[Lowfer] DSP IF receiver update

[Lyle Koehler]

I added some new stuff to my article at
http://www.qsl.net/k0lr/SW-RX/sw-rx.htm

The additions include a brief discussion on using the simple downconverter
with Alberto's SDRadio software, "dual watch" operation with Spectrum Lab,
varactor tuning for the input circuit, and a spreadsheet to help calculate
LO frequency settings, etc.

When Roger, Bryce, Mike and Bill were here last weekend, they got a chance
to see and hear a demonstration of the "dual watch" feature. The whole
receiver consisted of a little converter box feeding the sound card, and it
was monitoring two LowFER frequencies at once. One way of checking for the
"loners" while keeping an eye and/or an ear on the watering hole...

Lyle, K0LR