Twin Cities siren activation frequency

[STHboy]

So if you can figure out what the frequency is is there a possible way to manipulate that frequency? Im just asking I don't plan on doing anything.

Most likely not. The data packets heard are probably FSK (Frequency Shift Keying), which requires specialized equipment to interact with. It is an actual security measure, to prevent "manipulation". This is an improvement over DTMF (keypad tones), which was capable of "manipulation".

These days, all that "specialized" equipment can consist of nothing but a PC with the right software with a transciever by its side - that's all the hams use to do the same transmission modes. So I'd imagine that the business band packet radio transmissions I heard can be decoded by a PC running the right software. Besides, I don't know if the packets I heard were actually the ones that set off the siren or if they had nothing to do with the activation at all. I didn't hear any before the siren started for the second round of testing.

[Elliott]

The SCADA system is duplex; that is the sirens can "check in" with the controller, and update a condition change, such as a battery fault, tampering, lack of rotation ( T-128s do this), lack of proper motor current.

Here is some info from Federal.
http://www.federalwarningsystems.com/pr ... ?prodid=21

I would assume the codes change at random to prevent simple rebroadcast of an initial activation to prevent "malicious activation".

[NanSiren]

Unsure of the MSP freq's, but here in Austin they use 158.8350 and 154.1450 MHz for activation. It starts out with FSK to trigger our 2001DC system, then goes to 1+1 tone signalling to trigger the tbolts that were donated to smaller communities around the area, then DTMF for some city's siren.

Here's a recording I did using Scanner Recorder software (the beeps indicate the rec. start points.

Click here to watch Recording-of-siren-test-messagestones