Understand when we use antennas, when a Smart Node repeater is necessary, and when you can pair everything on a single channel to make strong communication
| What is a strong RSSI? (Received Signal Strength)
| What range can I expect on 900 Mhz?
The general rule of thumb and the rule you should apply to a standard design is 100' point to point. Many factors affect the range and you can generally rely on a direct connection with the CCU at 100' through most building materials.
(48-X)/N^2 = Y
X + Y = Total Nodes
N=# hops. Should always be limited to 2 hops
X = # of zone with single hop (generally within 100' of CCU)
Y = # of Zones outside 1 hop.
-Walls, concrete, metal, and other RF devices can cause a degradation
-OAOs typically work at about 60’ for reference through the metal roof deck, walls, and the metal walls of the RTU
In the example below the size of the building is the same but the location your CCU is mounted in is a worst-case scenario location where you would require multiple CCUs for a building that would otherwise need only one if the CCU were mounted in the center of the building.
| What do I do when line of site point to point is > 100'?
You have options here depending on your circumstances.
1. Add an additional CCU. You can add additional CCUs when the nodes are in standalone control. ***When the nodes are used to aggregate data for the system equipment (Think DAB, VAV zone controls) the CCU is controlling you should NOT add an additional CCU as the solution. Your zone data will then be isolated from the system and the system will never behave correctly. ***
2. You can add a Smart Node in between as a repeater.
3. If there are other CCUs with zones in the building and in between you can pair them on the same channel. ***WARNING # OF ZONES IN THE EQUATION ABOVE BECOMES THE # OF ZONES ON THE SAME CHANNEL SO LIMITS THE TOTAL # OF ZONES YOU MAY BE ABLE TO HAVE PER CCU ONLY USE WHEN DISTANCES ARE GREAT BUT NODE COUNT IS SMALL***
What is a channel? A channel is a primary frequency.
E.g. 8021, Channel = 8, Unique Identifier = 021
Example: You have a large retail space and all CCUs need to be mounted in the manager's office. There are 9 RTUs each getting OAO and a Smart Node zone. The Smart Nodes all are mounted at the unit but only 3 of the units are within 100', all others are beyond 150' but are within 100' of each other. The first CCU will have a Pairing Start Address of 1000. The second would by default have a pairing start address of 2000. But you will change the other CCUs to have pairing start addresses of 1100, 1200, 1300, etc. to keep ALL nodes in the building on the same channel so they can share messages.
4. You can add long-range antennas. This is the least and last resort option. You would use this option if you were in a large concrete structure or in a place where you cannot add a repeater in between because no power exists. You could also use this option if all equipment is mounted in the RTU, and you are jumping long distances over a roof where nothing exists in between.
If you use this option, it is important to know that both sides of the expanse need the higher power antenna for full effect, if you only put it on one side, you will not fix this issue. An antenna on only one end will boost the signal but will not have a full effect.
Reasons not to use this option: Difficult to support since it requires a physical modification to the CM hardware. So, all replacement parts will also need this change at the warehouse. Not a part of the inventory at this time and is made to order. Difficult to track what CCUs have this modification.