On 2/15/19 3:37 PM, Richard (Rick) Karlquist wrote:
On 2/15/2019 2:01 PM, n0tt1@juno.com wrote:
The question is, if a builder wants to make "loads" for bench testing
(to simulate the actual antenna feed point impedances), how is the
negative
load resistance simulated? If there is, say an impedance of -27 + j3.0
Ohms,
does the builder just ignore the negative sign of the resistive part of
the load
and use a 27 Ohm resistor in series with the required amount of inductive
reactance or what?
Thanks,
Charlie, N0TT
No, you definitely can't ignore the sign of the resistance.
See this construction article about how to realize a negative RF
resistance:
http://www.vk6fh.com/vk6fh/lambda_diode.htm
VK6FH shows how to use this to make a "Tunnel Dipper"
without the tunnel diode, but you can repurpose.
Rick N6RK
I'm not sure you can build a negative resistance antenna simulator with
that.. it's negative "dynamic resistance" (small increase in voltage is
small decrease in current), but still positive overall. I suppose you
can AC couple it, and then your circuit has to work at RF.
Another approach is use an amplifier, but that has all sorts of
complexities too - one could probably get it to work in steady state at
a single frequency.
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