[Guest columnist Wayne Stacey VE3QO shares some of his “Sixty Years of Weird Stuff in Radio”.]
Even when professionally installed, a residential alarm system can provide some interesting moments for hams. Hard-wired systems are especially entertaining in this respect. The rather long wire runs that link detection devices to the central control box can act as quite efficient antennas. And this sometimes will inject unwanted RF into devices that contain semiconductor components.
I learned this to my embarrassment late one evening, some months after having a centrally-monitored alarm system installed in my house. I was operating CW with 100 watts on several of the lower HF bands and everything was just ducky… until I went on 15m and cranked up the ol’ keyer to about 25 wpm. Suddenly the fire alarm sounded. Weird, I thought, since we were home and the alarm system was not armed. So I roared up to the control panel to silence the siren, all the while sniffing the air to see who burned the toast. No source of smoke or flames could be found anywhere.
In a few minutes, out of the night comes the sound of sirens and up to my house roll two Ottawa fire trucks, bearing enough flashing lights to be seen on Mars. That’s when I found out that, whenever a residential fire siren sounds, my monitoring company immediately informs the FD without first calling the customer. “It’s OK”, says the jovial head firefighter, “Sometimes water vapour from the shower or crawling bugs will set these things off. Better get your system looked at”. Off they go, while I stand there on the lawn in my slippers explaining to sleepy-eyed neighbours that it was just a “technical fault”.
Later that week my alarm company’s technician turns up. “Better replace the fire detector unit”, says he. So while he’s in there, and suspecting RF was the real culprit, I handed him some ferrites for the wires. No further problems arose for months. Then one evening, similar situation – except on 17m CW this time. Siren goes off again. “Aha”, says I, “This time I’ll be smart and call the alarm company and tell them it’s a false alarm”.
ME: “It’s definitely a false alarm caused by radio interference. There’s no fire. Do not send the fire department!”.
ALARM GUY: “Yessir, yessir, no problem. Thanks for informing us”.
Ten minutes later, again the wail of distant sirens comes wafting through the night. Same firefighters. Same discussion. Same neighbours, somewhat more p.o’d this time. The next day, after irate discussions with multiple service representatives, I learned that the alarm people who interface with customers via telephone and those who dispatch first responders are not one and the same and evidently don’t communicate very well.
The upshot of all this? Well, with a little inventiveness and a suitably-programmed Raspberry Pi, the alarm system now sends notifications directly to my cellphone and/or to anyone else I designate. No monthly monitoring fees and any alerts come to me even faster than they did from the alarm company.
Moreover, should the HF rig ever set off the alarm when I am away and operating under remote control, I can peek around the house with my internet-connected security camera to verify that the alarm is false.
And avoid the risk that my front door will be punched open by firefighters who arrive in my absence!