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Wellbrook's comercial K9AY system

By Dave Kenny, British DX Club
Communication, September 1999

Back in November 1998, Andy Ikin of Wellbrook Communications very kindly loaned me a pre-production model of a K9AY antenna system by Wellbrook Communications.
It is based on a system designed by Gary Breed (K9AY) published in the American ham radio magazine QST which Andy had tested himself last summer (see K9AY Terminated Loop Antenna by Andy Ikin, September 1998 edition of Communication).

The K9AY system comprises a very neat control unit which plugs into a 12v power supply (provided). From the control unit, a short lead plugs into the aerial socket on the receiver and two feeder wires (one is a standard RG58 coax, the other a 12v power supply feed about the thickness of bell wire) connect up to the loops which I constructed some 30m distant at the end of the back garden. On the front of the control panel are two switches: the first is used to select either A or B loop, the second to reverse the beam of whichever loops is selected. To the right of the switches is a small rotary control which is used to adjust the null.

The aerial itself consists of two large wire loops mounted at right angles and a small connection box. You also need to connect an earth to the connection box - I used a short copper pipe hammered into the ground nearby, and thanks to all the rain we've had this summer, the ground remained damp so there was no need to water it at any stage; in a dry summer it's always worth giving your earth rod a good soaking every week to help maintain good conductivity between the rod and the ground.
Wire for the loops was supplied in a 100m roll with instructions on their construction. At first I found the design quite daunting, but it is really quite straightforward and the actual shape of the loops themselves does not seem to be particularly critical. I supported the loops between the branches of three trees, the garden fence and a shed roof and was pleased to find that once up it was virtually invisible to the naked eye from the house. If you don't have convenient trees you could also use a pole (preferably non-metallic) or even perhaps wind the loops over a shed or outbuilding - as long as they are away from sources of electrical interference. The main thing is that each of the loops should be of a similar size and at right angles to each other.

The idea of the K9AY is that the control unit remotely varies the phase of the two loops by varying the termination resistance, this effectively enables you to steer a null electronically through 360 degrees - without the need for any moving parts. On an ordinary MW loop the signal peaks and nulls in two directions at the same time, so if you are trying to receive a weak station 180 degrees away from a stronger station, it is very difficult if not impossible to null out the stronger station without also nulling out the weaker station at the same time. With the K9AY however, the single null enables you to switch very effectively between signals from any direction.

I was delighted to find that despite my very rough initial construction of the two loops they worked straight away and despite the summer daytime conditions prevailing, found that I could now select either Atlantic 252 or Radio Algiers, both on 252 kHz - virtually interference free - at the flick of a switch.
On 828 kHz I could now choose between Classic Gold from Luton or Arrow Classic Rock from Holland virtually interference free - this was also impossible with my other aerials.
On 1548 kHz, Capital Radio from London or BBC Radio Bristol - easy.
On 1485 kHz, which is dominated by Classic Gold from Newbury in this area, I could now hear BBC Southern Counties Radio from Brighton by nulling out Classic Gold. This was previously impossible, as with a conventional loop both Brighton and Newbury are approximately 180 degrees apart, so the nulls of both are in the same direction.

Later that night, for the first time, I was able to log two of the 1 Watt low power AM stations currently operating on 1350 kHz - Radio Yare (Gt. Yarmouth) and Sunshine Radio (Liverpool) - for the first time, and what's more, choose between them at the flick of a switch! Signal strength and overall clarity was superior on the K9AY to either my 100m Beverage or 30m long wire and this was despite having constructed much smaller loops than recommended in the instructions that came with the K9AY.
It also surprised me to find that reception on shortwave frequencies up to about 12 MHz was almost as good on the K9AY as on my 30m longwire - although the directional properties of the phasing system tail off above about 2 MHz so that on shortwave it acts as an omnidirectional amplified wire, and although signal strengths are somewhat lower than on the longwire, being further from the house it is less prone to TV and other interference.

After some four months of using the K9AY I find that I am completely hooked and don't know what I'd do without it. On mediumwave, in virtually all circumstances, it outperforms my 100m Beverage and 30m long wire providing stronger, clearer signals. One recent annual RSL Raven Sound, had proved elusive for several years due to its exceptionally low signal strength, but with the K9AY I was able to pull it out of the noise for the first time (no signal at all on the other aerials).
Further afield, another first time for me was reception of the local Radio Rurale station in Labe, Guinea on 1386 kHz, heard clearly on the K9AY, but again inaudible on the other aerials. With the three recent "offshore" RSLs it has made the difference between good almost 100% listenable reception, to poor, often noisy signals on my other antennas.

While I was writing this review on 22nd August it again proved itself by enabling me to receive Radio Silverstone on 1602 kHz clearly for the first time by nulling out BBC Radio Kent on the same frequency.
So, for anyone interested in mediumwave DX I can heartily recommend this aerial.
The version I tested came with a 15dB amplifier which more than proved its worth, especially with the smaller loops I built. Ideally, the two loops should be 25m in circumference, but the ones I constructed were only about half that size - for which you will need around 5m x 5m of garden space to erect them.
Although the instructions advise that the lower part of the loops should be a minimum of 0.5m off the ground, mine just lies on the lawn and it seems to work well enough - it achieves nulls of between 30-40dB on most MW signals. I can only wonder at the sort of results that would be achieved with a full sized loop raised off the ground, but I would need to move house first as my garden is typical of most Victorian terraces, being long but narrow - only 5m wide.

Details of the K9AY and other aerials are available from Andy Ikin at Wellbrook Communications, Wellbrook House, Brookside Road, Bransgore, Christchurch BH23 8NA. Tel 01425 674174.

Reproduced with author's permission. First published in Communication, September 1999. Communication is the monthly journal of the
British DX Club.

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