The temperature has dropped to around 10 C today. Fall is in the air. So it was appropriate for me to do some work on an old tube radio. (Several of our correspondents have reported similar seasonal urges to melt solder and to heat filaments.) This week my trusty Drake 2-B was giving me trouble on 17 meters. It was working on all other bands, but not on 17. Today I put it on the bench, pulled out the schematic and started troubleshooting. I quickly determined that the problem was, in fact, with the 22 MHz crystal. The 2-B has a 24.5 MHz rock for tuning the lower portion of the ten meter band. When I put that crystal in the "E" socket (where the 22 MHz crystal normally sits), the local oscillator worked just fine. Putting the 22 MHz rock back in the E socket resulted in no oscillation. And when I tried to the 22 MHz crystal in the 10 Meter socket normally used by the 24.5 MHz rock... nothing. What causes a perfectly good crystal to go bad like this? Consulting the 2-B manual, I saw that I could also tune the 17 meter band by using (in socket D) a 14.21 MHz crystal from my junk box (it had been used in my 20 meter NE-602 DSB. transceiver). It works great. I'm listening to DK9KW calling CQ on 17 right now. Makes me want to fix up my homebrew 17 meter transmitter. (I need a final for it, and am thinking of using Farhan's JBOT circuit). I may even buy some telescoping fishing poles and rebuild my Azorean rotate-able dipole (I have the mast and the wooden center support for the fishing poles). This magnificent antenna is shown above, spreading its wings above Sao Miguel island in the Azores (our home from 2000--2003).
Icing on the cake: I went out to the mailbox, and, instead of the usual pile of bills, there was a SPRAT 148 and the G-QRP Club's Members Handbook.
Our book: "SolderSmoke -- Global Adventures in Wireless Electronics"http://soldersmoke.com/book.htmOur coffee mugs, T-Shirts, bumper stickers: http://www.cafepress.com/SolderSmokeOur Book Store: http://astore.amazon.com/contracross-20
Oh, man. A hot cup o' java , the latest SPRAT open on the bench and the 2B inhaling along in the background. How could it get any better!
ReplyDeleteAs far as the crystal goes, when was the last time you tried that band? Before you moved? Very likely that it got bopped during shipment which dislodged the wire from the plated crystal element. I've seen it happen.
73 from the warm and sunny Left Coast.......Steve Smith WB6TNL "Snort Rosin"
VERY inspiring stuff. I hope you do fire up the homebrew 17 meter rig! I've been missing 17. It was also one of my favorite bands.
ReplyDeleteStill need to subscribe to SPRAT! I need to make that happen this weekend.