Topband: Are stacked verticals feasible?

[Augie Hansen]

On 9/7/2013 11:42 AM, Bruce wrote:
> ...
> Many have tried 5/8 wavelengths on lower bands and experienced poor 
> long haul results.

Included among the many have been a number of medium wave broadcast 
stations, influenced I'm sure by the promise of intense low angle 
radiation, which covers the region where most of the recipients of the 
stations product  (usually advertisements) are located. But the 5/8-wave 
antenna splits the signal into the desired low angle lobe and a higher 
angle lobe that results in destructive interference at the outer portion 
of the coverage area.

On the low-frequency HF and MF ham bands, the null in the vertical 
pattern of a 5/8-wave (225 degree) radiator has a very negative effect 
on the range of angles where the bulk of the propagation we need for 
contacts is located.

Long ago broadcasters going for the "gold" backed off from the 225 
degree vertical to the 190 degree vertical. Being a bit longer that a 
half wave, which has a difficult-to-match high impedance at the base, it 
is fairly easy to match the slightly shorter vertical to a transmission 
line, and it produces a single strong low angle lobe.

Over the years I've had very good success with 190 degree radiators on 
several of the higher frequency bands (6-20m). Unfortunately my 
"postage-stamp" city lot with a big house and trees in all the wrongs 
places is not suitable for experimentation on the low-frequency bands.

Gus Hansen
KB0YH