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Date: Mon, 25 Jan 2016 14:23:14 +0100
From: DK7FC <selberdenken@posteo.de>
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References: <CAA8k23QbbgxAK2o70Q=orhXEjxgEiAB6ptmVX+_zX6zMe--bnw@mail.gmail.com> <Pine.LNX.4.64.1601251349010.27152@paranoid.lipkowski.org>
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Subject: Re: LF: Direct Upconversion from audio
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Hi Jacek,

What you describe is exactly what i'm doing here.
BTW i had to slightly modify the LO (xtal) circuit because it didn't 
start to oscillate at low temperatures (now proved at -20 C!). Now it 
consumes just 0.4 mA at 5 V DC, so quite acceptable for modern standards 
i find.

73, Stefan

PS: You forgot the 2x 4CX1500 in class-A mode for TXing :-)

Am 25.01.2016 14:10, schrieb Jacek Lipkowski:
> Hello,
>
> Why not try it another way: in software upconvert the audio to 20kHz 
> (or 40kHz if you have a 96kHz sound card), mix up to 136kHz or 472kHz 
> and filter out the remaining sideband which is 40kHz away (or 80kHz). 
> You can play with an image suppressing mixer here if you want, but an 
> LC filter should be sufficient.
>
> And if you want to use this also for receiving, then you can do it in 
> the opposite direction: downconvert to 20kHz, then downconvert to 
> audio in software.
>
> The upconversion/downconversion to 20kHz IF can be easily done in 
> software.
>
> Some programs can be persuaded to just tx at this frequency (so no 
> up/down conversion). Many programs are opensource, so this would be a 
> matter of a simple hack to change the tx frequency.
>
> Others (the ones which can't be easily hacked to tx at 20kHz) can be 
> up/down converted via external software. Under linux i would use 
> gnuradio and pulseaudio (to route the audio from the program to 
> gnuradio input). Under windows the same could probably be done with 
> Spectrum Lab and virtual audio cable.
>
> This leaves us with an NE612, some LC filtering and a crystal (the 
> upconverter can be made tunable, and the bands are narrow, so we can 
> use a fixed frequency source). Seems easier.
>
> VY 73
>
> Jacek / SQ5BPF
>
>