[hpsdr] Hermes transmit baseband frequency reversal ?

[Warren C. Pratt]

Hi Tom,

I think Phil already answered the question.  From the standpoint of 
another software developer, I can confirm that I have seen this too as 
I've developed new code.  I just take the pragmatic position of flipping 
I/Q and moving on.  I'm not sure I've ever even mentioned it to the 
firmware developers or asked about the history.  The history that Phil 
provided is interesting.

73,
Warren  NR0V

On 3/13/2014 3:26 AM, Tom McDermott wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>
>
>
> HI,
>
> In playing with some gnuradio sources, I am getting a baseband 
> frequency reversal going through Hermes.
> This using the definitions for I and Q in the HPSDR USB protocol 
> document (ver 1.43).
> That is - a downward frequency chirping IQ baseband signal into 
> transmit causes an upward chirping
> IQ baseband signal at the receive output.
>
> It appears that the transmit I & Q side is doing the reversal, while 
> the receiver seems to be normal, by testing this with an external SSB 
> receiver, and by using various gnuradio instrumentation.
>
> In looking through my own code that formats I & Q into the transmit 
> frame, I cannot seem to find any
> deviation from the protocol specification (rev 1.43).  Do I have a bug 
> in my code, or is there a known
> issue with Hermes that causes the frequency sign inversion on transmit?
>
> -- Tom, N5EG
>
>
>
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