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jober
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60GHz proximity and colocation

Sat Jan 05, 2019 12:15 am

Can you'll share your experiences with co locating multiple 60GHz MT radios and what the minimum proximity would be in the same direction or in a back to back mounting on the same pole?
I would like to mount four dishes on the same pole in a north, south, east and west setup. They would all be on different channels but it would be nice to do an ABAB setup would work.
 
mistry7
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Re: 60GHz proximity and colocation

Sat Jan 05, 2019 1:56 am

If you are able to do a metal shield on the back of the dish, you would not see any
Interfering
 
jober
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Re: 60GHz proximity and colocation

Sat Jan 05, 2019 3:32 am

We just installed another LHG60G link that sits about a foot over an existing LHG60G. The top one point up about 15 degrees and the bottom one points down about 20 degrees. So far they don't seem to be hurting each other. Maybe tomorrow when a few hundred megs is flowing we will see an issue or maybe not.
 
marekm
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Re: 60GHz proximity and colocation

Sat Jan 05, 2019 10:16 pm

In my case it was wAP60 (PtMP) about 1m above LHG60 (PtP), and PtMP started dropping connection when the PtP link had significant traffic, despite running on distant channels (wAP at 58320, LHG at 64800) so the radios don't have good selectivity (just like all cheap radios with no real analog filters but everything on-chip - not much different from 5GHz). So I'm a bit nervous as I plan to add a licensed 70/80 GHz link (Siklu EtherHaul-1200F) at the same mast (want to free 64800 for one more PtMP sector).
 
marcin21
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Re: 60GHz proximity and colocation

Sat Jan 05, 2019 11:34 pm

on what ros version You see problems with co-location?
I've got WAP60 and sxt60 ~25cm/30degree apart, and one LHG60 little bit lower ~2metres. all 3 within 90degrees without any problem.
WAP is ptmp, sxt and lhg are ptp.
 
jober
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Re: 60GHz proximity and colocation

Sun Jan 06, 2019 3:46 am

Well, no issues today. I will update Tuesday so we get the business customers back on Monday. Although all the hotels that link is servicing I would have thought packet loss and speed issues would have already happened. Oh, there is a lot of VoIP traffic on the link too.
To be continued.
 
mkx
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Re: 60GHz proximity and colocation

Sun Jan 06, 2019 11:01 am

As @mistry7 wrote: the biggest problem about antennae co-location is interference from other antennae on same location. Due to low-cost design of Rx part of devices there's not much to be done in settings. The only thing that helps is to have as much RF separation between antennae as possible.

If antennae have good directional characteristics, then one only has to care not to put one antenna inside direct beam of another one.
If directional characteristic of an antenna is not that great (wide beam or narrow beam with strong side/back lobes), one has to provide additional shielding (metal plate/grille on sides and back of such antenna do help).

Also one has to be careful not to have any obstacles near antenna in general direction of main beam (even if obstacle doesn't block direct LOS) as reflections from near obstacles may cause notable interference and/or change effective antenna radiation pattern.
BR,
Metod
 
mistry7
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Re: 60GHz proximity and colocation

Sun Jan 06, 2019 11:15 am

As @mistry7 wrote: the biggest problem about antennae co-location is interference from other antennae on same location. Due to low-cost design of Rx part of devices there's not much to be done in settings. The only thing that helps is to have as much RF separation between antennae as possible.

If antennae have good directional characteristics, then one only has to care not to put one antenna inside direct beam of another one.
If directional characteristic of an antenna is not that great (wide beam or narrow beam with strong side/back lobes), one has to provide additional shielding (metal plate/grille on sides and back of such antenna do help).

Also one has to be careful not to have any obstacles near antenna in general direction of main beam (even if obstacle doesn't block direct LOS) as reflections from near obstacles may cause notable interference and/or change effective antenna radiation pattern.
If you use different channels, colocation is no problem, if you want reuse channel you need a little bit shielding between the Antennas...
But in 60 ghz it is easy to build shielding.....
 
n21roadie
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Re: 60GHz proximity and colocation

Sun Jan 06, 2019 3:53 pm

If you use different channels, colocation is no problem, if you want reuse channel you need a little bit shielding between the Antennas...
But in 60 ghz it is easy to build shielding.....
As shielding changes the performance characteristics completely of a antenna, shielding + RF attenuation absorption material on the radiating element(s) side of the shield is advised.
 
mkx
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Re: 60GHz proximity and colocation

Sun Jan 06, 2019 10:03 pm

If you use different channels, colocation is no problem, if you want reuse channel you need a little bit shielding between the Antennas...
But in 60 ghz it is easy to build shielding.....
As shielding changes the performance characteristics completely of a antenna, shielding + RF attenuation absorption material on the radiating element(s) side of the shield is advised.

If original antenna is at least half-decent, then additional shielding won't change radiation pattern in main lobe direction much. If, for example, front to back (F2B) ratio of original antenna iz miserable 15dB and the shield manages to reflect all back-radiated energy to the side of main lobe (and by definition, main lobe ends at angle where signal strength is 3dB less than at its maximum), it will increase signal there to -2.73dB (instead of -3dB, not a huge difference) ... Surely the (relative) difference will be higher if reflected energy gets directed in direction where original pattern experienced deep signal dip, but probably nobody will care (it's outside main direction, right?). Specially as antenna with F2B ratio of 15dB is really shitty in the first place. But, if there are two such antennae mounted back to rack, it will increase isolation from misery of 30 dB (twice the F2B ratio) to something much more sustainable.
BR,
Metod
 
n21roadie
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Re: 60GHz proximity and colocation

Mon Jan 07, 2019 11:36 am

@mkx
Can I ask do you have actual real world figures to support the low loss mentioned when using RF shielding as from listening to RF Elements webinar (https://www.youtube.com/watch?time_cont ... Ao_AAbjnTg) @2.05mins..... speak of while reducing co-location interference.... totally change the RF performance of the antenna.....!
 
mkx
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Re: 60GHz proximity and colocation

Mon Jan 07, 2019 12:38 pm

I don't have any actual real-world numbers at hand. What I'm writing is a result of 17-year experience as RF engineer at a MNO, most of time dealing with single-frequency networks (UMTS, LTE ... indeed that's mostly FDD but the interference problem is the same regardless) where interference (cosited, non-cosited, even non-cochannel) is a bad thing. And believe me, we've done our share of research into it and develop some improvements - in few rare cases we also applied custom antenna shielding. Our actions were "complaint-driven", so we never did a full "scientific" report, while we did sometimes rethink the solution if it turned out to degrade significantly the service for users who were not suffering in the first place.

But then I'll quote myself: "If original antenna is at least half-decent, then additional shielding won't change radiation pattern in main lobe direction much". The problem is, that many antennae with price tag less than outrageous, are less than half-decent (and that, by the look of it, includes the antennae shown in the presentation near time-mark mentioned). When "improving" such antennae, it surely matters quite much how you do the shielding ... I agree if done poorly, it can degrade antenna performance considerably.
The basic idea when we were designing out network was: construct 3-sector site using antennae with 65° horizontal beam width (even though the sectors were spaced at 120°). Those users in sector main direction will have really great signal (with low interference) while users in between sectors will have interfered signal either way (and performance for those users will likely be limited by interference, not by somehow lover signal level). Rationale is that what's good for sector throughput (have a part of users in great signal, the rest in a mess) is actually good for all users (those in great signal will get their service while consuming low air-time making more air-time for those users with poor signal ... if all users were in mediocre signal, sector-wide throughput might be lower).
BR,
Metod
 
n21roadie
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Re: 60GHz proximity and colocation

Mon Jan 07, 2019 2:07 pm

I also have an RF background and have seen the results of custom shielding! It is not as a simple as bolting on a piece of metal and the problem is always solved?
There is two objectives to be achieved, one side of the shielding you require reduction co-location interference and the other side reduce the performance impact that shielding has on the antenna,

I would really like if manufacturers gave us a custom build option on antennas so that with in house RF shielding applied the performance figures were available,

I am somewhat dismayed when a manufacturer states "Back shield design - reduce co-location interference.." which is true for signals originating behind the antenna but make no mention of not having any shielding for co-location interference above and above the antenna?
 
mkx
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Re: 60GHz proximity and colocation

Mon Jan 07, 2019 2:57 pm

I am somewhat dismayed when a manufacturer states "Back shield design - reduce co-location interference.." which is true for signals originating behind the antenna but make no mention of not having any shielding for co-location interference above and above the antenna?

Antenna with high gain will usually feature a really well defined main lobe with sharp edges. And probably won't be susceptible to mentioned interferers much in the first place. Antenna with mediocre (or worse) gain will suffer from all sorts of co-sited interference. The sad thing is that many WISPs (and other RF "experts") don't understand the importance of using high-quality antenna (they dismiss it as "that's a piece of passive stuff, how on earth can it make any big difference") and decide to invest more money in active equipment and save on passive equipment (antenna, cables, ...). And try to fix things, which is not a simple task ... there are reasons for high prices of good antennae after all.
BR,
Metod
 
martineduar
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Re: 60GHz proximity and colocation

Sat Aug 15, 2020 11:26 pm

Hello,

Any experiences puting aluminium coil back and sides, for avoid interference from other antennas? Could It get worse pattern? (Antena is 6x6 array very small https://images.app.goo.gl/cqiNJpcLK6HhpNyg7

Is it possible reuse frecuency in same pole with 20 degree of distance like siklu?
How is thenperforance for 8 concurrent clients?Metrolink without tdma is fine. Is it possible use cst/rst Sync by command line?
Any experiences of deploys gigabit to home? Maybe with Aps for 48 clients with 6 wap for 500m of radius?

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