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Date: Wed, 16 Jan 2008 14:27:41 +0000
From: "Andy Talbot" <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org
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Subject: Re: LF: LF Receiver
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If you have the sort of SDR that uses I/Q drive to the soundcard, then it
can be tedious passing the recovered audio out to other software.  It can be
done using a utility called Virtual Audio Cable (VAC)  which effectively
creates an audio patch panel using digital buffers.  VAC sets up additional
virtual soundcards which you then route audio in and out of.

However, its probably easier to just get a second sound card, such as an
external USB one, and cross couple the audio.  They are quite cheap
now.   A USB headset can make a great second or third soundcard as well if
you want a voice input/output for driving SDR transceivers (see the
Radcom Data column this month - judging by the huge hit my website took
yesterday, it looks as if its just out)

The same comments apply to receivers like the SDR-IQ which digitise the
whole 30MHz spectrum, but then use the soundcard to deliver demodulated
audio.  VAC comes into its own here, as well.

Some datamode software can be persuaded to operate in parallel with other
packages, but it can be a bit hit or miss as to which software allows such
operation, and which blocks one process from working properly.

Incidently, I was monitoring the 500kHz band using my SDR-IQ one other night
when there was quite a lot of activity around.  With the maximum 256K FFT
size, I was seeing all the QRSS and CW signals present, plus things either
side of the Am band, in over 10kHz of bandwidth, simultaneously, at sub Hz
resolution.  The supplied Spectravue software is a really good waterfall /
spectrum analysis / Rx driver package, and doesn't use the soundcard at all.

Andy  G4JNT
www.scrbg.org/g4jnt

On 16/01/2008, lawrence mayhead <laurie.mayhead@googlemail.com> wrote:
>
> Many thanks to those who responded to my mail on the subject of receivers
> for LF/QRSS.
> and my problems with my 1792.
> Paul Hendrik for the URL re circuits Tracey Gardner for the e'bay lead,
> and Warren for suggestions
> re alternative Rx's.
> The lack of AGC OFF on DSP receivers is a worrying trend as Andy says.
> So I have been looking around!
> I have flirted with the possibility of  the Harris 590 or the Collins
> 2050, both have excellent specs and are non DSP, they look good,but do I
> want to take on another servicability problem, and they are not cheap.
> The Ten Tec RX340 also excellent spec. but its DSP and no AGC off.
> The AOR 7030 is non DSP and the spec is good but operationally it is very
> daunting,and it won't tune in 1Hz steps and it BFO offset has only 33 steps.
> I am concerned about setting it up for ARGO etc.Any comments Alan? also I
> guess its coming to the end of its production.
> So that leaves SDR receivers like the Perseus, thanks Johan, but these are
> digital, can the AGC be turned off? and another problem if my computer sound
> card is tied up  processing  I/Q signals can it  also  do the FFT analysis ?
> at the same time. Perhaps Andy can help?
> So I am still looking
> 73 Laurie.
>



-- 
Andy  G4JNT
www.scrbg.org/g4jnt

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<div>If you have the sort of SDR that uses I/Q drive to the soundcard, then it can be&nbsp;tedious passing the recovered audio out to other software.&nbsp; It can be done using a utility called Virtual&nbsp;Audio Cable (VAC) &nbsp;which effectively creates an audio patch panel using digital buffers.&nbsp; VAC sets up additional virtual soundcards which you then route audio in and out of.&nbsp;&nbsp; 
</div>
<div>&nbsp;</div>
<div>However, its&nbsp;probably easier to just&nbsp;get a second sound card, such as an external USB one, and cross couple the audio.&nbsp; They are quite cheap now.&nbsp;&nbsp;&nbsp;A&nbsp;USB headset can make a great second or third soundcard as well if you want a voice input/output for driving SDR transceivers (see the Radcom&nbsp;Data column this month - judging by the huge hit my website took yesterday, it looks as&nbsp;if its just out)
</div>
<div>&nbsp;</div>
<div>The same comments apply to receivers like the SDR-IQ which&nbsp;digitise the whole 30MHz spectrum, but then use the soundcard to deliver demodulated audio.&nbsp; VAC comes into its own here, as well.</div>
<div>&nbsp;</div>
<div>Some&nbsp;datamode software can be persuaded to operate in parallel with other packages, but it can be a bit hit or miss&nbsp;as to which software allows&nbsp;such operation,&nbsp;and which blocks one process from working properly.</div>

<div>&nbsp;</div>
<div>Incidently, I was monitoring the 500kHz band using my SDR-IQ&nbsp;one other night when there was quite a lot of activity around.&nbsp;&nbsp;With the maximum&nbsp;256K FFT size,&nbsp;I was seeing all the QRSS and CW signals present, plus things either side of the Am band, in over 10kHz of bandwidth, simultaneously, at&nbsp;sub Hz resolution.&nbsp;&nbsp;The supplied Spectravue software is a really good waterfall / spectrum analysis / Rx driver package, and doesn&#39;t use the soundcard at all.
</div>
<div><br>Andy&nbsp; G4JNT</div>
<div><a href="http://www.scrbg.org/g4jnt">www.scrbg.org/g4jnt</a></div>
<div>&nbsp;</div>
<div><span class="gmail_quote">On 16/01/2008, <b class="gmail_sendername">lawrence mayhead</b> &lt;<a href="mailto:laurie.mayhead@googlemail.com">laurie.mayhead@googlemail.com</a>&gt; wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">Many thanks to those who responded to my mail on the subject of receivers for LF/QRSS.<br>and my problems with my 1792.
<br>Paul Hendrik for the URL re circuits Tracey Gardner for the e&#39;bay lead, and Warren for suggestions <br>re alternative Rx&#39;s.<br>The lack of AGC OFF on DSP receivers is a worrying trend as Andy says.<br>So I have been looking around!
<br>I have flirted with the possibility of&nbsp; the Harris 590 or the Collins 2050, both have excellent specs and are non DSP, they look good,but do I want to take on another servicability problem, and they are not cheap. <br>
The Ten Tec RX340 also excellent spec. but its DSP and no AGC off. <br>The AOR 7030 is non DSP and the spec is good but operationally it is very daunting,and it won&#39;t tune in 1Hz steps and it BFO offset has only 33 steps. I am concerned about setting it up for ARGO 
etc.Any comments Alan? also I guess its coming to the end of its production.<br>So that leaves SDR receivers like the Perseus, thanks Johan, but these are digital, can the AGC be turned off? and another problem if my computer sound card is tied up&nbsp; processing&nbsp; I/Q signals can it&nbsp; also&nbsp; do the FFT analysis ? at the same time. Perhaps Andy can help?
<br>So I am still looking<br>73 Laurie.<br></blockquote></div><br><br clear="all"><br>-- <br>Andy&nbsp;&nbsp;G4JNT<br><a href="http://www.scrbg.org/g4jnt">www.scrbg.org/g4jnt</a> 

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