RF from amateur radio triggering squawks from outside alarm sounder

[CMW]

But the wire I cut to extend back to the alarm panel was one of the two inside the panel from the PCB going to the sounder "siren" itself. Unless there is a hidden wire also feeding the siren / speaker / call it what you will, there's no way it should make a noise. It is like cutting one lead to a moving coil speaker, it shouldn't sound. But it did, with no wires at all from the bell box connected to,the panel, so it must have been from the bell box internal battery as you say. I have to seal an insect entry via the bell box cable hole in the wall, so I will have a probe about to see how this could happen unless you have come across thi before? Cheers sparkymarka

 

[sparkymarka]

.....

 

[Nerdish Nerd]

But the wire I cut to extend back to the alarm panel was one of the two inside the panel from the PCB going to the sounder "siren" itself. Unless there is a hidden wire also feeding the siren / speaker / call it what you will, there's no way it should make a noise. It is like cutting one lead to a moving coil speaker, it shouldn't sound. But it did, with no wires at all from the bell box connected to,the panel, so it must have been from the bell box internal battery as you say. I have to seal an insect entry via the bell box cable hole in the wall, so I will have a probe about to see how this could happen unless you have come across thi before? Cheers sparkymarka

What I'm trying to understand is... did you cut the bell box battery? Because if you did, it won't sound when hold off voltage is cut.

 

[CMW]

No, I cut one of the two wires from PCB screw terminal connectors marked "sounder" that led seemingly directly to the sounder module (siren) itself. I spliced either end of the cut wires into 2 cores of the new screened 8 core cable to the panle, and these two wires at the panel end, (in fact all eight of them), were left unconnected to each other and to everything / anything else, yet the sounder started to sound weakly. So I have to presume the siren / sounder module has more connections to it than the obvious discrete wires to the PCB.

 

[Nerdish Nerd]

I presume you replecated the previous wiring you had going to the bell box, as, for some reason, the siren's not getting enough current. Also, it would be better if you actually connect the screened wire to the terminal blocks on both devices instead of wire splices.

 

[CMW]

A short length of screen is connected to mains ground at the panel end, the cores are directly terminated to the PCB connector screw terminal blocks. The two cores that break (or at least that I thought broke) the connection to the sounder itself are connected together in the panel as the screening seems to have fixed the RF issue. I should have taken photos I guess... I wanted the option of physically disconnecting the siren itself in the house, and maybe using the SET terminal going high on alarm set to close a pair of reed relay contacts or enabling a FET to enable it automatically upon me setting the alarm at the panel, IYSWIM?

 

[Nerdish Nerd]

Adding a bell box disconnect switch isn't a good idea, so don't do it until you've got the bell working properly. Have you replicated the old wiring before you replaced it with screened cable?

 

[CMW]

Yes, like for like.