Wellbrook Communications

The Wellbrook K9AY PHASED ARRAY 500kHz to 2MHz

K9AY PHASED ARRAY

This new array from Wellbrook is believed to be first commercial K9AY Array to offer enhanced MW and 160m reception.

The Wellbrook K9AY Phased Array is a sophisticated Broadband Antenna System, designed for enhanced MW and 160m Ham band reception. This Antenna System is the only Broadband Phased K9AY to offer a uni-directional pattern similar to the Beverage, over 360 degrees with electronic Null Steering. The design is the result of combining the Wellbrook Broadband Phase Loop array technology with a special K9AY antenna. This special K9AY uses a very low distortion phased match amplifier embedded into each Head Unit. The array is designed to provide a high front to back ratio and high rejection of rear high angle signals with a narrow front lobe. More importantly, there is the added ability for the user to optimise the F/B up to 50dB on steady signals; a must for MW Dxer.

The Phased Array has much higher directivity and F/B than a single K9AY, 2 element vertical and loop arrays. Also the array is far more tolerant of phase and amplitude variations compared to the 4 square array.

The maximum RDF is about 11dB, this is on a par with a 660foot terminated Beverage and a 4 Square vertical array.

K9AY Phased Array Control Unit.

Phased Array Design: The Phased Array consists of a Control Unit and 2 Special K9AY antennas. Each K9AY requires just one support pole. The K9AY Phased Array can be expanded to use four K9AY antennas to provide 360 degree coverage.

The output of the two K9AY antennas are combined using a phase tracking technique known as “Variable Cross-Fire” i.e. the antennas are combined in anti-phase using a variable time delay equal to approx. 70% of the spacing of the antennas. This phase tracking technique provides a uni-directional reception pattern over a very wide bandwidth. This has a considerable advantage over the majority other phasing (noise cancelling phasing) systems which require constant adjustment even with small frequency changes.

Special K9AY antennas: Each K9AY Head Unit has a low noise 18dB gain, high IOP2/3 close phase matched amplifier. This ensures that the array pattern tracks the design bandwidth. The Head Amplifiers are powered from the Control unit via the antenna feeders.

The Control Unit has an amplitude Balance control plus a Unique Continuously Variable Delay-line for the Phase control, this lets the user optimise the Front to Back ratio and for Null steering. The Control unit has two channels; Phase channel and an Amplitude channel. The Phase channel has the variable delay line and a very high dynamic range amplifier. The Amplitude channel provides the variable gain and also has a very high dynamic range amplifier. Both channels are buffered and are fed to the receiver output via a power combiner. A significant feature of the Phased Array, is complete antenna and receiver isolation. This prevents current from one antenna feeding back to the other antenna or changes in the receiver input impedance degrading the array performance. Most other phased arrays don’t provide any significant antenna/receiver isolation!

The Control Unit is housed in a grey powder coated die-cast enclosure, 6.75” x 4.75” x 2.1” (117x112x56mm)

K9AY PHASED ARRAY KEY FEATURES

· Uni-directional pattern similar to the Beverage	· Simple to erect
· High Front to Back ratio	· Min. real-estate; 20 to 40m ant. spacing
· Up to 50dB null steering	· Low noise high gain Head amplifiers
· Head Amp. OIP3 +43dBm; OIP2 +80/90dBm	· Control Unit OIP3 +43dBm; OIP2 +75dBm
· Much lower IMD compared to active 4 square	· Very high antenna isolation
· 360° with 4 Loops	· 12Volt DC power, ideal for Dxpeditions

The K9AY Phased Array is available in two versions:

2 K9AY - supplied complete with the Control Unit, 2 K9AY Head Amplifiers. Additional K9AY Head amplifiers can be purchased to upgrade to a the 4 direction array.
4 K9AY - supplied complete with the Control Unit, 4 K9AY Head Amplifiers.

The user must provide: The Antenna support poles, ground rod and the antenna wire, the RG58c feeder cable and a 12v 500mA regulated power supply.

The Phased Array is very simple to use, with just 3 controls; Direction, Phase and Balance. The Antenna input and Receiver are 5 BNC, a Binding Post for the K9AY beam reversal wire and a standard 2.1mm dc connector for the 12 Volt power supply.

The Control Unit is housed in a grey powder coated die-cast enclosure, 6.75” x 4.75” x 2.1” (117x112x56mm)

Phased Array Operation:- Connect the Receiver the loop antenna feeders to the respective Control Unit connectors. Also connect the 12volt power supply to the Control Unit. The Phase and Balance control should be set to the middle position. Tune the receiver to a station (mid band) with a steady signal that is approx. in line with loops selected by the Direction switch. Then change the direction switch for the same loop pair. The signal should be lower by several dB with Direction switch set to the 180 degrees from the station. Then adjust the Balance and the Phase controls to increase the null. Over the MW band the Front to Back ratio should be approx. 30dB, tweaking the controls should allow for station nulling of up to 50 dB. However, some experimentation with all the controls may be required to obtain the best null especially when the signals are fading. Maximum F/B will normally be +/- 60 degrees off the back of the antenna.

Antenna Positioning:- The basic 2 K9AY system requires the antennas to be spaced between 20 to 40m. The K9AYs are positioned in line relative to each other i.e. one K9AY is positioned North and the other K9AY is placed 20 to 40m to the South. Where the 4 K9AY system is deployed, the other 2 K9AYS are position as above but in East and West direction. The K9AY antennas should be positioned as for as possible from buildings, and sources of interference. In most cases satisfactory results will be obtained by mounting the antennas at least 20m away from buildings. See Figure 1.

Figure 2 shows a typical K9AY antenna. The antenna loop is approx. 8m high with a 9m base. The K9AY head Amplifier is connected at the centre of the base wire. A user-provided 8m high pole supports the antenna loop wire. Two 1.5m user-provided poles, support the ends of the base wire. The centre of the base wire should be approx. 0.5 metre off the ground. The Head Amplifier Earth terminal is connected to a user provided 4 foot ground rod.

Note: 40m antenna spacing will provide approx. +6dB higher gain.

Antenna Positioning

typical K9AY antenna

The plots below show the improved directivity afforded by the K9AY array compared to an active vertical array and a single K9AY.

K9AY array

Wellbrook Communications
The Farthings
Beulah
Llanwrtyd Wells
Powys
Wales LD5 4YD
UK
Phone 01591 620316

Specialists in Broadband Loop Technology!

Sales@Wellbrook.UK.com

Designs and specifications are subject to change without notice