Please read the description first.
A video about making/testing/developing coils between (say) 30/40 KC and 15 MC, for all kinds of (radio) applications.
Principle: connect your coil (a coil) to a test oscillator and read out the frequency via a frequency counter and an oscilloscope, or a scope with a built-in frequency counter. Now you know the frequency where the coil works/can work & also the frequency/frequencies where a coil performs best.
Please note: in this test-oscillator (link to schematic below) the (unknown) coil is connected to a FET, that has, by its properties, an enormous high input resistance/impedance, say in the order of 1 Mega Ohm or many Mega Ohms.
Could be that in a practical situation, the coil that you have made and tested, when taken out of this test-circuit and connected to another electronic (radio) circuit, does not work the same. You will/can see the so called “damping”.
Thus when connected to a transistor or whatever other electronic circuit with a much lower input resistance/impedance, compared to that FET input impedance in this tester/test oscillator, it can have a substantial effect on the performance of the tested coil, both in terms of frequency (it can drop down) and Q. The Q can get lowered.
Next video 24 sep 2023 (about that SW radio, an update) is here [ Ссылка ]
Anyway: you get a good insight (!), by using this circuit and this test procedure (!), about radio coils, how to make them, their quality factor (Q) etc, by simply “making” and “testing”.
Relevant earlier video’s and schematics:
1. The test oscillator where it is all about (published 3 oct. 2015)
[ Ссылка ]
When you bridge the coil under test with a 10-500 pF tuning capacitor, you could get more insight about the frequency and especially the Q (quality factor), thus the Q in relation to the frequencies where the coil (in theory & practical) can work. Every coil has a “bandwidth”.
2. The simple & cheap SW radio, for SW frequencies/radio reception around 7 MC is demonstrated here (22 dec. 2022)
[ Ссылка ]
The schematic of this (around 7 MC) SW radio is on 6.33 and further in this video of 1 March 2023
[ Ссылка ]
3. A general video about (radio) coils, how they look like, etc. is here (23 July 2015) [ Ссылка ]
4. Another video (23 March 2021, one of the many video’s about coils, inductance, radio coils, etc. on my YT Channel) is here (“how they look like”)
[ Ссылка ]
5. Another measuring circuit for small radio coils (practical inductance meter 10 uH-10 mH is here), 25 March 2023
[ Ссылка ]
When you connect a variable capacitor (10-500 pF), parallel to the coil to be tested, you can derive more information about “a” coil for shortwave.
Tuning that capacitor you can see where the coil performs best, giving out a high/higher peak on the oscilloscope. Higher peak means that the energy “swirled up” in the coil on frequency “X” is higher, thus a higher quality factor (“Q”).
Much more info about radio coils & radio can be found via my channel trailer.
Search with keywords (regarding this subject) like: coils, coil, shortwave coil, shortwave, short wave, resonance, inductance, test, tester, oscillator, generator, etc.
My You Tube channel trailer is here: [ Ссылка ]
When you search, search always “NEWEST FIRST” to get the right overview.
You can search via the “looking glass” on my Channel trailer via keywords like ”audio”, “radio”, “amplifier”, “filter”, “Shortwave”, “transistor”, “FET”, “oscillator”, “generator”, “switch”, “schmitt trigger” etc; so the electronic subject you are interested in.
My books about electronics & analog radio technology are available via the website of "LULU”, search for author “Ko Tilman” there.
[ Ссылка ]
I keep all my YT videos constant actual, so the original video’s with the most recent information are always on YouTube. Search there, and avoid my circuits that are republished, re-arranged, re-edited on other websites, giving not probable re-wiring, not updated video’s & schematics, etc.
Some persons try to find gold via my circuits. I take distance from all these fake claims. I cannot help that these things happen. Upload 23 September 2023.
