Broadside in a Compact 4-Square: Useful, but Not the Main Event
Broadside in a Compact 4-Square: Useful, but Not the Main Event
Eight switch positions do not create eight equally selective beams. In a compact broadband receive square, the diagonal end-fire combinations usually do the hard directional work; the side headings are useful views with different limits.
Here, “broadside” means the side-heading mode added to the four diagonal headings of a compact square of short active elements. It does not mean a large broadside-end-fire array with real aperture in two dimensions.
The practical point: optimize the directions, nulls and bandwidth you actually need. A side mode can fill an angular gap or inspect local QRM, but it should not be advertised as electrically identical to the diagonal subtractive mode.
The Diagonal Mode Has a Specific Geometry
For a square with side length d, the projected path difference between adjacent elements for a wave arriving along a diagonal is d/√2. LZ1AQ's compact-array treatment forms two subtractive virtual arrays with a delay of approximately 0.707d/c, then combines those virtual outputs.
τdiagonal = d/(√2 c) ≈ 0.707d/c
That cascaded subtraction is why the diagonal mode can produce useful cancellation in a physically small array. The array factor still depends on frequency, element spacing, amplitude and phase error, mutual coupling, ground and element mismatch. The delay value is a geometric starting point, not a promise of a fixed real-world null.
The Side Mode Solves a Different Combination
For arrival normal to one side, the projected separation and required combination are different. In the same small-array model, the relevant geometric delay is approximately d/c. The final combination is not simply the diagonal network pointed somewhere else.
τside = d/c
This distinction matters. One fixed compromise network cannot preserve the optimum delay for both geometries across several octaves. A controller may offer both modes, but their beamwidth, null shape, overlap and frequency stability must be measured separately.
More Labels Do Not Create More Aperture
Four physical samples remain four physical samples. Additional switch states can combine them in additional ways, which can be operationally useful, but cannot manufacture new spatial information or physical aperture.
The side headings often cover the angular regions between the stronger diagonal headings. That can make tuning around the compass more convenient. It does not establish equal RDF, front-to-back ratio or null depth. Those quantities belong to the measured pattern at a declared frequency and environment.
True Time Delay Helps, but Does Not Freeze the Pattern
A fixed phase shift represents one time delay at only one frequency. True time delay better preserves the intended geometric relationship over bandwidth. It still does not remove element-pattern changes, coupling, unequal electronics, cable delay error or the growing electrical spacing of the array as frequency rises.
For a multi-band 160, 80 and 40 m receive array, qualify each band. Record amplitude and group-delay tracking, reverse the signal paths, swap elements, repeat the pattern and measure the noise environment. A clean model is valuable; a repeatable outdoor result is the evidence.
Broadside Becomes Powerful When Aperture Supports It
Large broadside-end-fire arrays and broadside Beverage systems are a different class. Their spacing creates a genuine second spatial dimension. There, broadside is not merely an extra switch state in a compact footprint; it is part of the physical architecture.
This is why “broadside is weak” would be just as misleading as “eight headings are equal.” The conclusion belongs to the stated compact-array geometry, frequency range and combining method.
How I Would Qualify the Controller
- Measure every heading at every intended band, not only the design frequency.
- Publish the physical spacing, element type, reference direction and delay convention.
- Record amplitude, phase or group-delay error through each channel.
- Plot null direction, null depth, half-power beamwidth and RDF rather than only peak gain.
- Repeat after swapping elements and channels to expose hardware asymmetry.
- Confirm on-air SNR with simultaneous or rapidly switched A/B/A comparisons.
Primary engineering source
Mini-FAQ
- Does a compact 4-square really provide eight directions? It can provide eight switch states, but the side and diagonal states need not have equal beamwidth, null depth or RDF.
- Why is the diagonal delay about 0.707d/c? Because the projected spacing between adjacent elements for diagonal arrival is d divided by the square root of two.
- Is the side-mode delay the same? No. In the stated square geometry the side mode uses a different projected path, approximately d/c.
- Does true time delay make the pattern identical on every band? No. It preserves delay better than fixed phase, but electrical spacing, coupling and element response still change with frequency.
- When is broadside genuinely powerful? When real physical aperture and the complete array architecture support it, as in larger broadside-end-fire systems.