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Common Mode Noise Chokes
Common mode noise typically originates from Computers, TV’s, Motors etc. that couple their noise signals onto the outer shield of the coaxial cable between an Antenna and a Receiver. When the noise signal begins to travel along the outer shield of the coaxial cable it can travel towards the receiver, towards the antenna, or both directions. Therefore the outer shield of the coaxial cable can act like a noise conduit that then brings that signal out of the house and to the location where the main receiving Antenna is. At/near the Antenna location the noise can radiate from the outer shield to the Antenna, or wrap around the end and travel along the inside of the coaxial cable back to the receiver. It follows then that in erecting an outside antenna your local noise level has gone up because you are unwittingly transporting household noise out to the new antenna location. Enter the role of a Common Mode Noise Choke.
A Common Mode Choke acts like a resistor in that it can eliminate or greatly diminish the Common Mode noise level. The choking action can be supplied by two different, but not mutually exclusive forms of resistance/Impedance. One form is reactive (reacts to the load), and can therefore vary in it's effectiveness. The other form is resistive and is much more consistent, therefore a better figure of merit. We design towards and only quote the Rs resistive factor in our specifications. These chokes are NOT effective against atmospheric noises like lightning.
Broad Band Common Noise Choke 75m>10m
Common mode noise choking of greater than 1,500 Ohms Rs(Resistive Choking) from the 75m Band(3900 kHz) up past the 10 m Band(32,000 kHz) and a broad peak in the mid-Band(41m) of over 4,000 Ohms Rs(Resistive Choking). If your area of interest is the 41m Band and below may we suggest our “Tropical” Band Common Mode Noise Choke. Low insertion loss(0.2%) with an SWR of 1.1:1 or less from 500 kHz to 32,000 kHz.
Mod # RECV-CHK-BB $39.99 Shipping Included via USPS anywhere in USA
The “Tropical” Band Common Mode Noise Choke 75m>16m
Common mode noise choking of greater than 5,000 Ohms Rs(Resistive Choking) from the 75m Band(3900 kHz) up thru the 41m Band(7600 kHz). This choke maintains greater than 1,000 Ohms Rs(Resistive Choking) up thru the 16m Band(17,900 kHz). Low insertion loss(0.2%) with an SWR of 1.1:1 or less from 500 kHz to 32,000 kHz. For noise problems above the 16m Band please see our Broad Band choke.
Mod # RECV-CHK-LB $44.99 Shipping Included via USPS anywhere in USA
Both Common Mode Noise Chokes have the following features:
• SO239(accepts PL259) Cable Connector Gold+Silver Plated with Teflon® insulator.
• Internal Transmission line is Mil-Spec Teflon® with Silver Plated Conductors.
• 50 Ohm Impedance In/Out.
• Non-Directional.
• DC passing.
• ABS Plastic Enclosure.
• Wall Mountable.
Separate 10-32 Ground Studs tied to each SO239 Connector independently.
Compact (3“ W x 1.25“ H x 2.5“ D) Mtg Holes 2.5“ OC 0.186 dia
Receive only--not for transmitting and indoor use only unless mounted in a Waterproof enclosure.
Tech Tip: The chokes can be located anywhere along the signal chain, but may be more effective against a certain noise source at a certain frequency at a particular spot. Three good places to start in order of preference are:
1. At a mid-point, i.e. where the coaxial cable enters the house and access to a RF Ground is available.
2. Near the Receiver.
3. Near the Antenna.
In certain difficult circumstances more than one choke may be needed and at different locations.
Isolation Transformer
The 1:1 Broad Band Isolation Transformer MW>10m
This transformer provides Galvanic isolation with a separate winding for the primary and secondary sides of the transformer. It breaks or eliminates ground loops and the noise associated with them such as hum from the AC mains. It will also convert an un-balanced signal to a balanced signal. Low insertion loss(0.2%) with an SWR of 1.1:1 or less from 500 kHz to 32,000 kHz.
Mod # ISO-IND-WB $38.99 Shipping Included via USPS anywhere in USA
SO239(accepts PL259) Cable Connector Gold+Silver Plated with Teflon® insulator.
• Internal Transmission line with Teflon® insulated conductors for low loss.
• 50 Ohm Impedance In/Out.
• ABS Plastic Enclosure.
• Wall Mountable.
Separate 10-32 Ground Studs tied to each SO239 Connector independently.
Compact (3“ W x 1.25“ H x 2.5" D) Mtg Holes 2.5“ OC 0.186 dia
Receive only--not for transmitting and indoor use only unless mounted in a Waterproof enclosure.