Is dbm how you can tell the antennas strength on routers?

MacBH928

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May 17, 2008
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So I am searching to buy a new router, and thought maybe I benefit from a more "prosumer" device over the more archiac (and prone to failure) Netgear. I won't act like I do understand what dbm is but what I got is that the higher it is the wider the range is or stronger the signal.

I looked up Alien HD and the Ubiquity Dream Machine and they seem to have a dbm around 23-24, while the Netgear Orbi is at around 29-30 dbm. Does that mean the Orbi can reach further? I looked spec on my current Netgear R7000 and it seems like its 29dbm. I can't go any lower, its reaching all ends of the house and anything lower just won't cut it. So is the dbm reflective of the coverage range of a device?

I know some would suggest doing wired access points, but this is impossible in my current scenario.

Also, if anybody is in the know, the Dream Machine seems to have a limit of 300Mbps on the 2.4Ghz antenna. Is this right or am I missing something? sounds extremely low for a brand new $300 device.
 

mmomega

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Dec 30, 2009
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Wifi is measured in negative dbm.
0 dBm = 1 milliwatt
-10 dBm = 0.1 milliwatt
-20 dBm = 0.01 milliwatt

The more negative or higher - negative number, the less power is used to transmit signal.
So the Ubiquiti or the UDM, has more transmit power.

WiFi is a very, very complicated beast and there are many factors to be taken in that effect point A to point B.
Now I have not studied Ubiquiti's wifi tech inside out but many manufacturers use the same formulas. If you are seeing 300 Mbps on 2.4GHz, this most likely means there is 150 Mbps per stream on 2 streams equaling 300 Mbps. So to reach the maximum 300 Mbps, the receiving device will need 2 receiving antennas to match the 2 transmitting antennas.

Now let's get more complicated and say your wifi is using the 80MHz channel which can do gigabit wifi. So that would be broken down in to 4 channels.
2 x 150 Mbps 2.4 GHz streams
2 x 450 Mbps 5.0 GHz streams
for a 1.2 Gbps total

You would need a receiving device capable of receiving 4 streams simultaneously / or 4 receiving antennas.

Now you throw in a wall, bluetooth devices, neighboring wifi devices, cell phones, distance. Any little thing can and will negatively effect wifi.
So for me, I plan on worst case scenario when installing wifi equipment. Meaning, I will go out of my way to hardwire as many devices as possible and multiple access points. With a wire you have 3 failure points. It is either the port on either side or the cable.
There are few things more frustrating than wifi connectivity issues. So the moment you have the ability to remove that frustration, you do it.
 

MacBH928

macrumors 68040
Original poster
May 17, 2008
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Wifi is measured in negative dbm.
0 dBm = 1 milliwatt
-10 dBm = 0.1 milliwatt
-20 dBm = 0.01 milliwatt

The more negative or higher - negative number, the less power is used to transmit signal.
So the Ubiquiti or the UDM, has more transmit power.

WiFi is a very, very complicated beast and there are many factors to be taken in that effect point A to point B.
Now I have not studied Ubiquiti's wifi tech inside out but many manufacturers use the same formulas. If you are seeing 300 Mbps on 2.4GHz, this most likely means there is 150 Mbps per stream on 2 streams equaling 300 Mbps. So to reach the maximum 300 Mbps, the receiving device will need 2 receiving antennas to match the 2 transmitting antennas.

Now let's get more complicated and say your wifi is using the 80MHz channel which can do gigabit wifi. So that would be broken down in to 4 channels.
2 x 150 Mbps 2.4 GHz streams
2 x 450 Mbps 5.0 GHz streams
for a 1.2 Gbps total

You would need a receiving device capable of receiving 4 streams simultaneously / or 4 receiving antennas.

Now you throw in a wall, bluetooth devices, neighboring wifi devices, cell phones, distance. Any little thing can and will negatively effect wifi.
So for me, I plan on worst case scenario when installing wifi equipment. Meaning, I will go out of my way to hardwire as many devices as possible and multiple access points. With a wire you have 3 failure points. It is either the port on either side or the cable.
There are few things more frustrating than wifi connectivity issues. So the moment you have the ability to remove that frustration, you do it.
thanks for exlpaining, but the number on the Wifi router are not negative they are positive, it is stated as " 23dBm for 2.4Ghz and 30dBm for 5 Ghz" . Or do they not include the negative because Wifi is always measure in a negative form anyway?
 

hobowankenobi

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Aug 27, 2015
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on the land line mr. smith.
WiFi is very complicated.

Besides the excellent info posted above...you have to add in beam forming/steering, and signal reflecting and shadows which are unique to each environment, antenna design, size, etc. I would agree also: considering the amount of invisible variables, and the likelihood of both use requirements and noise/competition growing....never under buy wifi.
 

MacBH928

macrumors 68040
Original poster
May 17, 2008
3,676
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WiFi is very complicated.

Besides the excellent info posted above...you have to add in beam forming/steering, and signal reflecting and shadows which are unique to each environment, antenna design, size, etc. I would agree also: considering the amount of invisible variables, and the likelihood of both use requirements and noise/competition growing....never under buy wifi.
All I want to know is how can I tell if the router is going to give me enough coverage, it would be a really bad buy to buy a new Wifi6 router that you discover will not cover your house like your 2012 router.

Netgear uses sqft between models like enough for 2000sqft or 5000sqft but how can I compare against other manufacturers?
 

hobowankenobi

macrumors 65816
Aug 27, 2015
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on the land line mr. smith.
Well, Netgear is simply estimating averages for marketing purposes. Nobody can know because of all the things discussed above. Contruction materials of buildings, and random stuff like masonry walls, chimneys and plumbing can cause issues, including the floor plan affect range....especially with older designs and protocols. Thankfully, the most recent APs do a better job, negating environmental challenges much better than older APs could.

As a general rule, WiFi signal quality has improved fairy substantially in recent years. So newer designs are better than older ones by design. For that reason alone, I would be more skeptical of older, discounted wifi gear at blow out prices...unless I know the product.

The only way to really know if through actual testing. Folks that do actual tests like these guys that give you actual numbers of different models tested in a consistent manner. If you read through, you will see there are a lot of factors that count towards performance. Recommendations from end-users are too subjective; odds are most have not tested many APs; just offering their opinion on one they like (or don't).
 

MacBH928

macrumors 68040
Original poster
May 17, 2008
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Well, Netgear is simply estimating averages for marketing purposes. Nobody can know because of all the things discussed above. Contruction materials of buildings, and random stuff like masonry walls, chimneys and plumbing can cause issues, including the floor plan affect range....especially with older designs and protocols. Thankfully, the most recent APs do a better job, negating environmental challenges much better than older APs could.

As a general rule, WiFi signal quality has improved fairy substantially in recent years. So newer designs are better than older ones by design. For that reason alone, I would be more skeptical of older, discounted wifi gear at blow out prices...unless I know the product.

The only way to really know if through actual testing. Folks that do actual tests like these guys that give you actual numbers of different models tested in a consistent manner. If you read through, you will see there are a lot of factors that count towards performance. Recommendations from end-users are too subjective; odds are most have not tested many APs; just offering their opinion on one they like (or don't).
I used to try the Wirecutter but since New York Times bought them, I am more than skeptical. Their #1 choice is weird enough.
 

hobowankenobi

macrumors 65816
Aug 27, 2015
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on the land line mr. smith.
Nothing wrong with skepticism, nor disagreeing with their final choice. It weighs lots of things, including important parts of choosing a product well outside of measured performance (like features, warranty, and interface). We can still glean solid numbers to inform us while reaching a different choice.

For me, the biggest issue with any review (including WireCutter) is they typically test a small percentage of possible products. What to make of those choices not tested?

I for one am a big fan of Ubiquiti gear. Not tested. They don't make an all-in-one router, so I get how their products don't fit into this review...but still would like to see a side-by-side performance test vs. the wifi portion of the best consumer routers.

The point stands though...if you look at their testing criteria, you can see that it is not possible to simply say model A is better than model B, based on a single/simple spec....like signal strength or area of typical coverage.
 

556fmjoe

macrumors 68000
Apr 19, 2014
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There's some good info in this thread. But one thing to keep in mind that many review sites don't mention: wireless connections work both ways. Measuring dbm doesn't really tell you how good of a connection you will have because your end device has to be able to push data to your AP. It does you little good to buy a supermegapowered router/AP to blast through walls to your laptop if it can't "hear" your laptop's transmissions in response. Not to beat a dead horse, but this is one reason (among many) why serious network folks recommend multiple APs placed where you need them rather than a centrally located all-in-one wireless router.
 
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