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W8JI initially developed and used this array in the 1980’s. This array started appearing in the
1990’s at larger more advanced low-band DX stations. The phasing system in this array, as
well as the active
element design, offer much better dynamic range and directivity bandwidth
than other later copies.
Unlike unidirectional transmitting arrays using large elements, very small
elements do not create significant mutual coupling related current-
distribution and phase errors. Better control of phase and currents provides a
much cleaner pattern than found on available vertical antenna transmit
arrays.
Additionally, this array combines independent unidirectional cells across the
full width of the array to add additional broadside directivity. Broadside
phasing is also frequency independent.
Time-delay phasing produces a
frequency independent
rearward null.
Phasing remains perfect over very wide frequency ranges. This results in excellent front-to-back
performance on multiple bands, despite using a single delay line with fixed element spacing. The
deep rearward null reduces rearward noise and undesirable signals over very wide frequency ranges.
The rearward null is frequency independent up to element-to-element spacings of just over 1/4-
wavelength.
The DX Engineering
RCA8B-1
Receive Eight Circle Array Controller uses sealed relays sized for
receiving applications. (High current contacts, suitable for transmitting, commonly have unreliable
contact connections at low currents. This is because of the large surface areas and hard contact
materials necessary to support high contact switching currents.) The
RCA8B-1
Receive Eight
Circle Array Controller uses sealed relays optimally sized for receiving applications. Contacts are
bifurcated and gold-flashed, substantially improving low signal level switching reliability. The
improved low-level signal optimized bifurcated contacts virtually eliminate non-linearity,
rectification, and other maladies caused by poor relay connections.
Frequency Coverage -vs. - Element Type
The Eight Circle Array uses eight elements to form a clean, narrow beamwidth, low-angle pattern in
eight equally spaced user selectable directions. The elements form the most space-efficient type of
directional array, a broadside-endfire combination. With broadband active elements, this array has
an exceptionally good pattern over at least a 3:1 frequency range. With monoband passive resistor
loaded elements, this array has unbeatable performance across a single band.
The Eight Circle Array upper frequency limit for a clean unidirectional pattern is slightly above
where the array is .35-wavelength radius. The frequency of optimum performance is where the
array is approximately .327-wavelength radius. Construction care, element construction, desired
beamwidth, and local noise floor determines the minimum array size in wavelengths. Minimum
useful frequency typically occurs with an array less than 0.1-wavelength radius; although that limit
can be pushed lower with care in some situations. Careful construction will allow useful directivity
over the entire HF range with an exceptionally good pattern over a 3:1 frequency range.
