[Lowfer] Antenna Questions

[Jim]

I'm hoping to have a LowFER beacon on from West Georgia in a couple of weeks. 
Actually had hoped it would be on by now, but a bout with the flu and a lot 
of travel with a new job has interfered with the fun.

I'm thinking of building both a vertical and a loop antenna just so I can 
tinker with both styles. We have 20 acres and there are parts that are 
heavily wooded. Also the portion near the house is not the highest part of 
the property (but not down in a hole either).

My shack is in the basement and about 50 feet to the side is a fairly good 
sized (probably 50 x 50) pen where we keep the dogs when we don't want them 
running the ranch. It is constructed with t-posts and welded wire.

There are a few short trees to the back of the pen, but basically I've got 
tall trees on both sides of the pen with a clear shot across. The trees are 
pines and they sway heavily in the wind.

For the vertical, what I'm thinking is running about 30 feet up and then 
having a T at the top with maybe 20 feet on each side. (Staying within the 15 
meter total, just throwing out rough numbers. But also using what I guess 
some consider a liberal interpretation that you measure the radius at the 
top, not the diameter.)

One question I have is, does it really matter if the 30 feet are "vertical", 
or could they slope and still have the T for top loading? I'm thinking I'd be 
ahead to slope towards the corner of the dog pen so I can use the fence wire 
as the ground instead of having it all drop down in the middle of the pen.

Also, is there value in having a loading coil up where the T is formed in 
addition to the coil used for matching at the bottom? I was going to build 
the insulator of the T out of something like 4" PVC and wind a foot or so of 
coil on it in addition to using it for mechanical strength.

One the loop, there are a pair of trees about 40 feet apart and probably 60 
feet tall or so on one side of the dog pen. I'd like something easy to 
install and work on and I've had my share of frustration with slingshots, 
bows and such. So what I was thinking was getting around 50 feet of PVC pipe 
to put at each end. Basically I'd hook the side of the loop to the PVC pipe 
and then strap the pipe to the tree. I was going to try to get the bottom of 
the loop about 10 feet off the ground.

If I went that route, would there be any advantage to having what amounted to 
loading coils in the side of a loop? I could either have a gentle wrap (a 
turn a foot or so) up the entire length or I could put in more 
traditional "coils" bottom, middle, and/or top. I was thinking of using 2" 
PVC (because I've got some handy) with a gentle loop up the entire length. I 
have no particular reason for going that route, it just somehow strikes me as 
an interesting thing to try.

I've also thought that I might use two or three conductors up the PVC in 
parallel to reduce the resistance in that portion of the loop.

At this point, I'm just kind of tinkering. I figure I'll try a couple of 
different things that are fairly "low effort" and then put more effort into 
the approach that seems to get the best results.

I have got most of the hardware built. The only thing I need to do is build 
a "driver" circuit that will take the output from the crystal oscillator out 
over some coax to the final which will be at the antenna location. Right now 
I can drive the final with three or four feet of coax, but need something 
with more umph to drive 30 or 40 feet of coax. Keyer is a PICBeacon with 5 
wpm, QRSS-10, QRSS-30, or QRSS-60 being selectable.

Any antenna suggestions would be welcome. And like I said, looking more to 
tinker instead of for the definitive "this is the best" right now. With all 
the trees, I'm thinking the loop may be where I end up, but who knows. After 
all, that's how we justify going for Part 5 licenses from the FCC at a later 
point, isn't it? :-)

73 de
Jim W4JBM

http://www.geocities.com/w4jbm

"With a soldering iron in one hand, a schematic in the
other, and a puzzled look on his face..."

Working the world from the New Dog Iron Ranch!