Progress continues on my WSPR direct conversion receiver. The Colpitts oscillator is working nicely and is very stable. Yesterday I glued an SBL-3 diode ring to the board and hooked it up. With my 'scope and sig generator I can see it turning 30 meter RF into audio. So far so good.
Now it is time to build the AF amp. Here's my question: How many db do I need? The standard 100 db DC RX AF Amp seems like a bit of overkill -- this thing won't drive a speaker or a headphone, but instead, a computer soundcard. What do you guys think? How many db?
Monday, April 5, 2010
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Bill,
ReplyDeleteFrom what I have seen, 40-50 dB of gain will do the trick. You might want to go for 50 dB since you are using a diode ring. A NE5532 with two 25 dB gain stages would do nicely. And if you find that you need a bit more oomph, you can always just change some resistors to get more gain.
73,
Jason NT7S