Access Point 2800 antennas with single connection

[robinandjiang]

we purchased some AIR-CAP2802E-A-K9 APs to replace existing 2702E APs, we checked approved antennas with Access Points 2800 on Cisco website and found all the antennas are multiple connection (four cables), as we are using antenna cables (5 - 25 meters long) to extend the antennas, so we just need single connection of antennas, not sure if multiple connection antenna is compatible with single antenna cable (just need to use one connector, which cable can be connected?)
like AIR-ANT2451V-R, AIR-ANT2566D4M-R, AIR-ANT2566P4W-R

[Haydn Andrews · Accepted solution]

The 2802E has two separate antenna connection options - 4 x RP-TNC connections (same as the 2702E) and it also has the smart antenna connection which given the antenna models you listed this port wouldn't be compatible without the smart antenna to RP-TNC break out cable and unless your looking at dual 5GHz its not worth the added cost.
For the Antenna models you listed you can extend them (with a dB loss) using the Cisco low loss cable like the AIR-CAB005LL-R which is RP-TNC to RP-TNC more info on these cables here

https://www.cisco.com/c/en/us/products/collateral/wireless/aironet-antennas-accessories/product_data_sheet09186a008008883b.html 

So in a nut shell the same connections currently used for the 2702 will work with the 2802.

[Leo Laohoo]

Why would anyone still recommend 2800 when there are newer models (newer models mean longer support life)?

[Haydn Andrews]

He said he had already purchased the 2802. I am still installing them with customers who purchased bulk before the EOL was announced. That being said what i said about the cables and most of the antenna models he mentioned will come over to the 91xx APs as well. 

[JPavonM · Accepted solution]

@robinandjiang about your initial question if you can use single antenna connector to a MIMO antenna from an access point with four  dual-band connectors, the short question would be Yes you can.

All external antenna systems you've mentioned have individual antennas inside with its own radiation pattern so if you only connect one port because you don't want to spend more money in coxial extenders you can.

The only thing with that is that you will be missing the benefits of a multiple antenna system such as antenna diversity, beamforming, spatial multiplexing, so you will end up using a single antenna system, so lower MCS and throughput would be expected.

Important fact to remember is that if your AP is close to the floor where stations are you could be impacted by a hidden node problem.: as non-terminated antenna ports still transmit there is a chance that a station which is really close to the AP connects using that residual signal from the unconnected antenna ports, so you can end-up with collisions due to Hidden node.

So my recommendation is to move the APs close to the antennas to avoid using antenna exterders and improve signal (25m coax cable account for 5-7 dB loss so antenna gain is counterbalanced in this case), or buy antenna extension for all ports, or if none of the before is an option for you then buy additional coax 50ohm terminator caps.

HTH
-Jesus
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