[Antennas] A Sterba curtain on 6m

Tue May 20 00:51:16 EDT 2008

A Sterba curtain radiates with maximum signal broadside to the plane
that contains the wires: In other words, "NOT" towards the length,
but at right angles to it.
At 50 MHz it is not a difficult thing to suspend a Sterba from bicycle
wheel with a rope through the center, and two stuts of bamboo in the
plane of the wheel so that they make a length about the size of the
smaller dimension of the Sterba array. Rope and two tent pegs can
stabilize the hanging Sterba at the bottom.
The azimuth direction of the antenna can be changed by one man, and
additional pairs of tent pegs.
The advantage of this arrangement is the directivity can be changed,
the disadvantage of this arrangement is that skywave (not bounced off
the ionosphere) signal will be vertically polarized. When propagating
by E, D and F layers the vertical polarization is not a problem as the
signal is no longer vertically polarized after reflection by the
ionosphere.
For local skywave signals cross polarized signals are about 20 dB down
- most SSB/CW is horizontal, most FM is vertical. Cross polarization
loss of 20 dB down is like changing from 100 watts to 1 watt.
The disadvantage of horizontal polarization with long Sterba curtains
is that the lope is very loud but very narrow. If you live 100 miles
from New York, this is the antenna you want because you can CAREFULLY
adjust the position of the antenna so that NYC is directly broadside.
Even 10 degrees will knock the signal down - but few antennas can put
a distant station into a metropolis location like a Sterba. However,
stations 20 degrees away probably won't hear you.
A better antenna would be stacked horizontal dipoles with more
elements stacking than the longer Sterba curtain. Stacking dipoles
does not sharpen the azimuth lobe, but just compresses and strengthens
the lobe towards the horizon to achieve gain.
73
David N1EA
=30=
On 5/20/08, Ray Brown <kb0stn at sbcglobal.net> wrote:
> Subject pretty well says it all. I'd like to build one just for 6m for Field Day.
> (And run a dedicated 6m only rig on it.) Anyone actually build one and had
> good results with it? And how high off the ground should it be? I'd expect
> to point it north and south, since I've heard that it works best off the sides,
> and we're in SW Missouri.
>> Thanks!
>>>> _Ray_ KBØSTN
>>> ______________________________________________________________
> Antennas mailing list
> Home: http://mailman.qth.net/mailman/listinfo/antennas
> Help: http://mailman.qth.net/mmfaq.html
> Post: mailto:Antennas at mailman.qth.net
>