Questions tagged [transformer]
Impedance matching transformers as related to amateur radio.
29 questions
0 votes
1 answer
310 views
What kind of "balun" or "choke" or device is this? (Picture)
The image suggests that this is called a "1:1 current balun" but I'm not sure that (a) it actually is a true balun and (b) that it's a current balun at all. Also notable is that it doesn't ...
- 916
0 votes
2 answers
154 views
End Fed Ant w/o Tuner: Using 1:1 To Reflect
Imagine I have a 34 foot length of 12 gauge stranded wire that is my end fed 20 Mhz antenna, set up as a sloper. I've attached a 49:1 at the feed point and a 1:1 Guanella after that, then 20 feet of ...
- 301
6 votes
2 answers
379 views
Will 2 ferrite beads taped side by side perform the same as a single-piece binocular core?
I intend to make a beverage antenna and have quite a few spare ferrite beads of various mixes. If you look up binocular core ferrite on amazon you will see they are a single chunk piece of ferrite ...
- 61
4 votes
2 answers
452 views
Can the reactance on a transformer load, be "corrected" on the transformer primary, to improve transformer efficiency?
The following question is regarding the ability of a transformer, UnUn or BalUn, to be efficient, if the transformer (UnUn in my case), is feeding a load with reactance, and what can be done about the ...
- 1,150
6 votes
2 answers
1k views
Why do 9:1 ununs use type 2 material for the core?
I do not understand how a 9:1 unun wound on a T200-2 works. I understand the transformer voltage and current ratios. I have wound several toroid chokes and 49:1 ununs and know how they work. What is ...
user23405
3 votes
3 answers
146 views
Question about Isolating Transformer NZART exam question
I found this question about isolating transformers in the NZART question bank, but I can't figure out the meaning of the answer. Either the answer is misleading or I'm fundamentally misunderstanding ...
- 285
4 votes
2 answers
2k views
How to make a 1:2 UnUn
Does anyone have a drawing or instructions on how to make a 1:2 unun like the one in the picture below ? I searched this question on this site and on the internet with no luck.
- 3,817
2 votes
1 answer
388 views
Resonant RF transformer using a piece of wire (no capacitors)
I previously posted this in electronics StackExchange here, but I believe Ham is more proper place for it as it closely relates to antennas. I'm curious if it is possible to build a spark-gap Tesla ...
- 47
1 vote
1 answer
164 views
Current Transformers in Series versus a Single Voltage Transformer
I've read that the commonly used 49:1 (7t:2t) auto transformer for Multi-band End-fed Half-wave (EFHW) antennas has criticisms as not being very efficient. I haven't found any other designs that ...
- 301
2 votes
1 answer
155 views
Is there value in grounding the virtual null in an auto transformer?
I've been learning how to make 49:1 auto transformers to run end fed half wave antennas. As I understand it, the twisted lead forms a zero voltage point which acts like a ground. Assume I'm using ...
- 301
7 votes
1 answer
1k views
Why ferrite-core transformers are wideband while air-core are not?
While experimenting with end-fed antennas I've made two 1:49 transformers. The first one has an air core, as shown in the article by John, M0UKD. This transformer doesn't even work as a transformer ...
1 vote
1 answer
210 views
Why does transformer in mcHF kit use coax?
I'm building my first kit, it's the mcHF SDR radio. Two of the transformers, which relate to the Power/SWR circuit (no further explanation given) use coax on one of the coils (and only one turn at ...
- 411
6 votes
2 answers
935 views
Purpose and sizing of capacitors placed across RF push-pull power amplifier transformer windings
I keep finding RF push-pull power amplifier designs specified with a small(-ish) capacitor across the primary (or secondary) windings of the coupling transformers. Here's an example: This is one ...
- 989
1 vote
4 answers
547 views
What cause `multiply` has difference result between `float` and `complex` signal?
Construct 2 similar flow graph in Gnuradio,just different with data type. complex type data has a correct result.But ...
- 670
6 votes
2 answers
1k views
Why does a sine wave show two peaks in the frequency domain on GNUradio?
I constructed the flow graph in GNUradio 3.7 as below: I know a sine wave has only one frequency, so what causes the frequency sink to show two peaks?
- 670