This stuff is so much fun

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From: John J. McDonough (wb8rcr@arrl.net)
Date: Sat Aug 19 2000 - 08:57:04 EDT


I posted earlier about the simple 74HC240 15 meter transmitters N8ERO and I
were building. It's astonishing how well they work, but of course, being
addicted to the fumes of melting solder, we immediately had to move on to a
matching receiver.

After a certain amount of old-ladying around, we decided that an SG-8002
offset from our transmit frequency was the right choice for an LO. And
taking the simple approach, a DC receiver using the venerable 602 seemed the
ticket. One of the nice things about 15 is that there's just no QRM, so
most of the downsides to the 602, and the DC approach, just aren't an issue.

This morning, I lashed up an 8002 with a 602, hoping to see a few milivolts
out of the 602 when I excited it with some RF. I was astonished to see over
half a volt out of the 602 when I keyed my Icom.

Well, you know what comes next:

                                    | SG8002 |
                                    |7 8|-----
           | ---------- |
           | |
           | 602 -----
           | ------- .001
     ~12" -------|1 8|-Vcc -----
     wire -------|2 7| |
           | g-|3 6|-------------------------|
           | |--|4 5|--| |
           | | ------- | -----
           | | | 100
               | | -----
               | phones | |
                                                  |
                                               --------
                                               / / /

Sure 'nuff, it produces a nice tone in the cans when the Icom is keyed near
21.115. Absolutely amazing.

Now, on to the audio amp and the front end.

72/73 de WB8RCR http://members.home.com/wb8rcr/index.htm
didileydadidah QRP-L #1446 Code Warriors #35


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