RBI antenna question

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Rikkitic

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#191572 9-Feb-2016 10:47

Logically the RBI mast antenna has to be omnidirectional. So if I am 20 or so kms away from it, how narrow is the optimum reception path? In other words, how far off dead centre can my antenna be before I start to experience serious signal loss at 4G LTE frequencies?

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#1490351 11-Feb-2016 13:30

i do not think all RBI antennas are omni directional.

the ones in our area are not, they are sectored, but these are upgraded towers not new builds

Flickky

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#1490631 11-Feb-2016 16:46

Yeah I'm pretty sure they aren't omnidirectional (or at least the older ones aren't). Haven't dealt with RBI for a while now so this could be incorrect by now but the last time I did they had to be pretty dead centre and try for as much line of sight as possible in order to get a good connection.

Rikkitic

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#1490640 11-Feb-2016 17:09

I guess that answers my question then. But wouldn't the beam spread over 20km even if it was directional?

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Flickky

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#1490653 11-Feb-2016 17:16

Are you talking about the antenna on your own house/property, or the cellsite?

Rikkitic

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#1490760 11-Feb-2016 20:08

The cell site. There is no question that my antenna is directional.

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#1490779 11-Feb-2016 20:55

I think it's 15° off centre, so a range of 30°

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#1490791 11-Feb-2016 21:33

coffeebaron: I think it's 15° off centre, so a range of 30°

+1 for this.

That said, it ultimately will depend on what the specs of the antenna you are using are. If it's something like this:

http://www.gowifi.co.nz/antennas-1710-2100mhz-directio/11dbi-wideband-lte-broadband-directional-antenna.html

then as you can see the smallest beamwidth is 40 degrees so that would allow for you to be 20 degrees off centre either way.

While being 'spot on' direction to the transmitter is ideal, as long as you're within 10-15 degrees of centre (in both horizontal and vertical directions) then I don't think you'd impact your speeds at all.

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#1490794 11-Feb-2016 21:53

Cellular RF, particularly the newer 4G systems use MIMO (Multiple input multiple output) antenna techniques. The irony is MIMO is designed to work with reflections even more than direct transmissions. So going for direct line of site to the cell tower may not be the best idea despite it being logical at first glance. It pays to move antennas around slightly as you might be within a null signal and meters away may be a signal peak.

Also as mentioned already, antennas at base stations are normally sectorised. I've seen a handful of 2G/3G omnis but they are few and far between (and getting upgraded in recent times it seems as well).

Rikkitic

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#1490997 12-Feb-2016 10:36

tangerz:

That said, it ultimately will depend on what the specs of the antenna you are using are. If it's something like this:

http://www.gowifi.co.nz/antennas-1710-2100mhz-directio/11dbi-wideband-lte-broadband-directional-antenna.html

then as you can see the smallest beamwidth is 40 degrees so that would allow for you to be 20 degrees off centre either way.

That's the one. In fact, I have two of them though I am having other problems right now. I was getting constant 50 Mbps down on speed tests for some months. At the beginning of the year this suddenly dropped to 18 Mbps max, usually less, sometimes as little as just 2 or 3. We can't figure out why but our streaming has become unusable. The antenna's don't appear to have shifted, but that is the reason I asked my question. Now I am wondering if the Huawei could possibly be faulty. The speed has recovered briefly once or twice, but then it dropped back down again.

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tangerz

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#1492437 15-Feb-2016 09:56

Rikkitic:

tangerz:

That said, it ultimately will depend on what the specs of the antenna you are using are. If it's something like this:

http://www.gowifi.co.nz/antennas-1710-2100mhz-directio/11dbi-wideband-lte-broadband-directional-antenna.html

then as you can see the smallest beamwidth is 40 degrees so that would allow for you to be 20 degrees off centre either way.

That's the one. In fact, I have two of them though I am having other problems right now. I was getting constant 50 Mbps down on speed tests for some months. At the beginning of the year this suddenly dropped to 18 Mbps max, usually less, sometimes as little as just 2 or 3. We can't figure out why but our streaming has become unusable. The antenna's don't appear to have shifted, but that is the reason I asked my question. Now I am wondering if the Huawei could possibly be faulty. The speed has recovered briefly once or twice, but then it dropped back down again.

It's possible too that the tower you connect to could now be seeing increased load/use and your decreased speeds could simply be a result of that. Maybe some of the Vodafone geeks could tell you if that's the case.

Eos

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#1493758 17-Feb-2016 10:48

Hi there, I'm in a similar situation. I'm also with netspeed, and have one of the same external antennas as Rikkitic. My house is in somewhat of a deadzone, without the antenna I can only just pick up a 4G signal, and get about 4 or 5 mbps. Attached antenna last night, lined up to where I think the tower is and its barely increased, averaging 6 or 7mbps. Should I be expecting more from the antenna? Any suggestions would be great.

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nzbsgfan

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#1493791 17-Feb-2016 11:13

What RBI modem are you using?

If it's the Huawei one - try the left external antenna port (as you look at both the ports).

I believe left is tx/rx and the right rx diversity only.

It might not help but ideally you should have your antenna connected to the TX/RX port

Obviously the antenna should be vertically polarized, and the interconnecting cable keeped to a minimum distance to reduce cable loss.

Good luck.

_Edited for spelling mistakes.

Eos

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Wannabe Geek

#1493795 17-Feb-2016 11:18

Yeah, it's a B315 unit, and external is connected to left port. I've got the antenna mounted vertically on an old UHF tv pole that I repositioned from the other side of the house.

The cable is relatively long, 15m - though I've managed to keep it unbound from itself, so no tight coils etc.

nzbsgfan

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#1493949 17-Feb-2016 13:00

What coax are you using for your run ? RG213 or better ?

Also can you see your EcNo and receive RF level once you log into the modem ?

I work with these modems at work and I'm not sure what you can see without engineering software - but as a rule lower EcNo values are what you should aim for

Eos

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#1493952 17-Feb-2016 13:08

Wouldn't have a clue as to cable quality I'm afraid, pretty new to all this :) I'll check tonight and see if there is anything on the outer sheathing?

Will also log in to modem and check out those figures, will post up findings.

My gut is telling me this is as good as it gets, like I said I'm technically outside the area for coverage(on the vodafone map it literally just glances the edge of my property, about 10 metres from where the modem sits....), so anything is better than nothing. Just surprised at how little the antenna seems to be boosting the signal/speeds.

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