In a message dated 7/4/01 6:21:14 AM Pacific Daylight Time,
kbottles@rafn.com writes:
<< Here is another approach to "wires in the tree" that I happened across
this Field Day.
I was riding my bicycle on Field Day Sunday morning and I came across
the North Kitsap Amateur Radio Club gang.
After introductions and the such, I noticed that their wire antennas
were way the heck up in some Douglas Firs.
Like 80-100 feet up. So I asked "How the heck did you get them so far up
for Field Day?"
Answer: Potato Gun
Only took several shots from an experienced cannonier and they were in
business with some very high wires. Seems like there could be some home
application here.
Cheers!
Kim Bottles - K7IM
Bainbridge Island, WA
>>
I saw this Potato gun in action and it's impressive. A fairly heavy
weight of potato is very well accelerated at a fair velocity. Having a fair
knowledge of internal ballistics I would make this suggestion. I'd wrap the
combustion chamber with several layers of fiberglass cloth and resin and
progressively less to about 1 foot from the muzzle. As is don't stand
directly behind it. The pressure rise is very fast and that puts great strain
on the tubing and joints however joined? The quick squirt of gas in the
chamber is a bit hard to measure. Repeated firings will weaken any plastic
and joints. Just a suggestion. As I recall it's made from PVC tubing.
Another "Magnum Sling Shot" was shown in CQ Mag. A 3' 2"x2" is anchored to
the top of a 6-8' step ladder and surgical tubing is used to a leather pouch
to launch fairly heavy potatoes weights about as high as you would want to
go. The angle of the step ladder is about right also. I've used sling
shots, fishing rods and bow and arrows. The main thing is to get it high
enough so that it falls to the ground on the other side and that is why the
"Magnum Version" works so well--one shot if your aim is good. If it doesn't
it can get hung up on branches before it hits the ground and it's almost
impossible to pull it back.
One time I joking described gamma Matching a "Silver Maple of Iron Wood
Tree" by connecting the coax shield to the root system. Pull down limb about
10' high and make a "Limb O Match". Use the limb that gives the best match.
The branches are not too inductive so no series capacitor is needed. Some
limbs are fairly inductive if the SAP reactance level is high. A perfect
Limb O match can be made by using certain length of limb but connecting it to
a capacitor make from the outer bark. You cut a 1" groove in the bark all
the way around the tree about a foot apart to isolate it from the rest of the
tree making a tubular Bark capacitor. The width of the sleeve determines the
capacity. It's location determine the Z match. Start reducing the width of
the sleeve to reduce the capacity until 1:1 is obtained. It's called the
"Bark O Match. You might have to practice on a tree or 2. It makes a great
broad banded vertical and it's very quite. Pine trees have the right taper
for a circular "LOG PERIODIC" for talking to the satellites and Flying
Saucers. Their conductivity is on the low side but if you feed it salted
water for a day it becomes progressively conductive. The gain increases for
about a week before it tapers off.
Don't laugh--I've seen in Army Training Manuals some of these very
suggestions. They even suggested connecting to fence wires which I've
already done. On metal fence posts I've bent the metal tab back and added a
wrap around Delrin insulator and bent the metal tab back to secure it. I've
run green insulated wire on the ground on the 3 neighbors property edge under
a fence and they have mowed right over it. It blends right in the grass in a
short period of time. Its a great listening antenna on the BC band, 160,
80/75 and even on 40M. It matches easily with an L Network contrary to those
who have problems using them and the bandwidth is great. I've even grounded
it at the end and it's a "very quite antenna". Preamps enhance their
performance on receive and I've even transmitted on them. I will run a side
by side test on 2 of them with one ungrounded.
I have a lake in my back yard here and it freezes over for about a week once
a year. I ran an insulated wire over the ice and used it was an "Ice
Beverage." As the ice melts it fell to the bottom and becomes a "Mudder
Beverage." Would you believe it's very obvious it would never work in LSB so
it didn't work well on 160-40M. The Ice Beverage works great on both LSB&USB
and it's a real "cool antenna." It's a high angle Beverage on USB and a low
angle Beverage on LSB using the gain of a long wire and "Mud Reflections."
On CW it was both. Lake mud is a very high conductivity in particular in SD.
That's an absolutely true story, I just made it up. K7GCO
List Sponsor: Are you thinking about installing a tower this summer? Call us
for information on our fabulous Trylon Titan self-supporting towers - up to
96-feet for less than $2000! at 888-833-3104 <A
HREF="http://www.ChampionRadio.com";>
www.ChampionRadio.com</A>
-----
FAQ on WWW: http://www.contesting.com/FAQ/towertalk
Submissions: towertalk@contesting.com
Administrative requests: towertalk-REQUEST@contesting.com
Problems: owner-towertalk@contesting.com
|