SW oscillator on 4 MHz tunable over 380 KHz via 2 potentiometers & 1 cap demo and schematic

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The video gives the complete information. I will study the effect more to get a patent if possible.

on 3.08 I say 0.1 “Micro-Henry” but it is of course 0.1 Milli Henry at 8 Ohms DC resistance. The tank circuit wire diameter = 0,4 mm enemaled copper wire. On 8.22 I say “the oscillation stops” but it starts again, when a certain point on the potentiometer is passed, after that point the “cancel-out oscillation is “cured”, showing resonance again (dip-peak).

In the past I experimented this many times without success, but now it worked (by the way with 2 (!) paralleled variable resistors, switched in a certain way, 1 Mega Ohm and 1 Kilo Ohm). It worked over a small frequency band (380 KHz wide).

But of course that differs on the frequency where you want to use this principle + the value of the capacitor that is “switched parallel” (in a certain way) to the coil (in the schematic indicated as the “0-50 pF capacitor”). It is a resonant circuit with all the properties belonging to resonance.

In this case the 0-50 pF capacitor that was in series with the “R” (1M & 1 K potentiometer, bridged) was connected to ground, minus, thus via that R effectively bridging the coil, giving that coil/the FET (Gate-Ground) more parallel capacitance. So the 0-50 pF capacitor is one of the factors that determines the resonance frequency. the 1M resistor can not (!) be omitted, otherwise it does not work.

Tested were, as capacitors, a standard capacitive trimmer, 3-33 pF (standard available) and a fixed value capacitor of 47 pF (Wima, Germany).

So a lot more experiments to do and optimize this principle (= tuning via this resistance setup in series with a “C” parallel to a resonanant circuit on frequency X).

For a certain aim, be it on SW, VHF, UHF or in the GigaHertz range. The circuit obeys of course to the electric/electronic laws. I will try to do more experiments to get more out of of this principle/concept.

By the the FET circuit is also usable as an oscillator for crystals between 3 MHz and 6 MHz (watch the video for more info).

But (!) not many crystals of my stock wanted to work, perhaps because of the fact that my “salvaged” crystals were damaged when I soldered them out. Please there are many types of say crystals that were made via the so called “T-Cut” and other types.

Some crystals (=extremely thin crystal plates) cannot oscillate on frequency x because their physical properties (the way they were cut out of the mother crystal) makes that impossible.

The crystals that I have have no indication whatsoever regarding the way that they were cut, it means that I have no clue about the types of crystals that will work in this oscillator.

Best try it, this oscillator can be made in half an hour and can function as a crystal tester for crystals in the 2 MHz-6 MHz band. When your crystal works with this oscillator you can be sure it is OK.

For frequencies higher than 6 MHz the capacitive voltage divider has to be changed when you want to test crystals. Coils can work properly without adaptation. The capacitive voltage divider = the values of the capacitors Gate-Source and Source-Ground. General make them between 0,2 and 3 factors smaller and in an even way (C Gate-source and C Source-ground) but (so) keep the ratio or change that ratio slightly. The circuit with this transistor FET BF 245 can work up to 15 MHz (max).
All the videos hat I have published on You Tube can be found via my Channel Link is

In thematic order you can find these video’s under the “comments” section.
to find all the links to the (+/-700) video’s on my YT Channel, select, in the comments section, “NEWEST FIRST”

My books about electronics are available via the website from “Lulu”, search for author “Ko Tilman” there.

There is an important video via which you can buy a document where I give links to many of my video’s, published between 2020 and 2020.


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Regarding all my video’ I constantly keep them actual, so the original video’s with the most recent information are always on YouTube. That is the source, and search there. When my video’s are reproduced or re-edited on other websites/channels you can not (!) be sure about the original content (=really working electronics with real properties for a purpose) and important adaptations to the circuits.

Be aware of that, I saw on the internet my circuits reproduced in a poor or not proper way.

I also found that people probably republish my circuits under phantasy names and/or with phantasy properties. Sometimes they want to find gold with them. I take distance from all these fake claims; I cannot help that it happens, sorry. Upload 18 november 2020.

You can call this circuit “the Tilman oscilator” (-:)

you get all the crystals but rember dont try to get to much becuase admins see you got like 9999999 crystals and they know it a hck so
online like 200k a da or something like and subscribe

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