Common Mode Coax Noise Filter - 1500 Watts, .2-7 MHz, VLF
CMNF-1500LF for transmitter/receiver coax lines up to 1500 watts PEP At LF range of .2-7 MHz
For coax lines with receive and transmit signals, we suggest the CMNF-1 or CMNF-2 with SO-239 connectors in and out which are connected in series with the coax feed line to the receiver/transceiver effectively reducing common mode noise existing on the coax. For best results, and to reduce co-interference between choked and unchoked feed lines with multiple antennas, ALL antenna feed lines entering the radio room need to have a feed line choke particularly if they all feed a common coax switch. Choking only 1 line if you have 5 antenna coax feeds will do little good – you need to choke all five – use the feed line chokes for the individual feed lines and the CMNF between the antenna coax switch and the receiver. All CMNF models are SO-239 input and output. Adapters are available for converting to “F”, or “N” connectors.
The CMNF-2LF is meant to be placed in the coax line entering the transceiver or receiver (between the transceiver and amplifier or antenna tuner/coax switch if used). The CMNF-2LF has a high choking impedance from .2-7 MHz with higher choking on the very lower frequencies where noise is usually a larger problem then on higher frequencies. Convenient SO-239 input and output connectors all easy insert in series in your coax feed line. Use a short jumper from the CMNF-2LF to your radio and plug the feed line into the other SO-239 CMNF-2LF input. Either connector can be input or output. Rated at 1500 watts PEP – if you have a higher powered transceiver or amplifier, consider the CMNF-3 rated at 5KW.
Installation Note: Putting a CMNF at the output of your antenna tuner lessens the choking effectiveness since the impedance may be much higher or lower than the 50 ohm design impedance of the noise filter. The best place to install the CMNF is between the antenna tuner/linear (high power CMNF-2 or CMNF-3) or closest to the receiver/transceiver (CMNF-1). See diagram below. Use sleeve or CUBE™ feed line chokes at the antenna feed point and radio end of the coax to reduce RFI and common mode noise.
Enclosure is 4" x 4" x2" PVC weather resistatnt.