Does longer antenna improve wireless coverage?

[vrapp]

Did anybody try longer antennas on the router? such as those available on ebay , "3 7dBi 2.4GHz 5GHz Dual Band RP-SMA WiFi Antenna Linksys EA6900 ASUS RT-AC68U".

I remember experimenting with longer antennas in the past on other equipment, and I never noticed any difference. Did anybody try them and see improved coverage?

 

[wh7qq]

Did anybody try longer antennas on the router? such as those available on ebay , "3 7dBi 2.4GHz 5GHz Dual Band RP-SMA WiFi Antenna Linksys EA6900 ASUS RT-AC68U".

I remember experimenting with longer antennas in the past on other equipment, and I never noticed any difference. Did anybody try them and see improved coverage?

The problem with this is that longer antennas flatten out the donut shaped pattern of the stock antenna so that coverage in the vertical plane may be reduced, depending on orientation and placement. Depending on where your client devices are located, you may not be able to see a difference. If you were operating the router in an open field with no obstructions, you could probably see an increase in signal strength/range but in in a home with walls, ceilings, and furnishings, it is hard to predict or measure.

The best solution is an ethernet connection to a second router. WiFi is always going to be a second-best solution...it is just physics.

 

[System Error Message]

A longer antenna isnt necessarily better, it depends on the radio band. Better antennas are just constructed differently such as using better materials. The less energy that is lost in the antenna the better it is. An antenna with higher dBi setting is more sensitive. Other than that you can use directional antennas as well.

you can also use an amplifier if you dont mind lower speeds.

 

[TonyH]

A longer antenna isnt necessarily better, it depends on the radio band. Better antennas are just constructed differently such as using better materials. The less energy that is lost in the antenna the better it is. An antenna with higher dBi setting is more sensitive. Other than that you can use directional antennas as well.

you can also use an amplifier if you dont mind lower speeds.

Higher dBi means the antenna is directional

 

[System Error Message]

Not necessarily since using better materials would also mean a higher dBi

 

[TonyH]

Not necessarily since using better materials would also mean a higher dBi

Gain is measured by erp so material is out of the picture. Ever played with NEC antenna design
software(simple basic one of it's kind) My knowledge on antenna in general is from over 60 years
being an active ham(extra class) and professional career(AM broadcasting TX to m/w, sattelite work)

 

[jdabbs]

Gain is measured by erp so material is out of the picture. Ever played with NEC antenna design
software(simple basic one of it's kind) My knowledge on antenna in general is from over 60 years
being an active ham(extra class) and professional career(AM broadcasting TX to m/w, sattelite work)

The thing about ERP is this:
I take a pair of snips to a 5 dBi antenna and the end result is a .25 dBi antenna. RF folk generally know that passive gain isn't free. If an increase in passive gain comes at the expense of narrowed directionality, the implication is that decreased gain necessarily dictates an improvement in directionality. My pair of snips demonstrates otherwise--ERP is the benchmark, and a bad antenna is simply a bad antenna.

Does this mean we should all run out and gets Monster Cable™ omnis with a solid oak jacket (for a earthy and more robust radiation pattern)? Of course not. However, we should be aware that while there is a significant relationship between passive gain and directionality, there are other factors applicable that matter to overall efficiency (which ultimately determines ERP).

 

[dlandiss]

the implication is that decreased gain necessarily dictates an improvement in directionality.

Often antenna concepts can best be understood by comparing them to something more people are familiar with: light. Light is just shorter wavelengths of electromagnetic radiation, after all.

An antenna called "isotropic" is like a pinpoint-sized light bulb: it radiates equally in all directions. The unit "dBi" refers to decibels of gain compared to an isotropic antenna.

Now think of a flashlight. The same amount of power would now be focused into a narrower beam, and thus more light would reach a specific target at the expense of targets outside the beamwidth.

In many cases that is good -- it is why beam antennas can help me receive TV signals from 50 miles away, or a satellite dish can receive signals from a tiny transmitter 22,500 miles above me.

In other cases we may not want such a tightly focused beam, like trying to cover an entire house. Simple vertical antennas are good for this since their radiation pattern is like a donut laid down flat. You will get some signal one floor up and one floor down, but not as much as on the level where the antenna is located.

Every case is a tradeoff. The engineer has to choose more beamwidth or more gain. My 9dBi antennas were picked because I need more gain to get through a couple of brick walls into an outbuilding 50 feet from the router. It works -- the 2.4GHz signal inside that building is -50dB.

 

[Just Checking]

I do use longer antenna that are higher dBi (17dBi) for the 2.4GHz band. A longer antenna has the advantage in that it has a larger area to pick up the signal from the client devices. This resulted in higher uplink speeds as well as fewer dropped connections on the 2.4GHz band. I have one RT-AC66 router that has the antenna oriented at 0, 45, and 90 degrees. this covers multiple floors very good as well as compensating for rotational polarization of the signal.

Unfortunately, I have not found any equivalent antenna that attach to the router which have improved performance in the 5GHz band which provide significant improvement over the stock antenna. I have another RT-AC66 router with the stock antenna oriented in the 0, 45, and 90 degree positions that is dedicated to the 5GHz band wireless traffic.

 

[jdabbs]

Often antenna concepts can best be understood by comparing them to something more people are familiar with: light. Light is just shorter wavelengths of electromagnetic radiation, after all.

An antenna called "isotropic" is like a pinpoint-sized light bulb: it radiates equally in all directions. The unit "dBi" refers to decibels of gain compared to an isotropic antenna.

Now think of a flashlight. The same amount of power would now be focused into a narrower beam, and thus more light would reach a specific target at the expense of targets outside the beamwidth.

In many cases that is good -- it is why beam antennas can help me receive TV signals from 50 miles away, or a satellite dish can receive signals from a tiny transmitter 22,500 miles above me.

In other cases we may not want such a tightly focused beam, like trying to cover an entire house. Simple vertical antennas are good for this since their radiation pattern is like a donut laid down flat. You will get some signal one floor up and one floor down, but not as much as on the level where the antenna is located.

Every case is a tradeoff. The engineer has to choose more beamwidth or more gain. My 9dBi antennas were picked because I need more gain to get through a couple of brick walls into an outbuilding 50 feet from the router. It works -- the 2.4GHz signal inside that building is -50dB.

Lower passive gain does not necessarily translate into more beamwidth though--that's what people tend not to grasp.

 

[dlandiss]

Lower passive gain does not necessarily translate into more beamwidth though--that's what people tend not to grasp.

Well, the energy has to go somewhere. Unless there is a poor standing wave ratio and the reflected power is being re-absorbed by the transmitter, it is leaving the antenna. If it leaves in the same direction, the antenna has more gain. If it leaves in a different direction, it has more beamwidth.

The issue with small antennas is that they becomes closer to the theoretical isotropic antenna, so much of the power goes up or down into useless directions. The vertical antenna is useful for terrestrial applications because the energy spreads out horizontally and less is lost "straight up" -- which is why a standard dipole has about 2dBi gain.

 

[jdabbs]

Well, the energy has to go somewhere. Unless there is a poor standing wave ratio and the reflected power is being re-absorbed by the transmitter, it is leaving the antenna. If it leaves in the same direction, the antenna has more gain. If it leaves in a different direction, it has more beamwidth.

The issue with small antennas is that they becomes closer to the theoretical isotropic antenna, so much of the power goes up or down into useless directions. The vertical antenna is useful for terrestrial applications because the energy spreads out horizontally and less is lost "straight up" -- which is why a standard dipole has about 2dBi gain.

Right--compare a 5 dBi omni and a damaged 10 dBi omni that provides a gain of only 3 dBi. The assumption that higher gain = tighter beamwidth is a bit simplistic. You can't conjure up passive gain out of nothing, but you can certainly lose it without a corresponding benefit.

 

[dlandiss]

The damaged antenna still cannot violate the conservation of energy laws. Depending on the type of damage it either spreads the same power over a wider area, or if the damage caused a higher standing wave ratio it reflects the power back to the transmitter where it is absorbed and converted to heat.

Once the power is sent to the antenna it is either radiated or converted to heat. There won't be much heat loss in the antenna since it is made of very conductive materials, so that leaves radiation or reflection.

 

[TonyH]

The thing about ERP is this:
I take a pair of snips to a 5 dBi antenna and the end result is a .25 dBi antenna. RF folk generally know that passive gain isn't free. If an increase in passive gain comes at the expense of narrowed directionality, the implication is that decreased gain necessarily dictates an improvement in directionality. My pair of snips demonstrates otherwise--ERP is the benchmark, and a bad antenna is simply a bad antenna.

Does this mean we should all run out and gets Monster Cable™ omnis with a solid oak jacket (for a earthy and more robust radiation pattern)? Of course not. However, we should be aware that while there is a significant relationship between passive gain and directionality, there are other factors applicable that matter to overall efficiency (which ultimately determines ERP).

Your snip is detuning the antenna. Antenna radiator is infinite combination of C, L. R which
will be expressed as Z. Your snip just increased the value of C... When Z changes efficiency
goes down at the frequency presented(the design freq. like 2.4GHz) Ideal antenna on theory is C and L cancels each other and only R becomes pure radiating load which is Z of given antenna.
We can design antenna on a piece of paper and even can predict radiation pattern, angle in X, Y planes. and erp in free space. But this is only numbers on paper. In the field erp is measured, from there we can determine other things. We are just playing with phase angle between V, I. on the radiator, dBi is based on 1/4 wave vertical. dBd is half wave dipole. I notice some router antenna is vertical dipole element. Ideal antenna will radiate 1W when 1W of RF power is fed. In real world this is very rare. I very seldom see SWR of 1.0 on antennas 1.2 is very good.

Lower passive gain does not necessarily translate into more beamwidth though--that's what people tend not to grasp.

 

[TonyH]

Your snip is detuning the antenna. Antenna radiator is infinite combination of C, L. R which
will be expressed as Z. Your snip just increased the value of C... When Z changes efficiency
goes down at the frequency presented(the design freq. like 2.4GHz) Ideal antenna on theory is C and L cancels each other and only R becomes pure radiating load which is Z of given antenna.
We can design antenna on a piece of paper and even can predict radiation pattern, angle in X, Y planes. and erp in free space. But this is only numbers on paper. In the field erp is measured, from there we can determine other things. We are just playing with phase angle between V, I. on the radiator, dBi is based on 1/4 wave vertical. dBd is half wave dipole. I notice some router antenna is vertical dipole element. Ideal antenna will radiate 1W when 1W of RF power is fed. In real world this is very rare. I very seldom see SWR of 1.0 on antennas 1.2 is very good.

Just think doughnut and hot dog. It's elongated node is directional and more gain compared to doughnut omni directional pattern.

 

[TonyH]

Right--compare a 5 dBi omni and a damaged 10 dBi omni that provides a gain of only 3 dBi. The assumption that higher gain = tighter beamwidth is a bit simplistic. You can't conjure up passive gain out of nothing, but you can certainly lose it without a corresponding benefit.

Did you ever see omni-directional high gain antenna or vice versa? Give me an example. Again think doughnut and hot dog. Between simplest 1/4 wave vertical vs. 5/8 see the change in radiation pattern and Main node shape(the vector).