Re: [linrad] A simple front end

[W6WO <ron-skelton@xxxxxxxxxxx>]

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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