A3E Basic AM, Double side-band, full carrier modulator

Thread Starter

davidjohnhills

Joined Oct 8, 2017
61
Good Morning
My original post got moved to data sheets and parts and has not got a reply yet, so I have changed the question a bit to be relevant to General electronics chat.

Is it possible to build a A3E Basic AM, Double side-band, full carrier modulator with only passive parts plus diodes

thanks

David Hills
 

Thread Starter

davidjohnhills

Joined Oct 8, 2017
61
Hi
I was following the advise below, it it incorrect/incomplete then
I need full carrier AM modulator
"
Perhaps it should say "You cannot achieve (easily ,effectively or simply)AM using passive components only."

You cannot achieve AM using passive components only. By definition it requires an amplifier device that can be enhanced or depleted by the audio to create the wave. The carrier stays constant and the 'effect of the sidebands is to drive the amplitude of the carrier up to double its constant level on positive peaks and down to zero on negative peaks. Traditionally a valve amplifier was used for the RF and its anode supply was raised and reduced by the audio thereby creating a 4x increase of power on positive peaks and zero output on negative ones.
Today is is possible with transistors that will increase in gain with increased supply and reduce in gain with reduced supply. FETs do not do that. They conduct about the same regardless of supply volts. To make them increase or reduce conduction you need to apply the audio to the source which will produce the same effect."
 

nsaspook

Joined Aug 27, 2009
9,437
The key word is efficiency. I can AM modulate a RF signal with a potentiometer (or a FET acting as a potentiometer). Side-bands are created because of the changes in carrier amplitude from the message signal.

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