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Re: [linrad] A simple front end

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

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.


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


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


----- 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.

Roger Rehr