FW: [Elecraft] Baluns and 450 ohm line

[kc4kgu@ENTERZONE.NET]

On Wed, 5 Jun 2002, Dan Barker wrote:

> Wow! That's quite a bit of wire - weight - money - wind load - failure
> points - up there!
> 
> What's the point? Can you please explain why an open wire fed 160m
> loop and KAT2 would do worse? Maybe if each loop were lower with
> higher freq (to control the takeoff angle?). Beats the poop out of me.
> 
> Dan / WG4S / K2 #2456
> 
> <snip>I have since built full-wave loops for 160m, 80m, 40m, 30m, 20m,
> 17m, 15m and 10m.<snip>


The answers are:

(1) Pattern and angle of radiation.  When you start moving UP in frequency
from the design frequency, the antenna will begin to exhibit more gain,
flattening the nice sphere radiation pattern you get with a full-wave loop
into what sometimes looks like a clover-leaf and what other times
resembles a bug that hit a winshield at 75mph with little or NO energy
going to high angle radiation and most of it down in the 25-40deg takeoff
angles.  This is great if you want to work 10m DX with your 160m loop.  If
you want to talk to the guy 300mi away, you'll bounce right over him
though.  He'll never hear you.  With an antenna for each band of interest,
I have the choice.  I can use the one cut for the band and get the nice
sphere pattern, OR I can use one of the antennas designed for a lower
frequency and achieve gain and low angle radiation.  The best of both
worlds and it all fits in a nice square 135ft per side.


(2) It is seriously not that much wire, weight, wind load, or failure
points.  The ENTIRE antenna system has less wind load than your _average_
amateur tower.  There is about 1250ft of wire used for the antennas. They
weigh maybe 25 lbs or so, all together.  You call them failure points, I
call them REDUNDANT systems.  If something happens to one of the antennas,
I can use one of the others.  It may not be as efficient, but, it WILL
tune up.  If a person only has one antenna and something happens to them,
I suppose that they can load up their dummy-load but, I somehow don't
think it's going to have the radiation efficiency of one of my loops.  As
for it being lots of money involved, I have less than $300 or so invested
in this antenna system and that includes the remote coax switch.  Wire is
cheap at Home Depot.  Coax is cheap when you buy it in large bulk.  Remote
coax switches are cheap on eBay.  The only thing I've invested a lot of in
this project is my time.  It is something I enjoy doing.  I have been
planning an elaborate antenna system ever since the first snow hit the
ground last winter.  I made it through winter with a 75m dipole, coax
fed.  I promised myself that next winter would be different though.




73 de John - KC4KGU
K2/100 #2490