or more antennae are used to focus the signal in a certain direction.
3 the antennae rating is for the antennae, not the combined antennae/radio amp rating. By US law you can go as high as 25dbi combined. About 1 1/2 mile range with good line if sight and directional antennae aiming on 2.4ghz. 5ghz will never reach this range..
4That really depends on router /computer location, but usually helps as it gets the antennae above the steel case for better reception.

Thank you for your reply. However, I have a question regarding your answer to my first question:

The description of antennas state that they have a "frequency range" (not including the router itself). For instance, drone antennas have a frequency range of 5.8GHz, walkie talkie antennas have a range of 144 to 430MHz, and standard Wifi antennas have a range of 2.4GHz.

My main problem is that there is no Wifi antenna that offers a "frequency range" of 5GHz.
Will that give me any issues?

 

[Unolocogringo]

What about something like this.
Dual 2.4 and 5 ghz 9dBi gain.
https://www.amazon.com/Super-Power-RT-AC66U-WZR-HP-G450H-Nighthawk/dp/B00DMJI9TA/ref=sr_1_4?ie=UTF8&qid=1522969862&sr=8-4&keywords=5+ghz+antenna

It is a set of 3 keep one as a spare.

 

[DatGameh]

What about something like this.
Dual 2.4 and 5 ghz 9dBi gain.
https://www.amazon.com/Super-Power-RT-AC66U-WZR-HP-G450H-Nighthawk/dp/B00DMJI9TA/ref=sr_1_4?ie=UTF8&qid=1522969862&sr=8-4&keywords=5+ghz+antenna

It is a set of 3 keep one as a spare.

Oh
So they do exist!
Thanks for the link and help, but I don't live in the US.

 

[Unolocogringo]

Lots of antennae and accessories exist.
If I knew where you shopped I could help look it up for you.
I have several homes networked with wired/wireless connections, the farthest being 300 yds/meters through the woods.

 

[bill001g]

Antenna design is a extremely complex topic. There are RF engineers who have made their whole career in the field.

The legal maximum you are allowed to have in most countries is 30db of signal. It varies a bit from country to country and to a point depends on the radio channel.

The optimum combination of radio amplifier db gain and antenna gain is 25db radios matched with 5db of antenna. You could in this case illegally replace the antenna with larger ones but it does not always directly scale. The main issue you have is you may get more total signal but you also may get more noised.

This is why it is foolish to think you can buy a illegal "signal amplifier/booster" from china that puts out more power. Microwave amplifiers are extremely expensive to build that can amplify just the signal and not the noise. They make them for the cell phone industry but you are not going to get them for $29.99.

In addition the use of mimo to transmit multiple overlapping signals make things like antenna spacing very important. This spacing is affect by the gain of the antenna. So changing the antenna might get you more output power but decrease the amount of data you can transmit because the mimo is not operating as effectively.

Most the problems today with wifi are that there is actually too much signal being sent. The interfering signal form all your neighbors tends to cause more issue than just a weak signal from your router. This is like people in apartments just turning up their stereo louder to cover their neighbor stereo.

Now directly to your question, the difference a omni direction antenna optimized for 2.4g compared to 5g is extremely small. If I remember right the length is less than 1/4 inch difference in length. It is so close that it makes little difference.

In the real world the antenna are only a tiny part. Thing like what your walls are made up have far more effect. Walls can easily absorb more signal than upgraded antenna can produce. Almost all testing data you see for wifi signals assumes a large open area which is seldom the real world case.