[Lowfer] Re: Sound card measurements

[Lyle Koehler]

>I have been entertaining some thoughts on "front-ending" sdradio with
>the R2 receiver (KK7B).

Probably somebody has used a variation of the R2 on LF, although it looks to
me as though it would take quite a bit of modification.

The original article January, 1993 QST article on the R2  mentions that an
R1 board was used successfully down to 25 kHz, although an SRA-3 mixer was
subsitituted for the SBL-1. You would probably also want to replace U1, the
input power splitter, with a homebrew splitter designed to pass low
frequencies. The first L-C network following the mixers in the R2 are
low-pass filters with a bandpass of about 3 kHz, so to take full advantage
of the wide frequency coverage of SDRadio, you'd need to extract the signal
directly from the mixer outputs. And I expect that you'd need to use a
different quadrature local oscillator circuit than the ones shown in the
article.

In effect, SDRadio replaces all of the R2 circuits after the mixers, so it
might be just as easy to start from scratch.

Lyle, K0LR