Difference in antenna dbi with picture

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Alienbliep

Occasional Visitor
Goodday,

I have two routers
The rt-n18u and rt-n66u
The rt-n18u is 2.4ghz only
Rt-n66u 2.4 and 5ghz

Both have different antenna so i opened both antennas.
Inside they are different to. Is this because of dbi? Or 2.4 vs 5ghz?
The lower is rt-n18u 2.4ghz, upper is rt-n66u
I know the rt-n18u has 5dbi antennas
Are the rt-n66u antennas 5dbi too?
 

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L&LD

Part of the Furniture
Different because of one radio band vs. two radio bands.
 

Alienbliep

Occasional Visitor
Ok. And is there a way to pinpoint the dbi of the dual band?
I use only 2.4ghz on the dual band router
I'm not sure the 2.4ghx are 5dbi either
 
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L&LD

Part of the Furniture
Find the spec sheets. A picture can't tell you how the RF chain was designed and what parts were used.
 

Alienbliep

Occasional Visitor
Ok i had another 2 antennas laying around.
In the picture:
The little one was being rated 2dbi. But its exactly the same dimensions in wire and shape as the 5dbi asus one.
Is asus right in saying theirs is 5dbi or is it more like 2-3.5dbi by the looks of it

The coil one was 5 dbi when i bought it.

Edit:
I found another website: https://skootsone.yolasite.com/wifi-ant.php
It says in the pictures everything with an coil is 5dbi. Without is more like 3dbi. So the asus cannot be 5dbi like they claim i guess.

From fcc i get
rt-n18u:
Antenna Gain
Antenna Gain: The maximum Gain measured in fully anechoic chamber is 2dBi or 1.58 in linear scale.

Trendnet tew-690ap 2dbi antenne
2.412 ~ 2.472 GHz
3 x 2dBi detachable antennas
 

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L&LD

Part of the Furniture
I'm probably wrong ('m not an RF engineer), but I don't believe that the antennae gain isn't dependent on the circuitry before it.

With more gain, you'll get more 'noise' too. A complete RF design will give you a working solution that balances all the aspects possible.

Putting together a Frankenstein router may seem to work in a particular environment, but that won't necessarily extrapolate to general and varied expectations of how the RF circuitry before the antennae will work (and for how long) in another environment either.

If you found the spec sheets for both routers, what info are you hoping to uncover now?
 

Alienbliep

Occasional Visitor
Well if asus is saying rt-n18u has 5dbi antennas like 20cm long. And inside there is a 5cm antenna that doesnt look like 5dbi. They are wrong. I'm exchange one accespoint with 2dbi antenna for the other with 2dbi antenna thinking it was the antennas that made the improvement. But they are the same inside
 

L&LD

Part of the Furniture
The whole RF chain, including the antennae, are what determine the specs. Not how long they are (and a further variable, depending on where you're measuring from).

Does it matter where the improvement came from? Asus, nor any other wireless router manufacturer, doesn't claim the antennae is the reason for the increased performance. Otherwise, we would all have CB-like antennae from the 70's that towered over our houses.

You are paying for their whole RF chain/design. And they are not (usually) interchangeable. :)
 

L&LD

Part of the Furniture
Not for me. Stock works best. And if it doesn't, then the model that was chosen was incorrect in the first place.

Unless you can decode and reverse engineer what Asus or any other manufacturer has done with their RF design and implementation (or you're just willing to randomly test various parts until one may work 'better'), then all you're doing is wasting or otherwise 'investing' your time for naught.

Better to use your time to test an RT-AC66U_B1 instead. A much better router with great quality improvements over the models you're indicating.
 

Alienbliep

Occasional Visitor
Yeah. I know. But im fiddeling with these to only get an stable 2.4ghz connection. The rt-n18u has an different problem with sending/loading websites and whatsapps. Thats another thread of mine

Im looking for an aged model router that has great range and not ac or turboqam. Looked at the r7000 but it also has ac. There is no device in my home capable of speeds above 144mbps. The problem is i dont know the range of the r7000 versus the rt-n66u in 2.4ghz.

The rt-n66u has slightly better range then the rt-n18u. I use the same antennas when i switch them for trail and error.
It also doesnt have my loading website/sending whatsapp time out issue.

The only reasons i dont like the rt-n66u because its old. Gets hot. Even in AP mode. Is older has an slower cpu, less flash memory and consumes more power then the rt-n18u.
 

KsWoodsMan

Regular Contributor
Ok i had another 2 antennas laying around.
In the picture:
The little one was being rated 2dbi. But its exactly the same dimensions in wire and shape as the 5dbi asus one.
Is asus right in saying theirs is 5dbi or is it more like 2-3.5dbi by the looks of it

The coil one was 5 dbi when i bought it.

Edit:
I found another website: https://skootsone.yolasite.com/wifi-ant.php
It says in the pictures everything with an coil is 5dbi. Without is more like 3dbi. So the asus cannot be 5dbi like they claim i guess.

From fcc i get
rt-n18u:
Antenna Gain
Antenna Gain: The maximum Gain measured in fully anechoic chamber is 2dBi or 1.58 in linear scale.

Trendnet tew-690ap 2dbi antenne
2.412 ~ 2.472 GHz
3 x 2dBi detachable antennas

In your original post the antenna pictured on the bottom is considered a 1/2 wave dipole for 2.4 GHz with a maximum theoretical gain of 3.1 dB over an isotropic radiator. Hence it is referred to as a 3dBi gain antenna.

The top antenna pictured is considered a co-linear antenna or phased array with a theoretical gain of approx 2.1 to 2.4 dB over a 1/2 wave dipole or 5.1 to 5.4 dB gain over an isotropic radiator.
At 5 GHz it will look like a 1-1/2 wavelength co-linear antenna with about another 2dB gain over a 1/2 wave co-linear.

In a large single level home or application the co-linear antenna should always provide better signal to line of site stations.
In a smaller multi level home the dipole will not provide as strong of signals at the furthest reaches but will do a little better on the adjacent floors.
It's radiation pattern in the e-plane is more donut shaped and not flattened from the effects of phasing the arrays in parallel in the same plane.
When you squish the radiation patter of the 1/2 wave dipole it becomes flatter and wider. There will be minor lobes in the e-plane also. But they are outside the scope of this explanation.

Higher gain antennas don't pick up more noise per-say. But they do pick up more distant stations that might be causing adjacent channel interference , or noise.

Amplifiers inherently add additional noise to both your transmitted signal as well as the received signal.
I'm less interested in transmitting WiFi to the sky or into my attic. Given the choice between the 2 antennas pictured I would opt for the dual band 5dBi antenna for an access point that was operating as a single 2.4 GHz or Dual band 2.4/5.1 GHz . Your mileage may vary.

This link might be a good primer for omni-directional antennas used for WiFi.
WiFi Projects
 
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KsWoodsMan

Regular Contributor
Amplifiers inherently add additional noise to both your transmitted signal as well as the received signal.
But not antennas. What an antenna with higher gain will do is increase the received signal of other stations at your site plus the transmitted ERP power from your site.

The gain in line of site distance also means lower radiated signal and receive strengths from stations at a higher elevation or on adjacent floors.

20 years ago I was making a 25 mile "hop" on 2.4 GHZ with 2 - 20 dBm cards. One was fed into a 12dBi gain Pacific Wireless 12-24 omni with 12° beam width and 7° downtilt at 140 feet above average terrain. The other into a 14dBi flat panel directional at 25 feet above local terrain.
They both had full line of site. Using 802.11b the ftp throughput was a reliable 5.5 Mbs.

The drawback to this setup was, I could connect with a handheld device 1/2 of a block to 2 miles away and a cpe device on my car dash with a 3dBi antenna from 10+ miles away, but could not provide service to the building I was in at the time.

When it comes to beam width vs gain, your location and application matters.
 
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Alienbliep

Occasional Visitor
So to sum things up

The Rt-n18u has 3dbi dipole (for patterns upwards. Donut shape) for 2.4ghz only. While asus says its 5dbi
The rt-n66u has co linear (for patterns at ground level?)
(antennas both routers situations 45-0-45 degree orientation)

Can you explain this senctence to me: The top antenna pictured is considered a co-linear antenna or phased array with a theoretical gain of approx 2.1 to 2.4 dB over a 1/2 wave dipole or 5.1 to 5.4 dB gain over an isotropic radiator. Is it 2.1/2.4 dbi dipole wise(2.4ghz) and 5.1 to 5.4 for 5ghz?

My home is 10Lengthx5Width meters. The access point is in the centre at ground level (just below ceiling)where the stairs go up. Attached beneath Stairs (only gap in the concrete floor to reach other levels)
The shed is in the garden at 10m range but there is heat reflective windows which blocks nearly everything. I have 35-52mbps in the shed. which is fine.
The attic is 2 stories up and with rt-n18u had 30mbps and with the rt-n66u was 54mbps. Now it is stuck at 5mbps :/ With the dipole antennas it has -87dbm with the co linnear it's -81dbm


The problem is the rt-n18u had good coverage and was stable at speed ans signal. But has an problem with phone loading times for website. I press enter and nothing happens. Can wait for 20seconds then the fetching of the website begins.
The rt-n66u is an solution to that but it has irratic 5-54mbps problem.

The other strange thing i notice. My trendnet tew-690ap i use for reference is 20/40mhz setup. The phone sees that as 40mhz. While the asus i can use 20-20/40 or force 40mhz but it still will only connect at 20mhz. (i really don't care for the 40mhz but it's just strange thing)
 
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Alienbliep

Occasional Visitor
I'm getting the imrpession the are both dipole only one for 2.4 and other for both bands
I think the rt-n66u in 2.4ghz only with 2.4ghz antennas work best. Since it doenst have ta lag issue also
I made an drawing if i understand it right?
Can someone confirm this.

Is the netgear r7000 really batter device? I saw an youtube video ac66u vs r7000 and the ping was already asus 33ms vs r7000 18ms and download 0.6 vs 27mbps
 

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KsWoodsMan

Regular Contributor
Can you explain this senctence to me:

The top antenna pictured is considered a co-linear antenna or phased array with a theoretical gain of approx 2.1 to 2.4 dB over a 1/2 wave dipole or 5.1 to 5.4 dB gain over an isotropic radiator.
I do not know how to explain this any differently than stated.

My understanding of the antenna for the RT-N66U, you have pictured, is that the 2 sections are radiating in phase with each other. Which narrows their beam width and increase their gain. It is the same length but not the same design as a dipole. The depiction of the radiation patterns , though not 100% correct, are a good depiction of the difference or of what to expect each of them to be.

The side lobes are not shown but this might be a better depiction of width vs gain in single antenna radiation patterns.

69081_HTB1tIhOIXXXXXcEXpXXq6xXFXXXt.jpg


The lag problem you are having with the time it takes for a page to start loading is probably Packet Loss. Even though you are connected at a faster rate it is trading off thyroughput with one AP versus reliability from the other. That wait time tells me the DNS lookup for the web site is failing at the faster connection speed. When the phone isn;'t getting a response to the lookup , it waits. When it waits long enough it times out and tries again. It might have to wait for it a few times before giving up, or finally getting a response. Do you want the pages to load faster once they finally start ? or would you rather they start loading immediately and finish before the other one gives a reply to the dns query ?

At your test location, if you are getting -81 dBm with the co-linear antennas and only -87 with the dipoles, the co-linear antennas are delivering 6 dBm better signal strength. That's what I would use.

I have no experience with the netgear router.
My download speeds usually match or slightly exceed what my provider advertises them to be. My ping times with my RT-N66U are in the range of 30ms to 40ms to most sites . Some may be slower due to network congestion and server load. So that measurement is relative.
To me, that I get pings or dns queries are answered immediately and not lose any is important. My router adds less than 1ms to the ping time when compared to a direct connection to the "modem".

The 2 bands are harmonically related . The 2.4 dipole will look like a center fed extended zep at 5GHz.
 

Alienbliep

Occasional Visitor
I want the pages to start loading immediately. That you see the bar moving. I can live whit slow internet. But with slow internet there is at least something happening.
Now nothing happens. Whatsapp message are probably 1kb size or whatever but they are being sent with an delay of 15seconds sometimes. And that's within 3meters of the router at 130mbps.

Could the channel be a problem? I was at channel 6 the whole time. That was the least populated in the shed. But in the house and the attic (where the ap is) i receive the neighbours channel 6 router.
In the attic: ping:17ms jitter:5ms download 23mbps upload 16mbps. This is at my phone. But when i run an continous ping test it fails bad. See attached picture
 

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KsWoodsMan

Regular Contributor
This seems to be morphing considerably from "The differences of these 2 antennas" to my DNS servers are not responding for 15 seconds.

If the link below doesn't help your DNS problem, open a new thread that might help you find better answers.

Homepage for GRC.com - DNS Benchmark Utility
 
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