coil generator : tester of coils

[moorejl57]

That's pretty awesome sinewave, looks clean as a whistle. I noticed a negative supply voltage on the scheme.

I drove it with a isolated +5V supply, just used +5 as ground for scope measurement. It also works well at higher voltages, tested at 9V as well.

[dbanner]

I drove it with a isolated +5V supply, just used +5 as ground for scope measurement. It also works well at higher voltages, tested at 9V as well.

Just what the doctor ordered, a two transistor tank oscillator in the low kHz range operating with 9 volt supply. Producing a smooth sinewave with low thd.
Perfect for coil tester. The peak to peak isn't important, so low peak to peak is fine.

[kt315]

UNIVERSAL LC OSCILLATOR

Radio, 1979, 5

This oscillator is designed to be used in measurement circuits. The circuit diagram is shown in the figure 1. An important advantage of this oscillator is that in this circuit can be used a resonant circuit with almost any ratio of L/C. So, this oscillator operates stable even if the inductance of the coil L1 changes from 50 uH to 100 mH and the capacitance of the capacitor C1 changes from 50 pF to 5 uF. For example, the inductance L1 = 50 uH and the capacitance C1 = 5 uF, the oscillation frequency is about 10 kHz, while with the same inductance and C1 = 50 pF we get the oscillation frequency about 3.2 MHz. In addition, the advantage of this oscillator is the low voltage across the LC circuit - it is approximately 100 mV. In some cases it is important, for example, when measuring parameters of varicaps.

schematic diagram of the universal LC oscillator

Fig. 1.
V1, V2 - BC252; V3 - BC172C; V4, V5 - 1N4148; V6, V7 - BC172B; V8 - BF241.

The oscillator is based on transistors V1 and V2. The transistor V3 is a pre-amplifier, the signal from this stage is fed to an output amplifier (the transistor V and to the AGC circuit. The AGC automatically adjusts the amplitude level of the signal. Since the pre-amplified signal is fed directly from the LC resonant tank circuit of the oscillator, the AGC maintains a constant voltage across this resonant tank circuit. The AGC circuit is composed of diodes V4 and V5, this is the doubling rectifier circuit, the DC amplifier with transistor V7 and the regulating transistor V6. If the voltage across the output of the oscillator changes, for example, the voltage became higher, it increases the bias voltage at the base of the transistor V7. This will reduce the current through the transistor V6 (hence, the current through the transistors V1, V2), and the voltage across the output of the oscillator will be reduced to the initial value.

The output voltage remains almost constant when the supply voltage changes from 3.5 to 15 V. With the supply voltage of 5 V the amplitude of the output voltage of the oscillator will be compatible with transistor-transistor logic.

In this oscillator you can use any silicon high-frequency transistors. The transistors V1-V3 should have a sufficiently large current gain (not less than 150). In this circuit the parasitic oscillations can arise, in this case increase slightly the resistance of the resistor R2 to suppress them.

?Funkshau? (FRG), 1978, 18

http://zpostbox.ru/universal_lc_oscillator.html

[kt315]

on-line calculator. you can calculate F, L or C in resonance contour.

https://coil32.ru/calc/jslcc.html

[kt315]

BH coil, example of calculation. frequency 6.6kHz.

Yes, there is an internal capacitor. The TX inductance is 2.4 mH, and there is a parallel pair of ( 220 nF + 22 nF or 20 nF ) = 240 nF across it. I'm not sure of the capacitor type, the 22 nF was a common polyester type, the 'dipped mylar' that are usually green colour. The 220n may also be polyester, but polypropylene may be a possibility, for temperature stability?
RX inductance is also 2.4 mH, with no added C,R,etc. RX resistance is quite low, 2 Ohms.

L=2422.932 uH

[kt315]

ultra-precision soviet cap K71-7. 0.01uF 0.5%, good for research tester.

https://www.ebay.com/itm/0-01uF-250V...-/261456722733

[kt315]

can anybody share this magazine Funkschau 1978 N18? i believe if in russian magazine this is reprint from it then
original article was in american one. ie the source is american magazine be cause those BC... BF transistor types
and 1N4148 diodes sure say that the schematic was taken from western side or as we say US is 'new Atlantis'.

[WM6]

i believe if in russian magazine this is reprint from it then original article was in american one.

.

It was Deutsche Zeitschrift not American one.

Funkschau (FRG), 1978, 18

(FRG = Federal Republic Germany)

There are different magazine archives in Germany.

You can contact them and ask for copy of 1978 Funkschau article named:

"LC-Oszillator fuer beliebige LC-Verhaeltnisse" 78/18/898

Par example here:

https://shop.weka-fachmedien.de/de/c.../4-rueckfragen

[kt315]

thank you WM. in PM asking this guy to send me pic with the article. he attached this pic of the cover.
his listing https://www.ebay.com/itm/303387485435?ul_noapp=true

[WM6]

If whole year 1978 volume is 20 euro, then August issue only should be about 1 euro + shipping.

Does they sell single (august #18 ) copy too, or whole 1978 volume only?

[kt315]

now SOS-HELP from mine side. can anybody with clear German ask this German guy to attach a pic with the page in PM?
PM in ebay is allowed to attach pictures, but not links. links are banned.
main difficulty this guy is not so active, we know that those nordic folks sometimes are too 'frozen, slow-witted' on a reaction be cause they are living
under 'the cold Sun', northern Sun.
so still no reply from him. thank you guys.

[WM6]

. can anybody with clear German ask this German guy to attach a pic with the page in PM?

Asking him for article copy (in German), wiling to buy it, but no answer from him till yet.

Seems he is in large book commission business, so very busy. We will see.

[kt315]

this reply from address you gave above.

Sehr geehrte Kundin,
sehr geehrter Kunde,

vielen Dank f?r Ihre E-Mail, wir werden Ihre Anfrage zeitnah bearbeiten.
Sollten R?ckfragen auftreten, werden wir mit Ihnen in Kontakt treten.

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[kt315]

he sent me the pic...(i mean ebay listing) with cold german nature of Nordid Corded... he certainly did the pic in perspective.
yes, now i see it is primary source.

[WM6]

eBay guy answered.

I am in communication with him now.