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Powerbeam M5-400 (AP) and Nanobeam M5.22 (station) works better at feedonly ante4nna mode

by on ‎03-20-2017 03:37 AM

Hi there AIRMAX gurus,

I was quite surprised and confused because I have these multiple PtP links using UBNT and it apparently proves that feed-only mode (antenna setting on each equipment) works better in throughput and Arimax capacity than setting those same equipment on their corresponding antenna dish specifications.

Please see attached.

When I set the Powerbeam to FEEDONLY,Airmax Quality reaches 48% and station(NBE M5-22)  bandwidth reaches 40.5Mbps/6.5Mbps at Antenna Specs , but when Station is set to FEEDONLY (transmitted power reaches 26dBm).AIRMAX quality increases and bandwidth is better.

This is just confusing, why feed-only performs better than the specified antenna.


Thank youAntenna Gain Feed-only NBE-M5-22.pngAntenna Gain PBE-M5-400.pngStation NBE-M5-23 Antenna Gain.pngStation NBE-M5-23 Antenna Gain-AP at Feedonlymode.pngStation NBE-M5-23 Feedonly.png

on ‎03-20-2017 04:07 AM

By selecting Feed Only when you're using the parabolic dish antenna, you're possibly allowing the radio to emit more power than is allowed for the band.


You need to be very careful about exceeding legal EIRP on your networks. You can be subject to heavy fines/equipment confiscation/incarceration, depending on your location.


Select the antenna model you're using, and the firmware will help keep you within legal requirements.

on ‎03-20-2017 04:20 AM

Hi Flipper,

Your advise is well taken. But it makes me wonder how UBNT allow this "feed-only" option when there's no other antenna choice except the specified on the model. Would it be illegal if its there on the "choices"?

Thank you.

‎03-20-2017 04:43 AM - edited ‎03-20-2017 04:45 AM

It's illegal if the choice you make doesn't fit your antenna use, and that choice allows your radio to exceed the EIRP limits for the band you're using.


It is possible to use the radios without the dishes; that's why the 'feed-only' choice is there. Check the Quick Start Guide for the feed-only graphic illustration.



on ‎03-22-2017 12:19 AM

Hi Flipper,

Thank you very much for the advise.Thats an additional information I gained from UBNT's product line.

However, theres something that bothers me. If setting the antenna setting to FEED ONLY mode, how come it can stil transmit as far as 6Km? If we refer on the AZIMUTHS and ELEVATIONS of the Powerbeams/Nanobeams  antenna radiation pattern,with reflector antennas,what then is the RADIATION pattern for this FEED ONLY mode? it looks like forming a back lobes.


Thank you.

on ‎03-22-2017 06:59 AM

It can transmit that far because you are still using the supplied reflector. You should only select the feed only mode if the reflector is not installed otherwise you are likely exceeding the EIRP limits. 


on ‎03-22-2017 09:18 AM

hi, i can suggest you try to test under weather bad! with you own layout!, i think everything will go bad!


very sorry!  for my little bit english!

on ‎03-25-2017 06:07 AM


As I understand it, you don't change anything in the antenna configuration with this "feed only" option, it is still the same antenna pointing "backwards" towards the dish so there is no "secondary" antenna for this use. The only thing the option does is that it tells the device that you are not using the reflector dish that focuses the radiated power to a small beam so the device is now ok to output more power becuse there is no "focusing" any longer.

Think of it as a 30W lightbulb, first woutout a magnifying glass ("feed only"), it can be light up with full power without anything catching fire but if you add the magnifying glass you have to control the power (that happens in standard mode, that is without "feed only" option set) way down to maybe 5W for the focused lightbeam not to do any harm (or in wifi terms, legal radiated power limits).


So you are simply outputing much much more then legal power by using this option and the dish at the same time!

on ‎03-25-2017 06:16 AM

Also this should not be in stories section, it is more a support question...

This topic might encurage others to enable feed only on their links Man Sad 


I also think ubnt should warn more about the feed only option when a user enables it. Maybe even remove the option if installer control option is not enabled since I don't think any users use this feed only installation type seriously, they but a standard AP for this purpose I hope.

on ‎04-06-2017 05:40 AM

hi, i can suggest you try to test under weather bad! with you own layout!, i think everything will go bad!


very sorry!  for my little bit english!


Hi SANENR, we are frequently visited by LPAs..so far, I cant see a major attentuation of signal, just minimal.