Why add 4 resistors on a inductor on CATV outdoor AMP

[fnx7]

In CATV outdoor amplifier, there is a large inductor which get 60V 60Hz AC power form coaxial line. The question is why add 4 resistors on the inductor? Please see the figure.:?:

 

[E-design]

Maybe To lower the Q of the coils when used as a broadband choke.

 

[kspalla]

I feel it may be related to the circuit in which it is going to fit. May I ask to share the circuit?
some times, the resistor is used for damped fly back purpose to protect the inductor.

 

[fnx7]

Please see the outdoor figure

 

[kspalla]

Thanks for sharing the picture, there are asociated components like capacitors in connection with this coil( i guess) May be part of the filter as suggested by E-design.
May I ask you to share the schematic circuit if possible?

Added after 1 minutes:

It is also associated with the duplexer (biggest component ) I guess.

 

[g579]

Hi fnx7,

Could you upload a better quality image of the full amplifier, that we can zoom in without image quality degradation?

 

[fnx7]

The image is from internet. So I don't get high quality image.

The function of the inductor is get 60V 60Hz AC current from coaxial cable, the signal frequency is 5~860MHz. In the schematic, it is a broadband(5~860MHz)chock

Thanks.

 

[biff44]

Those are big turns of copper wire. Therefore they have a lot of parasitic capacitance. At some frequency the inductance and capacitance will resonate and cause trouble. By putting the resistors in parallel, those resonant peaks will get broadened out, and not cause as much trouble.

 

[dee25pak]

Dear biff44,
I am interested in knowing the parasitic capacitance of the coil. kindly help me, how to exactly know the parasitic capacitance of the coil before hand. Are there some empirical formula for this or experiment is the only option.

 

[FvM]

biff44 has given the most likely explanation. As an additional remark, it's also very likely a later correction of a design flaw, cause this kind of filigree hand-soldering would be strictly avoided in a design, at least in the US or europe.

Rod core inductors are generally interesting for higher current supply filtering and EMI suppression purposes. They are showing however self-resonance in the 100 MHz range. Typically a series circuit with an inductor or ferrite bead effective at higher frequencies would be used to overcome this problem.

Although the partial capacitances can be predicted with EM simulators rather accurately, a resonance frequency respectively impedance measurement would be a better method to characterize the part, I think.