Scott:
I just put up an inverted L for use on 160M for this winter. I have a =
very normal suburban lot about 75ft wide and 120ft deep or so. =20
I am lucky to have a tall tree that is helping with the end of the =
antenna. The antenna is basically a piece of No.12 stranded=20
wire insulated that is shaped like a distorted upside down "C" ...even =
though it is supposed to be an inverted "L" ....hi ! =20
The longer vertical part is about 45ft held up by my tower and then it =
runs about 65ft to the tree sloping as it goes....and then it=20
drops vertically down the tree about 25ft. At both ends it runs =
horizontally again for about 10 ft at the ends. The horizontal run=20
at the tree end is about 7 feet above ground and at the tower end the =
10ft horizontal run is about 3 feet above ground. I feed it near=20
the base of the tower at theend of one of the 10ft runs mentioned above. =
I am using only a 500pf transmitting variable cap to tune it=20
to resonance.
The lenght of wire I think is now about 145ft...I didnt measure it =
...just put it up so that it fit right on the property. One 10 ft pig =
tail
reaches the tuner box and the other for pruning to get it to resonate. =
Because it is longer than a quarted wave lenght at 1.8mhz it is=20
inductive and the series cap tunes it nicely.=20
When I first put it up it was too long and I couldn't get resonanceon =
160M ...it was resonating well below the band....so I pruned off about
18ft in 6ft lenghts until the capacitor started to kick in. Thats =
pretty dramatic pruning but thats the way it went for me.
I resonanted it for 1815khz and the SWR is about 1.2:1 ....it is about =
70khz wide between the 2:1 SWR points. =20
I want to raise the resonant freq a bit by cutting off more wire and =
getting the low SWR point at about 1825khz as thats where=20
most of the DX seems to hang out. The variable cap resonates the =
antenna with about 330pf as measured by my cap meter.
The wire also has a bunch of other resonace points as well that I have =
noticed but I havent tried to get a match to the 50ohm line yet!!
Also I guess I could put a motor on the capacitor so that I could move =
around the band a bit but that seems like more trouble then it
is worth. I have done this several times in the past and it is a real =
pain adjusting a motor driven capacitor because you invariably=20
run through the low SWR point and have to rock the cap back and forth or =
if you cant change the polarity of the voltage to the motor
you have to go all the way around again to get back to the low SWR. It =
much easier to use relays and fixed capacitors.
The ground system is very basic......at present there are 12 radials on =
the ground of various random lenghts of the same wire. If I can get
the time I may put up a couple of elevated radials for the weekend =
...every little bit will help. The capacitor is in a weather proof =
metal enclosure
from an old commercial tuner and the case is bonded to the ground rod =
that the radials are attached to. All of this is also bonded to the RF =
ground
wires that I have buried in the back yard with a number of 6ft copper =
ground rods scattered around. =20
In the past few nites have worked a bunch of Eu's and 4X4NJ and KP2 =
just running 100W.
Hope this is of help.
73 Frank VO1HP
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