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??

 

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.

 

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.

 

Interestingly I found this modified circuit simulation seemed to do the job OK.

 

Thanks for the help, more talking and info that component is used to forward bias D1