[Antennas] More Ladder Lines and Beams

[Sandy and Kees Talen]

Thanks, lots of good information coming in.  

One solution would be to lower the impedance of the ladder line to 
more closely match the beam antenna. The only way I know how to 
do this is by decreasing the gap (will increase the capacitance and 
loss) or increase the diameter of the conductors (I don't have a desire 
to run 4" or whatever parallel aluminum tubing). Parallel ladder lines 
would work too ....or stacking several ladder lines spaced apart by ?

How about things you could do with open line that are not possible 
with coax ....like progressively narrow the spacing on the transmission
line starting out with 2" (about 600 ohms) and ending with the equivalent

of twisted pair (about 100 ohms ....maybe less) which is one heck of
a lot easier to route around the rotor. The low Z end would be lossy 
but it's only that small portion. Or things you can do with the beam 
since you DON'T intend to drive it with coax ....like what is required to

make the beam look like 400 ohms, or at least higher than  50 ohms ? 
I see antenna articles all the time with ladder line tied directly to
dipoles, 
etc. I haven't seen problems discussed there......maybe an oversite. 
One of the beams I've had had one side grounded to the boom, this one 
does not and nowhere does it tell you to ground one side ...so this is 
essentially a dipole. The only thing it tells you is to add a choke (8
turns
of xx" diameter....or a ferrite bead choke) at the beam to force current 
off the outside of the coax since the beam IS a balanced load. 

Brings up another point, how many people ground the coax at the tower ?
Seems like creating a ground loop to me since the only "connection" you
want from the center conductor to the shield is the load itself.    

Please, any comment on : Another question:  how much loss can 
you expect across a 4:1 balun, say the typical small ones in an antenna 
tuner ? I've always assumed it to be 10%+/-. Why do most manufacturers 
assume a 4:1 is "good enough" for matching 50 ohms to 450 ohms ?  I
replaced mine with a 9:1 balun (three? cores which, of course costs more 
...that may be the answer). Loss effect of using three cores ? effect of
core 
material selection or just use the powdered iron "red" 3-30Mhz ones from 
Amidon. Ferrite vs powdered iron in this application ? Power handling ?

73s  Kees K5BCQ