Hi All,

I am considering purchasing some SXT-5Hnd to be used as CPEs. They will be used in 802.11a mode only, if that is possible. My main requirement is to be able to obtain a stable link by using the TDMA function, to avoid the hidden node problem. Are there dual polarity sectorial antennas with about 17DBi gain and 120 degrees beamwidth in both V and H plane, that has one N type female connector? THis would be ideal in my case since I already have veritically polarised CPEs connecting to the AP. The SXT would connect through the Horizontal portion of the Dual polarity antenna, if there is such a thing. If the is, pls advise manufacturer and model. TIA.

Hi All,

I am considering purchasing some SXT-5Hnd to be used as CPEs. They will be used in 802.11a mode only, if that is possible. My main requirement is to be able to obtain a stable link by using the TDMA function, to avoid the hidden node problem. Are there dual polarity sectorial antennas with about 17DBi gain and 120 degrees beamwidth in both V and H plane, that has one N type female connector? THis would be ideal in my case since I already have veritically polarised CPEs connecting to the AP. The SXT would connect through the Horizontal portion of the Dual polarity antenna, if there is such a thing. If the is, pls advise manufacturer and model. TIA.

Maybe try to use something like this:
http://www.cyberbajt.com/en/shop_item/3 ... b_box.html
or this:
http://www.cyberbajt.com/en/shop_item/3 ... v_box.html

You aren't going to find a dual polarity antenna with a single connector.

In addition to those recommended by czolo, ItElite makes dual polarity sectors with radio compartments. Ubiquiti makes dual polarity antennas, the radio is external and there are cases for RB411/711 that fit the Ubiquiti antennas.

Try also http://www.rfelements.com

You aren't going to find a dual polarity antenna with a single connector.

In addition to those recommended by czolo, ItElite makes dual polarity sectors with radio compartments. Ubiquiti makes dual polarity antennas, the radio is external and there are cases for RB411/711 that fit the Ubiquiti antennas.

Beware of the parameters from UBNT antenna specification. They gives values for beamwidth with -6dB. So comparing to other producers, they values are to high. 120 degree UBNT antenna is in the fact about 80-90 with -3dB loose.

Try also http://www.rfelements.com

Cross polarization parameter for MIMO 2x2 should be better than 24-25dB. In specification from RFelements site I found that their sector has only 22dB croospolarisation isolation. Anyone has used their antenna? Is it working OK?
I have many antennas from Cyberbajt in my network, so I'm sure that all will be working OK.

What Radio Card and Antenna are you using on the access point?

There are several Dual Polarity Sectors on the market that might meet your needs.

Assuming that the clients currently connected to the AP have adequate signals you should be able to replace your Single polarity antenna with a dual polarity and N Card (Like R52HN).

Depending on what card your replacing - you may see a drop in signals for your existing clients ( with only one chain - its 3db of loss). However - You'll have the added benefit of being able to use Both chains on the SXT and when time permits you can go change out those existing clients with SXT's or another Dual polarity antenna.

I've seen several setups in both 2.4 and 5 ghz where this has been done.

Oh - and NStreme and NV2 both resolve the "Hidden node" problem just in different ways.

If you have any additional questions don't hesitate to ask !

Hi All,

Thanks for all the responses. Really all I am hoping to do is to be able to use the SXT-5HND for the TDMA function. If that can be done in 802.11a mode, that would be okay for me.Where can I get detailed documentaion on the SXT? Can I get the TDMA with a single polarisation antenna? If so, what polarisation? I don't currently use/have any N card. TIA

TDMA in mikrotik world is the protocol NV2. It will work with nearly all routerboards models.
So you can't get TDMA using 802.11 or Nstreme protocols.
All you need is that the base station and clients must use mikrotik ROS.

TDMA of ubiquiti ap's/clients can't talk with mikrotik, is another protocol. (Really they did it before).

I operate a medium size ISP 100% mikrotik and I don't use NV2 at all cause it crashed all the times that i tried it. Randomly, a group of cpe's of a sector get freezed. No ping, no winbox, ... but they appear in registration list all the time. I didn't found the reason, not allways the same clients, different ROS, different routerboards and/or radios, ... Last try was with ROS v5.12.

I use only in a few point to point, and the ping is horrible, moving from 3ms to 25ms. With nstream in the same stations, ping is 0 or 1ms. But Nstream make a lot of interferences to my ap's 802.11, and nv2 don't do it.

So you are saying that if I have an AP running ROS and a SXT-5HND operating in 802.11a mode it won't work? Can someone pls clarify what exacly is needed to use TDMA/NV2. TIA

So you are saying that if I have an AP running ROS and a SXT-5HND operating in 802.11a mode it won't work? Can someone pls clarify what exacly is needed to use TDMA/NV2. TIA

If you set both to different protocols they cant talk to each other. Better set cpe to any so you can choose protocol at the ap and cpe follows.

I could be mistaken but as long as the other clients and access point are using wireless cards with Atheros Chip AR5212 or newer you can run NV2 on your AP.

All Mikrotik CPE's (SXTs, Sextant, Groove) support the NV2 Protocol.

Without getting too complicated - protocols like NV2 and NStreme operate "On Top Of" your the "Band" you choose (A,B,G,N)

When you setup your client you'll make two choices - You'll set the Band (5GHz-A, or if you're using and N card - 5GHz-A, A/N or only-N)...and then you'll choose the Wireless Protocol you want to use (802.11, NV2, or Nstreme).

The polarization of your antenna doesn't matter.

Hope that helps!

Thanks again for all the responses. One final question. In the normal mounting of the SXT, what is the polarisation of the antenna? Is the polarisation set by software, or you'd have to physically rotate the SXT 90 degrees. Pls advise.

Look at this post.

http://forum.mikrotik.com/viewtopic.php ... 62#p264462