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Re: LF: Unusual radio mast video Ukraine ??

To: <[email protected]>
Subject: Re: LF: Unusual radio mast video Ukraine ??
From: "Mark" <[email protected]>
Date: Sun, 23 Dec 2012 17:51:48 -0000
Importance: Normal
In-reply-to: <CAMFjj71=k9Abd_3_qS=ecX2EY2iXrjZSJpYjMtO+bSu5yLM+sw@mail.gmail.com>
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Warren and all
For a single service 1/4 wave system that may be true, my point is that there is a VERY REAL RISK of injury  from these systems especially in the UK
Many of the MF broadcast systems here have multi-coupled transmitters, and the mast is not a 1/4 wave at all these frequencies. The medium wave band spans about an octave. On smaller systems the antenna is electrically quite short compared to 1/4 wave.
 The DPI is frequency dependant but can be quite high (at least in the reactive part) leading to very high voltages at the base.. Multiplied by 4 or more transmitters each running 50 to 200kW of AM
 Mast base insulators that i am familiar with are typically rated at 120kV and there are some systems where the peak voltage here is the limiting factor for the numbers of services we can actually run into the antenna at once.
 I have seen small mammals and birds bridge the spark gaps..  there is not much left after.
 if an arc is generated, it ionises the air along the path, and this forms quite a good conductor to the nearest earth.    If the nearest earth is you...
 Arcs are also capable of being sustained for quite a while.. they do not necessarily cause the transmitters to trip.
 
 
A brief note about the effects of MF RF currents
The current will actually flow mostly over / through the upper layers of your skin, you will not be electrocuted. That would be a kindness
You will however be subjected to extreme temperatures associated with the plasma of the arc. These will be worst at entry and exit points for the RF current flow.
The guy holding the plants in the video almost certainly had small burns under his gloves, as an arc would form there too.  That's why he was felt pain without there being any obvious cause (from the video)
The effect would be like touching an arc welder.. there is probably not enough voltage to do any harm, but would you put you finger where the arc was struck?
RF burns wont necessarily kill you but lying helpless and undiscovered because you have severe burns etc. and can't walk, could.
 
I am merely pointing out that what the guys in the Ukraine did was incredibly foolish, but they got lucky.
If someone were to try the same trick on the wrong site they may not be able to post their exploits on Youtube
 
 

Sent: Sunday, December 23, 2012 4:58 PM
Subject: Re: LF: Unusual radio mast video Ukraine ??

Mark,
       I don't know what the power of the system is but I suspect that since at the base of 1/4 wave antenna the voltage is lowest this might be running substantial power. Also note that they are drawing arcs with grass, not metal or a graphite pencil. Very likely that they would have been killed if they had used a metal spike to draw the arc or if they had been standing on damp ground etc.

73 Warren K2ORS



On Sun, Dec 23, 2012 at 8:10 AM, Mark <[email protected]> wrote:
All
The antenna in the  Ukrainian video looks to be quite a low power system.
If you try that on a high power system  you would suffer serious injury or even death.
The arcs drawn in the video were a few mm long. I have seen arcs from high power systems over 6" long  and some considerably longer.  Once an arc starts it can self sustain, even bypassing the path that started it..
 if you became part of the path to earth things would vaporise quickly, including parts of you.
 These systems are very dangerous.  Don't try this at home (or on a local radio transmitter site)
 
You have been warned.
Mark GM4ISM
 Broadcast engineer...
 
 

From: Graham
Sent: Sunday, December 23, 2012 12:28 PM
Subject: LF: Unusual radio mast video Ukraine ??

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--
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1

 

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