On Nov 21, 10:51*am, Art Unwin wrote:
On Nov 21, 9:52*am, John Smith wrote:

Art Unwin wrote:
...
Seems to me you are recommending the "?slinky" !
Is that correct?
Art

I believe, he is speaking of rotating the flat surfaces of the
conductor(s) 90 degrees to what a "slinkys'" orientation places them at..

In which case, "mondo-capacitive loading to the 'environment'" is also
introduced ... while minimizing capacitive loading between turns.

Regards,
JS

Wouldn't that take more room than a slinky per turn?
His attic is very small!.I think he would be much better placing the
turns as close together as possible
to obtain axial directivity. The only mod required to the slinky is to
ensure the number of right hand turn loop
are equal to the number of left *hand turned loops. Feed could still
be at the center and depending on the amount
of wire used it would radiate like a dipole or axially. What this does
is cancel the lumped loads created in manufacture which
Wim suggests is a problem ie the two supposedly lumped loads will
cancel
*such that you have several wavelengths of wire helix style and no or
repetitive points of none *reactive impedances. He could ofcourse
place
the windings in a vertical direction to obtain an omnidirectional
pattern and utilise the available room to a maximum.
A lot depends on what frequencies he wishes to use as to what form the
radiator becomes.
Best regards
Art

I forgot to mention that a similar type radiator is shown in Antenna
Applications
Reference Guide by Johnson and Jasik with slight modification. This
design was succeeded by the helix antenna
to obtain circular polarization which is now universal with respect to
space communications.
The beauty of this design is the multiplicity of resonant points and
the use of different frequencies.
The economy of space is some what altered by the need of multi
wavelength of wire because
of slow wave.but then it enables axial directivity. There are many
hams who are delighted by the slinky performance
and they are still sold in huge numbers to the ham community, so it
must be performing!
Art Unwin