Basejumper.com - archive

Anyone encounter these?
http://img520.imageshack.us/.../whitecirclesnu9.jpg

Thanks

It's a microwave relay. The microwave signal is sent via repeater stations, from dish to dish. Probably one of those dishes receives and the other one sends, but it could be wired to send both ways, if this is the transmitting station.

Just don't stand in front of it and you should be fine.

I remember seeing a bunch of those on the lower sections of the Ostankino tower, with people jumping from above. Certainly can't be good for the people falling (or flying) directly in their transmission path. I've seen at least one video of a jumper passing (almost?) directly in front of one of those drums. A fall could be short exposure, but with a canopy flight, you would get a decently larger dose. They probably don't bother turning it off, but they might. I wonder if just flying a canopy in front of it would be enough exposure to heat the rings to the point of melting your gear...

I thought they were those things the football players ran out of before the game, only you jump out of them?

Negative. Not unless your canopy can hover in place. The beam is extremely tight and directional. I used to work with the microwave relay system for the University of California, in my last life (or maybe that was the one before the last one). Those dishes had adjustments measured in thousandths of an inch.

Correct answer, Tom. And it only took you three minutes to answer this newly started accounts post!

Over long distances, through remote distances, it is far easier to beam a very focused beam of data through microwave, than to run a copper line to the site. With a relatively weak signal, focused very tight, it can be "microwave relayed" from site to site, over long distances. These dishes are relatively common, and when you encounter them on taller towers, just plan your rest stops below and above.

Thanks again, Tom

in the winter, it's where i warm up my hands.

Its my understanding that microwaves heat the moisture in an object and not metals.

Is this accurate?

RF (including microwaves) heats pretty much anything. The microwaves move electrons around in the (surface of the) metal, and the electrical resistance of the metal turns that into heat. In other objects, it'll grab molecules and spin 'em up, but the result is the same -- heat.

I'd read somewhere that many (most?) of these dishes in the States are now inactive -- something about a country-wide network that has now been largely replaced by satellite or something? You have any better information on that?

google att longlines project...

giant bass drum's i tell you. yah i was/is a band geek.
bring something to pound on them with on the climb up.

haha thats the answer I was looking for!!!!THANKS!!

ATT longlines are a bit different, though.. they are huge cones on the top of certain 4-legged freestanders. Most are inactive but some aren't.

The drum-shaped ones aren't much of a problem, especially the smaller ones. Don't hang out in front of them, and if they are bigger than about 4 feet around I wouldnt hang around behind one on a ladder either.

Also, try not to step on one as a launch point, because either (a) if they arent tightened enough they will tilt down and you'll fall off (and anger the company who's entire path just went out of commission) or (b) you may simply knock it off of alignment a bit and not notice (and some poor sap will have to come back to the site and path it again)

overall, just bring a set of drumsticks and you'll be plenty prepared.

As far as my understanding goes a usual cooking microwave uses alternating directions of microwaves to get the water molecules turning through the dipole and the friction heats up the food. Those dishes are not alternating so why would it heat up? (I'm not saying it does not, I just don't understand why and would like to know).

Maybe it is because the signal being transmitted it an AC signal? Ie, the signal would alternate at whatever frequency is being used for transmission. Could there also be any kind of inductive effects between the transmitter and your gear, or your body? I don't know for sure... I'm just an embedded systems junkie, and this RF / microwave thing is a whole other weird magical realm to me.

Regardless, it doesn't really matter exactly why those things are bad for you, just as long as everyone knows not to stand in front of microwave dishes. Remember that video of someone setting coke on fire using two consumer-grade 2.4GHz video transmitters? Imagine similar kinds of signals, only at a much greater power.

Tom- you must have come across some microwave vs person stories in your work. Perhaps you can elaborate on what could happen to a person exactly?

I don't think an alternating signal could exist since for that there would have to be a sending unit opposite to each other or at least something that can send microwaves from both sides.

Those things are on the tower so you can watch them fly-by in freefall. They are a simple visual addition that tower owners install to increase the pleasure of our jumps.

Sometimes they are there to give you a reference on when to pull..those are the really cool ones.

All this geek talk about microwaves and repeaters...LOL. And whoever wrote that they are a Bass drum...what a joke. Bass drums are on the floor and you hit them with a foot pedal. Haven't you ever seen Tommy Lee play the drums???

true-unless your in a marching band or your tommy lee
http://youtube.com/watch?v=yuMrNMMgjGM

LOL...where the hell did you find the Tommy Lee on Extasy at a Rave clip??? hahahahaha.

All EM radiation is alternating. That's how it propagates -- think of sending waves down a rope, or ripples in a pond. Like that, the electric field goes up and down perpendicular to the direction the wave is moving. How fast it does that is what determines whether it's radio, or microwaves, or visible light, or whatever.

Same way the field grabs dipoles (as you mentioned), it can also grab conductive electrons -- hence the heating in metals.

Ah okey great thanks. I didn't expect radiation to be altering but more like a ray of light which just goes straight in on direction.

It's not alternating back and forth between the transmitter and receiver. It is a waveform moving through space from point A to point B.

Hey thanks I figured that out about 5 min. after I posted when I made lunch in the microwave. Don't know why it took so long.

That's exactly what they are There's one on each side of any path, so data can be sent both ways.

What happens is, somebody at one end of the big chain of dishes sends a message by banging the first drum in the line, and the message travels from drum to drum, until it reaches the last drum.. then someone on the other end drums back another message. Kinda like two cans and a string, but cooler

i wonder what the bandwidth on those are?

It's 6 Ghz most likely, they are microwave dishes with the drum style hypalon radome to protect the feed horn, we call them "Hypalon Dishes", they use them everywhere for all types of links for data and to connect way out towers to a T1 connection from other sites. I've changed a lot of torn covers on them over the years without shutting them down and have been all over them with no worries, jumped off a couple too.

I was trying to find a cool picture of my buddy Mike sitting on one eating his box of cold pizza for lunch last winter but it's lost on one of my drives. I did find a short clip I shot about 6 years ago of us removing some of those dishes, I made it a 3gp file to get it to up load here under 300kb.

I used VLC to read that video, but I think Quicktime works too.

Quicktime will run it, 3pg files were what some of the earlier cellphones used as a video format. Makes for a video about 1/3 of what a mpeg would have been. Good enough for the 300kb limit here.

I forgot to add that the tower was 385' with dishes 12' and larger on tower. TT

Hmm. so sad seeing it fall. Too bad it couldn't have been left as a gift to local jumpers, he he he