Re: Tesla Coil RF Transmitter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Gary Peterson" <gary@xxxxxxxxxxxx>


> Original poster: Ed Phillips <evp@xxxxxxxxxxx>
>
> . . . What is it you believe?  Do you believe he succeeded in making a device
> with NO capacitance?  "I have invented such an instrument and have
> demonstrated its efficacy."


It appears that Tesla was referring a vacuum-tube device for the 
detection of weak electrical signals mentioned in the original patent 
application for the 1898 U.S. Patent METHOD AND APPARATUS FOR 
CONTROLLING MECHANISM OF MOVING VESSEL OR VEHICLES;

". . . the by far most sensitive device of this kind of which I have 
knowledge, is a form of luminous discharge which is produced in an 
exhausted globe under peculiar conditions described by me, and which 
I have designated as the rotating brush.  This discharge is affected 
by the minutest variations of electrostatic potential or magnetic 
condition of bodies in its vicinity and may be utilized in a number 
of ways, as will easily suggest themselves to electricians, for the 
purpose here contemplated. . . ."

As can be seen from a comparison with the as-issued patent, some 
problem was found with this particular specification and it was removed.

It appears that Tesla used his rotating brush detector in conjunction 
with a helical-resonator receiving circuit to create his "ideal 
receiver."  He starts with his receiving transformer and then removes 
the "fourth circuit" or secondary, leaving just the elevated terminal 
and the ground connection. The coupling between the receiver's 
resonator circuit and the rotating brush detector is by electrostatic 
induction only, taking advantage of the small e-field the transmitted 
energy creates in the immediate vicinity of the resonator.  Keep in 
mind that he said the secondary of the receiving transformer had been 
removed.  That's the reason he says there is no "capacity current."

As for the practical application of this principle as it relates to 
this discussion, Tesla's rotating brush tube was improved upon by Lee 
de Forest resulting in the Audion triode detector.  Now we have even 
more sensitive detectors such as the solid-state MOSFET that can be 
used in the exact same way as Tesla's original device.

> Ed

Gary