The Low Frequency Transmitting Antenna
This is the new Low Frequency Transmitting Antenna. I completed the
top hat on 9/30/00 and RM and I tipped it up the same day. Due to
the fact that it is better built and is farther from the trees, it performed
better than the old antenna even without the top hat and I am seeing another
4 dB increase in signal strength with the top hat. The
old antenna was 50 feet from the house and close to the trees, this one
is 250 feet from the house and I cleared the trees back so that nothing
is within 50 feet of the antenna. The first set of guys is 24 feet
up from the insulator at the base of the mast, the second set is 39 feet
up and the top of the mast is 42 feet up from the insulator. The
top hat is made from the elements of the Mosely TA-33 that was destroyed
in the ice storm Easter 1999. It has an 8 foot radius (added to the
42 foot mast we have 50 feet, the limit of the law for Lowfers).
This is the base of the antenna. I found an old insulator and mounted
it on the top of an aluminum pipe that is 8 feet long with 4 to 5 feet
in the ground. The pipe that is the mast is hinged just above the
insulator so that the whole thing can be tipped over to work on it.
The radials are stranded number 12 house wire that are 50 feet long and
stapled to the ground with aluminum "j-hooks" that are used in chain link
fence work. The grass grows around the wires so that after a month
or two I have to really look to find them.
This picture shows the 12 inch long fiberglass rods that are used to insulate
the antenna from the guys. The insulators on the bottom guys are
4 inches from the antenna but the ones on the top guys are about 10 feet
from the antenna. This allows part of the top guys to act as a small
part of the top hat. If you notice a slight greenish tint to the
wires on the top hat it's because they are plastic coated aluminum clothes
line wire. (I had trouble finding aluminum wire but RM had some lying
around that he donated to the cause.)
The guys are anchored with 3 foot screw in anchors (Menards) 35 feet from
the base of the antenna. I'm using 3 foot fiberglass guy pull-offs
at the bottoms to further insulate and keep the guy wires out of the snow.
I cut up a couple of these to make the insulators for the top. (I
have access to the scrap bin at a power company, I wouldn't use these to
hold up a power line, but 50 feet of aluminum pipe...)
These last two pictures show the new loading coil and the transmitter box.
The old antenna required about 2.5 mH of inductance to resonate the antenna
(it had center loading and a helical wind for the top 14 feet). The
new one appears to needs about 2.8 mH. It required 3.3 mH without
the top hat. I built the new coil on 10/9/2000. The form 15
1/2 inches in diameter and is made from three rings of 1/4 inch plywood
and 1/2 inch pvc pipe. There are 100 turns of #12 stranded house
wire on the form. I have 5 taps, one every three turns up from the
bottom. I trenched in two 50 ohm coaxial cables and eight 18 gauge
conductors from this box into the house (250 feet). Take a look at
the inside of the box on the New Lf Transmitter
page.
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