All,

Can someone explain what is going on with this antenna? There are two resonant
points, one at about 4.5 MHz and one at about 6. The first one has a low
impedance and the second one has a high impedance. I actually saw this
phenomenon with a physical antenna being measured with an 8405a but had did not
recall ever hearing it discussed.

Thanks - Dan

CM Length X1 = 3
CM Length X2 = 2
CM Length Y = 2
CM X sections = 2
CM Y sections = 2
CM Rotate X, Y, Z = 0, 0, 0
CM Move X, Y, Z = 0, 0, 0
CE
GW 1 25 0.5 0 15 6.5 0 15 0.025
GW 2 25 -0.5 0 15 -6.5 0 15 0.025
GW 3 5 -0.5 0 15 0.5 0 15 0.025
GE 0
LD 0 2 13 13 1.e-3 3.e-5
LD 0 1 13 13 1.e-3 3.e-5
EX 0 3 3 0 1 0
GN 2 0 0 0 13 5.e-3
FR 0 1 0 0 4 0
EN

Dan, your LD commands are incomplete. You have specified a series RLC in
the middle of each of the end tags. You show an R of 0.001 ohms, and an L
of 30uH. There is no corresponding series C. What you have is an end
inductivly loaded dipole., with floating end segments. This probably
accounts for your anti-resonance at about 6 MHz.

Your GE 0 card is ok -- indicating no ground plane -- but you have retained
a Sommerfeld/Norton ground description in the GN card. Not that it makes
any difference to the final result.

Frank


"dansawyeror" wrote in message
. ..
All,

Can someone explain what is going on with this antenna? There are two
resonant points, one at about 4.5 MHz and one at about 6. The first one
has a low impedance and the second one has a high impedance. I actually
saw this phenomenon with a physical antenna being measured with an 8405a
but had did not recall ever hearing it discussed.

Thanks - Dan

CM Length X1 = 3
CM Length X2 = 2
CM Length Y = 2
CM X sections = 2
CM Y sections = 2
CM Rotate X, Y, Z = 0, 0, 0
CM Move X, Y, Z = 0, 0, 0
CE
GW 1 25 0.5 0 15 6.5 0 15
0.025
GW 2 25 -0.5 0 15 -6.5 0 15
0.025
GW 3 5 -0.5 0 15 0.5 0 15
0.025
GE 0
LD 0 2 13 13 1.e-3 3.e-5
LD 0 1 13 13 1.e-3 3.e-5
EX 0 3 3 0 1 0
GN 2 0 0 0 13 5.e-3
FR 0 1 0 0 4 0
EN