Why Broadside Does Not Really Add Much in a Compact 4-Square Receive Array

In this article, “broadside” refers to the side-mode, non-diagonal headings that some 4-square controllers add alongside the four main crossfire directions.

For a compact active 4-eProbe square with 5 to 6 meter elements, especially one intended for pure receive use on 160, 80, and 40 meters, the real question is not how many switch positions the controller offers. The real question is how well the array preserves directivity and null behavior across a very wide frequency range. On receive, that matters far more than raw gain.

This discussion focuses on compact active multiband receive arrays with short high-impedance elements. It is not a critique of true large-aperture broadside arrays used for other purposes.

Crossfire Is the Real Engine of a Multi-Octave Receive Square

The underlying logic is simple. A compact receive square meant to cover 160, 80, and 40 meters has to remain useful while frequency changes by a large ratio. That is exactly where crossfire earns its place. The diagonal mode behaves like a time-delay system rather than a simple fixed-phase system, which is why it holds together better across multiple bands.

This is also why traditional monoband thinking does not transfer cleanly. In a single-band phased array, fixed phase relationships can be enough. In a multiband receive array, they are not. Once frequency moves, fixed phase no longer maps to fixed geometry, and the beam moves with it. Time-delay behavior is much more stable because it follows real path length rather than a single design frequency.

For pure receive work, that stability matters because directivity is the real currency. The array does not need transmit-style gain. It needs useful nulls, predictable steering, and enough directional consistency to improve signal-to-noise ratio over a wide span of frequencies.

Why Broadside Is a Weaker Mode in a Compact 4-Square

The reason broadside adds so little in a compact 4-square is that it is not formed in the same way as the diagonal crossfire mode. In the small-array treatment published by LZ1AQ, the diagonal mode is built as cascaded subtractive end-fire stages with an optimum delay of 0.707d/c. That structure gives the diagonal mode its useful cancellation behavior and is one of the reasons it remains so attractive in compact broadband receive arrays.

The side or broadside mode is different. There, the intermediate virtual arrays see no relative time delay in the wanted direction, so the final combination becomes mainly additive, with the first-stage delay based on d/c instead. The result is a pattern that is broader and much less forceful than the diagonal mode. In practical terms, broadside in a small 4-square is not a second strong beam family. It is mostly an angular fill-in mode between the stronger crossfire headings.

That is the key distinction. Crossfire is where the compact array behaves like a real directional receive tool. Broadside is more like a convenience heading with softer edges.

Why Eight Directions from Four Elements Are Always a Compromise

This is why “eight directions from four elements” never comes for free. A standard 4-element receive array has overlap weaknesses between the main headings. Trying to label those overlap regions as if they were equally clean beam directions does not change the physics. It only changes the switch positions.

Manufacturers that wanted genuinely better intermediate coverage did not solve it by renaming modes. They solved it by adding more elements. That is the real clue. Once you want lower overlap loss and materially cleaner in-between headings, you need more aperture, more geometry, or both.

The processing side tells the same story. To get all eight headings from a 4-square, the diagonal and side circuits must be combined, but the delay requirements are not the same in the two modes. That forces more complicated switching and more compromise. Simplify the network too much, and the side directions become so broad that they are hardly attenuated at all. Keep the network more exact, and you pay for it in complexity and insertion loss.

Published comparisons of compact 4-squares versus larger receive geometries also show the practical outcome clearly: the sharper beams arrive when real aperture is added, not when extra switch labels are added.

How Monoband TX Thinking Influenced the Broadside Habit

A lot of the broadside enthusiasm does come from monoband transmit thinking. Traditional transmit four-squares are classic quarter-wave systems built around a single design band, and their phasing habits come from that world. That mindset makes perfect sense when the goal is monoband transmit pattern control.

But a compact active receive square for 160, 80, and 40 meters is a different animal. It is physically small, intentionally broadband, and designed around receive directivity rather than transmit efficiency. Once you move into that regime, the old “90-degree and 180-degree phase shift” instinct stops being the right design center.

That does not mean broadside is always wrong. It means that broadside as a switch state in a compact active RX square is often inherited from a TX or single-band mindset rather than from the real needs of a multi-octave receive array.

When Broadside Is Real and Worth the Trouble

Broadside becomes genuinely important when it is backed by real physical aperture. In that case, it is no longer just a switching mode inside a small footprint. It becomes a real second spatial dimension.

That is why broadside-endfire receive systems and broadside Beverage arrays can deliver strong receive directivity when the spacing becomes large enough. In those systems, broadside is not merely a mathematical option inside a compact box. It is supported by actual distance, actual path difference, and actual capture area.

That is the difference. In a compact square of short active probes, broadside is mostly a pattern-management mode. In a large-aperture array, broadside becomes real architecture.

Why Broadside Can Be Counterproductive on 160, 80, and 40 Meters

For a compact multi-octave 160/80/40 receive square, broadside becomes counterproductive as soon as you start compromising the crossfire mode to make the broadside mode cleaner or easier to implement.

First, the optimum delays are not the same. The diagonal chain wants about 0.707d/c, while the side chain wants about d/c. A single compromise network cannot be ideal for both at the same time. If you optimize the network around the side mode, you are pulling resources away from the diagonal mode that actually carries the array.

Second, the broadside mode is the broader additive mode. That means it admits more off-axis signal and more off-axis noise. On receive, that hurts the one metric that really matters: improved signal-to-noise ratio through directivity. A broader beam may feel nice from a switching standpoint, but it often sounds worse where it counts.

Third, compact 4-square processing already pays a price in effective height and combiner loss compared with simpler two-element receive systems. On 160 meters especially, that is not a trivial trade. Adding more side-mode complexity means spending more design budget on the weaker mode while the lowest band is already the least forgiving.

That is why broadside often does not add to the story in a compact active RX square. It takes attention away from the one mode that does most of the real work: broadband crossfire nulling.

Practical Conclusion

For a compact active 4-square meant for pure receive use on 160, 80, and 40 meters, the right priority is to optimize the four crossfire directions and preserve proper time-delay behavior across the bands. That is where the useful nulls, the better front-to-rear behavior, and the real on-air advantage come from.

Broadside directions can still be handy as convenience views or for checking a specific local QRM angle, but they do not move the array into a new performance class. If you really want eight clean headings, lower overlap loss, and materially sharper beams, the evidence points toward adding elements or moving to a true large-aperture broadside-endfire or 8-circle architecture.

In other words: crossfire is the engine. Broadside is mostly housekeeping.

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