Basejumper.com - archive

I have just done 2 first base jumps from the New River Gorge bridge during the 2005 Bridge Day. Since then I have been looking at many jumpable objects around me.

Though I feel I'm not experienced enough yet, I was looking at a few antennas. I wondered what the difference is between them. AM antennas, communication antennas, (which are more dangerous than others in the way of radiation) but more importantly how to tell them apart.

You know what weould be really cool? If someone gave picture examples of different antennas, different fixtures found on them (what's dangerous, what not to touch, etc.) and how to tell if the thing is hazardous to climb on or at least what to be aware of.

That would be really cool! I'm not jumping antennas anytime soon but I'm still curious to know all this stuff.

Anyone...?

Someone posted that a BASE jumper they knew worked on antennas. Where is that guy at? He could provide that info and maybe pictures.

That would be awesome actually.

dont touch anything... step away from the A

http://www.dropzone.com/...p;sb=score&mh=25

A guy I have not seen for maybe eight years was a tower mechanic and BASE jumper. IIRC, he worked on a variety of antenna types - TV/FM/AM - and would be the person to ask regarding the pitfalls of the various types.

From my limited (and probably out of date) academic background as relates to antenna theory, it seems that the risks are a function of frequency.

With AM, the whole tower is the antenna, and the biggest risk is shorting out the antenna to ground. You don't want to complete the circuit across any insulators.

With the higher frequency stuff - FM & TV - the antenna itself is a "stinger" atop the support structure. Here the real problem is getting nuked by being close to it for too long.

I have heard tales of fillings and hardware getting hot by induction when being too close to the stinger for too long, but am not sure quite what effect is expected of living flesh. In general, it is a good idea to have it off before going too near, according to the advice I have had from techs.

When you get into the millimeter wave stuff (radar, microwave), the effects of exposure range from sterility (like no babies) to dead and roasted.

Cell phone antennae have proliferated since I left school, so I would have to do some research before suggesting what to expect from proximity with them.

Depending to a large extent upon economics, a given tower can perform more than one function. Microwave dishes and/or cell antennae can show up on radio or TV antennae, so there may be more than one set of problems you face in using a tower as a jump platform.

In any event, asking local people about a site tends to be a good way to figure out what are its risks. There tends to be a pretty good knowledge base about commonly used objects.


Blue skies,

Winsor

That would be "towertopper".
he might be willing to add some info to this thread.

Just in general I say stay away from AM towers altogether. Since AM towers are the radiator of the signal you are really getting dosed with electro magnetic radiation the whole time you are on, or even near it. The other towers, FM, TV, or microwave, serve only to raise smaller radiators up into the air and staying away from these radiators is important.

For all towers the best advice is get on, get up, and get off as quickly as possible. I remember jumping a FM tower with Tom and Jan Sanders and while we were jumping they spent almost the entire day filming from the top. Both said they didn’t feel all that well later that night and Tom looked positively green . . .

There was a reason the late Mike Allen titled one of his best videos, R.A.D.I.O.A.C.T.I.V.E.

In any case the long term effects aren’t know yet but we know how much fun towers can be. I almost wish there was another way to complete the word without going near operational towers. The person, or persons, who invest in a non-radiating tower just for BASE jumping are going to get rich in the long run . . .

NickD
BASE 194

I'm no expert, but I know of one non-operational tower, anyway. I believe there are several more similar to it. There's another I know of that's long-since been stripped of anything except for a couple of local communications whips.
Is this unique to my region of the US?

No, you are right, I should have mentioned it, but there are such towers. We had some here in SD for a while before they helicoptered them out and dropped them in the ocean. Apparently dumping garbage in the ocean is alright as long as you are making a fish habitat . . .

Also, throughout the southwest U.S. you can still find microwave towers that are now non-operational.

NickD
BASE 194

Graphic illustration to the comments about AM antennas

I got my first on a receiving A.
pope

I'm down in Puerto Rico right now, and the A's here are a little different,(see attachment) but doable. 450' from catwalk to dish. Of course then you have to battle Dr. Evil, save the world, then bang some hottie.

would this be an "A" or an "O"?

Isn't that one of those Search For Extraterrestrial Intelligence (SETI) things:

"Professor, listen to these tapes from last night! We've found definite proof of life out there! We've even decoded their language which seems based on some kind of binary and vegetable system."

"One potato, two potato, three potato, Go! One potato, two potato, three potato, throw!

NickD
BASE 194

how about this upside down stretched out pyramid A with clamshells on top...

I believe that's a microwave array . . . from what I've gathered those beams are fairly narrow, so as long as you don't pass in front of them . . . but still who knows, even the experts argue about ill effects.

NickD
BASE 194

AT&T sold most of those off long ago and most if not all of the clamshells are inactive. There are even some of the old AT&T towers with Nuclear bombshelters underneath them. You just have to know where to look

mb21 - A UK site for true geeks but the basics should be applicable worldwide?

HOW TO RECOGNISE DIFFERENT TYPES OF BROADCASTING AERIALS FROM A QUITE A LONG WAY AWAY

Jules

TowerToppers the man. He climbs A's all day. When we were scouting recently he explained how to tell the height, what the different types of towers were, what the regs on striping and lights were...

Very good guy to have on an load.

maybe he could post some lines here or write an article for BASE-WIKI?