[hpsdr] An high dynamic QSD front-end

[Lyle Johnson]

> I think it's time to go ahead with Phoenix.

Here is an heretical thought: what if we used the QSD at a fixed IF 
frequency and thus didn't need a quadrature, wideband injection source? 
  That might make a PLL - or even a DDS - solution practical or easier.

If the revised QSD works well above 30MHz, we can use a high IF to ease 
image rejection and we wouldn't need much in the way of an IF filter, so 
we can still use the QSD to get the 200 kHz or so of spectrum display we 
have come to expect from this sort of design.

We need something in front of the QSD to suppress LO radiation, and the 
"front end" filters and whatnot are going to be required as well.  An 
H-mode mixer will preserve the dynamic range characteristics we want.

73,

Lyle KK7P





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