Dr Ronald Stiffler SEC technology

[gyulasun]

Hi erfandl,

Regarding the coil, you could make some taps on your coil as I sketched in the photo below.

Perhaps you could cut the wire at BC, DE, FG and HI winding places (I know it is not easy) and separate the ends so that windings A to B,  C to D,  E to F,  G to H and I to J would remain next to each other with say a single turn gap between each. 

With such taps, when all the wire ends are floating in the air, you could test several coils individually or combining the adjacent windings in series connection to find the 13.56 MHz resonance or near to it.

Obviously, for a continuously variable coil, a wiper (like in a variable potmeter) sliding on the top surface of the total winding coil length-wise and connecting to the scrapped winding surface would be the best and you can approximate this with the taps.

If your chosen coil section, say, has a higher self resonance frequency than 13.56 MHz, then a small piece of ferrite rod could be inserted to fine tune the coil and get more info.  Unfortunately, the moment you connect the LEDs or an AV plug or anything as a load to the end of the coil,  then these surely detune the coil towards a lower resonant frequency due to the capacitive loading.  The presence of the unused windings next to the used ones may also detune the used coil but this is but a small detuning effect.


If you use a choke coil instead of the 1 kOhm in the collector, you can use any coil which has at least 47 uH inductance or higher.  A 47 uH coil has about 4 kOhm inductive reactance at 13.56 MHz.
Gyula

[AlienGrey]

Guyula

Hi yes 47uh works fine for me, 47uh is a lot of turns on a air core I used some tube from a hardware store 12mm dia with 12mm of 28 swg
and a ferrite rod inside to tune it, from an old wall clock 'radio clock'. works a treat.

Re synth I used some CD4522 down counters (3) from a CD4046 that way i can dial in 432khz or any rep of it up to 1mhz, to get 1khz a CD4060 and a 4,096 xtal, next time I will try a CD4059 (SMD  ).

AG

[erfandl]

thanks all for helping. I did not find the 1000 uh inductor from local stores. is any repalcement for this ?

gyulasun - do you mean using 1kohm resistor with 47 uh inductor as coil ?

thanks

[gyulasun]

Hi erfandl,
I mean use 47 uH choke coil instead of the 1 kOhm collector resistor (or instead of 1000 uH choke).   You can even make such choke by winding at least 40-50 turns of enameled wire into a toroidal core or ferrite bead, found in discarded PC power supplies or in PC monitors mains supply etc
Have you checked the DC voltages?
Gyula

[erfandl]

Hi erfandl,
I mean use 47 uH choke coil instead of the 1 kOhm collector resistor (or instead of 1000 uH choke).   You can even make such choke by winding at least 40-50 turns of enameled wire into a toroidal core or ferrite bead, found in discarded PC power supplies or in PC monitors mains supply etc
Have you checked the DC voltages?
Gyula

thanks for reply. OK I understand. I checked the voltage the base voltage is 0.675 volt and collector voltage is 2.352
and a question I have a 1000 uh choke like below picture can I use that ?