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ACK Delay causes and solutions.


AES ACK delay definition

An Acknowledge Delay will occur after an antenna cut or loss of communication with the network. An Acknowledge delay occurs when a Packet Acknowledge (P_ACK) is not received for a transmitted Data Packet within the programmed Acknowledge Delay time. (Default Ack Delay Time for the fire subscriber unit is 60 seconds).  An Acknowledge delay occurs when a Packet Acknowledge is not received for a transmitted Data Packet within the programmed Acknowledge Delay time.

What it boils down to is either your signal strength is weak (NetCom 6 or higher) or your signal acknowledgements are taking a few seconds to come back.  Yes, that can happen even if you have a NetCom of 5. The majority of the ACK Delays generated on the network I help maintain occur because of delayed acknowledgements not NetCom or 6 higher issues.

Some of you might be asking yourselves so what if I have acknowledgement delays my signals report on time in less than a minute and I passed my fire inspection WHO CARES? Well the problem is now that jurisdictions are requiring local notifications of radio faults.  The 2016 fire code focuses more on local notifications of radio issues including antenna cuts ac fails acknowledgement delays and other hardware issues.

Aes radios have a J4 Relay the main board that you can set up for normally open or normally close.






According to AES:

 Look for trouble with the antenna or its location, coax, connectors, transceiver, radio or electrical Interference or with the electronics itself. Maybe the subscriber is just to far away

From other devices in the network. The problem could also be with the other Subscribers or receiver it is attempting to communicate with.


That is too vague of an answer. The solutions I have come up with usually work.


  1. (This is our problem on our network usually.) The subscriber can be directly talking to an IP LINK instead of other radio units around it.  I know it makes sense that you would want a radio to talk directly to the data node but the problem is data nodes are always busy and can delay signal confirmation.   We have some units with remote antennas that jump 20 miles to talk to a repeater on a building 70 stories in the air vs AES units or repeaters closer to its location.  A stronger antenna is not always better.  To find out if this is happening to you use the NMS Google Earth to view the paths. Right click on a path and it will tell you how far it travels.  You can also check the paths using the Linux interface they have for the AES receiver.

NMS example of ack delay accounts





  1. Sometimes or most of the time techs will install the rubber ducky antennas and tighten the washers by hand. The problem with that is the washer does not dig into the can and create good enough grounding. This can cause signal strength issues, NetCom, and ACK Delays.


  1. The AES install manual for 7788 units instructs techs to ground the radio using the Green nut on the right middle side of the radio. That goes to earth ground. I’ve been told by techs on site it has improved their signal strength.


  1. Sometimes ACK Delays are caused when your radio is NetCon 6 or higher. If you have a handheld programmer hit shift + f4 at the same time to get the NetCon rating.  It should be at NetCon 5 all the time.  If not check the rubber ducky install or battery and or install a remote antenna.  



  1. I have noticed that some ACK Delays occur when a radio starts repeating too many signals. It is normal for some Subscribers to repeat RF packets originating from other Subscribers, to convey those packets along their route toward an IP Link. However, excessive packet repetition by a single Subscriber may reduce network efficiency and cause delays. I have witnessed units 5 to 15 miles away talking to specific radios and ignoring many radios around the immediate area.   Check in your NMS software for the TOP REPEATERS section.


  1. Sometimes radios are programmed incorrectly and the test interval is off. Each Subscriber normally transmits Check-in messages at regular, pre-set intervals. AES recommends setting the Subscriber Check-in interval to 23:45. A shorter time interval increases RF traffic in the network. When a radio checks in it submits a bunch of data. Once a day is fine but multiple times an hour is a no no.




I think I covered everything that can cause an ACK Delay but if I missed something leave a comment. If this helps, leave a comment. 

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