Common Mode Choke Question

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Joined: Fri Sep 28, 2018 12:00 pm

Common Mode Choke Question

Post by Robert11 » Thu May 23, 2019 11:06 am


Hoping to improve somewhat the S/N on my <30 MHz listening.
Have a RSP-2

a. Regarding the common mode chokes, like the one WinRadio offers, do you think these would help any ?

I have a long wire ant outside, feeding a "long" run of coax into the house, then
one of those suggested 1:9 Noo Elec Baluns into the RSP-2 HiZ input.
Arrangement is essentially that shown in the SDRPlay dwg of using these 1:9 Baluns.

Does the 1:9 Noo Elec Balun offer any common mode noise rejection, or "might" a
unit like WinRadio's possibly, in addition, help ?

b. And, the green HiZ connector has a Gnd connection.
Do you folks ground this terminal to earth ground, or just leave alone ?


WinRadio Common mode Choke Descr.:

"This device provides a means of reducing or eliminating common-mode noise from an antenna feedline, resulting in a considerable increase of the received signal quality. Common-mode noise is generated by computers, lamp dimmers and other electric or electronic appliances. Such noise can be a problem especially in the lower portions of HF spectrum, where weak signals can be sometimes completely masked by assorted buzzes and other unwanted noises.
The Common-Mode Choke can be also very useful to provide an alternative earthing point for an active antenna, if the antenna itself cannot be grounded due to its location, or its ground connection is inadequate."

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Posts: 318
Joined: Mon Jul 24, 2017 8:24 pm

Re: Common Mode Choke Question

Post by Mike2459 » Thu May 23, 2019 4:22 pm


a) I have about 5 CM chokes that cover 300 khz to 14 mhz, each one is a different combination of ferrite core and turns of wire. IMO, one choke is not likely to offer much improvement over a broad frequency range. Winradio doesn't provide any performance data for their product.

Robert, Some research material for you:
Chokes and Isolation Transformers For Receiving Antennas

b) re: The ground terminal on HiZ. If using the ground terminal gives you a better signal to noise ratio then use it. In my case it resulted in higher noise levels.


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Fred M
Posts: 5
Joined: Wed May 02, 2018 8:53 pm

Re: Common Mode Choke Question

Post by Fred M » Sat May 25, 2019 12:54 pm

Mike is correct.
I also have several CM chokes along my system.
One CM choke is not going to make a big difference.

It really takes a plan and a few chokes.
I have chokes on every wire coming out of my computer Every Wire.
I also have a ground running between all the boards in the pc.
I have a 2.4" 31 mix on my internet wires.
I have several 4" 31 mix chokes made from RG-400 those are on my tramsmit lines for HF.

Then you have to take care of each noise that pops up.
For example my wife's treadmill is putting out signals all over 80m band.
We just bought a new washer so now I have qrm on 17m band.
So I'm putting out fires as they pop up.

And a good antenna.
if you have the room the Beverage/long wire antenna is the bees knees.
Anyway the the first few things I mention above helped a lot.

Good luck

Last edited by Fred M on Thu Jan 01, 1970 12:00 am, edited 0 times in total.
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