Motion sensors on towers?

[d-dog]

Heya, anyone out there know the ins and outs of motion sensors on radio antennas? Here's the scoop:

We went to jump a 600 foot-ish tower locally that has had only one jump, a long time ago. Rigged up, started climbing the external ladder which, we surmised, leads up to the internal ladder. No elevator.

About 5 rungs up, a shreiking siren went off when I grabbed a rung. I immediately dropped of the ladder to the ground; as soon as I let go, the siren stopped. Cooler heads prevailed, and we made ourselves scarce and jumped a different object.

I am taking this personally, and I intend to find a way to get off this damned thing and not go to jail doing it. Any suggestions? Ladder rigged with a motion sensor? Electric circuit on one of the rungs? Something else?

Any advice or wisdom appreciated. Again, the siren stopped the moment I let go of the ladder.

Peace,

D-d0g
ddog@wrinko.com
www.wrinko.com

[imported_Tom Aiello]

Did it stop when you let go of the ladder, or when you let go of the rung? It should be pretty easy to climb "rungless" for 20 feet and get past it.

Or maybe climb the structure, then transfer onto the ladder 40 feet up?

--Tom Aiello
tbaiello@ucdavis.edu

[guest]

Did you feel the ladder shake or move(more than normal)?
I've heard of sections of ladder that have switches that are activated by additional weight on the ladder. I would see if you can recognise what is tripping the siren in the unlikely event that the same system is used higher up on the tower.

[guest]

We have one in the UK with a similar deal..once you've climbed a little further though it stops...its activated by a P.I.R. cell like you get on security lights.

It may be worth setting it off and hiding in the bushes to see if anyone turns up so that you know it not hard wired to an alarm!!

take care
:o

[JOMAN]

We have one of these A's by me. We felt ours was a motion sensor that set it off. It went off for five min and then stopped. Probably on a timer. We sorta hung out close by to see if anyone came. The other thing is it could be a sorta light curtain or light beam that is being broken. There are a couple of good points made. Climbing the outer structure past the point is what we are going to try aftrer the snow!!!!!. Gotta love base in the north.

See Ya

JOMAN :-)

[crwper]

My friend and I were checking out this sweet freestander in a residential area. We climbed an outer fence and a tall inner fence topped with barbed wire. Thought we were good to go. But as I was getting my gear ready at the bottom, I heard this beeping noise coming from the adjacent building. My friend gets my attention and says, what do you think this is? We're looking right at a motion sensor, just like you would see in a house, mounted on the wall of the building and pointed directly at the ladder. I figured the beeping meant we had set it off.

I've never climbed a fence as fast as I did getting out of there. We waited nearby in the car for about 30 minutes to see if anyone would show up, but no one did.

Reading your post, I wonder if the beeping was a warning to say we were in the periphery of the sensor, and I wonder if a much louder alarm would have gone off if we'd started climbing. We're planning to go back to that antenna. As you said, I plan to find a way to jump this thing without getting busted. Sounds like climbing the structure for the first 50 feet or so might be the way to go.

The sensor we saw was a little white plastic box with a translucent window on the front, just like a typical residential motion sensor.

Next time you're at the site, have a look around for one of these things, and listen carefully for a periodic beeping noise. As others have suggested, it might also have been a switch or a light curtain you ran into, but I'd be very interested in knowing if this motion sensor thing is common.

Michael