[AMRadio] Valiant and Loop progress


Brett gazdzinski Brett.gazdzinski at mci.com
Mon Dec 5 20:13:10 EST 2005


While on the subject of antennas, I wonder if anyone knows of a way
to do what I want to do.
I had a resonant 80 meter dipole above the house, the length was only 
about 90 feet, so I had loading coils about 3/4 of the way out from the
center.
That worked ok for years, but the coax went bad at the feed point, and 
while the antenna seemed to work ok, I had a bit of RF in the house, since 
it was lengthwise over the entire house.

I have a resonant 40 meter dipole that runs at right angles to the house, 
and most of it is over the back yard, no RF in the house.

I likely have about 90 feet there also, if I stay out of the trees.

I would like to have one antenna that is resonant on 80 and 40 meters 
without an antenna tuner, that fits in the 90 foot space.

A trap dipole would be nice, but I have never found anything that holds up
to
AM at any but the lowest power levels.

I normally run about 300 watts carrier on 40 and 600 watts carrier on 80.

I made the mistake of trying one of those B+W all band folded dipoles, the
lowest
swr I could get about 4 to 1, maybe because of the close trees.
They are also only good for low power on AM.

The next experiment was as much wire as I could fit above the house, about
42 
feet each side, fed with open wire line for about 10 feet, then to coax.
The first test showed the swr way off, so I put the antenna tuner on, and it

started arcing. I added another 10 feet of coax and everything seemed to
work ok, 
but a lot of RF in the shack, and I bet I loose power in the coax with a
high swr.

I don't want to have to fool with an antenna tuner when changing bands, and
would rather not use one at all.

The best bet would be some sort of antenna where the 40 meter dipole is, but
I cant think of anything that would do what I want it to do.

The property is in the shape of a pizza slice, the point being my back yard.
half way up the sides I have a medium size oak tree, and a 36 foot mast on
the other side
that is against the garage.
Close to the tip of the slice, I have a real nice cedar tree that is like a
mast,
a very good antenna support.
Out front, away from the crust is another medium size oak.
The 40 meter dipole runs from that to the cedar, and is up about 40 feet.
 
Anyone got any ideas, other than ordering a pizza?

Brett
N2DTS




More information about the AMRadio mailing list

This page last updated 18 Oct 2017.