On 9 mar, 01:13, ka7niq wrote:
'Wimpie[_2_ Wrote:



;735960']On 5 mar, 16:25, ka7niq wrote:-
I have a tree here in the Tampa Florida area just begging to have a
Hustler 4 or 5 BTV stuck in it. I have had great luck with ground
mounted Hustler Verticals when I lived near the sal****er of Tampa
Bay.
I am now in Brandon Florida, east of Tampa, and far from salt water. I
have stuck Hustler Verticals in trees before with radials for most
bands, but had access to a bucket truck back then, and did not have
stents in my heart. I got to thinking WHY not take a hustler vertical
with only ONE *Tuned "radial" for each band in the form of the lower
part of a 1/2 wave dipole. In other words, make the Hustler Vertical
into a multi band center fed 1/2 wave dipole. It will be a lot easier
to
deal with only one radial for each band if they hang straight down the
tree vertically. Has anyone ever done this before ?

--
ka7niq-

Hello Chris,

From another thread I concluded you have a flat membrane roof.

If you plan to use the 80/75m antenna for NVIS (local traffic) mostly,
why not putting a horizontal dipole above your roof. It will be very
likely below resonance length, but you can match this to 50 Ohms. This
will almost certainly result in better efficiency w.r.t. the
commercial vertical. For 40m and below, you can go vertical.

If you like to experiment and know the problems w.r.t. RF high
voltage, you may try a vertical resonating antenna that is in half
wave resonance. You will get end-fed voltages in the kV range, but the
common mode current will be significantly less w.r.t. a quarter wave
resonating structure. This reduces the requirements for your ground
provision and the ground loss.

What is the height of the tree that you plan to use as support (in
other words what is the maximum vertical height you can use)?

With kind regards,

Wim
PA3DJS
www.tetech.nl

The *Tree is about 40 feet tall, and yes I do have a flat roof. I could
attach a sloping wire from the tree to the roof, and center feed it with
ladder line. This wire would be about 60 to 80 feet long, give and take
a little. Unfortunately, it will be very visible!

--
ka7niq

Hello Chris,

My idea is/was to have the (short) 75/80m dipole above your roof
(assuming that the roof supporting structure isn't conducting). When
you put the matching components and balun function in a box on the
roof, you can go down with just a coaxial cable. This will keep the
VSWR within acceptable limits to allow further matching in the shack.
If space/visibility permits, I would go for the ladder line as you
suggested. Main disadvantage of the dipole above the roof:
interference from and towards domestic equipment.

When the visibility of the dipole above the roof meets aesthetic rules
by far, you may put 2 or more wires to the dipole (fan type short
dipole). This reduces the reactive component, without reducing the
radiation resistance, so matching becomes easier. Visibility, is this
really a problem?

Given the size of the tree, 40m and below should be possible without
huge investment in ground provision. For 10m the wire/tube length
isn't good, unless you can add a reactance to get collinear
behavior.

The above doesn’t mean 80m isn't possible, but due to the low
radiation resistance (about 5 Ohms), you need a better counterpoise /
ground provision, and the NVIS performance of your vertical isn't
good.

As with many things, making a choice isn't easy. A tree 60..80 feet
from your house looks very attractive from an interference
perspective.

With kind regards,

Wim
PA3DJS
www.tetech.nl