Re: 1/4 wave transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: Mddeming@xxxxxxx 

In a message dated 5/6/06 10:04:48 P.M. Eastern Daylight Time, 
tesla@xxxxxxxxxx writes:
Original poster: "Langer Giv'r" <transworldsnowboarding19@xxxxxxxxxxx>

Hey everyone, I have been wondering for a while, where does the 1/4
wave setup get its name from?  (ex how does it transmit in a 1/4 wave)?

Thanks a lot



Hi Langer,

    Without breakout, a Tesla coil normally will have the minimum 
voltage at or near the bottom and maximum at or near the top, while 
current is maximum at the bottom and minimum at the top. This is the 
distribution pattern of a 1/4 wave at the operating frequency. Also, 
to a crude approximation, a TC of "average proportions" will 
frequently have a wire length "in the neighborhood" of  1/4 it's 
unloaded operating frequency.  This has given rise to a lot of myths 
over the last hundred years or so that the wire must be exactly 1/4 
wavelength for maximum efficiency. Tesla made such an assertion 
during his early research in the 1890's.It has since been repeatedly 
shown that this is not valid, but those who would burden Tesla with 
infallibility as well as genius keep propagating the myth.
    A moment's reflection will show that this is unreasonable:
1) Propagation along a coil is not the same as propagation along a 
straight wire.
2) Adding a topload drops the operating frequency ~50% and alters the 
current distribution.
3) Streamer formation also drops the operating frequency so that it 
varies with each spark.
Obviously, if an exact match were necessary, a TC could never operate properly.
Similarly, a double-ended coil, fed from the middle shows voltage and 
current  distribution patterns similar to a 1/2 wave antenna,

Matt D.