K9AY simply manual
This is technical manual page for K9AY simply feeder box. You can connect two loop antennas and switch four directions by the internal relays. Loop termination resistance could be fixed or variable. In the case of the variable Rload you are able to change resistance from 200 to 1200 Ohm. Direction relays could be controlled by external wires and DC voltage or by the coax cable with AC/DC. There are also front-end protections and you may not be worry about high power from TX antennas. This antenna needs good ground.
- Lower noise RX antenna
- RX antenna designed for FOUR directions
- Small design
- ideal for portable operation
- Noise source antenna for QRM eliminator
version with PL SO-239 connectors
version with F connectors
- RX antenna - Gain depends on loop size
- Four directions 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
1. JP1 Rload VAR/FIX
- You can select Fixed load resistance to about 460 Ohm / 4 W
- If you select Variable one, you have to connect external wires and apply DC voltage in range about 1.5 to 6 V
2. JP2 Coax output impedance
- There you can select between 50 or 75 Ohm output coax
3. JP3 CTRL over COAX
- Short this jumper when you control direction of this antenna over the coax with AC/DC voltage
- Jumper JP4 must be switched to COAX position
4. JP4 CTRL DC/coax
- Select direction switching between External DC voltage at J4 connector or AC/DC voltage over the COAX (+ JP3)
There is example of the controller which is switching directions by the DC voltage. You need 3 external wires (DIR1 RE, DIR2 RE and GND)
There is example of the controller which is switching directions by the AC/DC voltage over the coax cable. You need good Bias Tee to apply this voltage to coax and isolate it from RF. If you use Wide Band SDR, please use HPF or BPF to eliminate AC noise - you can damage your RX
- 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.