Re: About dipoles and current/voltage nodes
- From: Richard Clark <kb7qhc@xxxxxxxxxxx>
- Date: Tue, 28 Feb 2006 14:07:12 -0800
On Tue, 28 Feb 2006 14:25:32 -0600, Bob Bob <bob3bob3@xxxxxxx> wrote:
The question is this. If one hangs a 1/2 wave dipole in free space I
assume it receives such that current maximums are at the centre and
voltage maxiums at the ends. Is this the case whether a feedline is
connected or not?
Yes.
If I then take a stripline cct terminated at one end with a 50r resistor
and a detect diode at the other and is a half wave long, what is the
current/voltage distribution in this configuration.
The point of your need at work is to insure that stripline presents a
50 Ohm characteristic as an untuned line, not a resonant line. Of
course, you can perform the same using a tuned line, but this seems
unlikely barring new details offered by you.
What I wonder is if it is a halfwave there may be no voltage at the
detect diode input. (It could be 3/4 wavelength when one factors in pcb
dielectric and end loading)
And this would be reason why to NOT have it be a resonant line. I
presume there's a ground in the vicinity for both this sniffer section
and the main feed (which also needs to exhibit a characteristic Z).
Such devices are generally useful over an octave range.
Thoughts?
This, of course, does require attention to factors such as pcb
dielectric as you have already taken care of end loading with the
resistor and the diode.
73's
Richard Clark, KB7QHC
.
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