Re: NEC-LIST: Enhancing low-angle radiation for h.f.

Warren Ziegler <WZiegler_at_ix.netcom.com> replied to my original post:

> Using two phased antennas one above the other has been tried by
> a number of people I know. Chuck O'Neal, K1KW (formerly WA1EKV) has
> tried yagis with variable phasing and has good sucess in varying the
> vertical angle (by changing the phase relationship of the two
> antennas). Several people have used this trick on 75 meters, usually
> feeding two dipoles (one above the other) out of phase to enhance
> high angle radiation. The low dipole is usually about 1/4 wave above
> ground, and the high dipole is 1/4 to 1/2 wave above the low
> dipole. (On 75 meters only stations with substantial towers can get
> away with this!) I believe that Tom K1JJ has been experimenting with
> this for some time now.
>
> I believe one of the advertised advantages of stacked yagis fed
> in phase is a lower vertical angle, in addition to greater horizontal
> directivity.
>
> Don't know if this helps.
>
>73 Warren, NY2H

Thanks for these helpful and relevant examples. I played with the
spacing as well as the phasing and current magnitude ratio of the two
antennas, and found little benefit from one-quarter-wave spacing. (My
playing was limited to upper antenna heights of 3/4 wl or less. If
you can go higher, you should.) One-half-wave spacing with in-phase
currents seems to be good because it yields a radiation pattern with
nulls at both the zenith and the nadir, where radiation is wasted if
you're interested in DX skip.

73 de Chuck W1HIS
Received on Fri Oct 10 1997 - 08:59:37 EDT