DX Engineering High CMI Receive Feedline Chokes

DX Engineering High CMI Receive Feedline Chokes achieve exceptionally high isolation between the input and output connector shields to effectively block common-mode RF noise and unwanted signals that collect on 50 or 75 ohm receive antenna feedlines. Ongoing research and development by the design team at DX Engineering has produced two bidirectional Receive Feedline Chokes; a 50-ohm model with BNC female connectors and a 75-ohm model with Type-F female connectors. Both choke models cover the RF frequency range 100 kHz through 30 MHz. Both exhibit very high common mode impedance* (CMI typically over 8,000 ohms across the 160, 80, and 40 meter bands) and feature DC pass capability up to 700 mA at 13.8VDC, with extremely low SWR and negligible insertion loss. Very affordable DX Engineering High CMI Receive Feedline Chokes will be considered the best, most versatile feedline chokes ever produced for typical HF receive antenna applications.

High CMI Receive Feedline Chokes have 50-ohm BNC female connectors OR 75-ohm Type-F female connectors to prevent accidental connection to transmitting equipment. These compact receive feedline chokes are built into a 2 inch square plastic box (1.5 inches deep). Non-directional Input and Output connectors are on opposite sides; adjacent sides each have 7/16 inch flanges with 3/16 inch holes for mounting the choke. Hardware is not included. These chokes are permanently sealed to prevent changes to the precisely adjusted components by physical shock or internal moisture.

NOTICE: Receive feedline chokes do not reduce ambient or propagated RF noise that is received by the antenna. Receive feedline chokes do not reduce RF noise in a receiver that is conducted by a power main or noise that originates inside a power supply. To suppress power noise, use DX Engineering Ferrite on power cords and cables.

Low noise receive antennas are traditionally located away from electrical wiring and other noise sources for improved signal-to-noise performance. However, local and propagated RF noise and other unwanted long, medium and shortwave signals can energize the outside of the feedline shield. Installing a DX Engineering High CMI Receive Feedline Choke blocks the direct path for that RF noise into to the feedpoint of a low-noise antenna, through the feedline shield connections between the station equipment and the receive antenna system.

DX Engineering High CMI Receive Feedline Chokes should be placed at the antenna end of the feedline, at the receive array phasing unit or remote switch end of the coaxial cable. Especially for 50 or 75-ohm coaxial cables run on or above the ground, at least one choke should be placed at the shack end and one at the antenna end. It is very important to choke a very long receive antenna coax cable shield which collects unwanted broadband signals and noise like a short wave antenna. High CMI Receive Feedline Chokes are installed in line with the receive antenna feedline, and are passive devices which require no power, and they do not require a direct ground connection. If there is a grounded connector in the system, these chokes should be installed inline with the long coaxial cable. For example, this choke should be placed inline with the antenna feedline side of a surge protector ground.

IMPORTANT: Receive feedline chokes cannot be used on the output of a transceiver. Transmitted RF energy will cause permanent damage to the Receive Feedline Choke.

Specifications for DXE-RXFC-50 and DXE-RXFC-75 :

* Nominal Common Mode Impedance by Frequency (Approximate)

100 kHz – 1,250 ohms

200 kHz – 2,500 ohms

1.8 MHz – 8,000 ohms

3.8 MHz – 10,000 ohms

8.0 MHz – 8,000 ohms

21.0 MHz – 4,500 ohms

30.0 MHz – 2,500 ohms

Insertion Loss:

0.1dB at 1.8 MHz

0.2dB at 7 MHz

0.4dB at 30 MHz

VSWR: <1.25:1 maximum; 1.06:1 at 7 MHz, nominal

DC Current, Maximum: 700 mA

DC Voltage, Maximum: 15 VDC

Operating Temperature: -40°C to +80°C