[hpsdr] CW operation

[Phil Harman]

Luke,

Have a look in the PowerSDR Knowledge Base regarding the settings required 
for lowest CW latency.  There are a number of buffer sizes  to set as well 
as the sampling rate.

73 Phil... VK6APH


----- Original Message ----- 
From: "Luke Steele" <mail10 at barefoothorse.com.au>
To: <hpsdr at lists.openhpsdr.org>
Sent: Friday, January 07, 2011 8:15 AM
Subject: [hpsdr] CW operation


> ***** High Performance Software Defined Radio Discussion List *****
>
> Happy New Year all,
> I have a question on CW ops.
> My system is as follows:
>
> Mercury; v2.7
> Penelope; v1.2
> Magister; v1.7
>
> PowerSDR v 1.19.3.1 baseSVN3444
>
> CPU; i5-760
> 4 GB RAM
>
> OS; Windows 7 Ultimate 64 bit
>
> Also running Ham Radio Deluxe and DM780
> Virtual Serial Ports for interface HRD-PSDR
> Virtual Audio Cables for interface DM780-PSDR
>
> Right, all that out of the way, my question is; how do CW ops deal with 
> the
> latency of the sidetone?
> The latency I am experiencing is certainly not in the order of several
> hundred milliseconds mentioned in an earlier post on this forum, but is
> probably in the order of low tens of milliseconds and just enough to be
> annoying. It makes the paddle feel 'dead' in that if lags just enough to
> cause me problems with synchronisation. I like to operate around 23 WPM by
> the calibration on the slider in the CW dialog.
> I understand that the sidetone is generated by simply decoding the 
> transmit
> signal in the receiver card, therefore, the latency would be that of the
> exciter card processing plus that of the receiver. This is rather clever,
> in that one can therefore monitor one's actual transmission, but the
> latency introduced causes me problems. Are there some settings I should
> look at to reduce latency to an acceptable level? I have fiddled with the
> CW DSP settings, and found it a trade off between latency and filter
> performance. Is there a workaround in software?
> Or should I just build a sidetone oscillator and inject it at the 
> headphone
> like it has been done traditionally?
>
> The CW transmit is the only aspect that I feel needs improvement. The
> receive filters and functions are fantastic, and it operates in 
> superlative
> manner in phone. The receiver is first class, and hears as well as or
> better than anything else I have here. Digital ops using the VAC interface
> works very smoothly, and seamlessly.
> Oh, here's a tip for those using Windows 7 with the RealtekHD audio stuff:
> check in the "Sound Effects" tab, "Environment" is set to "None" or your
> digi transmission will be altered by the various environment sound effect
> schemes available, and it will be unreadable.
>
> Vy 73,
> Luke VK3HJ
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