Modulated signal and loaded to ground

Thread Starter

TBayBoy

Joined May 25, 2011
148
In the attached circuit L2 is a diode loaded inductor, however in some of the boards we usd there was a 220Ω resistor.

The question is whay is this component needed, and my first inclination is it allows the tank to build the negative half of the modulation.

Am I out to lunch??

:)
 

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t_n_k

Joined Mar 6, 2009
5,447
One observation without knowing component values would be that L2 perhaps presents a low impedance to (& thereby attenuates) the out of band unwanted low frequency components.
 

Thread Starter

TBayBoy

Joined May 25, 2011
148
Well I have a 150kHz carrier wave, with a 1kHz audio wave, so after the diode I have a 1kHz envelope with 150kHz inside, but only the + parts of the wave. Then the tank forms the negative portions as mirrors of the positive so the input to the tank is a 0-300mV wave, and the output is a 600mV peak to peak audio modulated signal.

Some boards had the L2 and some had a 220Ω resistor, but gave the same output.
 
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