Coax Common Mode Noise Filter - 1500 Watts, 1.8-60 MHz, -38 dB Common Mode Noise Suppression
| Quantity | Price per item | Discount |
| 2 items | $104.95 | 5% off |
| 10 items | $99.95 | 9% off |
| 50 items | $94.95 | 14% off |
| 100 items | $89.95 | 18% off |
CMNF-1500HF for transmitter/receiver coax lines up to 1500 watts PEP - 1.8-60 MHz, -38 dB Common Mode Suppression
For coax feed lines with receive and transmit signals, you will love the small size, wide frequency range and excellent attenuation of common mode noise interference
- Reduces broadband common mode receiver noise* picked up on the outside of the antenna coax feed line.
- Wide frequency range works on all brands of radios and coax fed antennas from 1.8-60 MHz
- Common mode noise rejection up to 20-38 DB (3-6 "S" units) depending on frequency
- Simple plug & play installation: plug a short jumper from the CMNF-1500HF to your amplifier output and plug the feed line (or a jumper to your antenna tuner) into the other SO-239 CMNF-1500HF input. Either connector can be input or output. Rated at 1500 watts PEP.
- will work with Bias-T antenna switches and will pass DC voltage from input to output with no attenuation
* not effective for noise from AC power lines or noise received directly by antenna
Installation Note: For best results, and to reduce co-interference between choked and unchoked coax feed lines with multiple antennas, ALL antenna feed lines entering the radio room need to have a separate feed line choke particularly if they are at a different frequency then HF, like VHF or UHF.
If you use a antenna switch for multiple antennas in the 1.8-61 MHz range, place the CMNF-1500HF in the "common" line of the antenna coax switch and the antenna tuner/amplifier.
For additional common mode noise reduction, consider the CMNF-500HF (500 watts PEP) placed between the receiver and the amplifier.
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SLIP-ON FERRITE BEADS
Baluns are used to connect balanced antennas to unbalanced transmission lines (Coaxial cable) and Ununs are used to connect unbalanced transmission lines to unbalanced transmission lines or unbalanced antennas (e.g. verticals). In the case of 1:1 baluns the input is usually an unbalanced coax cable and the output load is a two terminal balanced load like an antenna. Ununs are also called line isolators, feed line chokes, and 1:1 coaxial baluns (incorrectly). 1:1 Baluns and ununs stop common mode currents (flowing on the outside of the coax braid due to skin effect) when they are located at the antenna feedpoint. They can also be used as “line isolators/chokes” anywhere along the cable to suppress flow of induced RF (antenna near field radiation and neighborhood noise pickup) which helps suppress RFI into the radio receiver/transmitter. For best results, put one at the antenna feed point connection, and one at the radio room entrance, and for difficult common mode current cases, one every 1/4 wavelength along the antenna feed line. For low (below 3 MHz) frequencies, use two 5 bead baluns in series to double the choking impedance or order the 10 bead or 15 bead version for higher choking power.