AM Antennas

[Bennii 0]

I have been looking for thread i saw some time ago about am and fm antennas. if the thread is gone can any help me to understand what i have to consider before i jump one.

Thanks.

[base704 0]

Consider finding something else to flik...

You can get a lot more done with a kind word and a gun than with a kind word alone.

[Bennii 0]

but it is 1250 feet

[TomAiello 26]

Climbing 1250 feet of transmitting antenna is going to fry you.

I'd be sure I knew what the radiation level was, and what the safe exposure time is for that level.

I swore off AM towers after landing, retching, and laying in the landing area vomiting for 20 minutes under an AM tower I thought would be in the "safe" range.

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[truckerbase 0]

Something that tall is typically an FM antenna, most of the hazard is associated with the top stinger, and with the directional side transmitters (pods, drums, or dishes), or with any secondary stingers (omnidirectional transmitters). The antenna body (girderwork) is just a platform providing heighth to maximize signal strength over distance. Much of the climb shields you from much of the radiation because you are behind and beneath main transmission elements.

Am Transmitters tend to be smaller,and tend to occur in groups of 2,3, or 4 identical antennas with the same light scheme flashing simultaneously. The hazard traditionally is two-fold; one, the entire body of the antenna framework is used to transmit a signal, not just a stinger or whip on the top, hence exposure to electromagnetic radiation occurs uniformly from the ground up, exposing you for the duration of the climb (where an fm concentrates exposure only around transmission elements (top stinger, side mounted arrays, pods, dishes, drums, and whips) the intensity of which increases the closer or higher you get to these points.) And two, for an AM transmitter to put out its signal, it modulates the amplitude of a "carrier wave" with the signals "intelligence" (music, sports, christian nonsense, etc.). To produce the "carrier wave" the entire body of the antenna is literally electrified, when attenuated by the top, an echo of the signals modulation folds away in the electromagnetic spectrum radiating from the entire body of the antenna. Long story short, if you touch the antenna while standing on the ground or in contact with anything uninsulated you will be electrocuted. These are not necessarily popular BASE destinations.

Both Am and FM antennas come in two major forms: guy wired and freestanding. Or an antenna body which is held up by cables versus a pylon or pyramid shaped structure which supports its own dimensions internally. Typically the AM antenna that is guyed will always have multiple little black or grey "balls" or insulators visible on the cables. So there will be an antenna, then cable, then a little black ball connector then cable, then black ball, then more cable. This is a dead giveaway for the FM guyed tower. Dont mistake orange beach balls for insulator balls. Many guyed towers have these big colored beach balls on the wires to make them visible for crop dusting low flying pilots, and also because Tom Aiello is mesmerized by large orange things and will typically forget about jumping when confronted with evil orange. The freestander is a little less obvious. Small, probably unjumpable heights in this category can occur by itself (a single antenna), but very typically Am antennas of a jumpable height have a strong tendency to be in groups (like elephants or whales or prostitutes, or Tom Aiellos). They are all of the same type and height, with an identical light system which flashes all the antenna's lights simultaneously. These groups in the US tend to be in two's, three's, or four's all in the same area. Examined up close AM antennas will usually have a black insulator at the base (guyed and freestanding) although the freestander may be difficult to see. Also the freestander will have odd things at the bottom on one or more of the legs of the pylon, including massive magicians ring thru a ring perpendicular to each other, or wand like whips extending up from near the base. Also, because AM stations have smaller audiences and are less profitable, they have a tendency to have small, crappy, wooden fences around them, or even no fence at all, compared to their wealthier cousins the FM's which tend to have "cyclone" link fences with barbed wire, metal poles, etc. The AM towers fence can be as ridiculous as a three foot high white picket fence with no barbed wire. Or a Tom Aiello in a wingsuit.

The general philosophy of jumping both antenna types involves "get up, get off, and get away" to minimize exposure time, but because of the risk of electrocution on AM towers, typically people just say "stay away". To jump these you must get on the metal tower without ever touching the ground or anything in contact with the ground at any time in the process, requiring jumping on to the tower from some insulated base and grabbing non grounded antenna without flailing, stepping off, steadying yourself with anything grounded or the like due to imbalance or error. And yes, I drew a white arc off one freestander long ago by bending a grounded part of the antenna close to an electrified part of the antenna.

To sum up. Use the elevator if possible to minimize exposure. Dont rest near any pods, drums, dishes, or arrays on the antenna as you ascend. Never get in front of any transmission element as some of these are putting out a focused beam pointing away from the tower. Never touch the stinger on top of the tower (if there is one) and in fact, never ascend higher than the metal dais at the base of the stinger or above ladder accessability. Tend to stay away from the very top, and exit from 50 or hundred feet beneath the top. If you suspect an AM antenna, move on to the next jump site, Or get Tom Aiello to short it out for you. Get up, get off, get away. Dont get caught.

Lastly, take the antennas registration information, or Serial number or call sign to research further information on it, particularly on www.berkana.com or with the FCC.


Enjoy!

[hookitt 1]

Thanks truckerbase..... I will take Tom Aiello on all my antenna jumps from this day forward.

[Zennie 0]

I usually bring along a long stick and roast weenies in front of the transmitters as I climb up.

- Z
"Always be yourself... unless you suck." - Joss Whedon

[bps 0]

Excellent post Truckerbase! Your post should be a good reference for general antenna questions in the future.

I've moved to Idaho now (Mountain Home) so let me know if you ever need anything when you roll through. The Idaho Crew (aka the Spud Huckers) are working on opening up some new objects to compliment the bridge...so look for some new stuff in the future!

C-ya,

Bryan

[Skydawg 0]

Thanks 758, saved that for my reference library.

[Bennii 0]

thank you Tom and specially Truckerbase for your intelligent writing.

[Lee846 0]

Thank you Truckerbase for the full and usefull information. Is there any good methods to check if AM-antenna is working or not?

One AM-antennas complex i knew has 6 antennas. One in the center of the field and 5 other around it connetcted with the central one by the wires wide on the top.
Every antenna stand on an isolator. There is a metall 'ball' on the metal standing directly near the antenna' foot and another 'ball' attacher to the antenna' body a little bit over the top of isolator. It's the distance like several cantimeters bethween the 'balls'. I was told there should be 'electric flash' if you put some metal stuff bethween the 'balls' on the active antenna. Is it right?
Anyways we have an another method to check if that and other antennas switshed on or not... but that info i asked about may be usefull for the possible new sites. I guess that 'balls' are the typical stuff on the such AM-antennas.

Between two evils always pick theone never tried

[BASE813 0]

Quote

Is there any good methods to check if AM-antenna is working or not?

Last time I checked on some, I phoned up the Technical Director of the company that ran them, put on a geeky voice and explained I was an "antenna spotter" and could they give me some information on their set up..........

he was more than willing to go all technical and give out the information - out of the 12 AM'sthat used to be there and were running, he told me exactly which ones were live and which were dead...............

Nice one boys in opening up the dirty dozen before knock down.... may it all now rest in pieces..............

[TomAiello 26]

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Thank you Truckerbase for the full and usefull information. Is there any good methods to check if AM-antenna is working or not?

I believe TruckerBASE's method is to have a Tom Aiello grab the tower and see if he gets fried...

-- Tom Aiello

Tom@SnakeRiverBASE.com
SnakeRiverBASE.com

[truckerbase 0]

I jumped an antenna complex like that near Moscow (120 km north) with Den, a very rusted group of antennas in the forest near a road, that leaves your hands very red. This is near the "military complex" ? US AM antennas are usually in a line, but yes, that group was in a circle, and was visibly disintegrating. Basically if the antenna is standing on an insulator then you should assume its "on". The Balls you describe I remember, they allow a lightning bolt to find a ground without actually grounding the towers electrification, like the ring in a ring described above. Lightning hits the tower and then arcs over that short distance between the balls (or rings) to the ground, without any direct contact to the ground. The lightning is discharged, the electronics of the transmitter are isolated from the lightnings path to ground, and the antenna continues to transmit uninterrupted. Yuri, the master, and Den, the low puller, will rule your area and an understanding of local european objects; if they havent jumped it, it must have fallen down. You guys rock in the hardcore department.

Ps. I wouldnt play with am antennas to see if you can draw an arc from it, although some people suggest dragging a finger across it quickly to test it, this is like sticking a paperclip in an electrical outlet to see if its on or not. Even if it doesnt blow you to pieces, the electrical flash from such an arc has the ability to burn your retina. Please dont put metal stuff between an active antenna and any ground. Treat it as though it were live, even if it is a derelict ruins like the moscow site. Also, although that site was military (according to Den) a commercial am antenna will have listed hours of operation. The call signs or registration number should allow you to make an innocent call to the station to check on its status or to see if the broadcast day ends at a certain time, after which the antenna may be off. Still sounds like a lot of work, when you can always just go jump KGB buildings anytime!

ps. Inviting Tom Aiello over for a mushroom hunt (he loves sauteed mushrooms), and then casually and nonchalantly shoving him into the antenna body will instantly determine whether it is on or not. This has the added bonus of feeding Zennie who is perpetually trying to roast different things in different ways, and who always has a packet of hot dogs in his glove compartment for just such an occasion.

cya

[fab777 0]

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Zennie who is perpetually trying to roast different things in different ways, and who always has a packet of hot dogs in his glove compartment for just such an occasion.

cya

Hence the smell in zee german car...

Fabien
BASE#944