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Re: Softrock EMU Linrad

Hi Ken,

> However, I understand that a direct-conversion receiver like Softrock
> requires software to use the I and Q signals to cancel the unwanted
> image frequency. Linrad has an option for this.
> I read in another SDR forum that the EMU card has 2 or 4 clock cycles
> of delay between the I and Q samples.
I would guess that the EMU samples at something like 64*192kHz(=12.3 MHz)
so a shift by 2 or 4 clock states would be a small phase shift on the 
decimated signal at 192 kHz.

> I have found that Linrad has an IQ calibration routine that handles
> phase/time delays in some way.
> Does this take card of a card like the EMU?
Yes. As far as I know, but I do not have such a card
so I can not tell for sure. In case the time delay
is in clock states at 192 kHz I would guess it does
not work.

> Looking at the calibration screen on Linrad I see that I am instructed
> to connect a frequency generator - but there is no information about
> what signal is required. More info please?

You need a sine-wave that is reasonable staple. Feed it into
your system and make it strong in the receive mode which
you want to calibrate. Then go to the cal screen and you
will see something similar plus messages whether it is too
strong or too weak (or not stable enough)


  Leif / SM5BSZ

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