Dr Ronald Stiffler SEC technology

[gyulasun]

Hi Itsu,

Okay, so it seems your SA nicely shows the multiple output frequencies of an RF mixer and we can be sure the displayed amplitudes at their specific frequencies are present at the collector of the transistor, it is reality.

Regarding your 12 MHz crystal needed a higher input current: although there is the so called 'activity' (willingness to oscillate) behaviour for crystals in general (they are all 'different'), have you tried this: just start the same oscillator with a single 12 MHz crystal and try to run it with say 15-20 mA input current only to see how it behaves. If it is willing to oscillate 'normally', then plug in a single 13,56 MHz crystal in parallel with it and see it oscillate or not etc. Of course it is possible you find the need for increasing input current again to have both crystals work, you will see. Try a 2nd or 3rd 13.56 MHz xtal (one by one) instead of the first one if you find the need for increasing input current to have both crystals work.
And if you happen to have other crystals of yet differing frequencies, do test them when you have time.

We may deduce from your tests now why the SA is not able to display the multiple output frequencies of the 2 or 3 or 4 or 5 pieces of the 13.56 MHz crystals in parallel: the outputs of the frequency components due to the mixing process simply coincide. This means that say the sum of two 13.56 MHz xtals is simply almost equal to the 2nd harmonic, 27.12xx MHz, the small difference may range from some 10 Hz to some 100 Hz (up to some kHz at the higher harmonics) only, so that the SA resolution is simply not fine enough. I think it is the RBW (Resolution Band Width) setting on the SA which can only be reduced to a given smallest setting. depending on sweep time (SWT) or frequency span etc.  The RWB was set to 30 kHz on your SA when you zoomed in on the 13.56 MHz frequency and probably a 10 Hz or less RBW would be needed to see the different frequency components which differ from each other by say 34 Hz. Of course this 10 Hz RBW or less may be a strict requirement for an SA, though not impossible.   

Thanks, 

Gyula

[gyulasun]

Hi Lidmotor,

Yes, when energy is taken from a resonant LC circuit (i.e. from the 'L3' coil) by coupling to it another resonant LC tuned to the same frequency (or to a frequency close to it within the bandwidths involved), then the one wire energy transfer suffers: you 'tap' its source.

You may find this link interesting:  https://en.wikipedia.org/wiki/Grid_dip_oscillator  and this link on how to use it: https://www.electronics-notes.com/articles/test-methods/grid-gate-dip-oscillator-meter/how-to-use-gdo.php

If I may suggest another link: https://en.wikipedia.org/wiki/Absorption_wavemeter  and this video: https://www.youtube.com/watch?v=fOnlyU2Qlwg

Regarding your freak wave example, I will return to it later tomorrow or so.

Thank you for mentioning my name in the video. To pronounce it 'correctly',  say the word  'due'  for the 'Gyu'  (the 1st) syllable and add to it the 'la' syllable (which sounded ok).

Gyula

[seychelles]

THE ELECTRONIC FREAK WAVE PHENOMENA HAPPENS IN THE KAPADNAZE CIRCUIT. BUT HE USES
SWR TO GENERATE THIS.

[seychelles]

I SEE THIS HAPPENING ALMOST EVERY DAY ON THE BEACH ON PRASLIN SEYCHELLES.
FREAK WAVE THAT IS.

[TinselKoala]

Check this out:
http://www.eevblog.com/forum/rf-microwave/gan-class-ef_odd-hf-transmitter-logic-gate-drive-14w-out-90-efficiency/msg1693205/#msg1693205

I ran the drain supply all the way up to 15V, with 0.96A DC input current, yielding 14W RF output.  Not bad for active devices barely visible to the naked eye, and no heat sink!  (EPC says R(ja) ~ 100C/W.)  I wish I had better efficiency numbers, but I was measuring rms load voltage with my Rigol scope, which isn't terribly accurate:  I was calculating drain efficiency ~ 96% or even higher, awesome... until I started getting some "over unity" efficiencies at low power   Oops.