Transmitter and reception coil on VLF tuned: how they couple on their peak resonance 100 KC-200 KC

Please read the description first. A demo (VLOG) where I show how a transmission coil (L-C) can send out its energy (now in the VLF range, say between 100 KC and 220 KC) and how that frequency can be received (max energy/resonance peak out) via another coil that is layed down approx. 60 cm. from the transmission coil and connected to an oscilloscope (oscilloscope 2, its input).

Thus on that second oscilloscope we can see the resonance peak on certain frequencies in the (here) VLF band, by moving the ferrite rod on the receptor side in-out, tuning the coil there to the best resonance, directly related to the frequency sent out by the VLF transmitter (= the coil connected to the test oscillator, visible on oscilloscope 1).

That transmission coil (on VLF) can also be tuned via a ferrite rod.

So a kind of search where the frequency of the reception coil meets the frequency of the transmission coil at its best, giving out a peak resonance on frequency X. (visible in the video).

The video shows everything: setup and (say) the (resonance) frequencies used, both via the transmitter coil and the reception coil, that receives that frequency. The reception coil tuned at its best (peak resonance) or weak (out of tune).

It is showed here for VLF (say 120 KC-220 KC), but the principle is valid for all (radio) frequencies.

It refers to the resonance phenomenon, between a transmitting antenna and a receiving antenna.

All well known in physics and radio technology. Sureley more info can be found on the www. Or via Google.

Thus: in this case we have to do with 2 coils: one on a certain VLF frequency, sending out waves, here in a sine-wave way, and another coil (reception) with a parallel capacitance, that is tuned to the same frequency of the transmitter coil.

It is done by moving the ferrite rod in-out, to a certain position where the resonance in the receptor is at its maximum peak. Visible at the oscilloscope.

About the (stray) capacitance (not directly visible, but measureble) both at the radio transmission coil and the radio reception coil: In the transmitter there is stray capacitance inside the FET + inside the transmission coil, due the space in-between all the windings.

The same (internal capacitance due to the closely wound copper windings) happens at the reception coil. Of course we have no FET here (in this demo), but the input impedance of the scope: 1 M combined with 10 pF or 20 pF.

Values that can be (in a certain way) neglegted, when looking at VLF coils and frequencies, but surely not to be neglected when we use frequencies above 2 or 3 MC. At least: when you want to do very precise measurements.

On 4.36 I talk about "a good quality radio coil for Long Wave" and I show it. Forgotten to tell: you must lay, into that coil, inside that toilet roll, a ferrite rod of say 6 cm or 12 cm. By moving it up/down inside that toilet roll, you will get the best radio reception on LW, when the top of that antenna coil is connected, via a 120 pF cap, to the outdoor antenna (say 10-15meters long), free hanging outside. Especially the BBC (at least in Europe......) will come trough.

The FET test oscillator schematic that I used here is here    • FET test oscillator sine wave with ve...  


My You Tube channel trailer is here:    • Radiofun232 on YouTube (updated monthly)  


Type there the keywords that you like (e.g. radio/audio/amplifiers/test/filter/) in the “looking glass” = search function” and give “enter”. Via that you can find specific video’s (under the say 1500 published).

When you search, search always “NEWEST FIRST” to get the right overview.

You can also 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. https://www.lulu.com/search?adult_aud...
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, etc. Some persons try to find gold via my circuits. I take distance from all these fake claims.

Upload 15 May 2024.