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MA Ant 20 Dual Band Installation slots

SOLVED
Conversationalist

MA Ant 20 Dual Band Installation slots

Hi,

We have MR74 Access Points, which consists of 4 N-Type connectors 2 each for 2.4 GHz and 5 GHz. I am confused as to which slot should we install the antennae on; 

If need to install 2 Antennae on an AP, should we consider 2.4 slot or 5 Slot?

What if we install 4 Dual Band antennae on MR74 on every slot available? is there any harm?

 

Regards

Owais A. Khan 

1 ACCEPTED SOLUTION

Accepted Solutions
Meraki Employee

Re: MA Ant 20 Dual Band Installation slots

Correct, the MR74 has 2x5GHz band specific ports and 2x2.4GHz band specific ports.  The ANT-20 is a dual-band omni antenna, so they can and should be used on all 4 ports of the MR74.  Perhaps one exception is if you have the 2.4GHz radio turned off in the radio settings (you actually can turn off the 2.4 GHz radio by setting the Tx power to 0 dBm) and then you may not have any antennas physically connected to the 2.4GHz ports since the 2.4GHz radio would be off.  But generally speaking, you should always have a physical antenna connected, especially if you're running dual-band SSIDs.  

 

Theoretically, yes, there is possible harm to running "naked" antenna ports.  Whenever there's an impedance mismatch, there is a signal reflection, causing an energy loss, and in the world of RF, that energy loss is actually in the form of heat.  It deals with "match" meaning impedance match and gives rise to the term "thermal impedance", basically a measure of heat loss in degrees celsius per watt, so it's sort of an indicator of how much the equipment will heat up.


With no antenna, you've got an "infinite" resistance where it's expecting a 50-ohm terminator (the antenna).  So instead of a typical VSWR (Voltage Standing Wave Ratio) of maybe 1.2:1 or 1.3:1 (close to the theoretical perfect match of 1:1) you now have an infinite VSWR with no antenna, and a full strength signal reflection heading back towards the transmitter.  Such a high VSWR can damage RF equipment by (eventually) burning out the transmitter’s electronics, like output transistors. This is typically not a catastrophic failure all at once, but a cumulative one that can cause the equipment to fail prematurely.

 

Note that when you order ANT-20 there are 2 physical dual-band antennas in the box, they come in pairs.  So for any dual band AP like MR72/74/84 you would order 2 ANT-20 which would get you 2 pair, 4 physical antennas for the 4 physical ports.

Hope that helps!

 

View solution in original post

8 REPLIES 8
Meraki Employee

Re: MA Ant 20 Dual Band Installation slots

Correct, the MR74 has 2x5GHz band specific ports and 2x2.4GHz band specific ports.  The ANT-20 is a dual-band omni antenna, so they can and should be used on all 4 ports of the MR74.  Perhaps one exception is if you have the 2.4GHz radio turned off in the radio settings (you actually can turn off the 2.4 GHz radio by setting the Tx power to 0 dBm) and then you may not have any antennas physically connected to the 2.4GHz ports since the 2.4GHz radio would be off.  But generally speaking, you should always have a physical antenna connected, especially if you're running dual-band SSIDs.  

 

Theoretically, yes, there is possible harm to running "naked" antenna ports.  Whenever there's an impedance mismatch, there is a signal reflection, causing an energy loss, and in the world of RF, that energy loss is actually in the form of heat.  It deals with "match" meaning impedance match and gives rise to the term "thermal impedance", basically a measure of heat loss in degrees celsius per watt, so it's sort of an indicator of how much the equipment will heat up.


With no antenna, you've got an "infinite" resistance where it's expecting a 50-ohm terminator (the antenna).  So instead of a typical VSWR (Voltage Standing Wave Ratio) of maybe 1.2:1 or 1.3:1 (close to the theoretical perfect match of 1:1) you now have an infinite VSWR with no antenna, and a full strength signal reflection heading back towards the transmitter.  Such a high VSWR can damage RF equipment by (eventually) burning out the transmitter’s electronics, like output transistors. This is typically not a catastrophic failure all at once, but a cumulative one that can cause the equipment to fail prematurely.

 

Note that when you order ANT-20 there are 2 physical dual-band antennas in the box, they come in pairs.  So for any dual band AP like MR72/74/84 you would order 2 ANT-20 which would get you 2 pair, 4 physical antennas for the 4 physical ports.

Hope that helps!

 

View solution in original post

Highlighted
Conversationalist

Re: MA Ant 20 Dual Band Installation slots

Thats a great explanation.... cheers 🙂
Comes here often

Re: MA Ant 20 Dual Band Installation slots

hi,

what a about if i want to connect a single MA-ANT-27 to MR84, 1 just need a single Antenna for 5Ghz?,
Do i need a MA-ANt.20 antennas for the 2.4Ghz ports if they are off?

 

what happend if i want a 2.4 and 5Ghz , Do i need 2 Antennas MA-ANT-27 ?

 

 

Comes here often

Re: MA Ant 20 Dual Band Installation slots

hi,

what a about if i want to connect a single MA-ANT-27 to MR84, 1 just need a single Antenna for 5Ghz?,
Do i need a MA-ANt.20 antennas for the 2.4Ghz ports if they are off?

 

what happend if i want a 2.4 and 5Ghz , Do i need 2 Antennas MA-ANT-27 ?

Meraki Employee

Re: MA Ant 20 Dual Band Installation slots

Hi @lguerrero17 sorry for the delay.  The MR84 is a 4x4:4 AP and has a diplexer where 2.4Ghz and 5Ghz are mixed into each one of the 4 ports.  Each of the Meraki antennas like the ANT-27 you mention have 1 horizontal and 1 vertical plane.  For a 4 SS AP like the MR84, two Meraki antennas would be required and they would need to be angled to cover the same area.

 

It is not recommended to aim 2 ports of the MR84 in one direction and the other 2 ports in a different direction. This doesn't result in a hardware issue but would result in mis-advertising to clients that they would be able to use 4SS where there is very low chance they could actually do that, since only 2 may be aimed at it.

 

Either a 4 port Cisco antenna like the AIR-ANT2513P4M-N, or a pair of Meraki antennas (aimed in the same direction)  like ANT-27 would achieve the same thing for a MR84.  Both antennas would be radiating the mixed signal towards a client that is hearing beacons advertising the BSS is a 4SS capable AP.  And since each of the 4SS are radiated towards it, the client would be able to leverage 4SS.

 

 

So yes, even if this is 5GHz only, you need antennas connected to all 4 ports on the MR84.  If you are planning on using 2SS in one direction and 2SS in a different direction, the MR74 would be more ideal since there isn't a diplexer (2.4Ghz and 5Ghz are independent).

 

New here

Re: MA Ant 20 Dual Band Installation slots

Hello,

 

With an MR74, can you use two different types of antennas on the different frequencies?

 

For example, 2.4Ghz Sector and a 5Ghz Omni?

New here

Re: MA Ant 20 Dual Band Installation slots

are the band specific antenna ports on the 74 AP polarization specific?  one port for horizontal and one port for vertical polarization per band?

Head in the Cloud

Re: MA Ant 20 Dual Band Installation slots

Have a read of the MR74 setup guide - https://documentation.meraki.com/MR/Installation_Guides/MR74_Installation_Guide.

 

 The MR74 features band-specific antenna ports, and thus the corresponding band-tuned antennas should be paired with the AP. 

Eliot F | Simplifying IT with Cloud Solutions
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