Your rotor cable and control box can cause RFI into your radio station and you need to suppress common mode RFI induced into the cable from your antennas. In many cases the rotor cable acts as an unintended counterpoise for your rotated antennas and can cause weird SWR issues since the control cables become part of the antenna,
The SOLUTION is simple: isolate the cable from RFI by adding the Palomar RFI kit for antenna rotors. Add 3 snap on filters near the rotor and another 3 snap on filters at the rotor control box and a ring filter for AC powered rotor control boxes to suppress RFI common mode currents that can affect the antenna SWR and radiation patterns. In addition, these filters may also help reduce station receiver noise since many rotors are connected to the station ground and the rotor cable acts as an additional receiving antenna.
Isolating the rotor cable works on the same principal as isolating coax cable - keep the TRANSMIT signal on the antenna by proving a feed line choke at the rotor itself and keep noise out of the station on RECEIVE by choking the cable at the rotor control box ( by suppressing noise pickup on the cable).
Kit includes 7 filters -six 1/2" snap on filters for the cable and a ring filter for the AC/DC power supply for the control box. Simple to install and cheap insurance to solve both the TRANSMIT and RECEIVE issues caused by rotor control systems.
4:1 impedance transformers (Baluns and Unun configurations) are available in kit form or assembled form in a weatherproof Current Unun and Balun Enclosure which we call CUBE Baluns™ and CUBE Ununs™. All 4:1 impedance transformers use ferrite cores and the kit forms can be configured as a balun with balanced output of 200 ohms or as ununs with one side grounded.
4:1 baluns are designed for 50 ohm unbalanced (coax) input to 200 ohm output (either balanced or with one side grounded).
4:1 Baluns are useful between balanced lines for center fed Zepps, Off-center fed (OCF) dipoles with coax, G5RV antennas, full wave loops, NVIS dipoles that are close to ground and have impedance levels near 200 ohms or high impedance feeds for log periodic beams.
4:1 ununs are useful between coax and vertical antennas, monopole verticals or long wires with load impedances near 200 ohms.