Mikrotik SXT 5HnD troughtput problem

RouterOS Wireless Networking
1

I reaaaly need your help!!
I have a problem with linking 2 mikrotik SXT 5HnD. The situation is the following:

I have to SXTs on 5,17km distance. I get a signal of -74. I did the math:

FSL (Free Space Lost) = -92.4 - 20logR - 20logF + antenna gain (16) + power (25dBm) = -63dBm

According to my calculations theoretically I can get to -63 signal. In practice I have really wide open space and no other antennas on 5Ghz. So I need some info how I can get better signal.

Does the SXT sends the signal on both polarizations by default?
Does the SXT (when I select automatically for TX power) will adjust it to 25 dBm?

How can I increase my signal. I think its my lack of experience with wireless mikrotiks that I cannot get a better signal. I am 98% sure that the Aligment is great, cause I’ve tried it so many times, with so many different vertical and horizontal aligments.

If some know, I would be very grateful

Thanks,

2

The SXT, working with both extension channels (40Mhz) and two chains on different polarities can be a little much to jump right into. If you haven’t seen it already, I would suggest checking out the tutorial on setting up SXT’s for a point to point link:
http://www.wispforum.net/entry.php?5-How-to-Connect-two-Mikrotik-SXT-5D-s-In-Bridge-Mode-Part-I

Some people (myself included) have had stability issues when enabling both extension channels and both chains. I highly recommend upgrading to RouterOS 5.4 before starting, as it seems to have cleared up several of these issues with the SXT.

A fair word of warning, if you set up the link using NV2, you will initially see a very poor reading for CCQ and data rate. The readings do not become accurate until you push some bandwidth over the connection for a bit.

If that doesn’t take care of it, post your signal strenghts and wireless config and we will see what else might be going on.

–@CC_DKP

3

2xSXT, 2km, -66, so your math is not good. Strange, another pair of SXT have -63 on the same link. With nv2 you loose some 3-4dbi, maybe more.

4

Your calculations are right, but you need to look at sxt datasheet and see what is the tx-power for mcs-15.

The max tx-power (25dB) is the aggregated power from the two tx-antennas for mcs0, so for your calc, you need to remove 3db from the tx-power.

From my calc, with distance of 5170m and 5,6Ghz you will have fsl=-121,7db.

16dB ant * 2 + (MCS15 20Mhz txpower 19dB -3db = 16db) = 48dB

48-121,7= -73,7db(+/-5,5db) for mcs15 20Mhz channel and -74.7(+/-5,5db) for mcs15 40Mhz channel
for mcs0 20Mhz you should have signal=-67,7 (+/- 5,5dB)

The 5,5db variation comes from the antenna precision (+/-2db per each, so it can vary 4db in your link), and it´s not shown on the data-sheet, but the max tx-power can be +/- 1,5db on standard products, and this one should be the same.

In mikrotik, please go to “/interface wireless wlan0 current tx-power” and see how much db you have for each modulation scheme.

Best regards,

5

Thanks for your time people.

I’ve tried to the lowest loss as I can and I did manage to have an -71 signal. Still it wasn’t enough for roughly 100Mbps TCP bandwidth. I manage to put around 45-55Mbps U+D through the link. Anyways, I will need another equipment I guess.

I was wondering for your practical works with Mikrotik SXT, what is the longest distance that you’ve achieved and how many Mbps have you put through that link?

Thank

6

Hi,

It´s an excellent signal for your distance.

How did you config your devices?

First upgrade your devices to V5.4
Then use this:
http://wiki.mikrotik.com/wiki/Transparently_Bridge_two_Networks_using_MPLS

Don’t forget to enable the two chains, and set band for 5Ghz-only-N.

And now enable NV2. You should see an big improvement on TCP bandwidth.

Best regards,