Skip to main content
10 votes

Can a 1:1 transformer be used as a protection from static electricity?

A transformer can help and could also make things worse. I have some bad experience with this. The way that a radio is damaged by static is simple: Something charges up to a high voltage, and then ...
tomnexus's user avatar
  • 11.3k
9 votes
Accepted

How can a quarter-wave transmission line transformer be implemented with lumped elements?

It can be done! Remember that a transmission line consists of some self-inductance per unit length, and some capacitance per unit length, and the ratio of these determines the line's characteristic ...
Phil Frost - W8II's user avatar
8 votes
Accepted

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 ...
Josh's user avatar
  • 138
7 votes
Accepted

Why does a sine wave show two peaks in the frequency domain on GNUradio?

Because mathematically, a function like $\sin(\omega t)$ has an angular frequency of $\omega$ and $-\omega$. Consider: $$ e^{i\omega t} + e^{-i\omega t} $$ By Euler's formula this can be expanded to: $...
Phil Frost - W8II's user avatar
7 votes

Why do 9:1 ununs use type 2 material for the core?

I was taught the impedance of the windings at a minimum is 10X the circuit impedance or at least 500 ohms, and greater than 500 is better. That sounds like a good guideline for an isolation ...
hobbs - KC2G's user avatar
  • 12.4k
5 votes
Accepted

Can a 1:1 transformer be used as a protection from static electricity?

Assuming that power losses in the transformer are acceptable, and that it's placed after 1:1 current balun (which eliminates common-mode current), is there any reason why it might be a poor solution? ...
Phil Frost - W8II's user avatar
5 votes
Accepted

Toroid Coupling Issue in Common-base Amplifier

The problem is most likely the type 43 core material. It is quite lossy at 21 MHz and is a poor choice for the auto-transformer. Unlike a transmission line transformer, the auto-transformer relies on ...
Glenn W9IQ's user avatar
  • 18.6k
4 votes

What cause `multiply` has difference result between `float` and `complex` signal?

That's just the math behind it – everything is alright with these results! You need to write down the formula of the real-valued $\sin(t)$ in terms of $e^{j2\pi t}$ and $e^{-j2\pi t}$, and you'll see ...
Marcus Müller's user avatar
4 votes

How to make a 1:2 UnUn

I found this at this page by PA0ROB, which you should absolutely check out. He's focused on higher ratio ununs, but shows the general design principles that you can use to make a 2:1. One of the key ...
webmarc's user avatar
  • 4,234
4 votes

Why ferrite-core transformers are wideband while air-core are not?

"Why ferrite-core transformers are wideband while air-core are not?" Air-core "transformer" is composed of 2 inductors "TUNED" with a magnetic coupling slightly less than ...
Antonio51's user avatar
  • 161
4 votes
Accepted

Can the reactance on a transformer load, be "corrected" on the transformer primary, to improve transformer efficiency?

Is the reactance on the output of a transformer, that is connected to a reactive load, seen on the input of the transformer? Yes (transformed by the transformer's impedance ratio, and modified by any ...
hobbs - KC2G's user avatar
  • 12.4k
3 votes
Accepted

Is there value in grounding the virtual null in an auto transformer?

An end-fed acts more like a highly off-center fed dipole. Thus, the point you label "GND" is really the attachment point to the the remaining portion of the dipole, either something like a 5%...
hotpaw2's user avatar
  • 13.4k
3 votes

Can a 1:1 transformer be used as a protection from static electricity?

The answer is no. The best way to protect against static build-up would be to have both antenna elements DC-connected to ground. This would be automatically ensured with a 1:1 voltage balun. With a ...
vu2nan's user avatar
  • 757
3 votes
Accepted

Resonant RF transformer using a piece of wire (no capacitors)

Here's a schematic of a spark-gap Tesla coil from the Wikipedia article: L1 and L2 are coupled together by their magnetic fields, and so act as a transformer. Such a Tesla coil depends upon ...
rclocher3's user avatar
  • 9,242
3 votes
Accepted

What cause `multiply` has difference result between `float` and `complex` signal?

This is a consequence of what was discussed in your previous question, that any real-valued function like $\sin(\omega t)$ consists of both positive and negative frequencies. Multiplying by a complex ...
Phil Frost - W8II's user avatar
3 votes

Can I wind my 9:1 unun with two wires instead of three?

For illustration, here's a 9:1 unun construction using 3 wires from M0UKD: Since the A and B windings are connected together in series, there's no compelling reason you couldn't replace them with one ...
Phil Frost - W8II's user avatar
3 votes

1:4 Guanella unun current balun

It may help to consider that this: is equivalent to this: The lines above the transmission line indicate it is wound on a ferrite. Because only the common mode affects the electromagnetic fields ...
Phil Frost - W8II's user avatar
3 votes

Broken IF Transformer (tiny and 455 KHz)

The transformer is most probably a part of a critical tuned circuit. If the ferrite is broken then the radio keeps working but the filtering is worse. There a a number of ways to find a replacement ...
Decapod's user avatar
  • 131
3 votes
Accepted

How to build a balun transformer for 2m RX with low insertion loss

VHF transmission line baluns are very difficult to construct due to interwinding capacitance. As a result, the balun will have an undesirable self resonant point and will not typically reach the ...
Glenn W9IQ's user avatar
  • 18.6k
2 votes

Carrier telephone system adaptation

I am still of the opinion that it is “unclear what you are asking”. But I will try to answer the two questions that you actually wrote: Q. How does the carrier telophone system works on the conext of ...
Scott Earle's user avatar
  • 4,599
2 votes

1:4 Guanella unun current balun

The voltage doubles because the two coaxial cables are connected in parallel on the input side, but in series on the right hand side. In the diagram, there shouldn't be a little i in the middle of the ...
tomnexus's user avatar
  • 11.3k
2 votes

How to make a 1:2 UnUn

@webmarc mentioned the ratio 1:1.4, which is an approximation of 1 to the square root of 2, which is approximately equal to 1.4142135..., but how do you approximate this infinite number with a finite ...
EdvinW's user avatar
  • 378
2 votes

Question about Isolating Transformer NZART exam question

I agree it's poorly worded, but with MCQs you have to choose the least incorrect answer. 2 is still the obvious choice, the rest are totally wrong or deliberately opposite to the truth. What they ...
tomnexus's user avatar
  • 11.3k
1 vote
Accepted

Question about Isolating Transformer NZART exam question

Yeah, it's a poorly worded question/answer. There's no DC voltage developed between either output lead vs ground. You're absolutely correct that there's AC potential developed, because... well... duh. ...
webmarc's user avatar
  • 4,234
1 vote
Accepted

Current Transformers in Series versus a Single Voltage Transformer

From memory, I don't have Sevick's book and it's been a long time since I saw it. Maybe someone with the book can correct me. All high ratio transformers in the book use mutiple cores. If you want a ...
tomnexus's user avatar
  • 11.3k
1 vote

Purpose and sizing of capacitors placed across RF push-pull power amplifier transformer windings

I have tried to simulate a part of this PA, where the serial capacitor with resistance is present (not the same value). I found also something interesting despite the difficulty of simulating ... (AC ...
Antonio51's user avatar
  • 161
1 vote

Purpose and sizing of capacitors placed across RF push-pull power amplifier transformer windings

If these are broadband (toroidal, coupling ~ 1.0) transformers, then the capacitors in series with the resistor can be used to dampen the resonance that takes place at the edge of the band (higher ...
Antonio51's user avatar
  • 161
1 vote

What cause `multiply` has difference result between `float` and `complex` signal?

A real-valued multiply is the same as an AM modulation, where the result includes both upper and lower sidebands. (Similar to the spectrum of an AM radio station on an SDR waterfall.) A complex-...
hotpaw2's user avatar
  • 13.4k
1 vote

What cause `multiply` has difference result between `float` and `complex` signal?

If I understand your question correctly, the issue is that you have one graph producing a complex output of an FFT and the other producing a floating point output from an FFT. When you produce an FFT ...
David Hoelzer's user avatar
  • 1,053

Only top scored, non community-wiki answers of a minimum length are eligible