[hpsdr] Penny PTT unkeying spike - T/R sequencing?

[Steve Bunch]

Is the amplitude of the I/Q signal that is sent to Penny ramped up and down, like it would be for shaping CW keying, in the case of T/R switching it the way Tom is?  If the I/Q values are abruptly dropped to zero, you would expect to see some energy corresponding to that essentially square-edge get generated -- same principle as key clicks on a CW transmitter that's keyed too sharply.  Since there aren't any tuned circuits in Penny itself, there's no mechanism for traditional "ringing" to be taking place -- this seems like it virtually has to be software-generated.

Steve, K9SRB

On Feb 4, 2011, at 7:28 PM, Phil Harman wrote:

> ***** High Performance Software Defined Radio Discussion List *****
> 
> Hi Tom,
> 
> Thanks for your additional work on the unkeying spike.
> 
>> ****  New question:  Is there a simple way to monitor the output of an
>> EXTERNAL linear amplifier on the Mercury panadapter during normal Penny
>> transmit? It would mean disconnecting the internal Penny to Merc RF sampler
>> and inputting the external linear sample somehow, no?   Obviously, Penny's
>> clean output is meaningless if the external amplifier is not clean, thus the
>> motivation to monitor the last component in the RF chain.
>> 
> 
> The spectrum you see in PowerSDR whilst transmitting is not the RF output from Penny. Rather its the  I and Q signal that is being sent to Penny at some point in the DSP chain.
> 
> In theory it should be possible to modify PowerSDR to run in full duplex but I not away of anyone actually doing this.
> 
> KISS Konsole will run in full duplex so you can see your transmit signal as it is received by Mercury.
> We are presently merging the USB and Ethernet versions of  KK ready for the release of  Metis.  We plan to do this over the weekend and will advise when the latest version is available.
> 
> It will be interesting to hear your results of doing the same tests using KK since it  could help us narrow down where the spike is occurring.
> 
> 73 Phil...VK6APH
> 
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