CABLE TV/Satellite RFI Coax Noise Filter, Suppresses 1-60 MHz common mode interferenceProduct DetailsMPN: CMNF-TVCountry/Region of Manufacture: United StatesFilter Power Rating (PEP watts): receiver onlyChoking Impedance (ohms): 1000 - 7000Common Mode Attenuation (db): 21 - 36 dbRFI Suppression Range (MHz): 200 KHz-30 MHzInsertion Loss (db): .02# Ferrite Filters: 3Enclosure Size (inches): 4" x 2" x 1.5"Typical Use:: Noise filter at radio end of coax next to receiverCABLE TV/Satellite RFI Noise Filter for AM broadcast & shortwave from 1-60 MHz – Receive Only - F connector I/O - 75 ohm input/output, will pass DC straight thru
Purpose. The CMNF-TV is used to suppress RFI noise and common mode interference on the coaxial input line of satellite and cable TV receivers often caused by nearby transmitters
The filter is designed to have a high RF impedance to noise and interference from common mode currents on the outside of the coax braid while passing RF signal currents on the center conductor and inside of the coax braid to the antenna.
The effectiveness of the filter is dependent upon the amount of common mode noise encountered on the feed line. If your receive system has a large amount of common mode noise current then you should experience a reduction of common mode current which usually as heard as background noise level. Typical choking impedance is shown in the gallery picture.
Got Common Mode Noise? Not Sure - Find out now by clicking link below:
Palomar Engineers Common Mode Noise on Coax User Diagnosis Test
The filter was quite effective. Was surprised that it actually reduced the noise level
more than the signal so S+N/N improved by 1.9 S units.
Bill
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CABLE TV/Satellite RFI Noise Filter for AM broadcast & shortwave from 1-60 MHz – Receive Only - F connector I/O - 75 ohm input/output, will pass DC straight thru
Purpose. The CMNF-TV is used to suppress RFI noise and common mode interference on the coaxial input line of satellite and cable TV receivers often caused by nearby transmitters
The filter is designed to have a high RF impedance to noise and interference from common mode currents on the outside of the coax braid while passing RF signal currents on the center conductor and inside of the coax braid to the antenna.
The effectiveness of the filter is dependent upon the amount of common mode noise encountered on the feed line. If your receive system has a large amount of common mode noise current then you should experience a reduction of common mode current which usually as heard as background noise level. Typical choking impedance is shown in the gallery picture.
Got Common Mode Noise? Not Sure - Find out now by clicking link below:
The filter was quite effective. Was surprised that it actually reduced the noise level more than the signal so S+N/N improved by 1.9 S units. Bill
TECH NOTE: We also stock RFI kits to protect effected devices such as garage door openers, computers (laptops, desktops), dsl/cable routers, ethernet hubs and many more devices. If you run a high powered RF amplifier in your ham station also consider a linear amp RFI kit which will cut down RFI transmitted by your station. Remember there is always a “transmitter” and a “receiver” of RFI and the quest is to find and choke the “path” the RFI has selected – you need to add ferrites to both the transmitting side and the receiving side to eliminate RFI problems. The RFI-HTS kit only helps suppress RFI on the receiving side.
Typical RFI Problem/Solution:
Hello, I am Larry, a ham operator and I am having interference issues with my Direct TV system. My station is a FT450D through an Ameritron ALS-600. From the amp through a coax switch to choose between an OCF dipole or an Hustler 5BTV vertical. Any power over 100 watts and my DTV goes off the air and must completly reboot/format. Coax is RG-8. The DTV dish is pointed away from the dipole and separated by about 25'. DTV was totally useless! They suggested I not talk on the radio while she is watching TV! Please help me with a reasonable, cost effective soultion. (The wife gets really pissed when I shutdown the tv!) Thank you, Larry
Hi Larry,
Your RFI problem is quite common and is usually a sign of either a radiating coax feed line or reception of your radiated signal (source) by the Direct TV (the victim) through either the AC power lines acting as “antennas” for your ham signal or the coax braid of the satellite antenna acting as an antenna for your signal.
The solutions are straight forward:
1. To make sure your feed line is not radiating you need a feed line choke at each antenna feed point (also makes your antenna work better since it is not using the coax as part of the antenna). You can use our simple Kit 110 with 5 snap on chokes on each antenna for this purpose. Part # Kit 110 at $27.50 each – one for each antenna. These chokes will keep your feed line from radiating and coupling into your ac power lines. INFO HERE
2. The radiation from your antennas themselves may also be getting into the ac power lines and coax braid of the Direct TV antenna so you need to protect the victim receiver. Depending upon the sophistication of your direct TV setup (e.g. home theater, dvd, tape player, sub woofer speakers, etc), the path of the RFI may be coming thru the AC power lines of any connected device to the video including the video monitor itself! To help solve this problem we have a home theater RFI kit for up to 5 devices (you need a minimum of two – one for the Direct TV receiver(AC and coax input) and another for the video monitor AC power lines and HDMI or video input cable. Our kit part # is RFI-HTS. INFO HERE
These items should help reduce the RFI and let you operate on the air while your wife watches TV.
Bob Brehm, AK6R
Chief Engineer