Dr Ronald Stiffler SEC technology

[Lidmotor]

 erfandl--- I worked on the two paralleled crystal oscillator setup again today.  My results were disappointing. Not enough light increase for the additional power required.   I probably will not spend any more time on it.   

---- Lidmotor

[erfandl]

erfandl--- I worked on the two paralleled crystal oscillator setup again today.  My results were disappointing. Not enough light increase for the additional power required.   I probably will not spend any more time on it.   

---- Lidmotor

Hi lidmotor. thanks for reply. do you using MPSA06 or BD243C transistor ? yesterday I test with 2n2222 and MPSA18 but the result is not like BD243C. I'm not using ferrite rod

[NickZ]

Nick,

Nice progress!  Would like to ask you did try the 13.5MHz crystal with this D13007K transistor but it simply did not oscillate?  Or you thought the transistor simply is not suitable due to its 4 MHz frequency limit and you did not test it?

You surely have to increase the L3 coil size for the 3.5 MHz crystal. I suggest to follow what Lidmotor built as a variable coil with a wiper wire sliding on the surface of the coil. Wind a coil at least on a 4 cm OD bobbin with at least a 6 - 7 cm long winding. With the wiper this can be tuned by watching the LED brightness.
When this coil is in resonance, the cliplead from the diode may be removed and the diodes common point may be connected to battery negative or positive, I mean to include the LED board by capacitive coupling into the L3 circuit and tune it by the wiper too.

If you or someone near you has an old, unused AM pocket radio then its ferrite antenna could be taken out and you could use the ferrite rod to tune this L3 coil you have for the 13.5 MHz and lower the coil resonant frequency toward 3.5 MHz. I mean such ferrite rod: https://i.stack.imgur.com/7QaIR.jpg 

Gyula

  The oscillator will only start when using the 3.5MHz and the 7.2MHz crystals. But the 7.2MHz runs at a much lower amplitude, like 12v at the collector/emitter.   I will add more turns to my L3 today, and see if I can get the 13.5MHz crystal to start up. And I need to find a power transistor that can run at least to 13.5MHz also.

[AlienGrey]

  The oscillator will only start when using the 3.5MHz and the 7.2MHz crystals. But the 7.2MHz runs at a much lower amplitude, like 12v at the collector/emitter.   I will add more turns to my L3 today, and see if I can get the 13.5MHz crystal to start up. And I need to find a power transistor that can run at least to 13.5MHz also.

I had a problem like that it was the low frequency band width of the transistor.

try a BC337 the one i tried had an HFE of 250 I also found the higher the gain the more the current draw,

[Lidmotor]

erfandl---- I am using the BD243C transistors on my setup.  I'm also using two small breadboards instead of just one like what you showed.  Perhaps that is the problem. 

-----Lidmotor