B24 collocation with UBNT AF-24


#21

Considering most providers are probably using any new AF24 links primarily for distance, a B24c would be a great long term solution.


#22

I don’t think a B24c would be legal so easily. 24 GHz has funny rules. You need at least 33 dB gain to be legal (antenna performance), but the EIRP is limited to +33 dBm, so you’d need to certify that you were transmitting with <1mW if using a bigger dish. Yes there are 24 GHz radios sold that way, and the installer is responsible for lowering the power accordingly. But the B24 is aimed at a lower price point and easier installation.
It’s the AF24 that’s really the problem – it uses 100 MHz wide channels whether you need them or not. The B24 can go to a narrower channel, so multiple B24s can get along with each other, or get along with other narrow radios. Not every link needs that full gigabit! The point of 24 GHz is to escape the noise of 5 GHz without the extremely tight aim or rain sensitivity of 60 GHz.


#23

@Fred You bring up a good point. We designed the B24 to be a smaller, discrete radio to help solve the need for shorter links and be easy to install (mind you with a narrow beam width so aiming requires some care). The 24 GHz regulations limit EIRP to a 33 dB EIRP in the US so having a solution like a B24c makes it challenging to keep the product small and comply with regulatory requirements. The AF24 gets around this by having a larger receive dish - but introduces quite a bit of bulk and cost to the radio solution.
We are pretty excited with the potential opening up of the U-NII-5 band (5.925-6.425 GHz) for public use! [https://docs.fcc.gov/public/attachments/DOC-354364A1.pdf](http://FCC Draft NPRM for 6 GHz) as it gives us some expanded frequencies for longer distance links.


#24

Interesting point about U-NII-5 (and U-NII-7). You may want to be sure you join us in filing Comments on the NPRM. As it is written, we cannot use it: It limits all “client” power to +24 dBm EIRP. So PtP links, which have one client end, and WISP clusters, which need >+24, are not included. That may have been an oversight, since the FCC was addressing Wi-Fi foremost. But we need the +36 limit for coordinated devices to be applicable to clients as well as APs. It should allow “coordinated devices”, including all APs and coordinated clients, the same power. And the over-the-air DB query process used for TVWS could be applicable here too, to allow clients to get coordinated via the already-coordinated AP.