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This device provides a means of reducing or eliminating common-mode noise from an antenna feedline, resulting in a considerable increase of the received signal quality. Common-mode noise is generated by computers, lamp dimmers and other electric or electronic appliances. Such noise can be a problem especially in the lower portions of HF spectrum, where weak signals can be sometimes completely masked by assorted buzzes and other unwanted noises.
The Common-Mode Choke can be also very useful to provide an alternative earthing point for an active antenna, if the antenna itself cannot be grounded due to its location, or its ground connection is inadequate. |
The WiNRADiO WR-CMC-30 Common-Mode Choke is especially suitable for use with WiNRADiO AX-81S and AX-05E shortwave antennas.
Installation
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The WiNRADiO WR-CMC-30 common-mode choke is inserted in the antenna coaxial feedline close to the receiver, in order to "choke" off common-mode noise currents and passing them to ground without affecting the useful signals between the antenna and the receiver.
The common-mode choke will let through DC current, which is useful in situations where an active antenna (for example the WiNRADiO AX-81S) is powered through the coaxial cable. The power can be provided directly by certain receivers (for example the WR-G33EM receiver), or using a power injector ("Bias T") such as the WR-BT-650. |
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In situations where an active antenna is to be powered via a power injector such as the WR-BT-650, it is recommended that the power injector is placed after the WR-CMC-30 Common-Mode Choke, as indicated. This arrangement prevents common mode noise which could be introduced by the power injector from making its way to the antenna.
In extreme cases of common-mode interference, it is also possible to employ several WR-CMC-30 chokes in series, placed strategically along the entire length of the feedline, in those locations where good quality grounding is available. |
| Technical Specifications |
| Application |
Receive only |
| Frequency range |
0 to 30 MHz |
| Insertion loss |
Less than 1 dB |
| Impedance |
50 ohm |
| Common mode inductance |
250 uH |
| DC Current |
150 mA max. |
| Connectors |
2 x BNC
M4 screw with winged nut (ground) |
| Enclosure |
Diecast aluminium |
| Size |
60 x 35 x 30 mm (2.3 x 1.4 x 1.2 in)
(excluding connectors) |
| Weight |
110 grams (3.8 oz) |
Specifications are subject to change without notice due to continuous product development and improvement.
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Frequency range DC to 30 MHz 
