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8 votes
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How to measuring ferrite core efficiency vs frequency

To help identify a mystery ferrite core mix, the most common method is to take some measurements to determine the initial permeability (µi). Then compare your results to a table of µi for common core ...
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  • 138
7 votes
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How does a loopstick antenna actually receive signal?

The basic operation can be understood by Faraday's law of induction. Any loop of wire will exhibit an electromotive force proportional to the rate of change of magnetic flux encircled by it. Since any ...
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7 votes
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Can ferrite beads lower coax cable velocity factor?

No, adding ferrite beads to choke currents on the outside of the shield of a coaxial cable does not affect its impedance or velocity factor. Impedance and velocity factor are determined by the inside ...
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  • 7,685
7 votes

Why are loopstick ferrite antennas commonly wound with Litz wire?

The advantage of Litz wire —lower loss than solid wire— is realized below about 1 MHz. It is of little use above 160 meters. From https://en.m.wikipedia.org/wiki/Litz_wire Litz wire is a particular ...
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  • 7,485
6 votes

Can ferrite beads lower coax cable velocity factor?

For well-designed coax, the EM fields are confined to the space between the inside of the braid and the center conductor, i.e. the dielectric insulation region which affects the velocity factor. ...
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6 votes

Ferrite rod or core permeability determination

Following up on @dfannin's excellent answer: The most intuitive way of dealing with this would be: wrap your ferrite rod in halfway stable paper or so, something that certainly doesn't have high $\...
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6 votes
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What is the maximum number of turns in a ferrite core used as a common mode choke?

The K9YC paper you mention gives data up to 1 GHz on page 49: These data show for these core types the maximum number of turns is just one or two. Furthermore, it's quite difficult to achieve a ...
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6 votes
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How to effectively test and interpret the "working range" of a ferrite core with a signal analyzer?

It appears that all three 'scope probes are set to their "X1" position. As such, each probe includes the oscilloscope's internal 1M input resistance in parallel with about 20pF input ...
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  • 516
6 votes

Core mix preferences for a balun (or unun) vs a choke

With thanks to John VE3WNA from the comments of this question for the reminder, the answer (rationale/guidelines) is here: https://palomar-engineers.com/ferrite-products/ferrite-cores/ferrite-mix-...
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  • 615
5 votes
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Importance of Ferrite Size in Coax Choke Balun

When making a coax choke balun, does the size of the ferrite matter, and if so, why? Simplest answer: If the choke impedance is low enough to allow some common mode power through, then there is a ...
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  • 1,022
5 votes

What is the maximum number of turns in a ferrite core used as a common mode choke?

The primary issues with coax wound common mode chokes are; The inductive reactance of the choke can cancel out the capacitive reactance associated with the feedline shield thereby worsening the CM ...
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5 votes
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Need a ferrite suppression material for choking 15 kHz to 60 kHz

I don't think it will work to add suppression to the fence. The fence charger is designed to support heavily reactive loads by generating pulses every second or two. The pulses are formed by dumping ...
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5 votes
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Ferrite rod or core permeability determination

you're on the right track to measure/calculate effective permeability. However, you need to use an inductance meter that can measure up to 1 nH accurately or so. If you're trying to use one of ...
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  • 66
5 votes
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Are some ferrites porous enough they should be protected outside?

I've had a couple turn up cracked when left outside in an enclosure that wasn't waterproof, but I can't say if that was freezing that did it, or just thermal cycles on a compromised toroid causing ...
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  • 1,814
4 votes
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Can I make ferrite paint? Will it shield my antenna from my roof?

No. At best it will do nothing; if it did something, it would probably turn your roof from a relatively good reflector (which may mess with your SWR, and may distort your pattern, but the energy that ...
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  • 8,750
4 votes
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Ferrite Rod Price Differences

"Ferrite" is not a fungible material. There are many kinds of ferrite materials, each with very different properties. To make a comparison, you need the material datasheets, which answer questions ...
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4 votes
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How does this 3 dB splitter/combiner work?

SPICE modeling shows that replacing T2 and R with a 22.2-$\Omega$ resistor, the impedance looking into T1 is indeed 50-$\Omega$, as expected: Similarly, replacing the 50-$\Omega$ generator and T1 ...
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  • 7,685
4 votes
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Can a slinky serve as a ferrite core and if so, is there a prefered configuration?

A ferrite core used for radio is specially constructed to conduct magnetic fields while not conducting electrical current, especially eddy currents. A slinky is (typically) an uninsulated conductive ...
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  • 4,168
4 votes

Is this the Correct Ferrite Core to Reduce RFI as a Common Mode Choke?

That does look like a fine core to use, and the photo of your construction looks good. Your coax isn't causing any problems with noise. Try putting the choke at the feedpoint, not at the radio, in ...
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4 votes
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Is this true about ferrite loop antennas?

Now if I imagine the coil without the ferrite but I multiply the area by 1000, that will be a huge area, how can it be 1000 times more power? Because, as the article says, the magnetic permeability ...
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3 votes

How to effectively test and interpret the "working range" of a ferrite core with a signal analyzer?

So the problem here is that your setup is not sufficient to tell you what you want to know about the ferrite core. In my set up I have a ferrite core where I made a number of turns on. I connected ...
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3 votes

Importance of Ferrite Size in Coax Choke Balun

I believe the choice of the core size is twofold. As from K8NVH good answer a minimum impedance is needed for the balun to do its job. A common mode impedance much higher than differtial ones ...
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  • 171
3 votes

Is this the Correct Ferrite Core to Reduce RFI as a Common Mode Choke?

The answers here are excellent and I have little to add other than to emphasise / RFI problems are hard / Consider the case of the RFI problem discussed in Electronics Stack Exchange ( https://...
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  • 1,022
3 votes

Can ferrite rod antenna be made out of the choke?

A ferrite rod antenna is a small loop antenna, just with more than one turn (usually lots more), and wrapped around something with a relative permeability of greater than one (usually much greater). ...
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2 votes
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Do a toroid's specs matter much in an antenna matching transformer?

Transformers are inductors. They just happen to have mutual inductance with another inductor. Like inductors, they also have self-capacitance, and so a resonant frequency. They also have loss, and ...
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2 votes
Accepted

How to make a ferrite bar antenna for RTL-SDR?

Looking at an Amazon listing, it appears that the Degen 31MS active antenna has three ways to connect to a radio. The first is via a direct ANT jack, the second is via clips to existing wire (likely ...
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2 votes

Ferrite rod or core permeability determination

Because ferrites aren’t marked, it is difficult to know what frequencies they work on. However, now we can use the popular NanoVNA along with free software (and Excel) to graph the unknown ferrite’s ...
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  • 7,485
2 votes

Is this true about ferrite loop antennas?

Nearby antenna elements do affect each other. Consider a Yagi-Uda. Pointed in the "wrong" direction, the director and reflector elements will reduce the EM power that the driven element ...
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  • 12.4k
1 vote

Can a slinky serve as a ferrite core and if so, is there a prefered configuration?

A slinky as in the one you watch go down the stairs? I'd assume not. Any winding on a slinky would probably act as inductor/transformer with an air-core. Ferrites have special magnetic properties. ...
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