Jerry,
I am not an expert, but I have been working on my 160 Inverted-L all weekend.
I have a space problem also, but not as severe as yours. Here is what I would
do and the books and experts say it will work. Go up the tower as far as you
can, go out as far as you can and then let the remainder droop down...or go to
another point. The horizontal length does not have to be in a straight line.
Just let the remainder come down the wooden pole and hang a weight on the end
of it.
The key to a Inverted-L is grounding. I just installed 15 radials under my
Inverted-L and it made a hugh difference in how the antenna matched. I am
using a Palstar 1500CV to tune the Inverted-L. A true Inverted-L is just a
quarter wave end fed wire and I believe it is around 30 to 35 ohms at the end.
So, that is not to far from 50 ohms. You can put a capacitor in series with
the antenna but you have to be carefull about the power rating of the cap if
you want to run high power.
Some books and experts say to go for 138 feet and then match it with a cap. I
tried that and what I got was the Inverted-L resonating around 1.7 to 1.65 Mhz.
I could match it very well from 1.8 to 1.60, but I cannot get a match above
1.60. I measured the antenna with my antique Heathkit Grid Dip Oscillator.
Worked very well. Then couple the GDO to the RX and so where the actual dip
was. I will be chopping off 10 or 12 feet today when I get home from work. (I
hate working by flashlight in the dark too.)
Radials are a must. My radials are from 50 to 90 feet long. The radials fan
out over the back yard and only covers a "half-moon" under the Inverted-L. I
have over 800 feet of wire on the ground right now. Home Depot has 500 foot of
#14 stranded wire for about $16.00. I got green so it blends in with the
grass, but I had some orange left over from another project and used it as
well. I went to Dollar General and purchsed some bobby pins for a buck and
then pinned the radials into the ground. I am trying to make it a permanent
installation so I can mow over the radials. Before I had all the radials in, I
was getting about 10 khz bandwidth at 1.5 to 1. Now, I am getting 40 khz
bandwidth at 1.5 to 1. Them I have to retune the match.
That was my experience this weekend as I worked on the antenna for next weekend.
73 - Lee - K0WA
Jerry Connelly <jerryc@clinchrivercorp.com> wrote:
Hello all
I'm trying to get something up for 160m. I've been using my 80m loop
and a tuner but its real hard to tune and not very effecient. Maby when
I get my balanced tuner project done that won't be a problem but for
now it is. Thinking about a 160m inverted L but space is still a problem.
I can support the vertical portion with my 40' tower and I have about 80'
from it to a tall wooden pole. Thats too short and too close but thats all I
have to work with. I try to avoid loaded antennas because of effeciency
but what if I added a helical loaded section near the end of the horizontal
leg (opposite end from the vertical segment)??
I would end up with a 38' vertical section, a 70' horizontal section and
about a 5' section of helical loaded wire. That gives me about 5' for rope
on the pole end.
Any thouights on this or should I go back to a low dipole or some commercial
vertical and live with it???
Thanks
JerryC
KC8TES
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
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