9-Circle vs 4-Square on 160, 80 and 40 Meters

A 9-circle offers eight selectable headings where a typical four-direction 4-square offers four. That extra steering granularity is real. It does not, by itself, prove more gain, RDF, signal-to-noise ratio or null depth. Those outcomes depend on the complete array geometry, complex channel weights, element terminations, loss, calibration, arrival angle and site.

Start With the Published YCCC Geometry

The controlling construction record is the YCCC low-band receiving-array manual, revision 4.0. It supersedes the 140 ft diameter and 70 ft spacing used in John Kaufmann W1FV's 2011 two-part NCJ design article. The revised implementation uses:

• one vertical at the centre and eight verticals equally spaced around a circle;
• 60 ft (18.29 m) from the centre to each perimeter vertical;
• a 120 ft (36.58 m) circle diameter;
• four physical three-element inline axes sharing the centre element; and
• eight selectable headings at 45° intervals, because each inline axis can be phased in either end-fire direction.

The manual specifies electrically short, nominally identical verticals with high-input-impedance feedpoint amplifiers, equal-length 75 Ω feedlines, delay networks and a combiner/controller. This is not nine ordinary quarter-wave verticals driven as one nine-port beam. Nor is “9-circle” enough to specify a different controller, spacing or element design.

The 9-Circle Is Four Reversible Inline Arrays

For a selected azimuth, the combiner uses the centre vertical and the two diametrically opposed perimeter verticals on that axis. Their complex amplitudes and phases produce the intended unidirectional end-fire response. Selecting the opposite heading reverses the directional phasing; selecting another axis chooses another perimeter pair around the same centre.

This distinction prevents two common mistakes. First, physical element count is not the same as the number of receiver channels combined for one beam. Second, unselected channels are not proof that the other verticals vanish electromagnetically. Their conductors, feedpoint amplifiers, feedlines and controller states determine how they load and couple to the selected group.

W1FV's 2011 model treated active-to-inactive coupling as negligible for its declared construction. That is a model result, not a general law for every nine-vertical circle. NASA and NTIA array studies show the wider principle: mutual coupling changes element impedance and embedded element pattern, while calibration is needed to separate systematic channel errors from the intended weights. A defensible model therefore includes all nine physical elements and their actual terminations, even though only three signal paths are selected at the combiner.

Heading Granularity Is a Genuine 9-Circle Advantage

Eight headings put adjacent switch positions 45° apart. A four-direction 4-square normally changes direction in 90° steps. The 9-circle can therefore place a declared forward lobe or rear/side rejection region closer to a wanted station or a dominant interferer when either falls between the coarser headings.

The YCCC manual makes a precise, narrower comparison between its five-element square and nine-element circle. Both are assembled from the same three-element inline building block, so their selected-direction pattern shape is the same in the model. On its 160 m adjacent-pattern plot, the five-element version falls 4 dB below a beam peak at the crossover between its 90° headings, while the nine-element version falls 1 dB below a peak between its 45° headings.

That crossover result belongs to the published YCCC five-versus-nine model. It must not be copied onto a generic four-element 4-square, whose elements, weights, spacing and pattern can differ. It demonstrates smoother azimuth coverage, not a universal 3 dB improvement in RDF or received SNR.

A 4-Square Must Be Defined Before It Can Be Compared

“4-square” covers more than one receive-array implementation. Four high-impedance amplified short verticals, four passive low-impedance verticals with radial systems, different side lengths and different phasing networks do not share one pattern. Some controllers select four cardinal or diagonal headings; others provide additional modes or continuously adjustable combining.

Frank Donovan W3LPL's Contest University example is one useful declared case: four 20 ft high-impedance verticals on an 80 ft × 80 ft square, four switchable directions and a published 100° modelled 3 dB beamwidth. That is an example, not the definition of every compact 4-square.

Aperture Is More Than Footprint Area

Physical footprint is easy to compare; effective aperture and directivity are not. Pattern depends on element locations, embedded element patterns and complex excitations. In the YCCC design, the selected inline baseline is 120 ft for every heading. In a square, relevant projected spacing changes with look direction and phasing mode.

More physical elements can add heading choices without enlarging the selected baseline or narrowing an individual selected beam. Conversely, four elements with a larger declared spacing and suitable weights can produce a narrower modelled pattern than a smaller array, but may demand more land and tighter control of frequency-dependent phasing, sidelobes and grating responses.

Do not use diameter, side length or element count as a proxy for RDF. Calculate the three-dimensional pattern with the exact site model, then state the elevation angle and integration convention used for any RDF value.

The Published YCCC Band Behaviour Is Bounded

The revision-4 manual reports NEC-4 calculations using its high-accuracy ground model at 20° elevation. These values describe that model and geometry; they are not guaranteed installed measurements:

RDF is the peak-direction gain relative to the average gain over the relevant solid angle under its defined convention. It is useful for comparing far-field response to an angularly distributed noise environment. It is not forward gain, front-to-back ratio, null depth or a promise of the same SNR improvement against one local noise emitter.

The manual's fixed delay-line design is broadband enough to cover 160 through 40 m without band switching, but broadband does not mean constant pattern. Spatial phase changes with wavelength, while the delay network, amplifiers, feedlines and element coupling also vary with frequency. Compare each band independently.

Pattern and Signal Level Answer Different Questions

Short receive verticals can have very low absolute gain. Feedpoint amplification restores usable receiver level but does not create antenna directivity. Array comparison should therefore keep at least four quantities separate:

• Pattern directivity: concentration of response with angle, independent of overall loss in the ideal definition.
• RDF: the declared peak-to-average pattern metric, with its angular and elevation assumptions.
• Realized system gain: element response plus mismatch, preamplifier, feedline, combiner and switching loss or gain at a named output plane.
• Received SNR: wanted signal and the actual directional noise/interference field, plus receiver noise, overload and common-mode pickup.

A 4-square can deliver more or less output voltage than a 9-circle without having a better or worse receive pattern. Normalize levels before an A/B listening comparison, and check that neither preamplifier nor receiver is compressed by broadcast, amateur or other strong signals.

Phasing and Calibration Decide Whether the Model Survives

A phased receive array relies on vector addition. If the intended voltage for channel n is w_nV_n, then cable delay, amplitude error, amplifier phase, mismatch and combiner error all modify that complex term. Small errors can fill a deep null even when the forward lobe looks normal.

For the YCCC system, the manual requires equal-length element feedlines, a maintained 75 Ω environment and delay lines cut from measured velocity factor rather than a catalogue value. It also prescribes a common-mode choke in every element feedline near the combiner. Those are functional pattern requirements, not tidy-cabling preferences.

Apply the same discipline to either array:

• measure each element, amplifier and cable as a complex channel over 1.8–7.3 MHz;
• verify cable electrical length and attenuation rather than matching physical length alone;
• measure combiner weights and isolation in every switch state with all unused ports terminated as intended;
• check common-mode current on RF, control and DC cables;
• normalize output level before comparing patterns or listening results; and
• repeat calibration after water ingress, cable replacement, amplifier repair or ground change.

The Site Is Part of the Array

The YCCC manual calls for level ground, identical verticals, tight 60 ft spacing, and separation from large metal objects, wires through the array interior, towers, antennas and power lines. It explains that stray coupling can upset the amplitude and phase needed for a directive pattern. A compact 4-square is subject to the same physical problem even when its exact sensitivities differ.

Soil and foliage can change element response; resonant conductors can reradiate; unequal cable routing can introduce common-mode pickup; and local noise can arrive in the near field rather than following the array's far-field model. The array that wins on one site may lose on another because the interference geometry and installation error are different.

A pattern check should use several known far-field signals at useful arrival angles, not one station in one direction. Where possible, compare against a calibrated reference antenna and rotate or switch rapidly enough that propagation is effectively unchanged. IEEE 149-2021 provides the broader measurement principle: define the measurand, range, instrumentation, calibration and uncertainty before claiming a pattern difference.

A Fair Decision Workflow

1. Map the target directions. Plot wanted paths and persistent interference azimuths by band; determine whether 45° rather than 90° switching materially improves placement.
2. Declare both geometries. Include element type and height, spacing, return system, feedline route, channel termination and maximum physical baseline.
3. Model complete arrays. Include every physical element, intended loads, major nearby conductors, representative ground and the actual complex weights.
4. Compare whole patterns. Examine azimuth and elevation response, beam crossover, sidelobes and null regions—not only one forward or rear number.
5. Budget gain and loss separately. Include element response, amplifiers, cables, switches, combiners and receiver noise or overload margin at named planes.
6. Build calibration access in. Provide ways to inject or receive a common test signal and record complex channel balance without dismantling the site.
7. Validate on every band. Measure switch-state patterns, common-mode current, output level, stability and SNR on 160, 80 and 40 m independently.
8. Choose by the limiting requirement. The 9-circle is attractive when intermediate headings matter enough to justify nine identical channels and greater physical complexity. A defined 4-square can be preferable when four headings cover the paths and its simpler calibration is more likely to remain correct.

Engineering References

• YCCC Low-Band Receiving Array Kit User's Manual, revision 4.0
• John Kaufmann, W1FV: A Compact Dual-Band, 9 Circle Receiving Array — Part 1
• John Kaufmann, W1FV: A Compact Dual-Band, 9 Circle Receiving Array — Part 2
• Frank Donovan, W3LPL: Easy-to-Build Low-Band Receiving Antennas
• NASA: Modeling and Simulation of Phased-Array Antennas
• NTIA TM-05-426: Mutual coupling and calibration in a four-element array
• IEEE 149-2021: Recommended Practice for Antenna Measurements

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