Increasing Range of 868Mhz system
Increasing Range of 868Mhz system
(OP)
We need to increase the range of 868Mhz intruder/fire systems to allow us to cover multiple buildings or floors within construction sites using a single control panel with paired wireless smoke/intruder detectors. Would I be correct in thinking that increasing the size of the antenna at the control panel would do just that?
RE: Increasing Range of 868Mhz system
You need to take into account the building construction, as steel buildings will attenuate the signal more that wood/composite buildings would.
You also need to take into account antenna placement. If it is possible to elevate the antenna into an overhead space while adding a higher gain antenna (larger antenna) you can increase your range.
It is near impossible to say how great an increase you can expect without knowing all the details of the system. Some of the factors that will affect the overall range are:
TX power at the panel
RX sensitivity at the panel
TX power at remote
RX sensitivity at the remote
modulation scheme & data rate
height of the main antenna
Height of the remotes
distance of the remotes
building construction
other obstacles between
RE: Increasing Range of 868Mhz system
Are these the usual consumer version intended to be used within a single family dwelling? If so, then they're probably designed to provide reliable radio range of perhaps 30m. It's almost certainly 'too big an ask' to expect them to cover "multiple buildings or floors within construction sites" over perhaps hundreds of meters. There's a square function to face when trying to increase radio range.
If they're something different (designed for this application), then (as above) much more information is required.
RE: Increasing Range of 868Mhz system
The problem we currently face is that although the trials were successful, it can be seen that we will need multiple control panels, batteries, signalling systems as the wireless detectors can currently only operate at best in a single block of say three town houses. I have begun a dialogue with the manufacturers to see if they can give us an interface to which we can screw in a suitable external antenna and I posted my question to see if this is likely to help.
From what I gather, if we were to install at the highest point and have a larger antenna then we may be able to increase range enough to perhaps halve the number of control panels we need which would be a good result.
While I have your attention, if manufacturer can not give us the interface for external antenna, is there any other way I could take the existing signal and boost it?
Saquib.
RE: Increasing Range of 868Mhz system
A better solution would be to employ a different technology for the 'Wide Area' side of the link. The alarm system panels must each have a discrete output for the alert (intended to be wired to a siren). This could wired to a more-suitable radio system to send the signal for several miles. Some alarm systems have built-in cell phones that can be programmed to call out. But they incur a monthly cell phone fee.
RE: Increasing Range of 868Mhz system
what is your brand of intruder fire detection system? If we can access a specification of transmit power and receive sensitivity, it'd be simple to estimate what improvement you need.
RE: Increasing Range of 868Mhz system
The product code is SW-1070.
What I am keen to learn is if the manufacturer is not prepared to provide an interface for connecting bigger antennas then could we have this work carried out ourselves by commissioning an RF/electronic engineer assuming that a larger antenna would increase range?
Saquib.
RE: Increasing Range of 868Mhz system
The OEM / importer is very unlikely to participate in such changes.
Suggest you look again at the other options suggested above.
RE: Increasing Range of 868Mhz system
Regards,
Saquib.
RE: Increasing Range of 868Mhz system
A half wave dipole would be 6.8" long.
Guessing they didn't want too much range, and used a simple inefficient antenna.
RE: Increasing Range of 868Mhz system
Thanks for your assistance in this matter.
Saquib.
RE: Increasing Range of 868Mhz system
If you have a spare sensor, and you're interested, since I'm a bored antenna engineer, send it to me and I'll add a free antenna to it. You could try it out.
RE: Increasing Range of 868Mhz system
G1/G2 regulations: ≤25mW ERP (effective radiated power)
Interestingly, G3 is 869MHz and allows 500mW.
Ref. http://
RE: Increasing Range of 868Mhz system
I could send you the repeater which if this works could then just be mounted next to the main panel thus negating the need for running a cable through the houses under construction.
Where can I send it?
Saquib.
saquib@icu-secure.com
RE: Increasing Range of 868Mhz system
"Up to 2 wired/wireless repeaters" and "wired or wireless"
per the bottom of this link (click on RF-Interface) h
That means you don't need to wire it to your panel I believe. Just get it power somewhere else and it should extend your range.
It says antenna diversity too, so I'd guess they use two antennas at 868 Mhz. If you have the unit, peak if they gave you two antenna that are cylindrical and about 8" long. The unit would need two external connectors protruding from the box to attach the antennas. If not, the antennas are built onto the circuit board.
There must be a brochure on how to use the repeater?
RE: Increasing Range of 868Mhz system
They do have two short thin straight antennas built in to the circuit board arranged vertically and horizontally.
Saquib.
RE: Increasing Range of 868Mhz system
It might be worth a try to call the manufacturer and ask for technical support on how to setup the wireless repeater.
If they sell a repeater that is wireless, then it should work wirelessly. The only reason it wouldn't function is that the signals don't get to each antenna. i.e. inside metal building to outside of building, when it's very well sealed.
Don't trust a salesman to save you money.
RE: Increasing Range of 868Mhz system
If it is not viable to use the repeater in wireless mode to extend range, can the additional antennas you mentioned earlier be added to this type of device or is that not an option?
Saquib.
RE: Increasing Range of 868Mhz system
Antennas can be added, but only if current antennas are proven not very good, otherwise you'd be wasting effort and get the same range.
In any link, transmit to receive, both directions, both antennas and both transmitter powers affect range. You really have two ranges mostly because power transmitted is different from each end.
To maximize coverage, you can try to improve one antenna (base station) and see if it helps. Both antennas improved gives max range. I expect the antennas in the sensors, if very small, may not be good antennas.
Are you going from inside metallized buildings to the outside of the building? What is you physical layout?
RE: Increasing Range of 868Mhz system
Construction material varies but more often than not its timber frame (foil backed), brick outside and often scaffolding to get through as well.
Saquib.