Hi, apparently my previous post (http://forum.mikrotik.com/viewtopic.php?f=7&t=98137) was a bit to extensive.

We suffer from a neighbor with high power antennas destroying our network in the 2,4GHz spectrum.

We asked the authorities to assist us in proving that they are sending way beyond legal boundaries. In Denmark, we are obliged to stay below 100mW transmitting power in the 2,4GHz band.

The signal from our "neighbor" is used by a WISP to provide 4-8km access to clients using Ubiquity equipment. My common sense tell me immediately that this is simply not possible in the 2,4GHz band as 100mW would not allow access beyond max a few hundred meters.

To complicate things, they try to hide the signal by using "in between channel frequencies" and by using non 802.11 protocols.

We discovered the interference immediately when the system was started, our upload went from fantastic to almost non-existent. We even got them to turn off the signal for a short period of time and this immediately solved the problem - until the system was powered on again.

Luckily for us, the Mikrotik Routerboards come with a nice build-in spectrum analyzer that helped us "see the noise" - thanks guys!

The antennas are located 500m away but still we see a -40 to -20 dBm signal using a MT SXT (500m away).

The "specialist" from the authority came with an expensive spectral analyzer and measured -62dBm in that distance and calculated that that was within legal boundaries.

We then asked him to measure on 2 of our MT Groove 2,4 GHz with a 6dB antenna attached and adjusted for this (TX power reduced as described in all MT documentation). He concluded that we could easily turn up the power as it was VERY low.

I then turned the power up to max and removed the damping for the 6dB antenna - in my calculations, this would give me a 1W x 6dB = 4W e.i.r.p.

He concluded that we were just below legal boundary and that we could send even stronger - at least double, maybe a bit more.

I know by experience that this would allow me access on a SXT from 4-6km distance with a fine bandwidth.

I do not know where to turn.

Either Mikrotik is "dead wrong" about the effect from the radio in the Groove (spec's state 1W - according to the "measurements" it should be more like 25mW at max power (I know this is not true) - or the way the authorities measure is simply wrong.

I am dealing with the highest authority in Denmark that is very close to "blue stamping" illegal use of the ISM band here with 10W effect and I am not "educated" enough in radio technology to point him to the documentation that proves that he is dead wrong. Anyone? Please? links to official documentation on how to measure the e.i.r.p correctly?

As I recall it, it should be measured as "radiated effect on a well defined surface in a very short distance" - But then again, I may be utterly wrong!

Even though it could seem attractive to be able to use the 2,4GHz for long distance links "legally", it would ruin the future for our net of 20 masts giving free access for more that 1.000 people on our camping site just to give access to a few customers on "the noise generator" - I dare not think of the consequences when this become commonly known. It would mean that anyone could set up 10W e.i.r.p transmitters in the ISM band "legally" all over the cities. This would potentially destroy any and all access to the 2,4GHz band in Denmark.

Also a solid investment in a lot of fine MT wireless equipment would be wasted. Masts are interconnected by 5GHz MIMO Sextants carrying 300/300mbps without problems and the site is fed with a 1/1Gbps fiber. However the "last meter" may only gain as low as 100kbps upload because of the intruder.

We need help to prove the "expert" wrong.

Thanks in advance.

/Nisse

You should try to put radios power to default, the competitor should "feel" that but because he is using Airmax, his radios will work better than yours if you use only 802.11.

BTW Groove have 500mw not 1W.

Also "being able to do long haul 2,4GHz with as little as 100mW - My experience say "no more than max 100m" - but then again - I may be wrong...", you are wrong indeed. Use an wireless link calculator and set a link between two AirGrid M2-HP-20 and you will see that you can make link at 20km.

With sector and Ag20, 10km is achievable (100mW)

http://www.mikrotik.com/test_link.php

Hi InoX,

Thank you very much for reply. I see that the device is "only" providing a max of 500mW TX power. With a 6dB omni antenna this should result in a radiated 2W transmission right? (assuming that 3dB = 2x power)?

I am well aware that links of several hundred kilometers have been testes to work. I myself have never achieved more than 70km in a test with parabolic antennas - the bandwidth measured there in 802.1b was a merely 1/1Mbps but still... it was possible back in the last millennium

I find it very difficult to read the "harmonized standard" - EN 300 328 V1.8.1 (http://www.ietf.org/mail-archive/web/6t ... acPkgu.pdf) related to "what is legal and what not.

I am not seeking for an answer on how to make long-distance high-performing links, nor point-to-multipoint connections but merely some arguments that this is not legal - according to Danish law (which follow the Harmonized European standards)

As I reed the regulation, a max of 20dBm e.i.r.p may be transmitted and in this value, the bandwidth of the signal should apply (5/10/20 or 40MHz) - I also read that this would be the result of transmitting 100mW without any antenna gain.

I do not know the spec's of the "intruders" panel antennas but looking at them, I would guess at least 20dB

Danish law state:

"Maximum allowable transmit power: 100 mW e.i.r.p. and 100 mW / 100 kHz e.i.r.p. density when using frequency hopping modulation, and 10 mW / MHz EIRP density when using other types of modulation"

If it is legal to transmit directional (or as here - limited radiated) with such effects that several kilometers may be accessed, how should we ever get access in the band?

Finally: You may be quite right that the Ubiquity net may be better than MT since they do not use the 802.11 standard, but how should I convince Apple and any other end-user equipment manufacturer that they should support AirMax or Nstream or similar ? We need the 2,4GHz for legacy access net to end-user equipment.

I really hope someone would help me clarify on how to interpret the standards and how to measure correctly.

Thanks in advance

/Nisse

Wi-Fi is not frequency hoping, so it other modulations.

10 mW / MHz EIRP density when using other types of modulation"

Formally it mean You can use 200 mW e.i.r.p. in 20 MHz band (10 * 20). But modulation go in play, because power not aways equally distributed by band, so really must set less power, depends on modulation.
Extension channel (40 MHz = 20 Mhz conrol channel + 20 MHz extension channel) not make additional limitation.
Because it simultaneous transmission on separate frequency band.
Antenna amplification count in e.i.r.p. calculation.
If legal e.i.r.p in 20 MHz band is 200 mW (23dBm) and antenna has 6 dBi amplification, transmitter must set to 23dBm - 6 = 17 dBm

If we look at narrow band 5/10 MHz, we get more spectral density. So in band 5 MHz - 50 mW (10 * 5) e.i.r.p allowed.

Also it depends on chip programming logic.
For example in 802.11n MIMO2x2 2 spatial streams, at least in Mikrotik we must set two times (3 dB) less power,
but for 802.11ac cards Spatial streams calculation do automatic in chip, as I know.

Hi InoX,

Thank you very much for reply. I see that the device is "only" providing a max of 500mW TX power. With a 6dB omni antenna this should result in a radiated 2W transmission right? (assuming that 3dB = 2x power)?

I am well aware that links of several hundred kilometers have been testes to work. I myself have never achieved more than 70km in a test with parabolic antennas - the bandwidth measured there in 802.1b was a merely 1/1Mbps but still... it was possible back in the last millennium

I find it very difficult to read the "harmonized standard" - EN 300 328 V1.8.1 (http://www.ietf.org/mail-archive/web/6t ... acPkgu.pdf) related to "what is legal and what not.

I am not seeking for an answer on how to make long-distance high-performing links, nor point-to-multipoint connections but merely some arguments that this is not legal - according to Danish law (which follow the Harmonized European standards)

As I reed the regulation, a max of 20dBm e.i.r.p may be transmitted and in this value, the bandwidth of the signal should apply (5/10/20 or 40MHz) - I also read that this would be the result of transmitting 100mW without any antenna gain.

I do not know the spec's of the "intruders" panel antennas but looking at them, I would guess at least 20dB

Danish law state:

"Maximum allowable transmit power: 100 mW e.i.r.p. and 100 mW / 100 kHz e.i.r.p. density when using frequency hopping modulation, and 10 mW / MHz EIRP density when using other types of modulation"

If it is legal to transmit directional (or as here - limited radiated) with such effects that several kilometers may be accessed, how should we ever get access in the band?

Finally: You may be quite right that the Ubiquity net may be better than MT since they do not use the 802.11 standard, but how should I convince Apple and any other end-user equipment manufacturer that they should support AirMax or Nstream or similar ? We need the 2,4GHz for legacy access net to end-user equipment.

I really hope someone would help me clarify on how to interpret the standards and how to measure correctly.

Thanks in advance

/Nisse

This is very interesting topic ?

(1) " The "specialist" from the authority came with an expensive spectral analyzer and measured -62dBm in that distance and calculated that that was within legal boundaries. " I can only only assume that the instrument used had its calibration certification in date + the antenna used to connect to the analyzer also had a its own calibration report with dbm correction values for "x to y frequencies on a attached log chart"

(2) 500mW into what RF Load ?, Is this the theoretical power achievable into an "Ideal RF Load"

(3) If the frequency used was presenting a higher than optimal SWR load to the groove, the EIRP is greatly reduced
( I remember some years ago having checked several frequencies on a 22KMs PTP which at the end resulted in a 7db increase in signal, above and below this frequency the signal was reduced),

You may not be getting 500mW from the Groove + add insertion loss + SWR and the frequency used the antenna may not be giving the 6db gain.......

(4) "the antennas are located 500m away but still we see a -40 to -20 dBm signal using a MT SXT (500m away)."
Is this your signal or the nearby signal , or before / after you removed the 6db damping ?