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K9AY one direction manual

This is manual page for K9AY single loop as one directional antenna. This antenna missing second loop and relay direction switch. This antenna is designed for Multi TRX QTH. You can use this antenna as one direction which you can share to more receivers. This feeder box includes impedance transformer, terminator load resistor with 8 values and high voltage and current protection.

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- lower noise receiving antenna
- one direction
- sharing one antenna to more receivers at multi QTH
- ideal for phased antenna array
- source antenna for QRM eliminator

example for SO2R or Multi/Multi

This is example for SO2R or Multi/Multi RX antenna system where you can share all inputs of the switch to all RX. There the K9AY one direction is a good RX antenna for the short skip as well as for DX.

rx antenna k9ay one direction with 7ant modular switch bi-directional beverage qro.cz hamparts.shop

version with PL SO-239 connectors

k9ay one direction with pl so-239 connector qro.cz hamparts.shop

version with F connectors

k9ay one direction rx antenna with f connector qro.cz hamparts.shop


- RX antenna - Gain depends on loop size
- One direction
about 110 degrees
- F/B depends on loop size and construction
Find more design hints (phased array)
- Feed line impedance
50 or 75 Ohm
- Common-mode choke isolation
more than 30 dB
- Current protection > 100 mA and Voltage protection > 65 V


schematic k9ay one direction qro.cz hamparts.shop


pcb k9ay one direction qro.cz hamparts.shop


You are able to change the loop load resistance. By the Jumpers J2 and J4 in the steps: 340, 380, 440, 460, 480, 1200 and 1300 Ohm.


  Read article about K9AY design and phasing array.

k9ay loop size qro.cz hamparts.shop

k9ay one direction design array qro.cz hamparts.shop


  • GND screw on feeder box is insulated from Coax shield. This isolation prevents introducing unwanted signals and noise into the antenna system. Grounds are insulated by Common-Mode filter.

  • Connect the ground terminal screws only to earth ground using at least one (copper/army GND rods with screw) ground rod. Use as large diameter ground rod as possible.

  • A good ground system improves performance (lower noise) and enhances lightning survivability.

  • Mast holder works also as a ground connection. You can mount this feeder box directly on GND rod. Then you do not need to connect wire from GND screw.
  • There are front-end protections and strong signal from close TX antenna should not damage anything. But mounting RX antenna close to the TX one has got bad effect on RX antenna parameters. Vertical elements close to the loops can increase antenna noise and degrade antenna radiation pattern. In the worst case antenna does not work.

  • There can be different shapes of the loop. You can find some designs also at our blog. Shape of the loop has got effect on elevation pattern and F/B.

  • Please, place end of the loop as close to ground as possible. There is some more info and simulations in the manual.

  • Mount RF feeder box higher - protect it from snow, water etc. and connect loops by the twisted wires from ends of the loops to the screws at the box - more at manual.
  • K9AY++ has got seven control wires. There are all DC signals. Two wires there control all four directions.

  • K9AY simply feeder could be controlled by the same way - two wires (+ GND) and DC voltage or you can use AC/DC voltage over the coax cable.
  • It is recommend to check voltages. Switching voltage must be higher than 10 V DC. The same at the preamplifier.

  • You can check switching matrix table and LED diode indication.

  • If you use variable Rload, you can test resistance vs. voltage.
  • Due to storms, lightning and animals we recommend to check SWR of the antenna time to time. Switch off BPF and preamplifier. If there is any problem with high SWR, please check loop and ground connection and also terminator resistance.
  • K9AY is antenna for small place. The loop size is usually smaller than wavelength. Gain of the antenna is in negative numbers. Difference in the signal strength compared to the dipole or vertical antenna could be more than 20 - 30 dB (3 to 6 S). Advantage of this antenna should be in the Signal-to-noise level. Gain of the antenna could be compensated by the preamplifier.
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