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Common_Mode_Chokes Video

 

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Not sure if this will be of any help to anyone but a couple of years ago I made up some different CMC and measured their CMR aimed towards VLF-MF use. At the time I was messing around with some of my own modified (larger) youloops etc. Suggest you speed up the video as I tend to babble :-)? 73


Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
 

I use 77mix for my AM BCB filters. I have to get some 75mix for the usb cables to my Airspy for VLF.
?
?I used my giant ferrite VLF loopstick in the aftermath of Helene here in Asheville for some natural radio listening in the middle of the blackout. It was beautiful listening. I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long into a 33k to 600 ohm transformer into a MM-1 Sound Devices preamp using Sennheiser HD620S headphones. It was incredible listening...the best of my life.
? I ran the gain @60db and had to be careful to avoid feedback!
?A real bright spot in the disaster! I could also listen and tell how fast they restored the grid. It was epic. I had no power for a week and no water for 2 weeks. No potable water for over a month.
?
?But no AC grid for miles and miles working? Fantastic for natural radio!!!
 

On Tue, Jan 14, 2025 at 06:31 AM, VLF Dilletante wrote:
I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long
Wow. From where did you got that ferrite?
?
73, Jukka
 

Quick Question.? Who do you purchase your 77 and 75 mix from?

Fred
N4CLA

On Mon, Jan 13, 2025 at 11:32?PM VLF Dilletante via <brownpiggin=[email protected]> wrote:
I use 77mix for my AM BCB filters. I have to get some 75mix for the usb cables to my Airspy for VLF.
?
?I used my giant ferrite VLF loopstick in the aftermath of Helene here in Asheville for some natural radio listening in the middle of the blackout. It was beautiful listening. I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long into a 33k to 600 ohm transformer into a MM-1 Sound Devices preamp using Sennheiser HD620S headphones. It was incredible listening...the best of my life.
? I ran the gain @60db and had to be careful to avoid feedback!
?A real bright spot in the disaster! I could also listen and tell how fast they restored the grid. It was epic. I had no power for a week and no water for 2 weeks. No potable water for over a month.
?
?But no AC grid for miles and miles working? Fantastic for natural radio!!!
 

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I stocked up from Fair-Rite at Mouser about a year ago. Digikey also had them as well as several other companies.
Gedas, W8BYA EN70JT
Light travels faster than sound.....
This is why some people appear bright until you hear them speak.
On 1/15/2025 3:46 PM, Fred Moore via groups.io wrote:

Quick Question.? Who do you purchase your 77 and 75 mix from?

Fred
N4CLA

On Mon, Jan 13, 2025 at 11:32?PM VLF Dilletante via <brownpiggin=[email protected]> wrote:
I use 77mix for my AM BCB filters. I have to get some 75mix for the usb cables to my Airspy for VLF.
?
?I used my giant ferrite VLF loopstick in the aftermath of Helene here in Asheville for some natural radio listening in the middle of the blackout. It was beautiful listening. I used the 1246 turns of #20 over over 10lbs+ of ferrite 45 inches long into a 33k to 600 ohm transformer into a MM-1 Sound Devices preamp using Sennheiser HD620S headphones. It was incredible listening...the best of my life.
? I ran the gain @60db and had to be careful to avoid feedback!
?A real bright spot in the disaster! I could also listen and tell how fast they restored the grid. It was epic. I had no power for a week and no water for 2 weeks. No potable water for over a month.
?
?But no AC grid for miles and miles working? Fantastic for natural radio!!!
 

Hi

Just DONT buy on ebay/ preferred vendor from China! ( even if cheap!) Always more expensive but as above..mouser etc.

Simon g0zen
 

The ferrite used all came from digikey and is a product of fairite corporation. The coil I used has 3 rod assemblies inside.
? 1 assembly is made of 1.02 inch diameter beads 1.125 inches long. The other 2 rods are a stack of .736 diameter 1.125 inches long.
40 beads in each rod for a 45 inch long rod bundle. Mix is 75. Total weight is 10.14788 lbs.
? I use polyester printer media cut in strips to string the rods on...then one layer of a clear plastic tape over the beads. The whole stack pretty much fills the pipe and dense urethane foam is in each end cap of the PVC pipe which puts the stack under compression.
?
?2.39 Lbs of # 20 wire on the 2.375 inch outer diameter PVC.
?5.04mh in the audio range with no core.
?331mh with the core installed.
?Q is 362 @ 2.5 kc.
?
?It is a heavy antenna that works well. The winding is secured and ruggedized by using 3 inch diameter marine shrink wrap with a hot glue lining installed with a heat gun.

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