JB wrote:
"Jim Lux" wrote in message
...
Ralph Mowery wrote:
Why are you using a 4:1 balun with a dipole ? If it is a simple dipole
with
only one wire in each direction instead of a folded dipole the impedance
is
around 70 ohms. If you decide on a balun it should be a 1:1.
When adjusted for the lowest swr you may find that 1.4 to 1 is about as
low
as it will go if you use a 50 ohm coax.

"Pete" wrote in message
...
I question my calculations for a inverted-V dipole length for 50150 and
28400 into a 4:1 balun. I think they came out too short for 200ohms
center Z

Can someone confirm my two calculations?

Thank you!



With a V, you can get the feedpoint impedance right to 50 ohms..
somewhere around 120 degrees included angle

Dittos. Radiates equally poorly in all directions though

The pattern from a inverted V with 120 degree included angle (30 degree
droop from horizontal) is almost the same as a horizontal dipole at the
same height. If the apex of the V is about 1/3 of the droop distance
higher than the dipole, the "ground reflection" component is about the same.

For the 10m example here, the dipole is 5m long, roughly. A 30 degree
droop is about a meter on the 2.5 meter leg on the dipole. (e.g. sin 30
is 0.5), so putting the dipole a foot higher (30cm) will give you almost
the same pattern as a horizontal dipole.




A rotatable
dipole or 2 el beam would be a simple project.

given the complexity of rotators in general, rigging up two crossed
dipoles and a switch might be a better solution.