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COMMON MODE CHOKES - DOES ONE-SIZE-FIT-ALL??

 

I measured four of my common mode chokes (CMC) for CMRR (Common Mode Rejection Ratio) using the HP 3585 with its tracking generator. Then I took a picture of them lined up so anyone who reads this can ascertain the effectiveness of the various ferrite materials. While they are not all identical or the same size, the peak effectiveness and falloff of each material is quite evident. The tag below each CMC shows the frequency of measurement in MHz on the left and the CMRR in dB on the right column. ? From left to right are 75, 31, 43, and finally 61 material.
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Since these sites do not allow for embedded images, please see the attachment.?

I believe from my measured data it is quite evident that there is "no-size-fits-all" when it comes to CMCs, baluns, and transformers!!! The suppliers have you believe otherwise, of course. This is rigorously measured data which refutes supplier claims. And......once again.......buyer beware! And........measure everything!

Dave - W?LEV



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001.jpg

 

The picture came through at 488x290 resolution and the numbers are very difficult to read, even if blown up on my laptop screen. Maybe send the numbers in a table instead??
 

Very useful photo and data, Dave. Confirms some of the 'folk wisdom' in HR about these
cores. I have tended to choose #31 if I need good performance on 80 and 160m. And
#43 for most everything else. I did have a bunch of the 2.4 in. #61 cores from surplus on
hand, and so I did use them in the past as low as 20M and even 40M. I see now they are
really much better for use on and above roughly 15m.

73, David K3KY
Derwood, MD



On Wednesday, February 12, 2025 at 07:46:20 PM EST, Dave W6OQ via groups.io <david.hostetler@...> wrote:


The picture came through at 488x290 resolution and the numbers are very difficult to read, even if blown up on my laptop screen. Maybe send the numbers in a table instead??
 

For those who are unable to read the numbers (my copy is fine with a single "SHARPEN" in Irfanview) I have posted the same image on QRZ under the "ANTENNAS, FEEDLINES, TOWERS, and Grounding" thread.? You might have a look there as QRZ does not play with resolution.

Dave - W?LEV

Virus-free.


On Thu, Feb 13, 2025 at 1:13?AM K3KY via <geodyne49=[email protected]> wrote:
Very useful photo and data, Dave. Confirms some of the 'folk wisdom' in HR about these
cores. I have tended to choose #31 if I need good performance on 80 and 160m. And
#43 for most everything else. I did have a bunch of the 2.4 in. #61 cores from surplus on
hand, and so I did use them in the past as low as 20M and even 40M. I see now they are
really much better for use on and above roughly 15m.

73, David K3KY
Derwood, MD



On Wednesday, February 12, 2025 at 07:46:20 PM EST, Dave W6OQ via <david.hostetler=[email protected]> wrote:


The picture came through at 488x290 resolution and the numbers are very difficult to read, even if blown up on my laptop screen. Maybe send the numbers in a table instead??



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Dave - W?LEV



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Dave - W?LEV
 

I just increased the allowed resolution to 1024 x 1024.

After we run out of room for attached pictures, the oldest will be deleted
first, which shouldn't cause any problems.


Donald KX8K


On Wed, 12 Feb 2025 16:46:19 -0800, "Dave W6OQ via groups.io"
<david.hostetler@...> wrote:

The picture came through at 488x290 resolution and the numbers are very difficult to read, even if blown up on my laptop screen. Maybe send the numbers in a table instead?

----------------------------------------------------
Some ham radio groups you may be interested in:
/g/ICOM /g/Ham-Antennas
/g/HamRadioHelp /g/Baofeng
/g/CHIRP

 

I must admit Irfanview does a better job of clearing it up by using Sharpen than PSP sharpen does. I may have found a nice program to use in the future. Thank you Dave W0LEV.
Dean - KC9REN
 

Glad you found it!? I've used IRFANVIEW for some 25+ years.? Even the medical profession here in Northern Colorado uses it.

Dave - W?LEV

On Fri, Feb 14, 2025 at 7:36?PM Dean - KC9REN via <deanberg2044=[email protected]> wrote:
I must admit Irfanview does a better job of clearing it up by using Sharpen than PSP sharpen does. I may have found a nice program to use in the future. Thank you Dave W0LEV.
Dean - KC9REN



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