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Sunday, December 12, 2010

A good radio morning at N2CQR

Today I had one of those really good ham radio mornings in the shack. My objective was to add one more amplifier stage between the balanced modulator and the power amplifier in my Roman WSPR DSB Direct Conversion transceiver. First I had to take the balanced modulator (trifilar transformer and two diodes in a singly balanced configuration) off the board and move back, closer to the AF input jack -- I needed to make space for the new amplifier stage. For that stage I consulted Doug DeMaw's books and Wes Hayward's EMRFD. I went with a feedback amp using a 2N3904 in Class A.

With coffee brewed and with my Drake 2-B tuned to the very congenial DX-60 net (75 meters AM on Sunday mornings), I turned to the junk box. It was like meeting old friends! I pulled out parts that Michael, AA1TJ had sent me. I pulled out others that had been sent by Jim, AL7RV. I got out my box of isolation pads that Jerry Felts, NR5A had sent in. Soon the parts were glued and soldered to a board that already had an AF amplifier designed by Roger Hayward, KA7EXM and a PA that is my "Manhattan-ized" version of Tony Park's SDR rig PA. At the center of the board is little Colpitts oscillator that I took from a WSPR rig designed by Gene, W3PM -- earlier in the week Gene had posted a comment on this blog saying he was pleased to see my call on his WSPR screen. I wonder if Gene realized that he was seeing the signal from an oscillator from his design! The laptop was provided by a listener who prefers to remain anonymous -- thanks OM! Nearby, a copy of "Lid, Kid, Space Cadet" by Jeff K1NSS provided encouragement.

The rig passed the smoke test so I moved it over to the operating position and put it on the air. I got immediate gratification: the WSPRnet map right away showed my signal (now around 200 milliwatts) being received all round North America. You can watch this LIVE by going to http://wsprnet.org/drupal/wsprnet/map Just plug N2CQR into the "Call" box and hit UPDATE.

I know that WSPR is not everyone's cup of tea, but I like it. It was fun to build this rig. While WSPR is almost exclusively a mode that uses store-bought equipment, I get a kick out of being one of very few ops using a homebrew transceiver in this mode. (Are there any others?)

Next steps: I need to figure out how to set up automatic switching (by the computer) from transmit to receive. And I want to make some PSK-31 contacts with this rig.

Thanks to all who contributed!

73 Bill

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