Re: Antenna physical size & shape

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Vardan <vardan01@xxxxxxxxxxxxxxxxxxxxxxx>

Hi,

At 09:39 AM 4/8/2006, you wrote:
> I have an idea.  A transmitter antenna radiates output power just 
> like the topload of the tesla coil radiates sparks.
>
> Does the physical size of an antenna increase or decrease the output 
> power?  I know an antenna needs to be tuned to the circuit.   A 
> multi element beam antenna for example, 2 element beam compaired to 
> a 4 element beam.  Next a 4 element beam antenna compaired to an 8 
> element beam antenna.   The 8 element is physically larger than a 4 
> element and it is larger than a 2 element.   Reception and power 
> output are both better with the physically larger antenna.
>
> My next thought is, an anateur radio antenna like 80 meters, 40 
> meters, 20 meters, 2 meters do not physically radiate visible 
> discharge sparks like a Tesla coil.   WHY?    If the anateur radio 
> antenna were to be retuned would it radiate sparks that could be 
> seen just like a tesla coil?  If so then would it still transmit a 
> signal several 100 miles to a receiver?  If a tesla coil topload 
> were to be retuned would it transmit just like an anature radio antenna?
>
> Maybe we should think of our tesla coil topload more like an antenna 
> or maybe we should think of an amateur radio antenna more like a 
> tesla coil topload.  What if an amateur radio antenna were made of a 
> toroid shape or sphere shape with smooth round surfaces that would 
> not have permature discharges would it transmit better?  What if a 
> tesla coil topload were though of more like an amateur radio antenna 
> could be be designed to produce better discharge sparks?
>
> Gary Weaver

Normally a "tuned" antenna no matter what it's shape or configuration 
presents a resistive load of 50 ohms.  If we load our Tesla coil with 
a 50 ohm resistor, the voltage will be trivial as it is for radio 
antenna's  The top voltage is simply a function of power and 
resistance.  At 10,000 watts into 50 ohms we get 707 volts...

A Tesla coil could not directly drive a real antenna due to enormous 
impedance miss match.  We could redesign it to match into 50 ohms but 
then we would just have a dull old radio transmitter of the spark gap 
transmitter days...

In the Tesla coil, we tune into a low capacitance high resistive 
component top load to get super high voltage at the expense of radio 
radiation (a good thing, less we attract the attention of the federales).

Cheers,

        Terry