Hi Andrew
He concept is very simple, you can phase 2 verticals. 3 verticals or 4
vertical. See you got, two verticals in phase give you a cardioid pattern,
only one deep null on the back. Moving to 3 or 4 verticals gives you two deep
side nulls plus some front back.
The SAL does not have side lobe nulls. The feed system does no change the fact
that you have only two vertical wires as antenna, the inclined wire can be
describe as two vectors one vertical and another horizontal. The two vertical
vector and the center of the inclined wire define the pattern.
See the case of a DHDL, invented by George AA7JV, the vertical wires are far
apart and the two inclined wires vertical vectors are half way each other. The
DHDL has 4 verticals as the Waller Flag with two independent loops making 4
verticals as well, but the gain of the DHDL is 1-2 db below the WF. Why? the
reflection between the two loops and the proximity of the two vertical vectors
impact the DHDL pattern, as well the two verticals wires on the SAL.
The SAL and the DHDL does not have side lobe nulls.
One Loaded loop or EWE, K9AY RDF is close to 9 db, the SAL and DHDL are
slighted better RDF 10 db on EZENEC, but again on practice, measuring the
diagram of irradiation the SAL never achieved the extra 1 db in RDF. Two
loaded loops has side lobe nulls and RDF is close to 12 db, very similar to 3
element yagi azimuth diagram. Both antennas, the SAL and the K9AY have
impressive deep null on the back, giving you a good front back. It is a null on
the back , very different than front rear, that take the 180 degree energy
between the front and the back.
You can find several stations using two DHDL in phase and it does work, but you
wont find any array of two SAL because the phase is so critical that became
impractical.
73's
JC
N4IS
73
Andrew Ikin
G8LUG
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