Cecil Moore wrote:
The T and the 1/4WL vertical
have about the same performance if the T's vertical
section is not too short.
--
73, Cecil http://www.w5dxp.com

The closer to a 1/4 wave for the combined vertical
plus top hat wire , the better. You can even improve
farther as far as current distribution if you make it
longer. IE: 3/8 wave total length. That will raise the
max current point up into the vertical section more
towards the top, rather than the bottom. Course,
if you do this, you will need a cap to tune out the
reactance. Like Roy says, the hat radiates little.
Even just two wires is a pretty clean vertical pattern with
little radiation from the hat unless the total length
is so long as to place the current max at the apex
or into the horizontal wires . So I wouldn't get too
carried away with the total length past a 1/4 wave
if I wanted a strictly vertical pattern. When I ran both
an L and a T, the L would often do better at close to
medium distances in the early PM. But the T was
usually better once it stretched out a bit. So most
of the time, I preferred the T. At that time, I also had a
Z dipole, which was better for NVIS than the L.
Now all I have is the "coax dipole" T. I did away with the
others.. The Z dipole was generally the worse of the
three as far as DX. Course, I don't work too much DX
on 160m. I can't hear most of them with my micky
mouse receiving antennas... :/ I've heard W8JI working
stuff that didn't exist here on my radio.. I've pretty
much faced the fact I won't be having a killer 160 setup
until I can get out in the boondocks.
MK

On 13 Jan 2007 09:23:32 -0800, "AC7PN" wrote:

Because the trees are virticle conductors I'm thinking that a
horozontal dipole might work better. I'll only be able to get it as
high as the tree tops. Maybe an average of 55ft high near the edge of
an east facing clift. Since I live on the West Coast this might give me
good coverage on the States on 40 and 80 meters for next falls Salmon
Run? What do you think?

What do you think about a vee beam? Look over
http://www.cebik.com/gup/gup42.html to see if you think that might
work for you.

S.T.W.

Sum Ting Wong wrote:
What do you think about a vee beam? Look over
http://www.cebik.com/gup/gup42.html to see if you think that might work for you.

S.T.W.

I would have to run the wires down the face of the cliff to make one of
those. Using NEC I just don't know how to simulate the ground effects
when the land falls away at a 30-50 degree angle. At one place there
is a 60 ft shear verticle drop. My unterminated beverage off the cliff
headed East works well on receive but it is terrible on transmit.

On 13 Jan 2007 17:46:15 -0800, "AC7PN" wrote:

I would have to run the wires down the face of the cliff to make one of
those. Using NEC I just don't know how to simulate the ground effects
when the land falls away at a 30-50 degree angle. At one place there
is a 60 ft shear verticle drop. My unterminated beverage off the cliff
headed East works well on receive but it is terrible on transmit.

Beverages aren't supposed to work for transmitting so don't be
discouraged by that. I would think that the ground falling away would
be an advantage. Maybe Roy would care to comment on this, but I'd
just model it using the slope on those wires as if you have a really
high support point on the apex of the vee. Keep in mind that if you
don't terminate the legs of the vee then it will be bi-directional, so
if you're in the San Juans and point that sucker toward Florida you
should do equally well into Asia. Gee, I wish I had your problem! ; )

S.T.W.

Sum Ting Wong wrote:
On 13 Jan 2007 17:46:15 -0800, "AC7PN" wrote:

I would have to run the wires down the face of the cliff to make one of
those. Using NEC I just don't know how to simulate the ground effects
when the land falls away at a 30-50 degree angle. At one place there
is a 60 ft shear verticle drop. My unterminated beverage off the cliff
headed East works well on receive but it is terrible on transmit.

Beverages aren't supposed to work for transmitting so don't be
discouraged by that. I would think that the ground falling away would
be an advantage. Maybe Roy would care to comment on this, but I'd
just model it using the slope on those wires as if you have a really
high support point on the apex of the vee. Keep in mind that if you
don't terminate the legs of the vee then it will be bi-directional, so
if you're in the San Juans and point that sucker toward Florida you
should do equally well into Asia. Gee, I wish I had your problem! ; )

S.T.W.

NEC is of course limited to perfectly flat ground of infinite extent. If
the ground slope is constant for a great distance, you can simulate it
by tilting the antenna model the opposite direction then tilting the
resulting pattern. But that's about all you can do. I still use Brian
Beezley's TA program for analyzing the effects of non-flat ground, but
it's long been unavailable and I don't know of any program since which
does the same thing.

Roy Lewallen, W7EL

Roy Lewallen wrote:
NEC is of course limited to perfectly flat ground of infinite extent.
If the ground slope is constant for a great distance, you can simulate
it by tilting the antenna model the opposite direction then tilting the
resulting pattern. But that's about all you can do. I still use Brian
Beezley's TA program for analyzing the effects of non-flat ground, but
it's long been unavailable and I don't know of any program since which
does the same thing.

N6BV's HFTA program is supplied with all recent ARRL Antenna Books, and
is updated and improved in each edition. For anyone who doesn't live on
perfectly flat ground of infinite extent, HFTA can provide a lot of
answers to the old question: "How good is my QTH?"

However, HTFA is limited to horizontal antennas, and I don't know of any
program that does the same for verticals (it's a much more difficult
problem).


--
73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek