Coax antenna switches generally only switch the center conductor of the coax and all the coax braids remain connected in parallel summing the common mode noise off ALL coax lines onto the coax selected - this means you may be picking up common mode noise from coax lines that are not even connected to the coax antenna selected. The only practical solution is to isolate the coax braids from each other BEFORE they connect to the antenna switch as shown in the picture for a simple 2 position antenna switch.
This product listing is for use with your antenna switches which have 2 - 8 antennas. Each switched line needs a common mode noise filter prior to being connected to the switch. In some cases you can use a double male barrel connector to attach the filter to the switch or you may need a short jumper cable. (ANTENNA SWITCH SHOWN IN PICTURE NOT INCLUDED - SHOWN FOR ILLUSTRATION OF USE ONLY)
We offer a low power filter (CMNF-500-50 up to 500 watts PEP and up to 46 dB of common mode noise suppression per line) or a high power (Maxi-Choker, MC-1-3000 up to 3KW PEP and up to 60 dB of common mode noise suppression per line) and 2-8 ports of antenna switch. If you use a dummy load for one of the switched ports you do not need a filter for that port. Each filter has a range of 1.8 to 61 MHz (see individual listing on this website for specifics).
A simple ferrite ring filter on the DC power line can help suppress the RFI noise affecting the victim device or keep the DC power cord from acting as an antenna and radiating RFI into other victim devices. This kit is also useful on laptop computer supplies, routers, cable modems, wireless phone charges, etc.
Installation is quick and easy: Just wrap the DC power cord through the center of the ring filter as many times as you can and reinstall. For best results with long DC power lines, use one at the ring filter at the wall wart end (to prevent the wall wart power supply from using the DC line as an antenna) and another at the DC plug end (to prevent the electronics in the powered device from using the DC power cord as an antenna). Typical installation is shown below:
The filter suppresses RFI in from .1-100 MHz. Inside diameter is 3/4 inch/19 mm.
Since most households and office environments have multiple wall warts we offer the Wall Wart RFI Filter kit in bulk quantity packages.
Known RFI Generators include Roku/Sling-TV power adapter - Interference heard in the AM broadcast band and harmonics. Also many ethernet Cable/DSL modems, cell phone chargers, computer power adapters have the same issue: using the AC or DC side of the power supply as a radiating antenna. RFI solution is to use a linear power supply, change adapters or wall wart ferrite filters