Thinking of giving it another try - questions

In the very early days we purchased (4) B5c and (2) B5 units - back when the B5c’s were around $899 a piece - so we sunk a bit of money into them that’s never really paid off. At the moment all these units are collecting dust on the shelves because we could never get them to work well for us. Now before anyone goes down “this road”, we even had someone from Mimosa fly out to our location and see if they could help resolve things and it was a no go. It was the early days and our particular use case just wasn’t a good fit.

We’ve been holding on to the equipment always keeping in the back of our mind that we’d have a way to give things another short and we think we might have one.

We’re installing a 1 Gbps fiber connection and throwing up a roof top tower on a 2 story building in a small rural town and have a 3.8 mile (6.12 km) link to a remote tower site. The building and first 1/6 of the link is over a business/dense residential neighborhood wile the rest is essentially farmland.

We have not done a spectrum analysis of the area yet,however, our question is whether or not the B5 units we have should be expected to serve 1 Gbps over that distance in DFS (planning for lowest power spectrum)?

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I have a 1.7 mile link with two B5’s that is performing good now, after having two failed B5’s replaced under warranty. One B5 had one missing chain out of the box. The replacement worked OK for a day and then lost 3 chains.

The firmware that works best for me is version 1.4.1, since it gives me 3dB better signal to noise ratio. This indicates that I have 3dB higher power than later firmware. I have tested version 1.4.4 and 1.4.5 and ended up with lower signal to noise ratio and also strange ethernet speed negotiations.

Hope it works for you.

Good luck.

Okay - so our link is about twice the distance of yours - but what capacity are you getting and at what spectrum usage 2/40 Mhz or 1/80 Mhz, etc.

I am using 2 X 40 and you can see the result below. You would need 2 X 80 to reach close to 1 GB speed.
I have tried 2 X 80 with good results, but decided on 2 X 40 to leave spectrum for a backup link since the link need very high reliability, and 2 X 40 gives me sufficient performance.
Bottom is a speed test with 2 X 40, and speed is 630Mb in each direction.

I have NO experience with longer link, and 2 X 80 might work if there is clean spectrum.

One correction, this link is 1.5 miles.

I wish Mimosa would allow us to set power level in each end. The noise floor in one end is -90dBm and the other end -80dBm, so I have to select a power level to get a good signal to noise ratio in the -80dBm end. I could have used 8-10dB lower power to the opposite end and still get good signal to noise ratio.

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Thanks for the information - that’s a good link at the distance and makes me think that there is a reasonable chance that even at twice the distance with the spectrum and available power it could work.

Hi, The longest link we have is 9.8 km - 6.1 mile. The customer is using 400 mbps download on location and it works with no problem.

The link is working on capital of Turkey a crowded city.

The shortest link with Mimosa is about 1 km. In highest traffic we do see 850-900 mbps download on that link on ethernet side.

We have a 17 mile link, running 2-40 mhz channels. It gets about 400-600 Mbps download (doing 75/25 on it). I would think that if you did 2-80 mhz channels you could get that 1 Gig through it (in one direction)and about 200 Mbps the other direction.

Just remember to get the best modulation on it, you have to find the transmitter sweet spot, which is right around 16-18 DB TX power. You also need about 30 Db SNR (Signal over noise) to get 8x connections.

This means that you need to calculate your link with those figures in it, and make up the needed gain by going to the proper size dishes on both ends. Then you need to also check the “rain fade”, to see what you will lose during a rain event, and see if you need even larger dishes.

Biggest problem people have is that they use the smallest dish they can, and try to turn up the Transmit power to then make it work. It doesn’t work that way !

You can set power levels, unless you have selected “Auto” !


You can not set power level for each end on B5. The power level you set for the AP will set the Station to the same level.
In my case I could probably have lowered the Station end TX 8-10 dB and still get the same result.