No. ?The desired drive into a balanced ring mixer is a square wave.
You are driving diodes, the current through the diodes is an exponential function of the voltage across them.
So they are effectively either on or off, with very little transition between the two.
Which is not necessarily a bad thing.
The diode ring is best thought of as a commutating mixer. ?
Which means it is best analyzed as switches.
Something like a Gilbert cell can be used to truly do an analog multiply of the incoming signal with the local oscillator.
But even these mixers are typically driven hard to where the Gilbert cell acts as switches.
If you really want a sine wave into your diode ring mixer, you will have to choose
between a sine wave in voltage presented or a sine wave in current through the diodes.
You can't have both, as them diodes are far from linear.
Some in this forum have experimented with adding filters between the si5351 and the diode ring mixer.
Some do report fewer birdies, though there are lots of possible reasons for that.
I doubt it has anything to do with presenting a square wave to the mixer.
If using more than one of the si5351 outputs, a filter might help reduce crosstalk.
It would also help prevent vfo harmonics from radiating into off the open cabling into other parts of the radio.
Jerry
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On Mon, Oct 23, 2017 at 10:08 am, Gordon Gibby wrote:
but the DESIRED frequency is a sine wave.? ??
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