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What is the best resistor material for a damping resistor?

A

Anonymous

Guest
Hi, have some technical question...
Which resistor material is the best to use as a coil damping resistor? Metal film, carbon or wire wound resistors?
Where is the best place to connect the damping resistor? At the coil (search head), inside the connector or on the PCB (electronic)? And...How does the internal resistor noise factor effects the analog signals in the receiver circuit?
Chris
 
Chris,
On my PI I use 1% metal film resistors. You want stability and the least amount of noise as possible generated by resistors. PI's inheriently are noisy, so stay away from wire wound because weird things can be generated from them. Carbons can work in a pinch, but 1% resistors are what to use for a PI project.
Now for the mounting of the damping resistors can be at the coil itself(the best placement) or coil plug or on the PCB. Anyway can work well. I use the coil myself, so I can interchange different coils easily. Friend of mine mounts his resistors in the plug and gets great results. Your choice.
Rick S
 
Would you expalin how you mount your resistor at the coil please? Thanks!
 
Don,
It is really simple to install damping resistor(s) in the coil housing. Where the coil wires and the cable connect in the housing is where I have soldered my resistors. I make sure that once they are soldered the wires and resistors cannot be moved or shorted between each other. I use either hot melt glue or two part resin after I make sure the value picked works correctly.
Rick S
 
Hi Rick and Chris,
I use metal film for low power transmitters, and metal oxide for higher powers. Damping resistors have to dissipate much of the coil energy and can get quite hot. Also have to stand several hundred volts spike in some cases. For higher powers, mounting in the coil would not allow the heat to dissipate sufficiently.
Eric.
 
Eric,
Thanks for filling in what I missed with damping resistors.
Rick S
 
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