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Established Member
Posts: 2,052
Registered: ‎05-30-2012
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AF5 co-location same TX settings

I tried to configure both my AF5's in the chimney with same TX channel.

 

When I did that modulation dropped on both units and bandwidth for one of the units dropped 25 Mbit/s and other unit could only do 2x modulation :-(

 

Shouldn't it be possible ?

Actually what I don't get is that they can't see each other physical as they're located on different sides of the chimney.

 

When I remove same channel use for one of the units the other runs perfectly on that channel, so it looks like they're interfering with each other...

Regular Member
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Re: AF5 co-location same TX settings

You need to have them in Slave or Master modes.

Established Member
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Re: AF5 co-location same TX settings

Both in chimney are slaves.....

Member
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Re: AF5 co-location same TX settings

We have the same channel operating no issue. Thing is they need to be 90 deg off or more. Ours are 180 deg from each other pointing and both operating at 8x modulation with the exact same throughput as without colocation.

Make sure you're in full duplex mode as well, you can't do this in HDD it needs to have a separate TX and RX channel. What we do is designate an upload channels, and a download channel and colocate which has worked perfectly so far.

Also reducing ouput to 44 max will help with colocation and reduce bleed off.

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Re: AF5 co-location same TX settings


jim4394 wrote:

We have the same channel operating no issue. Thing is they need to be 90 deg off or more. Ours are 180 deg from each other pointing and both operating at 8x modulation with the exact same throughput as without colocation.

Make sure you're in full duplex mode as well, you can't do this in HDD it needs to have a separate TX and RX channel. What we do is designate an upload channels, and a download channel and colocate which has worked perfectly so far.

Also reducing ouput to 44 max will help with colocation and reduce bleed off.


I can't move them 90 deg off. I think they're probably 75 - 80 deg off.

I'm in FDD mode. I was configuring same TX channel and different RX channels.

I can only do 30 dBm at the moment. Looking forward to new Beta firmware that will allow 36 dBm on higher channels.

 

Member
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Re: AF5 co-location same TX settings

It sounds like they are hearing each other as noise because the azimuth angle is not great enough. Typically it needs to be more than 90 degrees to reuse the same channel, otherwise you cannot re-use the channel. It's just how the technology works. You will need to use different channels unfortunately for these 2 links.

We have 2 channels for TX and 2 channels for RX on our main tower so that we can make sure we are able to re-use channels on certain links, and have alternative frequencies for the angles that are too close to the other ones.

You'd need to enable GPS Sync at that angle, however I'm not sure how well that will work, we have never had good luck with GPS sync. You definitely will loose quite a bit of bandwidth with GPS from our experience.

Ubiquiti Employee
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Re: AF5 co-location same TX settings

It should work very well with GPS sync enabled and using the same TX frequencies at the colocated site.  There is no impact to bandwidth (other than needing to be operating in TDD mode) as a result of using GPS sync.

Gary

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Re: AF5 co-location same TX settings

[ Edited ]

@UBNT-Gary If I enable GPS I will still have the noise they hear each other with because of the angle ? So I will still have lower bandwidth (2x modulation on one device) than now, correct ?

Ubiquiti Employee
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Re: AF5 co-location same TX settings

Synchonization does two things; it very precisely aligns the master RF oscillator on the radio so it is absolutely locked to a common global reference so the transmit and receive carrier frequencies become very precisely regulated, and it causes the frame timing on the the co-located radios to become precisely time-aligned.  This means that all radios that are co-located with transmit at the same time and receive at the same time.  It will completely eliminate any residual interference due to the co-located radio.  It will not mitigate the effects of interference generated by remotely located third party devices unless they are also capable of being synchronized.

Gary

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Re: AF5 co-location same TX settings

@UBNT-Gary Thanks!

 

I will try again with GPS on :-)

SuperUser
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Re: AF5 co-location same TX settings


jjonsson wrote:

@UBNT-Gary Thanks!

 

I will try again with GPS on :-)


Don't forget to switch back to TDD mode also! =)

Tony Pierro
CTO - Wireless Internet Services, Inc.
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Re: AF5 co-location same TX settings

Please explain the difference of TDD and FDD to me as it relates to the af5 settings.  I think the GPS Sync option will help me in a couple of places in the network.

SuperUser
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Re: AF5 co-location same TX settings

Time division duplex, where the units are half duplex, but packets meet in the middle on the link. FDD is full duplex, where the Master TX transmits to the slave receiver on the opposing end, and the TX on the slave end transmits back to the receiver at the Master. Both modes are useful depending on your particular deployment. You cannot use GPS sync in FDD mode, but you can have opposing links transmitting at one location on the same frequency, and with enough isolation, receiving on the same channel (or close).
Tony Pierro
CTO - Wireless Internet Services, Inc.
New Member
Posts: 2
Registered: ‎02-10-2015

Re: AF5 co-location same TX settings

Thanks.
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