FM/AM A´s

[Faber]

Just found out that a A nearby me (looks like AM tower),i just found out it has a working FM unit onit aswell(acording to thier web).

Now this made me wonder,can both AM and FM work on the same tower?
If not,can a old AM tower be used as FM tower if the AM part is shut down(ie safe for me to climb the thing)?

how much is 2000W on a tower compared to other towers?

Please help me out to understand before i make the call to be 100%sure..

Thanks

[Mac]

Just found this in the archives............... I only looked over it quickly so not sure it helps you.

PS) Faber dont be lazy and search the net!!! hehehe


Name: Inbar Raz
E-Mail: inbar@glx.chief.co.il
Subject: AM and FM antennas
Body of Message:
Hi everyone.
I'd like to get some information as for climbing the above antennas.
I know that an AM antenna broadcasts from its entire length, and that touching it while standing on the ground gets you fried.
Does anyone have a safe way of climbing such an antenna? I've heard stories as freaking as "you can get electricuted just from walking clost to it".
Also, suppose I found a way to climb it - say, some long, wooden ladder, is staying on a broadcasting antenna too dangerous, radiation-wise?
What about FM's?
Thanks,
Inbar.
Added on Date: 11:30:19 12/19/98
Name: Mark
E-Mail: msheehan@networksplus.net
Subject: Re: AM and FM antennas
Body of Message:
: Hi everyone.
: I'd like to get some information as for climbing the above antennas.
: I know that an AM antenna broadcasts from its entire length, and that touching it while standing on the ground gets you fried.
: Does anyone have a safe way of climbing such an antenna? I've heard stories as freaking as "you can get electricuted just from walking clost to it".
: Also, suppose I found a way to climb it - say, some long, wooden ladder, is staying on a broadcasting antenna too dangerous, radiation-wise?
: What about FM's?
: Thanks,
: Inbar.
You are correct that AM towers broadcast over its entire length. I've also heard stories of arcing between the tower and the ground producing a "lightning bolt" appearance. I simply avoid them. I have heard people have stood on milk crates or have simply jumped to avoid contact with the ground at the same time. Just remember, once you're on the AM tower, your body becomes part of the transmitter.
As far as FM towers go, the tower itself is simply a platform for raising the antenna high above the ground. There shouldn't be any problem touching an FM tower and the ground at the same time. Most I have seen even have a grounding strap connecting the base of the tower to the ground. FM towers can also have multiple antennas attached to them. The owner of the tower will often lease space at different altitudes to other companies. The main mast on top probably has the strongest signal and should be avoided. I like to stay 50-100 feet below it. The other antennas on the tower could be HAM radio/trucking company/service company repeaters, or the like - who knows... They are generally much less powerful. How can you tell? Look at the signal conduit running to the antenna in question. The larger the conduit - generally the stronger the antennas transmission signal. Many times you will also see small conduit join into a large piece, go up the tower, join to another small piece next to the antenna and go to the antenna. In this case, the smaller pieces are simply used as flexible "jumpers" and they determine the max signal strength capability. The larger, less flexible conduit is simply used to reduce the signal loss over the large distance travelled going up the tower.
Hope this helps some.
Mark
Added on Date: 16:54:54 12/19/98
Name: Orn
E-Mail: orn@vTuner.com
Subject: Re: AM and FM antennas
Body of Message:
Whatzup Inbar, one guy that works a lot with power towers and antennas told me that one of his group just climbes the fences surrounding the antenna that has power on it and jumps over to it in order not to get fried !
I don't know but it sounds pretty extreme to me.
bsbd
Orn
Added on Date: 22:35:59 12/20/98
Name: Paul
E-Mail: tourist@cam.org
Subject: Re: Re: AM and FM antennas
Body of Message:
Can you tell by looking at an antenna whether it's AM or an FM? Could someone describe the visible differences? THanks
Paul
Added on Date: 23:19:06 12/20/98
Name: BASE428
E-Mail: fixed@321cya.com
Subject: Re: Re: Re: AM and FM antennas
Body of Message:
: Can you tell by looking at an antenna whether it's AM or an FM? Could someone describe the visible differences?
FM antennas are grounded. You'll usually see large copper wires running from the structure into the ground nearby. They are typically taller and have a central weight bearing point on a concrete pad.
AM antennas are evil. They are typically freestanding due to the requirement to sit on porcelin/ceramic bases to isolate them from the ground. If you see this ceramic base (6-15" high and near the base) on each leg, stay away unless you know what you're doing.
Unfortunately, I joined the "SHOCKED BY AM ANTENNA" club back in 1996 when a inexperienced base jumper took me to his favorite freestander that he had jumped over 5 times. He assured me it was cool and I didn't think much of it since he had jumped it so many times. I didn't notice the porcelin bases at first. This turned out to be a big mistake. Anyway, the other jumper started climbing and I grabbed a steel support on the antenna. A few seconds later, I felt a massive sting on my fingers that felt like a hornet had stung me. Pulling my hand back in pain, I got stupid again and wondered what the hell had zapped me. So I grabbed another part of the antenna to have a look at the area where I got "stung" and then got nailed again on the same hand. By this time, I got just a big smarter and noticed the porcelin bases and realized it was a hot AM antenna. Just then, my friend got zapped also. My hand was OK, his glove had a hole in it and he had mild burns to a few fingers. The reason we didn't notice the porcelin bases was because someone had PAINTED over them with the same color paint as the entire antenna. The lesson here folks is to check your entire thoroughly before climbing. This porcelin base was very hard to see for us. We climbed it and jumped it anyway. A picture of this antenna is my picture of the month located at:
Click Here For the Killer Antenna
I jump another AM antenna near my house, but the current is too low to shock us. We jump onto it anyway. Maybe I'll just bring my multimeter next time - one probe into the ground, the other on the structure
base428
*Can you say "President Gore" ???
Link: The fixed page!
Image: Click for IMAGE
Added on Date: 23:54:26 12/20/98
Name: Dwain
E-Mail: DwainWeston@bigpond.com
Subject: Re: AM and FM antennas
Body of Message:
: Does anyone have a safe way of climbing such an antenna? I've heard stories as freaking as "you can get electricuted just from walking clost to it".
Hi Inbar,
AM antennas are jumped on a regular basis in Australia. A number of people have been zapped and burnt (some quiet badly) getting onto them over the years. We always jump onto them (and we jump as high as we can before we contact them).
A local 400ft AM antennae has 10,000 volts running through it and transmits 10KW of power. It has a friendly sign at the base that says "Danger. Extreme Electromagnetic Radiation. Do not climb...blah blah blah". A friend contacted the owner to ask if we could legally jump it for an advertisement. He talked to the chief engineer who said it was likely that 30 minutes exposure time (the average time we spend on the tower) would result in cancer within 20 years or so (due to mutation of the cell DNA from the electromagnetic radiation).
The BASE jumpers theory is the chief engineer is trying to scare us off, however are there any BASE jumpers in the world who have been jumping AM towers for over 20 years?
Apparently if you climb inside the antennae you don't get exposed to as much electromagnetic radiation because the transmition from the three corners of the triangle cancels each other out in the centre.
The general advice to newbie BASE jumpers is "If you don't want two-headed children then stay clear". No regular AM antennae jumper that we know has produced any children yet (that they know off anyway), but we await in interest for the results.
Anyway, no one in Australia has felt any adverse effects to jumping them (other than the odd electrocution, object strike and angry security guard/policeman).
Added on Date: 02:38:11 12/21/98
Name: Tom B
E-Mail:
Subject: Re: Re: AM and FM antennas
Body of Message:
: "No one has felt any affects" apart from Little Buddy who got violently ill for a whole day after waiting up the top for quite a while for daylight. Also recall your own experiences at those antennas in NthEast Australia. You were supervising a few jumpers at the top for a while and you got a little sick afterwards.
I have felt electric energy (probably static charge only but who wants to take chances huh) on the 400 footer you were talking about.
Having said all of that most BASE jumpers don't want kids and they don't care if they live another twenty years anyway, so go for it. Jump those antennas.
Added on Date: 06:00:42 12/22/98

[Faber]

good tread dude but it dosnt really clear my Q´s does it ;)

[mt7wildcard]

I've never seen or heard of AM and FM sharing an antenna.

The average handheld FM transceiver radio is 5 watts and automobile mounted units can be 25 to 50 watts. 2000 would be a 'normal' wattage amount for an FM tower.
2000w is relatively low for any AM transmissions. They can be 50,000 and up. Way up.
It all depends on how far they want their signal to travel.
Do you ever pick up German stations there at night? Stay away from those towers.

[Faber]

I've never seen or heard of AM and FM sharing an antenna.

The average handheld FM transceiver radio is 5 watts and automobile mounted units can be 25 to 50 watts. 2000 would be a 'normal' wattage amount for an FM tower.
2000w is relatively low for any AM transmissions. They can be 50,000 and up. Way up.
It all depends on how far they want their signal to travel.
Do you ever pick up German stations there at night? Stay away from those towers.
Living really close to Germany i can actualy get german channels on a houseantenna..(theese inside)

Thanks alot for your answer.i think this A will have a visit soon(as the weather premits) :p

[TowerTopper]

Yes, an AM tower and some FM bays can be co-located as the same tower, The tower may or may not be "hot" if you touch it while standing at the base of it, it depends on which way they planned it and how much they wanted to spend on it, if it's "shunt fed" it's ground at the base, so go ahead jump on it and don't touch any antenna elements and you'll be OK, if it's "base loaded" and sitting on giant glass insulators you best take an old spare tire to stand on while tring to climb on, RF burns suck, they burn from the inside out and can be painful. Becareful about climbing on any equipment boxes around the base of the tower also if "base loaded", they could be part of the tuning circut and zap you just as fast, the best thing besides the spare tire to get safely on the tower is a picnic table from the employee smoking area.

Here's a link on co-located am/fm towers...

http://beradio.com/departments/radio_multitenant_towers/