CCTV NVR - Why two antennas??

[anonymous-user]

Anyone know why most CCTV NVR have two WIFI antennas?

I had assumed that one was for 2.4GHz and the other for 5GHz but as far as I know most cameras use 2.4GHz.

If the cameras are all 2.4GHz then in effect is one of the antennas (the 5GHz one) redundant?

The reason I ask is that I plan to remove both the antennas on my NVR and replace with high gain ones on the outside wall where they should get a more reliable signal but just can't work out why I have two antennas in the first place?

TIA.

[megaphone]

MIMO? https://en.wikipedia.org/wiki/MIMO

[OldGermanHeaps]

why would you use wifi for cameras? lots of criminals are carrying £8 wifi jammers with them now for just that reason.

[anonymous-user]

OldGermanHeaps said:

why would you use wifi for cameras? lots of criminals are carrying £8 wifi jammers with them now for just that reason.

They also wear £1 balaclavas to defeat CCTV wired or not, so pointless going to the cost of running wires.

Frankly they are just a boys toy to keep an eye on the house when I am away and also as a basic deterrent so the crims go next door.

Any idea on the question I posed as to why two antennas?

[OldGermanHeaps]

one for connection to cameras, one for connection to lan at a guess, but as no decent quality nvr comes from the factory with wifi built in its only white label chinese landfill the reality is anyones guess, maybe the second aerial is purely for sending your credit card details directly to xi jinping.

[megaphone]

Does the system actually connect to your WiFi network or, is it a stand-alone system with its own signal/network? Post up the details and we may be able to help.

[VEX]

It is usually for what is called ‘signal diversity’

A signal might be poor on one antenna but better on the other and yes even a small separation distance can make a difference.

V.

[Mr E]

VEX said:

It is usually for what is called ‘signal diversity’

A signal might be poor on one antenna but better on the other and yes even a small separation distance can make a difference.

V.

More importantly, two marginal signals can be combined for a significant gain in receive performance.

[anonymous-user]

Hi Megaphone. The NVR has an ethernet connection to the router (to give internet access, App access etc).

It also has two wifi antennas as per the model below as the individual cameras (8 off) connect via Wifi to the NVR). I am replacing the antennas with high gain outdoor antennas to get a more reliable signal from the external cameras that are some distance from the NVR. I am just unclear why the NVR has two WiFi antennas. If one is 2.4GHz and the other 5GHz then I need to be sure to get antennas in that range. Right now instead of getting antennas for one band or the other I aim to simply replace with two dual band antennas. But I like to understand why there are two antennas in the first place. The cameras work on 2.4GHz.

https://www.amazon.co.uk/New%E3%80%91Wireless-ANRA...

[anonymous-user]

Mr E said:

VEX said:

It is usually for what is called ‘signal diversity’

A signal might be poor on one antenna but better on the other and yes even a small separation distance can make a difference.

V.

More importantly, two marginal signals can be combined for a significant gain in receive performance.

Sounds plausible and I think is what Megaphone was suggesting with his MIMO comment above.

Thanks all I think that covers it.

[Mr E]

Ok, hang on.
What problem are we trying to solve here?

The cameras connect to your WLAN. The screen thing with the two antenna also connects to your WLAN?

Or do the cameras connect directly to the screen thing?

[megaphone]

MikeStroud said:

Hi Megaphone. The NVR has an ethernet connection to the router (to give internet access, App access etc).

It also has two wifi antennas as per the model below as the individual cameras (8 off) connect via Wifi to the NVR). I am replacing the antennas with high gain outdoor antennas to get a more reliable signal from the external cameras that are some distance from the NVR. I am just unclear why the NVR has two WiFi antennas. If one is 2.4GHz and the other 5GHz then I need to be sure to get antennas in that range. Right now instead of getting antennas for one band or the other I aim to simply replace with two dual band antennas. But I like to understand why there are two antennas in the first place. The cameras work on 2.4GHz.

https://www.amazon.co.uk/New%E3%80%91Wireless-ANRA...

If the cameras are 2.4ghz then that's what you need. As far as I can make out this is a standalone system, it must set-up its own network, separate from your normal WiFi. You need to check what channels are being used and what channels your Wifi is using, could be causing issues. If you have a windows laptop, download inSDIDer which is a good wifi scanning tool.

Some of these stand alone systems don't actually use real IP Wifi, they just send analogue video over the same 2.4Ghz frequencies, can cause havoc for normal wifi as they take up huge chunks of the available frequencies. May not be the case here but without a manual it's difficult to tell.

Edited by megaphone on Sunday 14th June 14:09

[anonymous-user]

The NVR/screen does indeed set up its own network with the cameras independent of my ISP's LAN. There is an ethernet connection to the ISP's router simply to give internet/App access to the cameras.

My ISPs LAN is on channel 13 (or 16 I can't remember) as I changed that to give good separation and the CCTV NVR's private LAN is on channel 1 so should be no interference there.

The issue is that the NVR/screen is in my front room and has several 2ft thick stone walls to go through to reach the cameras on my garage 30Metres away. Without the walls in the way the signal is fine, with the walls in the way the signal is intermittent.

Inside the NVR are the two existing antenna connections (see below), so plan is to replace one of those with a short lead that goes from the connection below to a bulkhead SMA connector on the NVR external case. Then screw to that bulkhead connector the lead from an external high gain antenna mounted on the wall outside at the same height as the CCTV cameras at the garage end with line of sight.



I just couldn't understand why there were two antennas when all the cameras are 2.4GHz types, but I think it must be as someone above said that two are better than one even when both are in the same band.

The garage end CCTV cameras will also get some high gain antennas too.

(PS - I appreciate this is a cheap/nasty CCTV system as someone above pointed out. It's really only so I can see what is going on at home when I am away and hopefully make any crims jog on by. At the end of the day CCTV isn't a massive deterrent as far as I can tell but it's another small deterrent imo.)

[anonymous-user]

PS - My biggest challenge is pulling that existing antenna connection off with my fat fingers without damaging the connector on the pcb board ... it all looks very delicate and fragile and much much smaller than the image above suggests it is.

[anonymous-user]

First thing I would try is to check those little u.fl connectors that connect to the wifi module are on properly. The cable routing over the metal cover maybe lifting them, move the cables to the side to avoid any stress.

Other than that, thick walls and wifi don't work that well.

[Mr E]

Right, understood.
Does it really setup WLAN, or does it do something proprietary on the 2.4 gig band? (Edit; just read the specs, it’s WiFi, likely 802.11g)
The two antennas will be for diversity gain.

Those look like ufl connectors, they’ll just snap off I think.

Edited by Mr E on Sunday 14th June 19:20

Edited by Mr E on Sunday 14th June 19:22

[anonymous-user]

gottans said:

First thing I would try is to check those little u.fl connectors that connect to the wifi module are on properly. The cable routing over the metal cover maybe lifting them, move the cables to the side to avoid any stress.

Good point, I am sure they are but as you say I'll check they are under no stress and seated properly.

[anonymous-user]

Mr E said:

Right, understood.
Does it really setup WLAN, or does it do something proprietary on the 2.4 gig band? (Edit; just read the specs, it’s WiFi, likely 802.11g)
The two antennas will be for diversity gain.

Those look like ufl connectors, they’ll just snap off I think.

Edited by Mr E on Sunday 14th June 19:20

Edited by Mr E on Sunday 14th June 19:22

Re proprietary spec, that I don't know. The spec just says "WiFi" and no other clues. It is plug and play, so power a camera up and if less than 50Metres range in free air they just connect so could be a WiFi standard or proprietary, I'd assume standard to use standard components to keep the cost down.

Got the new flying leads today (as below image) to replace the existing antennas with a bulkhead connector. Heck those ufl connectors are small!

[OldGermanHeaps]

What you describe sounds like a massive security hole on your network, are you sure you feel comfortable with that setup?

[anonymous-user]

You could also use a wifi app on your phone to see if you can connect to it. If you can a bog standard wifi repeater might help with range.

I suspect it might be a proprietary system working in the wifi band but the test above should give you a clue.