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K9AY++ RX Antenna

The K9AY is terminated loop RX antenna. It consists of a wire loop of any convenient shape (diamond, delta, etc), hung from a single support and with a ground rod at the bottom. A 9:1 impedance-matching transformer is connected from one end of the loop to the ground and a terminating resistor is connected the other end of the loop to the ground. This antenna is directional. Favoring signals are arriving from the feed point end. You can also change the antenna far field by changing RLOAD (RTERM) of the loop. This set including the RF feeder box and the controller. Antenna has got Band Pass Filters and Preamplifier in the feed point of the loops. It is advantage of filtering and amplification small signals directly from antenna.

This is plastic box with the aluminium holder. Inside it, there is transformer with insulated windings, variable and FIXed Rload for the antenna loop, input and output protections. And in the middle of that there are 160/80/40m BPFs or bypass and 15dB preamp with variable ATT. You can set the Gain of the preamp very easy as you need. From 0 to 18 dB.

All you need is connect loops' wires, GND, coax cable and control cable (CAT-5 UTP or better FTP)

Jump to

Antenna Ground
Locating your K9AY Loops
K9AY Loop design
Loop connection
What is inside
Variable and Fixed Rload resistor
Tune and test points
Connector description resistor
Options: Recommendations to buy
Videos
FAQ


Antenna Ground

This K9AY antenna doesn't work without ground:

  • - it loses the f/b directivity
  • - this means that it needs good ground

A 4-foot ground rod (such as 3/4" diameter copper pipe) is often sufficient. It the earth is very dry, a longer ground rod is advised, to reach permanently moist earth - or you may install four or more 15 to 20 foot long radial wires for better coupling to ground. The grounded design of the K9AY Loop has several advantages over ground-independent versions of the terminated loop (Pennant and Flag), including simpler switching, no feedline isolation problems, and greater signal capture for the same size loops (source: K9AY AY Technologies).

Connecting the GND

- there is common GND on the screw under loops connections and also on the aluminium holder
- you can mount box directly on the GND rod
- for Coax and control cable are recommended Common-mode current chokes (CMCC)

k9ay++ grounding by qro.cz hamparts.shop



k9ay++ with cmcc by qro.cz hamparts.shop



k9ay++ with common-mode current choke by qro.cz hamparts.shop



Locating your K9AY Loops

Since you have chosen a small receiving antenna, it is likely that your transmitting antenna will be nearby. Transmitting antennas, power lines, towers and other nearby large conducting objects can re-radiate signals that are coupled to the receiving antenna. To avoid this problem, locate the K9AY Loop as far from the transmitting antenna as possible. Because the loop is small, it is often possible to place it among trees or shrubs in a front or side yard, while the transmitting antenna is in back. Another way to minimize the interaction is to locate the loop toward the most important direction you want to hear. For example, if you are most interested in hearing Europe from the US,  locate the loop Northeast of the transmitting antenna. When pointed toward Europe, the null will be in the direction of the transmitting antenna, reducing the pickup of re-radiated signals. Some European users of the K9AY Loop have chosen single loops, placing one of them Northwest of the transmitting antenna to hear US stations, with another East of Northeast to hear Asia and the Far East (source: K9AY AY Technologies).

Controller is universal for 0 or 45 deg orientation - image


K9AY Loop design

  • Please read our short technical article about K9AY loop design and simulations. You can select some size or download MMANA files and play with your own one :) You can try different shapes, height and load resistance. You can better understand how it works and how you can build it better.

k9ay loop design by qro.cz hamparts.shop


Loop connection

  • - this is very important thing which has effect on final antenna parameters
  • - if you end lower part of loops as close to ground as possible, you can obtain better F/B
  • - install RF feeder box higher - protect from snow, water etc. and connect loops with twisted wires from loops to screws

k9ay++ twisted line by qro.cz hamparts.shop



effect of low part of loops

Place loops as low as possible. GREEN = on ground, RED = 0.5m, BLUE = 0.8m

k9ay loop height by qro.cz hamparts.shop


What is inside

There is PCB in the feeder box which is assembled with Direction switch relays, Rload system (fixed and variable), Impedance transformer, Band Pass Filters, Preamplifier with Variable Attenuator, Protections and Common-mode filters.

k9ay++ inside feeder box by qro.cz hamparts.shop




Variable and Fixed Rload resistor

Antenna Loop needs LOAD resistance at one side of the loop. It is connected between end of the loop and ground. Size of the Load Resistance (Rload) - depends on size of the loop and frequency. You can set optimal value what effect on SWR and F/B. It is not very critical and in the most cases you can switch to FIXed value.

k9ay++ variable and fixed rload resistor by qro.cz hamparts.shop

k9ay++ antenna radiation pattern vs RLoad by qro.cz hamparts.shop


Connector description

  • - there is standard RJ45 (ETHERNET) connector with shielding - THIS IS NOT LAN PORT!
  • - you can use cheap CAT-5 or CAT-6 cable up to 100m - FTP version - shielded
  • Please read this instruction, use ONLY Copper wires

k9ay++ connector RJ45 by qro.cz hamparts.shop

k9ay DC direction matrix table by qro.cz hamparts.shop


Tune and test points

Antenna Loop needs LOAD resistance at one side of the loop. It is connected between end of the loop and ground. Size of the Load Resistance (Rload) - depends on size of the loop and frequency. You can set optimal value what effect on SWR and F/B. It is not very critical and in the most cases you can switch to FIXed value.

k9ay++ schematic tune and testing points by qro.cz hamparts.shop

1. Variable ATT

- preamplifier with 2SC5551A has got 18 dB of total gain
- in many cases it is more than you need
- there is VARIABLE ATT trimmer (R_ATT1), it allows you to set gain from NO signal to maximal gain of the preamplifier
- ATT trimmer has got 30 turns with no end stops
- total gain including BPF is PRESET to 10 dB from our final testing
- for higher gain turn clockwise

2. Preamp BIAS

- this is trimmer (RBIAS1) which sets transistor bias current
- higher current means higher IP3
- recommended is 40 to 50 mA - higher currents need better cooling
- with bias current around 15 mA, the noise figure of the preamplifier is around 1
- for setting this bias current open jumper JP1 and measure it there

3. Rload tune

- this trimmer (R6 SET Rload) can be use for final loop resistance tune
- there is a trimmer for maximal resistance in the controller - front panel trimmer MAX
- set Rload potentiometer on controller to middle position (5)
- jumper JP2 must be set to Variable (see next notes)
- set DIRECTION switch to NE
- disconnect antenna loops
- left coax connected to antenna and controller
- use Ohm meter and measure between GND and SW screw
- tune Rload trimmer to resistance you like (400 to 500 Ohm)

IMPORTANT NOTE: Final Rload resistance may vary with the direction switching. This is caused by thin GND wire between controller and RF feeder box. If the changing is lower than 10 % then all is OK, if more, then more GND wires are recommended. Using CAT-5 FTP (shielded) cable can be big advantage in this problem.

IMPORTANT NOTE: For final tuning and measuring, please connect control cable as well also the coax one!

4. Direction LED

- LED indication for checking
- LEDs must follow matrix table on the PCB while switching by the direction knob on controller

5. Rload VAR/FIX

- jumper JP2 allow to select FIXed or VARiable resistance for the loops
- FIXed one is around 470 Ohm/4 W, knob on the controller does not work
- while it is set to VAR, you can tune resistance from typ. 200 to 1000 Ohms
- there is a trimmer for maximal resistance in the controller - front panel trimmer MAX
- load resistor has got high voltage and current protections

6. Preamp current TP

- you can open this jumper (JP1) and check/set transistor current
- set switch on controller to preamp ON
- Bias current should be in range 10 to 50 mA - recommended is 40 mA


Options: Recommendation to buy CMCC

Common-mode choke coils work as a simple wire against differential mode current (signal), while they work as an inductor against common-mode current (noise). This box is designed as a common-mode filter for RF cable and also for analog AC/DC controller wires. This version is directly designed for K9AY++ antenna system. Our offer of CMCC.

effect of cmcc ctrl cable by qro.cz hamparts.shop

Common-mode filter for K9AY++

cmcc ctrl cable by qro.cz hamparts.shop

Videos

FAQ

  • 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.

continue to manual for K9AY/4-WAY antenna switch controller

manual page for k9AY/4-way controller qro.cz hamparts.shop

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