We've got an interesting discussion going over in the qrplabs group regarding
a possible way to transmit SSB signals much more efficiently (and cheaply) than
through the use of a linear amp:? ??
/g/QRPLabs/topic/29572792EER is an acronym for Envelope Elimination and Restoration.
Traditionally, this apparently meant to build an SSB exciter, then amplify and limit the?
output such that all that remains is a square wave with the frequency information.
Amplify that square wave efficiently with a class C or D or E amp, and restore the
envelope information by modulating the power supply to that amp.
The envelope information could be obtained with a diode detector that watches the output
of the SSB exciter.
A more interesting approach might be to do away with the SSB exciter entirely.
Audio comes into a uC through an ADC from the mike, calculations are performed
on that audio to compute the desired frequency and envelope information,
then the uC steers the frequency of a PLL (such as the si5351) and also modulates
that final amp with envelope information.
Seemed only fair to mention it here.
One possible piece of the puzzle might be to modulate an si5351 clock by
jerking around the reference oscillator as Farhan first described in this forum:
? ?
/g/BITX20/message/34020Jerry, KE7ER?
