RX antenna - K9AY loops switch with remotly VARIABLE Rload

This revision is from 2022/01/10 02:06. You can Restore it.

Current version 3.1 - Variable Rload with FIXed JUMPER(Edit)

Quick Start Guide(Edit)

Assembling KIT(Edit)

Why variable Rload???(Edit)

- look at far field plots from MMANA

The drill drawing(Edit)

Paste the drawing on the box and fix it with some tape.

Schematic diagram(Edit)

- Schematic Version 3.1

  • Direction switching matrix table for DC control inputs ( apply +12V for logic 1 )
  • Direction switching matrix table for AC/DC voltages over the coax

Rload resistors for VARIABLE and FIXED(Edit)

  • There are TWO resistors. First 1k2 in paraller to VAC and second 750 R as option for FIXed Rload - see below.
  • NOTE! Solder 1k2 resistor on the botom side after the protection diodes!

Voltage controlled resistor(Edit)

- insert VAC plus to plus - check package


- there are two resistors. Both are 100uH. But L1 is for higher current. L1 is black axial inructor. L2 is small resistor size green one.


- solder 100nF YELLOW capacitors

- some older versions do have 470nF capacitor

Protection diodes(Edit)

- solder 6 + 6 diodes

- these diodes protect Rload resistor against high power, electrostatic etc.

Insert PTC 100mA and rest parts(Edit)

- PTC EX10

- Varistors

- rest parts


- By the jumper JP3 you can select 50 or 75 Ohm coax output

- Jumper JP1 must be short if you want to control direction over coax

  • NOTE: If you use external DC control, please disconnect JP1. If not, you will have DC voltage on the coax!

- By the jumper JP2 you can select controlling over coax or DC voltage on connector X3

  • NOTE: If you use external DC control, please disconnect JP1. If not, you will have DC voltage on the coax!

FIXed Rload !(Edit)

- You can use this VARiable Rload KIT as FIXed one.

- Than you need only coax cable to control direction etc

- Conect JP4 to SHORT - and you have fixed Rload abt 460 Ohm / 4W


TRANSFORMERS winding - very important thing!(Edit)

    • for 50 ohm coax feed line : 2 turns on primar (coax) and 6 turns on secondar side (loop)
    • for 75 ohm coax feed line : 2 turns on primar (coax) and 5 turns on secondar side (loop)

- In version 2.3 and higher, you can select Coax impedance by jumper JP3.

- Transformer should have 5 + 1 turns.

Common mode coax choke(Edit)

- choke measurements

Wind the coax(Edit)

  • Common mode current choke construction
  • Wind 4 turns on one side than cross to another side of cores and wind rest turns.

Solder the coax (Edit)

KIT - all parts assembled.(Edit)

Example of controller(Edit)

- Injector to coax line:

- direction and VAC Rload controller

K9AY loops design example.(Edit)

  • It is VERY recomended to place K9AY loop antenna as far as possible from metal towers, antennas and wires. This hepls to obtain better paramaters of antenna ( directivity and noise ).
  • K9AY Loop design page