Re: Terry's New Plane Wave Antenna & DC's capacitive antenna

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Original poster: Steve Conner <steve@xxxxxxxxxxxx>


> One question I have been pondering is the transient response for 
> Terry's antenna.  At frequencies below the pole formed by the 20 nf 
> base capacitance and the 100 ohm impedance (50 ohm coax + 50 ohm in 
> series) or about 80KHz, neither end of the scope will be effectively 
> terminated.

There is no 50 ohm terminating resistor to ground in Terry's design. 
It goes into the 1 Meg input impedance of the scope, and the coax 
just looks like a capacitance which adds to the 20nF loading 
capacitor. So the pole is not at 80kHz like you say, in fact it is about 10Hz.

I can't remember if there is a series terminating resistor at the 
antenna end to stop reflection effects in the coax at higher 
frequencies, but it wouldn't really affect the conclusion of my 
argument if there was.

Merry Christmas all!

Steve Conner
http://www.scopeboy.com/