yandoo wrote

That's the firmware I have, Release 38185MAXtream: OffRegion: Test_ModeChannel: 1Width: 20/40mhzMode: B/G/N MixedMax TX Rate: 300MbpsTransmit Power: 27dbmDistance: 0.2km

TX/RX rates are dynamically negotiated between both devices. If the rate drops to 1 Mbps this means that the radio link is of a very bad quality. Much more significant then TX/RX rates are signal strength, noise strength, signal-to-noise ratio (SNR) and transmit CCQ shown on the status page of the CPE.

1 Mbps is probably negotiated b/c of fall-back to 802.11, a very ancient standard included in 802.11g.

First of all, set channel width to 20 MHz only. 20/40 MHz mixed mode means that the CPE tries to use up to 8 channels simultaneously - hopeless in today's 2.4 GHz band (except if you are living in the jungle or in outer space).

Next, set wireless mode to 802.11n only, if your router supports n mode. If not supported by your router, set it to 802.11g or 802.11b/g. If the radio link is bad (due to TX power of your router's antennas, which almost certainly don't match the characteristics of the CPE's directional antennas), then n mode will not work at all even if your router supports it. You can find out by setting a fixed mode as described.

BTW: 27 dBm with CPE's 9 dBi antennas gives you 36 dBm radiation power in total (that's 4 Watts or 4,000 mW). 4 Watts is o.k. for 10+ kilometers as long as regulatory authority of your country allows it at all, but over a distance of 250 meters it is like talking to a person standing beside you with a megaphone. Try to use 11 dBm TX power (yielding 100 mW) or 14 dBm (200 mW) and increase until you find best signal rate/noise strength/SNR. Note that exceeding the legal limit can get you into big trouble, not only of technical nature.

Also important: carefully align the directional antenna of the CPE to the antenna(s) of your router.

Compare signal rate/noise strength/SNR between each setting while you change them. This is how to calibrate your radio link by trial and error.

If you still can't get more than a few Mbps out of your link, you are probably living in a very dense populated area with some dozens of 2.4 GHz APs in your neighborhood. Then all bets are off: too much interferences. If there are not that much APs around, but still no improvement by above measures, consider use of a second CPE at your router's side for the radio link. It will greatly improve the quality of the radio link, but still all variations of settings described above will apply to such a setup, too.

Do your neighbors also use 4 watts TX power? :o Then that would pretty much explain casual drops back to 1 Mbps. :D

Try to find the most unused channel. Note that in n mode using OFDM modulation, the CPE will use 4 channels @20 MHz channel width, so be sure to set it to 4 channels apart of your neighbor's device if possible (e.g. on ch 1, 5, 9 or 13).

yandoo wrote

I've attached a screenshot from spectrum analysis but I don't know how to interpret the graphic.

It means that channel 5 (2432 MHz) is the best channel, while channels 9 to 13 are overcrowded or have interferences.