Isaacs DMR Repeater interference problem. #dmr

Since late November or so there has been an interfering signal appearing on the Isaacs DMR repeater and it has been broadcasting this interference to over 50 other repeaters nationwide.

The signal appears as a short (0.5-5 second) transmission, on the repeater input, seemingly at random, but often immediately after a valid transmission, either local or from the network.  The really odd thing about it is that it is retransmitting the DMR ID of other stations.  We can tell it’s spoofed the ID’s as they are usually the ID of someone who is definitely NOT in the DMR repeater coverage area.  We’ve yet to see a valid locally verifiable ID.

So, we’re currently investigating two possibilities, firstly that it’s some sort of internal corruption or overloading in the MMDVM modem. To that end we have rebooted and reset the modem several times and updated the firmware.  This has made no difference.  This is something we’re continuing to investigate.

The other possibility is that someone locally has a misconfigured radio or transmit capable SDR monitoring the repeater regularly that is causing the interference.

So, can I ask everyone with DMR capable equipment to check their gear.  If you normally leave it on, or turn it on regularly to monitor, then please watch the TX light to see if it’s keying up.  If you’re not sure, or you see something then please contact me privately via email and we can discuss it.

Otherwise, unless you have specific information regarding the issue, then please don’t comment.