[Lowfer] Re: 600MRG> Link to some darn good antenna designs...

[Bob Roehrig]

On Fri, 1 Feb 2002, Lyle Koehler wrote:

>
> Bill Ashlock is correct in stating that if you make the capacitance in the
> return wire very large, eventually you have created a loop antenna. However,
> unless the enclosed area of the loop is very large (Bill's antenna must be
> something like 225 square meters), it probably won't radiate as well as the
> top-hatted vertical without the shunt capacitor. Since the author mentions
> using 6-foot top radials, it doesn't sound like something that would make a
> very efficient loop!

Lyle, I assume, since you mentioned 6 foot radials, you were referring to
my setup. My original LF antenna was originally put up for 600 meters.
It is a 30 foot vertical with a 2mh loading coil at the top (that much
has not changed). Originally I had a set of three 6 foot long radials,
scrounged from a 6 meter ground plane, which resonated the system at 480
kHz. I figured that these were pretty small to be effective at 1800 meters
so I removed them in favor of 3 wires (2 are about 20 feet long and the
third one is 50 feet). It is really an umbrella configuration, I suppose,
since the 3 capacity hat wire do slope.

What I have been playing around with is either adding inductive base
loading and/or various values of capacity from the end of the 50 foot
sloping wire to ground.   In a way, it is a loop, although really
triangular shaped. The ground, besides being the ground at the ham tower,
is also the end of one of the vertical's radials.



                    73        Bob Roehrig        K9EUI
                    Aurora University Telecom/IS dept.
                    630-844-4898   broehrig@aurora.edu