[Elecraft] how did I calculate the loss?

Wed Dec 17 11:20:02 2003

Stuart,

I just ran a simulation of this and I get a 20 dB imbalance. That is, =
the antenna current is 10X higher on one side than the other.

This particular case, and many of the other cases sited in the past two =
days are incredibly easy to simulate with NEC. The case of routing the =
feedline away from a dipole and what balun impedance is needed to reduce =
feedline radiation to some desired level is another example of what can =
be modeled with NEC. I will write an article this month on this subject =
to get more people thinking about, and modeling, antenna =
balance/imbalance.=20

  Dave WX7G

-----Original Message-----
From: [email protected]
[mailto:[email protected]]On Behalf Of Stuart Rohre
Sent: Tuesday, December 16, 2003 5:08 PM
To: Don Wilhelm; Jimmy Lee
Cc: [email protected]
Subject: Re: [Elecraft] how did I calculate the loss?

Don makes good points about balance.   Hams may over react to issues of
balance.
According to the noted antenna guru L. B. Cebik, he has calculated that =
even
in the extreme unbalanced case of the parallel line feeder end feeding a
half wave doublet, there is only about 10 per cent imbalance even with =
one
side of the feeder not connected to anything at the antenna end =
insulator,
and the other conductor connected to the end of the doublet.  That was =
an
eye opener.  Naturally, the capacitance from conductor to conductor and =
the
series inductance of the feeder must mitigate the extreme imbalance an =
open
circuit feeder appears to be.
73,
Stuart
K5KVH

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