Re: [linrad] A simple front end

[W6WO <ron-skelton@xxxxxxxxxxxxxxx]

Thanks Roger, nothing so valuable as practical advice HI.  I was 
pleased to find that there is a DIP version of the AD797 and from its 
specs it it truly a very fine component. As it is such a wideband 
device I would ask if there any merit in limiting the bandwidth into 
the sound card?


> If you want only the lower 25 KHz then you don't need quadrature 
> detection and can
> get that with just an ordinary soundblaster type card running at 
> 44100 HZ sampling
> rate.
>
> to play around just do this:
>
> Direct conversion:
>
> antenna to
>
> [RF amp if needed] to
>
> TUF-1 to
>
> single AD797 to sound card
>
>
> or dual conversion like I did, but omitting the crystal filter to 
> start.  As you
> know, if you omit the filter you will then have images to worry 
> about, twice the
> noise, etc, but for quick and dirty it will work.  I know because I 
> played with it.
>
> Try:
>
> antenna to
>
> [RF amp if needed] to
>
> TUF-1 to
>
> simple single transistor or ERA or MAR 1st IF amp to
>
> second TUF-1 to
>
> AD797 or other baseband amp to
>
> soundcard.
>
> You can make it as simple as you want and add the extra pieces 
> later.  I had a lot of
> fun doing this and seeing what the practical effects of adding / 
> changing filters
> were, etc., as I am not an electronics person and so it was all 'new 
> territory' to
> me.
>
> 73,
>
> Roger
> W3SZ
> ----- Original Message Follows -----
> >  Thank you all for the suggestions regarding a simple front end. Many
> >  of you are aiming much higher than I am. My operation is almost
> >  exclusively in the low 25 kHz end of 20 meters so I am not seeking
> >  wide bandwidths and given the inherent atmospheric noise I am not
> >  seeking VHF noise performance.
>
> 73,
> Roger Rehr
> W3SZ
> FN20ah
> http://www.qsl.net/w3sz


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