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Date: Tue, 5 Oct 2010 16:50:46 +0100
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From: Andy Talbot <andy.g4jnt@googlemail.com>
To: rsgb_lf_group@blacksheep.org, sub9khz@yahoogroups.com
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Subject: LF: Remote LF Rx
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I've been following the VLF receiver threads with interest, particularly the
need for remote operation to get away from noise.
How much interest would there be in a digital remote receiver, linked via a
UHF amateur band - or possibly the 868MHz / 2.4GHz licence-free band for
SWLs?

16 bit sigma-delta  A/D converters cost peanuts these days, and the
resulting data could be streamed over 1.3 or 2.3GHz with low cost equipment
and simple modulation.    Or perhaps an optical link

The ADS1113 A/D converter, for example, is specified for sample rates up
860kB/s, so in theory could even cope with 137kHz reception.
However, for anything above audio I'd be inclined to downconvert first to
get to a lower sampling rate to allow a more sensible link cpability.   137
and 503 witj their narrow bandwidths could be converted without much
difficulty.   The output data rate is going to approach 1MB/s which is
nothing for the 1.3/2.4GHz UHF modules that have been used by the Am TV
community

One thing to watch out for is going to be frequency stability for very
narrow band signalling.   The remote  A/D and downconverter will have to use
a high stability reference - at least a TCXO for 1ppm stability.   Which is
better than most sound cards anyway.

At the receiver end, you could either have a D/A converter for a transparant
link, or find some way of reading the digits straight in - making them look
like a .WAV file may be one way.

A kit may be feasible
Thoughts please.

Andy
www.g4jnt.com

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<div>I&#39;ve been following the VLF receiver threads with interest, parti=
cularly the need for remote operation to get away from noise.=A0 </div>
<div>How much interest would there be in a digital remote receiver, linked=
 via a UHF amateur band - or possibly the 868MHz / 2.4GHz=A0licence-free=
 band=A0for SWLs?=A0=A0 </div>
<div>=A0</div>
<div>16 bit sigma-delta=A0 A/D converters cost peanuts these days, and the=
 resulting data could be streamed over 1.3 or 2.3GHz with low cost equipme=
nt and simple modulation.=A0=A0=A0 Or perhaps an optical link </div>
<div>=A0</div>
<div>The ADS1113 A/D converter, for example,=A0is specified for=A0sample=
 rates up 860kB/s, so in theory could even cope with 137kHz reception.=A0<=
/div>
<div>However, for anything above audio I&#39;d be inclined to downconvert=
 first to get to a lower sampling rate to allow a more sensible link cpabi=
lity.=A0=A0 137 and 503 witj their narrow bandwidths could be converted wi=
thout much difficulty.=A0=A0 The output data rate is going to approach 1MB=
/s which is nothing for the 1.3/2.4GHz UHF modules that have been used by=
 the Am TV community</div>

<div>=A0</div>
<div>One thing to watch out for=A0is going to be frequency stability for=
 very narrow band signalling.=A0=A0 The remote=A0 A/D and downconverter wi=
ll have to use a high stability reference - at least a TCXO for 1ppm stabi=
lity.=A0=A0 Which is better than most sound cards anyway.</div>

<div>=A0</div>
<div>At the receiver end, you could either have a D/A converter for a tran=
sparant link, or find some way of reading the digits straight in - making=
 them look like a .WAV file may be one way.=A0</div>
<div>=A0</div>
<div>A kit may be feasible</div>
<div>Thoughts please.=A0=A0=A0</div>
<div><br clear=3D"all">Andy<br><a href=3D"http://www.g4jnt.com">www.g4jnt.=
com</a><br></div>

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