Topband: Advise on lowband array idea

[Henrik Weiss]

Fellow Topbanders,
Summertime is in-field time. 

For give me for taking space on a lowband antenna subject but have tried to get advice on the antenna reflector with no reply !!! :)

Been bogling my mind for some time on the best 160 / 80 array for this location (physical restraints). The W0UN 9 el circular array for 80 M has had my interest and is still not ruled out (ON4UN Low band Dxing)

At first I plan to do the following and would like some advice.

I am going to put up a 110 ft. free standing tower this autumn and would like to apply 4 el. phased arrays for 80 & 160, supported by caternary ropes from the top of the tower. 

My idea goes like this:

3/8 wl. vertical for 80 M spaced 1/4 wl. with ground mounted radials
1/4 wl. vertical for 160 M spaced 1/8 wl. (Same radial system and radiating wire as for the 80 M) utilising the 80 3/8 wl. as the vertical part off the antenna and a topload sloping wire (as part of the caternary).

Between the top load and the vertical wire will be installed a trap (either coaxtrap or L/C). Limited bandpass on 160 is acceptable.

This configuration has the following advantage:

1. Utilise same ground mounted radial system
2. One central support
3. 3/8 wl. on 80 M increase the single vertical wire resistive radiation (from about 36 to 50 ohm) which would lower possible ground losses as current max is higher above ground.

Disadvantages ?

Any thoughts very welcome !!

With regard to feed system I anticipate to go by practical real life measurements.
80 M, standard quadrature 90 degree phasing, Christman or Lewallen.
160 M, 135 degree phasing, modified Lewallen.

I am not a modelling expert but would be grateful if someone could look at this array in EZNEC for me. 

Thank you in advance,

Henrik - OZ1ING





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