GMRS set off a car alarm

[dosw]

I was in my vehicle the other day when my daughter reached out to me over GMRS (simplex). I was in a parking lot adjacent to some sort of construction business; they had some heavy machinery on-site.

 

When I keyed up the MXT275 with MXTA26 antenna to respond, a tractor with an alarm in it started sounding off. When I released the PTT, the tractor quieted down. Keyed up again, and again the alarm started sounding. I was about 20 feet away from the tractor when this happened.

 

Because I'm curious and can't leave things alone, I tried a frequency at the other end of the GMRS band, and the same thing happened.

 

Is this common? Was something wrong with the tractor alarm system's wiring?

 

Really, it's just curiosity getting me. I'm not likely to be hanging out in that particular parking lot... probably ever.

[WRNV967]

RFI better know as Radio Frequency Interference can do weird and funny things to near by equipment. It overloads the equipment's  frontend and electronics and causes all kinds of fun things.. Just like you experienced with the alarms that was on the tractor around the construction site. I bet if you move further away than 20 feet from it it might not have happened. I have been behind many of my buddies knowing they are speeding and have set off there radar detectors with my gmrs radio and other radios because i was close to them and overloaded the frontend of the radar detector. Funny as crap to watch them hit the brakes cause they thought a cop was around radaring.. RF can and will do very weird things.. That's why the FCC has RF Exposure limits on certain frequencies. 

 

https://www.fcc.gov/general/radio-frequency-safety-0#:~:text=The SAR is a value,(1.6 W%2Fkg).

[SteveShannon]

In one of my other hobbies, high power rocketry, we find that the electronic flight computers sometimes get triggered into setting off their black powder charges.  It helps to have any pairs of wires in the electronics bay twisted to prevent them from working like antennas.  The inputs to the alarm systems might benefit from having their wires twisted to help with rejection. 

[wayoverthere]

When I first set up my btech, I had the 1/4 wave antenna sitting on top of my printer, mag mounted to a piece of sheet metal. When I keyed up, the printer woke up and printed a page of gibberish characters.

Setup has since moved, and the antenna is on top of a bookshelf now.

[KAF6045]

1 hour ago, wayoverthere said:

When I first set up my btech, I had the 1/4 wave antenna sitting on top of my printer, mag mounted to a piece of sheet metal. When I keyed up, the printer woke up and printed a page of gibberish characters.

I would like to introduce your printer to my paper shredder... Keying up an HT in the same room causes the shredder to cycle (for whatever time-out period it has to ensure paper has cleared the blades).

And in the 80s or 90s, I recall tales (may be urban legends, though I was living in the South Bay at the time) of newer model cars getting disabled on CA highway 17 (now I-880). Seems there was one mountain pass on the route that aligned with either a radar site or microwave relay towers... RF bursts were essentially doing the equivalent of an EMP on some of the poorer shielded engine management systems of those cars.

 

[wayoverthere]

23 minutes ago, KAF6045 said:

I would like to introduce your printer to my paper shredder... Keying up an HT in the same room causes the shredder to cycle (for whatever time-out period it has to ensure paper has cleared the blades)..

 

Sounds like a match made in heaven

[BoxCar]

5 hours ago, KAF6045 said:

I would like to introduce your printer to my paper shredder... Keying up an HT in the same room causes the shredder to cycle (for whatever time-out period it has to ensure paper has cleared the blades).

4 hours ago, wayoverthere said:

Sounds like a match made in heaven

 

I'd just put that on the trash heap.

[marcspaz]

Man, do I have e stories. LOL. When I use my GMRS radio while in my driveway, the garage door opener lights turn on.  In my last Jeep, I had to move the antenna because when I keyed up, my dash would reboot, run self diag, and my windshield wipers would turn on.

 

I also have a HF radio and an amp that puts out about 1,100 watts.  If I run it full-tilt, LED lights in my house that aren't even plugged in will actually light up. It trips my wireless surround sound, turning that on. And depending on the frequency, it makes my radio/alarm clock's radio turn on until I let the mic go.

 

RFI does some wild stuff.

[wayoverthere]

1 hour ago, BoxCar said:

I'd just put that on the trash heap.

It probably will be, it's been showing it's age and I don't even know if I can still get toner for it. (Circa 2000 or so Samsung laser, on clearance from CompUSA).

[BradfordD]

12 hours ago, marcspaz said:

I also have a HF radio and an amp that puts out about 1,100 watts.  If I run it full-tilt, LED lights in my house that aren't even plugged in will actually light up. It trips my wireless surround sound, turning that on. And depending on the frequency, it makes my radio/alarm clock's radio turn on until I let the mic go.

 

Jeez - you're going to give your cat cancer.

 

[WRQI583]

While working for a newspaper company years ago, one of the drivers would set off the building alarms at his last stop when he would call in to let dispatch know he was done.

Currently, my wife and I can make the CO2 alarm downstairs go nuts if we operate our portable radios in the same room on GMRS.