Australian Ham Radio Discussion Forum ( AHRDF )

Well it seems all has not gone smoothly in getting the faulty paging transmitter replaced - to the extent that it was actually placed back in service last night after the alternative transmitter failed. The interference was plainly audible on at least 3 repeaters and visible on the SDR spectrum displays this morning. Somehow the transmitter didn't get sent back to the supplier after it was determined as being faulty.

The hospital coordinator's email advising the transmitter changeover was responded to today and a few more emails have been exchanged since. The ACMA was also updated as to the return of the interference and they may yet take the lead in achieving a permanent solution.

As quoted in the last email: "Patient care is the most important aspect and it is vital we have paging communications until this issue is resolved " and I agree with that statement. They will try to find a remedy as soon as they can. In the meantime, we will have to take note that they are well aware of the interference issues and are dealing with it as quickly as possible, keeping in mind the care and safety of patients is their highest priority.

I will update here as further developments occur.

We will just have to "grin and bear it" just for now....

Interesting.

We've also been plagued with digital noise on VK4RRC 146.925 (input 146.325) for the last week. It seemed to (mostly) go away with the rushed implementation of a 91.5Hz tone for access (still occasionally coming in in short bursts on tails) but it seems worse again today.

We didn't see the hospital pager hitting that repeater (as far as I recall) last time, so this is probably a total coincidence, but... do you know if their issues also started about a week ago -- or if they pulled the faulty pager back out of its box around then?

-P.

The (faulty) pager was only placed back in service on Tuesday evening/night (16th May) so is probably NOT responsible for the other issues that the RRC repeater has been suffering. I note that there has been an upswing in the digital signals visible so the question arises: is it a half (12.5KHz) channel signal getting into a wide (25KHz based) receiver at the repeater?

A search of the ACMA Public Register should show which digital repeaters are in this overall geographical area and indicate what frequencies are actually in use around here. That is not to say that it might not be local but more than likely it is. Of course, it could also be an unstable transmitter being used by someone frequently accessing a DMR or DStar repeater, a link node or other source.

A spectrum analyser or SDR-kept watch across the 144-148 spectrum might reveal a coincidence of both the 6925 repeater triggering and another digital-use frequency near its input frequency...