8 votes
Accepted

How different is Q-factor of SMD inductor from regular one?

SMD chip inductors, compared to larger ones, will generally have: lower Q higher DC resistance higher SRF lower DC saturation current, if they're ferrite cored But read the datasheet and see if they'...
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  • 8,171
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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  • 7,515
6 votes
Accepted

What types of materials increase the inductance of a coil when inserted inside it?

Any material with a relative permeability greater than 1 will increase inductance when inserted into a coil. Note that permeability is a complex number and frequency dependent. The imaginary part of ...
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5 votes

Power rating of a selfmade air coil

The coil needs to dissipate approximately all of the transmitted power so it sounds a bit lightweight. It's not so much the copper wire thickness itself, but the rest of the mechanical details. Final ...
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  • 8,171
4 votes

In the context of the mixer in my radio, what does balanced and unbalanced mean?

A balanced mixer is one that suppresses the local oscillator (LO) input in the output. A double-balanced mixer (like the one you show here) suppresses both the RF input and the LO in the output. This ...
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4 votes
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What dimensions to choose when winding your own inductor

It boils down to practical issues — you want to make it as small as possible, but no smaller. The power-handling requirements will dictate the wire diameter (to handle the current) and the end-...
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4 votes
Accepted

What happens to the "Yo-Yo Tenna" when you coil up its ends for use on higher frequencies?

I'm not certain of this answer, but this is my approximate understanding: Yes, the coiled-up ends form inductors at the ends of the antenna. But the ends of the antenna are the part of it where (...
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  • 23.1k
4 votes

What types of materials increase the inductance of a coil when inserted inside it?

TL;DR: It's NOT mild steel, brass, or aluminum. I connected two different inductors to an antenna analyzer, and all of the above materials decreased the inductance as they were inserted. The larger ...
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  • 7,515
3 votes

Power rating of a selfmade air coil

Sorry for not putting a simple positive answer here, but: "Allowed current" ratings for domestic wire aren't applicable at all to something like an antenna matching coil. They're based on ...
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  • 9,021
3 votes

Under what circumstance does non-toroid former lend itself to HF?

HF or not, toroidal transformers are pretty great. They'd be the only kind anyone would use were it not for: Fabrication cost. They are hard to wind with automated machines, since you have to somehow ...
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2 votes

Toroidal inductor and transformer basics

Inductors act analogously to a flywheel for electrical current. That is, they want to keep the current steady. To increase or decrease the current requires work, like speeding or slowing a flywheel ...
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2 votes
Accepted

In the context of the mixer in my radio, what does balanced and unbalanced mean?

Looking at T1, on the unbalanced side of the transformer, one leg of the input is tied to the chassis ground (the zero volt reference); the other leg is driven by a voltage source. Because the ...
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  • 8,922
2 votes

How to choose right inductors for a matching circuit

As others have pointed out, the discrete components, suchs as capacitors and inductors, start to be quite challenging in higher frequencies. In general, transmission lines tend to have lower losses ...
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  • 960
2 votes
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pull-up inductors for a differential PCB trace antenna

The value is specified as "large". The idea is to use the inductors to provide a DC bias without affecting the RF circuit. This works because an inductor has 0 impedance at DC, but increases with ...
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2 votes

Rotary Inductor Replacement

One thing you might try is to add a fixed inductor in series with your rotary inductors to reach the overall required inductance. To maintain balance, I would wind two identical inductors, each on a ...
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2 votes

Why are hand-wound coils so common if commercial inductors are available?

There is also the matter of how much current the device needs to carry. A hand-wound coil made from a few turns of relatively heavy copper (compared to the off-the-shelf devices shown in the question) ...
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  • 4,329
2 votes
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Using PVC coated solid-core wire for a small number of turns on toroid

You should be fine with the hookup wire for all the reasons you note. Another item to take into consideration is the additional distance of the wire from the toroid, but for this application it ...
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  • 2,885
2 votes
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change LC parameter digitally

Perhaps you are thinking of a switched capacitor filter? Unfortunately, most switched capacitor IC components are (were) designed for audio frequencies, not VHF. Another possibility is to use an LC ...
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  • 12.5k
1 vote

change LC parameter digitally

A "simulated inductor" might work in your application: You could adjust the simulated inductance by using an analog multiplexer IC and resistive ladder array IC to change the values of RL ...
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  • 7,683
1 vote

Rotary Inductor Replacement

Here is a schematic for a simple, wide range balanced to balanced tuner: simulate this circuit – Schematic created using CircuitLab It consists of a 32 $\mu$H variable inductor (which you ...
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  • 18.1k
1 vote

Why are hand-wound coils so common if commercial inductors are available?

Speaking only for myself... I have found air-wound coils to be relatively easy to make and tolerant of misuse. In the several instances I would have preferred to buy an inductor, I found it difficult ...
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  • 1,022
1 vote

Inductors for Impedance Matching

In general, a choke would not be a good choice for this type of circuit as explained below. Given the relatively high frequency of your application, I would expect that you could find more suitable ...
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  • 18.1k
1 vote
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How to make an inductor?

First thing first: Whenever you make an inductor, wire must be insulated for the working voltage of the circuit or higher. Otherwise, you get shorted turns and your inductor turns into jut normal ...
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  • 2,715
1 vote

How to choose right inductors for a matching circuit

Would an inductor with SRF > 7 GHz and Q > 10 be okay at above frequency? Could it be made to work? I suppose. But any discrete inductor at 6 GHz is going to have significant non-ideal behaviors that ...
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