Rangecast FAQ
[FAQ-1195] Error: HIGH RECEPTION LOAD (Code 23)

Page Type: SYMPTOM

OVERVIEW

The HIGH RECEPTION LOAD error message indicates that the scanner is receiving content during a very high fraction of the time, and it is very probable that additional broadcast content is being missed because there are too few scanners in operation for the quantity of content assigned through the scanner programming system.

BACKGROUND

If all the scanners at a feed site are recording audio, any additional transmission that occurs simultaneously will be missed and not recorded. There should be a sufficient number of scanners to handle peak loads on the broadcast channels designated for reception.

Note that it is normal in Rangecast for the PLAYER to operate at 100% loads (continuously playing audio). The player pools content from multiple scanners, and gives the user the ability to select which specific content should be played.

Regardless of how many people are listening, each transmission is recorded by only one scanner. And each listener will hear a series of transmissions that may have been received from different scanners.

Although the Rangecast player can operate at 100% loads, the scanners should not operate at such a high load. The scanners need some free time between transmissions to scan and detect signals. If a scanner spends too high a fraction of time recording audio, this indicates that there are insufficient resources to detect new signals.

When there are multiple collaborating scanners at a feed site, they will share the reception load, no single scanner should be significantly more loaded than the others. Therefore, a high reception load on one scanner is taken as an indication of excessive loads on the entire block of scanners at the feed site.

The appropriate action is to either increase the number of scanners (so there are sufficient resources to reliably receive the selected channels), or reassign some channels to other feed sites (rebalancing the loads between sets of scanners), or removing some channels entirely from the programming (lightening the loads.)

METHOD

1. Check for a continuous signal

Rangecast operates "clusters" of radios (usually 1 to 8) with identical programming, co-operatively scanning a group of channels. A system may include multiple clusters, at either a single or multiple physical locations.

High Reception Load usually indicates that some specific cluster is overloaded (too much content on these channels for the number of radios assigned.) This condition will be reported by all the radios (or many of the radios, if the condition is borderline.)

However, if only ONE scanner in a cluster is reporting this condition, and the other radios in the cluster show normal loads, it is possible that there is a specific broadcast channel that is continuously active (and therefore tying up the particular radio that happens to have captured that channel.)

On the status page, Senders tab, compare the "Xmit Load" percentage shown for the scanners in the cluster. High Reception Load is triggered if the load exceeds 80 percent; observing the actual percentage for each radio provides a clearer picture than relying on the binary yes/no existence of the High Reception Load error message.

If one scanner is showing a much higher load than the others in the cluster, check what that particular scanner is receiving, and see if there is something anomalous. You can review recent traffic by clicking on the number in the "Xmit New" column (this takes you to a list of recent transmissions recorded by that scanner, with a link to directly access each audio file within the browser.) As an example of traffic causing this condition, scanners have been observed continuously recording an airport weather broadcast that transmits 24/7.


2. Check for error messages from other scanners in the cluster

If a cluster contains several scanners, and one of the scanners is not working correctly, then the operational scanners (fewer in number than intended) will be carrying all the load onto themselves. This can produce high reception load conditions on the remaining scanners, but where the fault is that another scanner is not working correctly. Check for error messages being reported from other scanners that share the same feed site number, especially errors such as "radio missing", "no audio port", or "no antenna" that could entirely prevent another scanner from participating in reception activity.


3. Load balancing

If your system includes multiple clusters, and the load percentages are significantly different between clusters, you can consider either:

(a) load balancing - shifting some of the channels away from sites where the radios are overloaded, and towards sites where the radios are not overloaded

(b) moving scanners - shifting some of the radios away from sites where the radios are not overloaded, and towards sites where the radios are overloaded

Option (a) can be explored through the signal survey, which measures and compares the quality of reception of all channels from all scanners. Look for content currently assigned to the overloaded site which can also be received from sites with extra capacity, shift these channels as indicated, and see what happens to the loads.

If you have multiple receive locations where one site has a lower load percentage, you could consider offloading some of the content from the high load site to
a lower load site. However, you must take into account whether or not this alternate site can receive the systems and channels you are considering offloading. For more information on the Rangecast signal survey:

[FAQ-1200] Applying signal survey results

Signal surveys provide a way to determine reception patterns in a region (which receive sites are good for which radio broadcast signals, and for trunked systems, which towers carry which talkgroups.) This is an overview of the steps for applying survey results to improve Rangecast performance.

[FAQ-1231] Interpreting control channel signal strength and quality chart

For each measurement of the signal strength and quality of a trunked system control channel, the Rangecast survey presents a graphical chart for easy interpretation. This report summarizes the interpretation of this chart.



Option (b) usually involves hardware adjustments, such as moving radios between physical locations, or changing which antenna some scanners utilize.

In rare circumstances you may have multiple clusters at the same location using the same antenna, and in this case you may be able to simply reassign a scanner from an underloaded to an overloaded cluster. (For example, if you have identical radios 11-ABC and 12-AB connected to a single antenna with the same filter configuration, where 11 operates with normal squelch and 12 operates with zero squelch to optimize P25 reception, and you find that 12 is overloaded but 11 has extra capacity, you may rename scanner 11-C to 12-C to rebalance loads between these clusters and more efficiently utilize the scanner hardware present at this physical location.)

If moving radios between co-located clusters where the radios have some difference in reception characteristics -- for example, the cluster 11 radios use a yagi antenna or an 800 MHz filter, and the 12's do not -- then you can still shift radios from one cluster to the other, but you must re-cable them so that the radios within each cluster are all using the same antenna and filter, so reception on all the radios within a cluster are equivalent. Someone on site must do this work. If you are unsure whether there is a difference in antenna or filter configurations, you should have someone on site check the hardware.


4. Adding Scanners

While load balancing can help optimize the utilization of your existing scanners, in many circumstances High Reception Load is drawing attention to the fact that more scanners are needed to capture all of the desired radio traffic.

If you have only one cluster (all radios have the same site number), load balancing is not an option. In this case, your options when you a High Reception Load are either to reduce the number of channels that the scanners are receiving, or increase the number of scanners.

For advice and references for purchasing additional scanners, RCX boxes, multicouplers and other components that may be necessary such as rack panels and jumper cables, contact Rangecast at the address below for more information [img-tech-rangecast-com]

Rangecast feed site PCs typically support four scanners but that can be increased to five or six radios. We do not recommend exceeding 6 scanners per PC, for reasons of both performance and redundancy, but there is no precise limit (in practice the limiting factor is usually the performance of the Windows audio system, which is not easily quantified, and depends on many factors specific to a particular customer's IT environment.) Thus, at some point you'll need to add PCs if you're also adding scanners.

CITATIONS

INDEX

Images blocked - [show]