[hpsdr] Penny FPGA Load

[Joe Martin K5SO]

Bob,

Changing the sampling rate changes the bandwidth of the IQ stream  
passed to the PC;  192,000 yields 192 KHz bandwidth, 96,000 yields 96  
KHz bandwidth, and 48,000 yields 48 KHz bandwidth.  The amount of  
bandwidth displayed by the panadapter is user controllable, up to the  
maximum bandwidth set by the sampling rate.

Changing the buffer size does not affect the bandwidth or the  
display.  Neither sampling rate nor buffer size affect the update  
rate.  The display update rate is also user selectable in the menu  
settings.  Changing the buffer size simply reduces the amount of IQ  
data that the PC loads before needing to go back for more data.  The  
reason that lowering this value sometimes helps audio drop outs is  
that on some machines the process of loading the buffer takes too long  
to keep up with the audio output stream rate, thus there is a period  
of no audio (a drop out).   This is especially true with USB  
interconnection between the PC and the HPSDR board set, not so much  
with Ethernet connection.

Audio drop outs are especially prevalent with slower computers and  
with computers that are running many processes simultaneously so it is  
a good idea to stop all unnecessary processes that may be running on  
your machine if you are experiencing drop outs.

Hope that helps.

73,  Joe K5SO

On Jul 14, 2011, at 5:49 PM, Bob G Mahrenholz wrote:

> Joe,
> Does changing the buffer size and/or sampling rate change the  
> bandwidth
> of the panoramic display, its update rate or what?
> Bob


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