Rangecast FAQ
[FAQ-1129] What is a Cluster?



A group of radio scanners operates as a "cluster" when all of the scanners are programmed to receive the same channels, and the scanners operate collaboratively via Multisync to efficiently receive transmissions on these channels. Each cluster is associated with a "cluster number", channels are assigned for reception to a particular cluster (by number), and scanners within a cluster (with the hub and number as part of its Rangecast ID) are programmed to match the programming assigned to the cluster.



A group of radio scanners operates as a "cluster" when:

a) all of the scanners are programmed to receive the same channels, and

b) the scanners operate collaboratively via Multisync to efficiently receive transmissions on these channels

The scanners in a cluster must be connected to PCs on the same LAN (local area network), so that the software controlling the scanners can communicate with low latency to coordinate scanning patterns and signal reception for optimal efficiency. (In many cases, the scanners are all connected to the same PC; but it is permitted to use multiple PCs on the same LAN.)

Note: There is one circumstance where the programming of scanners within a cluster may not be identical. A cluster is allowed to contain a mix of scanner models (the scanners do not need to be identical), but some channels can only be received by certain models of scanner. In this circumstance, it is possible that some channels assigned to the cluster may be omitted from the programming of some scanners (those scanners that are physically unable to receive the channels.) This is permitted, although it will invalidate the accuracy of the "Cluster Metrics" report that is used to evaluate performance of the deployed set of radios (to determine, for example, if additional radios are needed to reliably receive all content on these channels.)


A unique two-digit number is assigned to each "cluster" within a hub. Using this number, in the forms that define the scanner programming for a hub, channels are assigned to a specific scanner cluster (not specific scanners). When scanners are automatically programmed in the field, the scan list is set to match what is on file for the cluster to which the scanner belongs.

The Rangecast ID for each scanner (established on the Configuration screen, shown below) must include the number of the cluster in the second field. (The first field is the name of the hub; the third field is a single upper-case letter identifying the specific radio within the cluster.)


On the status page (Senders tab) there is a report titled "Cluster Metrics". For each cluster, there is an hourly report listing how many scanners were participating in the cluster, what percentage of audio uploads failed (usually zero), approximately what percentage of time all scanners were occupied simultaneously with reception (during this time, new transmissions on additional channels would pass unrecorded), and overall what percentage of transmissions (by statistical estimate) were captured.

This "cluster metrics" report depends on the assumption that all participating scanners were programmed and fully operational, with similar and adequate receiving conditions (antenna performance, etc.) If any scanner in the group was deficient in performance, the calculated performance of the cluster may be incorrect.


The cluster number is often referred to in colloquial speech as a "feed site number". In most circumstances, all scanners at a feed site (physical location) are programmed in the same way, and belong to the same cluster. Therefore, it became customary to speak of the cluster number as if it were a number for the location where the radios were physically located (e.g. "10 is the studio, 11 is the tower site, 12 is the north bureau".)

However, there are some circumstances where scanners at the same physical location are programmed to receive different channels (instead of the usual case of all the channels being pooled together for scanning by all radios.) This may happen, for example, if using antennas optimized for reception on particular bands, or using different models of scanner for different purposes for which they are best suited.

In this situation, it is important to recognize that the cluster number refers to the *group of radios with the same programming*, not merely the physical site. And therefore a feed site (physical location) may be associated with more than one "feed site number" (when this term is used loosely in speech, instead of the more technically correct "cluster number.")




Rangecast FAQ - ID 1129 - last updated 18 October 2017     Images shown - [block]