Topband: Quarter-wavelength patterns available

[Tom W8JI]

> I have experimented (successfully) with two sets of loops spaced 1/4-wave. 
> They were wired to be in phase when broadside, and 180 deg. (phase 
> reversed) when in endfire mode. Endfire could be improved with different 
> phasing, but the 0/180 setup is very simple.
>
> When broadside, the main lobe is narrowed somewhat, with better S/N but 
> not a big difference to the ears.
>

The difference in directivity is less than 1 dB. The additional side null 
depth is less than 3 dB.

> Endfire, you get the same F/B as a single loop, but add two very deep 
> nulls off the sides. Since the null is also overhead, the array now 
> rejects high angles. The pattern improvement is quite dramatic in many 
> cases.
>

There are two ways to fire end-fire. If you use a phase around +110 or -110 
with 1/4 wave spacing, you will enhance back null with little side null 
change. If this is made crossfire it can be made to work on multiple bands 
but will have a side null change with bands. If you flip 180 and feed, it 
adds deep side nulls and will also add additional nulls on higher bands.

The only real noticeable change would be some form of endfire, either the 
180 to improve sides or the more complex unidirectional to improve rear null 
depth.

73 Tom