External Antenna for Cisco 881w Firewall

[heyring]

As you know, the 881w Firewall is also an access point. Most of the time, this is in a secure location which blocks the signal from this access point from being used as a significant part of the overall meetinghouse internet wireless coverage.

Cisco makes an external ceiling mounted antenna that comes with three 36" cables. This antenna can usually be mounted outside the secured area allowing the 881w's WiFi signal to be better utilized.

The link for the information about this antenna is below - and I will attempt to attach the data sheet to this post.

http://www.cisco.com/en/US/docs/wireless/antenna/installation/guide/ant2430v.html

ant2430v.pdf

(661.57 KiB) Downloaded 3041 times

[johnshaw]

Thanks for this... might be helpful for buildings that don't have a very convenient place to put the firewall. I've forwarded to my FMG so they have the information.

[john84601]

This looks like a nice solution. The only downfall is that CDW has it listed for $179. For another $100 you could get another 1041n instead If it were < $100 I would probably buy it...

[rknelson]

We have used 2 approaches: purchased the connectors and LM400 coax, or purchased pigtales pre-fabricated like this: ($45 for a set of three) http://www.ebay.com/itm/RP-TNC-female-P ... 4cf0b049d9. Both approaches have worked fine.

We have used them when the 881W was mounted in metal cabinets, and when they 881W is in a telcom room made from concrete block filled with rebar and concrete.

[Mikerowaved]

Just be careful of using too thin a coax for too long of a run. At 2.4 GHz it can really get lossy fast. For example, the above pigtail set from eBay is built with 5 Meters of LMR195, which equates to approx 3dB loss per cable. This means BOTH your outgoing Tx and incoming Rx power levels will be reduced by HALF just by traveling through the extra cable. It helps if you keep the runs as short as practical. If you need a run longer than about 3 feet, I would recommend switching to a coax with less loss, such as LMR400.

Another thing to consider is when using pigtails, the task of mounting the (now loose) antennas should be carefully planned out. The Cisco 881W firewall (like nearly all of their wireless routers) use the antennas in spatial diversity mode to greatly reduce multipath interference. Without getting into the physics, it simply means the firewall works best if the remote antennas are spaced about the same distance apart from each other as they would be if mounted on the back of the box. Depending on the remote location selected, this can be far from trivial to implement.

[moberle]

Typically it is the construction of the building (cinder block with steel reinforcement) that attenuates the signal so much.

Install the antenna in the attic maintenance spaces. Much less attentuation there.

-Mike O

[rolandc]

The antenna from the OP is regularly on ebay for ~30.00

[moberle]

I realize this is an old thread but thought it worth a bump. My current assignment has necessitates revisting this topic.

I am interested in the use of passive and powered antennae with the 881W. I am certain there is adequate information available for each but want to take this a step further. My employer specializes in application and network performance analysis. I intend to take a tour of all our ward facilities and profile the coverage, network behavior, and how well the Church provided media is working in our facilities.

-Mike O.

[russellhltn]

The older 881W had external antennas. I'm unaware of a powered option for them. The newer firewalls have internal antennas.

[Biggles]

The older 881W had external antennas. I'm unaware of a powered option for them. The newer firewalls have internal antennas.

In fact the latest version doesn't have wireless at all.