[hpsdr] Pactor on PowerSDR

[John Laur]

Hi, Gary.

The PACTOR modems require a ridiculously fast T/R turnaround time in
the radio. This must be <35ms with PACTOR II. While the current
releases of PowerSDR can be configured to be *almost* this fast and
are indeed much faster than any other direct sampling SDR today, the
DSP latency present in the software chain plus the use of relay
switching, etc. means that it will be basically impossible to get a
hardware PACTOR modem working reliably without significant
modifications to the software and possibly the hardware.

PACTOR's strict TR turnaround requirements are in fact a problem for a
large number of current non-SDR radios, particularly those which rely
heavily on DSP functions or use very safe (slow) timings on their T/R
relays.

All that being said, you may be able to experience some limited
success by running the sampling rate up to the maximum 384kbps,
choosing the minimum phase filters available since PowerSDR 3.3.8, and
reducing the buffers and relay delays as much as you are able to avoid
hot switching. You will still likely be right at the edge of the
threshold.

There is some buffering in the onboard audio codec and network rx/tx
buffers in order to handle a small amount of network jitter. Some
users have been able to get slightly better latency by using low
latency ASIO devices with a high samplerate and small buffers in lieu
of using the onboard audio, but this is not a simple setup.

73, John K5IT

On Mon, Jul 18, 2016 at 8:24 AM, Gary <gibog1 at iinet.net.au> wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>
> I am having no luck using an SCS PTCII usb Pactor modem running Winlink2000 on an ANAN 100D
>
> Audio connections Via line in and line out on the db25 connector and running powersdr in digital mode.
>
> I can successfully connect using Winmor but not with the pactor modem.
>
> Has anyone had any experience with this issue?
>
>
>
> Gary VK8BN
>
>
>
>
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