On 03/15/2010 04:09 PM, Marcus D. Leech wrote:
Does the “tune” function actually do anything for the BASIC_RX? Does it
just set the DDC
Tune on the basic and lf rx only sets the ddc. In other words, the IF of
the dboard is always 0 Hz in this case.
Because this tuning relies entirely on the ddc, you are really aliasing
in frequencies above ddc_rate/2. Because of this, your RF frontend
should need a bandpass filter so only the desired range can be aliased
The tune method should do the right thing.
For example, if I have a quadrature HF receiver, centered at let’s say
20MHz, with 4MHz either
side of 20MHz, can I use “tune” and setting the decimation to pick out
a particular chunk.
Let’s say I wanted the 250KHz “chunk” that’s +500KHz from the center
frequency, would I set
the decimation to 256, and ask “tune” for 500KHz?
Assuming center_freq+500KHz is the center of the “chunk”, that is
center_freq+375khz to center_freq+625khz: you would do
tune(center_freq+500KHz) and the tune method figures out what the ddc
should be set to.