[hpsdr] Hermes transmit baseband frequency reversal ?

[Steven Doyle]

This is interesting since I noticed the same problem when trying to use Mercury as a Panadapter for another rig’s IF out. It would be really cool if there was a checkbox say on the transverter screen that would flip I & Q

73

Steve
G1YLB

From: Warren C. Pratt 
Sent: Thursday, March 13, 2014 3:23 PM
To: hpsdr at lists.openhpsdr.org 
Subject: Re: [hpsdr] Hermes transmit baseband frequency reversal ?

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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:

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  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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