I am considering using a crankup antenna as a1/4 wl antenna on 75/80m and
was wondering if ther is any history of someone doing this and using the
crankup feature for tuning the antenna. My guess is that it would be too
difficult to maintain electrical contact between the movable and stationary
pieces to be able to do this but still I am interested if anyone has
successfully pulled this off and how they did it.

Jimmie

On Mon, 11 Dec 2006 20:04:23 -0500, "Jimmie D"
wrote:

I am considering using a crankup antenna as a1/4 wl antenna on 75/80m and
was wondering if ther is any history of someone doing this and using the
crankup feature for tuning the antenna. My guess is that it would be too
difficult to maintain electrical contact between the movable and stationary
pieces to be able to do this but still I am interested if anyone has
successfully pulled this off and how they did it.

Jimmie

I have a tubular crank up as you describe. I have never even attempted
to use the tower as a radiator because of the number of for seeable
problems. Since it is grounded, a shunt feed of some sort would be
required. It seems that anything that changes on the tower requires a
corresponding adjustment in the feed.

The raising scheme in my tower presents an unpredictable electrical
bond in the structure. I don't think minute to minute conditions are
predictable.

I considered a steel tape measure alongside the tower as a radiator,
but the model of a grounded structure did look promising!

A remote antenna tuner might show some promise but I will shy away
from it for fear of damaging the electronics with a rapidly changing
load.

As long as there is a need to raise & lower the mast anything
(dipoles, inv v, etc) are messy when lowered.

I consider it essential to be able to retract my tubular mast with a
Cushcraft A# on it!

John Ferrell W8CCW

I consider it essential to be able to retract my tubular mast with a
Cushcraft A# on it!

John Ferrell W8CCW
That should read Cushcraft A3.
John Ferrell W8CCW

I have successfully done exactly what you propose. I have one crankup
tower that works on 80 and another that works on 160. Both benefit from
HF and VHF antennas on the top for top loading.

There was an article about this some years ago, I think in CQ.

The main trick is to operate the tower as a reverse ground plane.
At the highest point on the tower which does not move, attach the ground
side of the coax to the tower (bare metal). Also install 4
quarter-wavelength insulated horizontal radials from that point to
remote points, such as trees etc. Connect all the radials and the
center conductor of the coax together.
Then run the tower up and down and tune for minimum swr. My larger
tower with several HF beams on it tunes fine on 160. My smaller tower
with VHF beams on it tunes fine on 80. The last time I used it, I worked
Morocco on 75 SSB in the late afternoon.

As the tower moves, the connection is not perfect, so the SWR jumps
around a little. But once the tower stops moving, the connection is
solid and works fine.

Bob W8ERD



In article ,
John Ferrell wrote:

On Mon, 11 Dec 2006 20:04:23 -0500, "Jimmie D"
wrote:

I am considering using a crankup antenna as a1/4 wl antenna on 75/80m and
was wondering if ther is any history of someone doing this and using the
crankup feature for tuning the antenna. My guess is that it would be too
difficult to maintain electrical contact between the movable and stationary
pieces to be able to do this but still I am interested if anyone has
successfully pulled this off and how they did it.

Jimmie

I have a tubular crank up as you describe. I have never even attempted
to use the tower as a radiator because of the number of for seeable
problems. Since it is grounded, a shunt feed of some sort would be
required. It seems that anything that changes on the tower requires a
corresponding adjustment in the feed.

The raising scheme in my tower presents an unpredictable electrical
bond in the structure. I don't think minute to minute conditions are
predictable.

I considered a steel tape measure alongside the tower as a radiator,
but the model of a grounded structure did look promising!

A remote antenna tuner might show some promise but I will shy away
from it for fear of damaging the electronics with a rapidly changing
load.

As long as there is a need to raise & lower the mast anything
(dipoles, inv v, etc) are messy when lowered.

I consider it essential to be able to retract my tubular mast with a
Cushcraft A# on it!

John Ferrell W8CCW