Envelope-to: dave@picks.force9.co.uk
Delivery-date: Wed, 15 Feb 2006 21:36:43 +0000
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Date: Wed, 15 Feb 2006 21:37:08 +0000
From: Wolf DL4YHF <dl4yhf@freenet.de>
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To: rsgb_lf_group@blacksheep.org
References: <021520061715.18320.43F361A7000959930000479022007613940B97010D0A020E06979D0E03@comcast.net> <43F369DE.3080405@usa.net>
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Subject: Re: LF: Re: DSP Question I/Q inputs?
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Hi Warren,

Just returned from a QRL trip to Bavaria so sorry for the delay.

Not much to add to what Alberto said.. it's nice to have I/Q output from 
the frontend of an image-cancelling DC receiver, and to effectively 
double the bandwidth of the soundcard input (for example, observe a 96 
kHz wide spectrum band if the soundcard supports a true sample rate of 
96 kSamples per second). But for LF... well ..

To decode a PSK(31) signal from such a receiver, you could use SpecLab 
with I/Q inputs (stereo mode), use the mixer/multiplier block in "I/Q" 
mode to convert the signal back into a single-channel audio signal (can 
be done but tricky to set up; please ask if you need further 
instructions).  The PSK decoder (aka "digimode terminal") must be 
connected to label L5 in the circuit diagram, after combining the 
downconverted I- and Q channels.

Cheers,
  Wolf .