[aprssig] KPC3+ induced errors

Stephen H. Smith wa8lmf2 at aol.com
Sun Mar 27 18:10:48 CDT 2011

On 3/27/2011 1:59 PM, Andrew Rich wrote:
> Is it a genuine delay?


> Are packets lost ?

Apparently not.  It acts as though some sort of buffer fills up, and then the 
oldest packet gets pushed out when a new one arrives.  Depending on the volume 
of traffic on the channel, this FIFO buffer effect can cause packets to delayed 
anywhere from  10s of seconds to 10s of minutes.

> Is it a flow control issue ?

It shouldn't be since KISS doesn't use flow control.

A similar issue arose with a Kenwood D700's internal TNC being used for an 
igate for a balloon launch in Colorado. In this case, operating in NON-KISS 
mode with UIview with X-On/X-Off flow control enabled, long delays were 
experienced.   Setting the flow control in UIview to "None" eliminated the 
problem.  [ I suspect that random bytes in binary telemetry steams (or 
corrupted incoming packets) were being interpreted as X-On(11 hex or Ctrl-Q) ) 
and X-Off (13 hex or Ctrl-S) control characters. This would cause the data flow 
from the TNC to the PC to randomly stop and then later resume. ]
> Does the test setup use no flow control ?




Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      WA8LMF  or 14400    [Think bottom of the 2M band]
Skype:        WA8LMF
Home Page:          http://wa8lmf.net

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