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SXT signal level disproportion

Thu Jul 11, 2013 1:37 pm

Hello to guys, just want you to know, as I am not waiting any reasonable reply from MT, but good to know, there is some bug about SXTG 2HnD showing up too high level of signal on receiver..

Physics says, If I have 2 antennas each against other with gain of 10dBi, and i am putting those on distance of 1 m, I cant have signal level +20dBm on receiver !!! Watch out, diagnostics give false data. You need to deduct at least -40dB to get approximate correct level..

So be carefull. If I am wrong and SXTG is able to do 65dBm IRP with set 25dBm Pout on it (not really not - we measured it by P meter, the wrong is P Detector calibration on RX). The good news is, that consumption then is 5 Watts and it emmits 2500W ERP, watch out for burns. Anyway 125dB dynamics of RX detector is breathaking as well :lol:
SXTG bulshit.bmp.jpg
trasa.jpg
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normis
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Re: SXT signal level disproportion

Thu Jul 11, 2013 1:59 pm

Please put them further away. Screaming in your ear is not a good way to measure hearing :)
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Re: SXT signal level disproportion

Thu Jul 11, 2013 2:23 pm

Please put them further away. Screaming in your ear is not a good way to measure hearing :)

What you mean Normis, I do RF development too long to know what I am doing.. Physics is Physics, you cant cheat it.
I made same test using cables with attenuators on it, and your detectors are simply calibrated wrong, believe me or not. If calibrated Power meter from HP thru 10dB divertor says with peak detector -50dBm, your box says -20dBm, i can give it how far i want, but it will not help, because the link disconnects on -60dBm signal already..
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Re: SXT signal level disproportion

Thu Jul 11, 2013 3:22 pm

1. The refrigerator is in the way and affects your measurements, there are reflections and other problems in your test
2. RouterOS RX level is only informative, it is not a measuring device, the value is very approximate
3. What are you measuring with your HP device? If you don't use an identical antenna, comparison is not possible
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Re: SXT signal level disproportion

Thu Jul 11, 2013 3:35 pm

Just put them at least 10m apart 50 cm away from any reflective surfaces, ground both antenas
, set tx-power all-rates-fixed to 3 or 5dbm and check again.

I'm not a fan of method - "lets test it the wrong way to see that it gives correct wrong result"
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Re: SXT signal level disproportion

Thu Jul 11, 2013 4:48 pm

1. The refrigerator is in the way and affects your measurements, there are reflections and other problems in your test
2. RouterOS RX level is only informative, it is not a measuring device, the value is very approximate
3. What are you measuring with your HP device? If you don't use an identical antenna, comparison is not possible
I think, you pointed next achievement of SXT - the first now produced radio from MikroTik with intolerance larger then 5dB. RB951G approximity +-2dB,711,751G approximity +-2db, SXT +-40dB - you mean that?

By HP I am measuring REAL value of signal level... Excluding antenna, connected directly to uFl connector attachedto your PCB.. I am saying you there is a bug in it - serious bug, watch out..
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Re: SXT signal level disproportion

Thu Jul 11, 2013 4:54 pm

Just put them at least 10m apart 50 cm away from any reflective surfaces, ground both antenas
, set tx-power all-rates-fixed to 3 or 5dbm and check again.

I'm not a fan of method - "lets test it the wrong way to see that it gives correct wrong result"
:lol: MIMO OFDM right?

I had it on 5 dBm dont worry, I am not wondering if it bugs or not, it is statement of fact. I will post you, how do I measure, the photo I posted is just picture with complete antennas to exclude or refurbishment mistake.. Those are brand new from box having the same misconduct as the others and I really do not need to make reflection less line to see, that 40dbs are just crap of calibration. We overhaul yearly over 1000pcs of MTs, so that I am pretty sure, what I am saying.. We use it to make 9GHz radio relays based on MikroTik :?
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Re: SXT signal level disproportion

Thu Jul 11, 2013 5:16 pm

Here is measuring eq. The two antennas on fridge 1 m. away each other is just wery simple very no specified line, where +10db are ok.. but +- 40dB is really slur.

Bratva, my ne chrenovie wifiki s dermom na shtanah pover me! Znaiu chto govoriu. Figovoe delo ot MT etot raz, ne chasto bivaet, no tak i est
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Re: SXT signal level disproportion

Thu Jul 11, 2013 6:22 pm

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Re: SXT signal level disproportion

Thu Jul 11, 2013 9:08 pm

Who cares about indoor tests with outdoor products anyway...
 
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Re: SXT signal level disproportion

Thu Jul 11, 2013 10:32 pm


Vážený pane Peterko,
myslím, že právě vzhledem k vašich znalostem a zkušenostem jistě víte, že Mikrotik není jediný spoj, který se podobně chová. Před mnoha a mnoha lety jsme používali SVMka a chovali se stejně signál při ladění klesal z cca 2V na asi 0,68 a pak lup a skočilo tam 0,16-0,19V. Prostě to bude jen chyba. Zjevně výrobce nepočítá s tím, že by někdo chtěl přenášet data na 50cm nebo 4metry. Víme o tom, že pod -50dB přijímaného signálu už jednak spoj ukazuje občas (většinou) hlouposti a pak také začíná zhoršovat přenosové parametry. Proto když na vzdálenost 1-2km chceme dosáhnout dobrého spojení, použijeme J&J paraboly s límcem a High power karty, ale utlumíme výstupní výkon z karty tak aby signál dopadající na druhou stranu nebyl silnější než -50dB ideálně -52 až -55dB. Výhodou tohoto řešení je dobré odstínění antén, nízký výstupní výkon z karty a především se tím eliminuje přepínání modulací, protože pokud omezím kartu na třeba 2dB tak vysílá 2dB při 1Mbitu i při 150Mbitech (modulace). Při výchozím nastavení výrobce při vyšší modulaci klesá výkon a tak často karta přepíná sem tam a zde vždy nastává rozkolísání prodlevy či v krajním případě ztráta paketu.


English:
For realistic measurement try to achieve -50dB signals or lower by lowering output power on transmiting side. Looks like software is showing wrong numbers Over this power. We see less speed on stronger signals than -50dB on receiver.
 
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Re: SXT signal level disproportion

Thu Jul 11, 2013 10:59 pm


Vážený pane Peterko,
myslím, že právě vzhledem k vašich znalostem a zkušenostem jistě víte, že Mikrotik není jediný spoj, který se podobně chová. Před mnoha a mnoha lety jsme používali SVMka a chovali se stejně signál při ladění klesal z cca 2V na asi 0,68 a pak lup a skočilo tam 0,16-0,19V. Prostě to bude jen chyba. Zjevně výrobce nepočítá s tím, že by někdo chtěl přenášet data na 50cm nebo 4metry. Víme o tom, že pod -50dB přijímaného signálu už jednak spoj ukazuje občas (většinou) hlouposti a pak také začíná zhoršovat přenosové parametry. Proto když na vzdálenost 1-2km chceme dosáhnout dobrého spojení, použijeme J&J paraboly s límcem a High power karty, ale utlumíme výstupní výkon z karty tak aby signál dopadající na druhou stranu nebyl silnější než -50dB ideálně -52 až -55dB. Výhodou tohoto řešení je dobré odstínění antén, nízký výstupní výkon z karty a především se tím eliminuje přepínání modulací, protože pokud omezím kartu na třeba 2dB tak vysílá 2dB při 1Mbitu i při 150Mbitech (modulace). Při výchozím nastavení výrobce při vyšší modulaci klesá výkon a tak často karta přepíná sem tam a zde vždy nastává rozkolísání prodlevy či v krajním případě ztráta paketu.


English:
For realistic measurement try to achieve -50dB signals or lower by lowering output power on transmiting side. Looks like software is showing wrong numbers Over this power. We see less speed on stronger signals than -50dB on receiver.
Vážený pane Karlosi jste mimo mísu..

Sorry you missed the issue.. Unfortunately system says it has -40, but the real value is by this one -60dBm.. You can see full quality, so that is it. Not you casse. Thats what i am talking about..
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karlos
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Re: SXT signal level disproportion

Fri Jul 12, 2013 10:28 pm

Sorry you missed the issue.. Unfortunately system says it has -40, but the real value is by this one -60dBm.. You can see full quality, so that is it. Not you casse. Thats what i am talking about..
Ok, my calculated values are neraly the same what i see in real usage (not on table). I dont have an problems wtih signal strength. Just the real usable bandwith is much lower then numbers shown in Btest.

So its no HiFi ist just WiFi, (joke) and proffesional equipment costs more but does right what you want.

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