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GWISA
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Heads up on SR2 + power setting offset - Not as UBNT say?

Fri Jun 15, 2007 12:15 pm

Hi Guys,

Just thought I'd give a heads up on my recent discovery on a tower using SR2's.

Ubiquity networks say that the power setting in Mikrotik has an offset of 10dB's according to the data sheets on their website.

Faithfully following this, I set a tower's output to 13dBm, thinking I'd be running it at 200mW. We have been having a lot of problems with a particular brand of CPE, which uses (I think) Engenius components where they continually disassociate.

With a technician doing a site survey at a client, we found the following -
Tx power set at:

13dBm, client signal 15%
23dBm, client signal 30%
default, client signal 35%
MT v2.9.27

When I set it to default, the CPE's reassociating problem stopped.

The above results lead me to believe that the offset table is not correct - anybody else seen anything similar?
 
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GWISA-Kroonstad
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Re: Heads up on SR2 + power setting offset - Not as UBNT say?

Fri Jun 15, 2007 11:46 pm

Hi HQ.

Had the problem in Welkom today even on default setting. Though I noticed the number of enable/disable was much less.
 
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mkbatur
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Re: Heads up on SR2 + power setting offset - Not as UBNT say?

Sat Jun 16, 2007 12:16 am

I sent a lot of e-mail to Ubiquiti Support but no answer!.

I tested 2 mini-pci to same system:
RB133 + 18v 800mA

Oem Atheros AR5213 : -70
Oem Atheros AR5213 (TX 26dbi) : -62

SR2 (TX default) : - 74
SR2 (TX 26dbi) : - 71


I think Ubiquiti SR2 isn't a powerfull card.

Any opinion?
Last edited by mkbatur on Sat Jun 16, 2007 2:03 pm, edited 1 time in total.
 
0ldman
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Re: Heads up on SR2 + power setting offset - Not as UBNT say?

Sat Jun 16, 2007 6:35 am

I dunno. My SR9 shows roughly the same receive level if it automatically chooses 26dB or if I set it to 28dB.

Keep in mind, in the specs it lists +/- 1.5-2dB.

I am definately interested in this topic, not trying to rain on your parade, just listing my experience.
 
BurstNET

Re: Heads up on SR2 + power setting offset - Not as UBNT say?

Mon Jun 18, 2007 3:24 am

I tested two different XR5 cards recently with a power meter from Berkeley Varitronics, and and a 17db setting was only yielding like 22-23db power output. Setting it to 22db was required to get it to output 27-28db. Setting it to 28db or even slightly lower actually made the cards "click"...which was weird. Setting it to "default" power seemed to only output like 19db.


The whole offset is rather annoying, and hopefully Mikrotik can update the software to report the XR cards properly.

SMA
 
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Re: Heads up on SR2 + power setting offset - Not as UBNT say?

Sun Jul 01, 2007 7:51 pm

We have been struggling with several SR9 cards and have actually weeded out two completely defective ones. The other 5 SR9s including the good one of two just received from Ubiquiti all exhibit the SAME behavior in our test setup. We are using RB112’s with Router OS 2.9.44 (upgraded from 2.9.42 while testing), SR9’s and a Spectrum analyzer (hp8595e). The “default” settings for power delivers 17-19 dBm, way below the expected 28 dBm. Setting the power manually definitely allows the adjustment of the output power with something like 15dBm being the lowest setting that can be chosen and 28dBm being the highest. The actual measured output power does very, but within a range that peaks as the same 17-19dBm that the default setting gives. There does NOT seem to be any indication that the 12dBm offset is in play here at all ( http://www.ubnt.com/downloads/SRXR_power_offset.pdf ). It looks like MikroTik has adjusted their selectable range but maybe missed the actual values to send to the driver to select the proper power settings, or the 12 dBm offset magic thing is broke on ALL cards.

The interface was set as AP-Bridge during the testing which gave a reasonable looking trace on the analyzer, in station mode the spectrum trace looks strange. I am sure there is an explanation for that, I just don’t know what it is.
 
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Re: Heads up on SR2 + power setting offset - Not as UBNT say?

Mon Jul 02, 2007 2:09 am

When I test MT with SR9 and compare it to a Canopy 9000APC to SM Here is what I've found.

The Canopy gear puts out 26dBm

The MT with SR9 provides better NLOS penetration and signal levels using the default power setting which leads me to believe it is indeed achieving the high power output.

Every SR9 I have set the power manually on craps out after a very short time - first symptom is the signal gets crappy. Eventually they quit working altogether.

I believe your trouble is you've already ruined your cards. Buy new ones and test them side by side without ever manually setting the power and see what happens.
 
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Re: Heads up on SRx + power setting offset - Not as UBNT say?

Mon Jul 02, 2007 4:31 pm

Out of the bag not ONE of the SR9's I have has ever put out over 19dBm. Unless the default setting in Mikrotik blows up the card immediately I don't (hope) think that our attempting to figure out why we are having trouble is the cause of our trouble. We were having trouble with the cards before we started trying to figure out why. The two cards that were bad out of the bag were obviously defective, one puts out something way less than 18dBm and the other just makes noise over the entire spectrum. Every other card, plugged in, enabled, checked with default settings showed something in the 17-19dBm range. We then tried manual settings. It is interesting that the manual settings do control the output nicely, its just that the range of actual power out does not reflect the 12dBm offset that should be there. It is also interesting that the Mikrotik software does allow power settings upto 28dBm, which indicates to me that some attempt has been made to support this card specifically.
 
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Re: Heads up on SR2 + power setting offset - Not as UBNT say?

Mon Jul 02, 2007 6:59 pm

I think you guys should keep any discussion oft he power offset of the SR9 seperate, i really think its completly different as it has that special 2.4 to 900mhz converter so that may be throwing things off.

im pasting something i had posted in another thread reguarding the XR2....my tests indicate the same findings you guys have reguarding setting TX power to 20-22:
I have a install with alot of radios on each floor, on top of each other..all same antennas.

the point is, i can very easly see the TX power of a MT device, as seen by multipul other MT devices. at this install i mostly have nmp-8602s, some SR2s and 4 XR2's

I have found that setting the TX-power, to ALL rates fixed = 20 gives mes the most power and best RX from as seen by other MT devices (i see about a 6 RSSI signal gain)

from what ive read on the forums, this may mean im running the radio at 30db, or 1 W as the xr2 data sheets states the power offset is +10. How does MT OS affect this?

can you really run a 600mw radio at 1 W? why would ubuquiti allow this?

(also what about damage to the card, personally i dont think its an issue on these cards as they are indoors and have that very large heat-sink on them.)
 
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GWISA
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Re: Heads up on SR2 + power setting offset - Not as UBNT say?

Tue Jul 03, 2007 1:32 am

I believe your trouble is you've already ruined your cards. Buy new ones and test them side by side without ever manually setting the power and see what happens.
I don't think so, although I have had 2 SR5's dead out the bag. The ones in this thread I've only ever had set at default or 13dBm - the settings I described above were for a very short period but who knows - maybe that was long enough to kill them...
 
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airstream
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Re: Heads up on SR2 + power setting offset - Not as UBNT say?

Wed Jul 04, 2007 12:34 pm

My experience with SR2's is just a nightmare. In fact we are now arranging replacement of all our SR2's in service. Aside for the TX power settings being totally wacked, the performance of these cards has been a most trying ordeal. Lined up against senao 400mw B/G cards these are just expensive headaches.

We have never had any problems with our senao NMP-8602's 400mw cards, years of service with NO hiccups, yet the SR2's are always a pain.

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