Bobik

Please click here for schematic

Bobik is an 80m CW transmitter built from a pair of (circa-1976) Soviet-made tunnel diodes. The circuit is a push-pull LC oscillator; frequency-locked to a quartz-crystal. The oscillator output feeds a 51 Ohm resistor while I'm receiving. When the key is depressed the signal is diode-switched into the antenna. On the first night of operation Bobik worked seven stations!


Station          His    My       QTH                   Distance       Output Power

AA1MY      589   569    Bethel, ME              162km         12mW
VE3DJX      569   439   Smiths Falls, ON      274km         12mW
W1PID        589   449   Sanbornton, NH       112km         12mW
W2SH         559   339   Millington, NJ           405km         12mW
W4AG        599    449   Hillsborough, NC   1038km         10mW
KB1KGA   579    329   Mt. Vernon, NH       152km         10mW
W4OP        599    449   Glenville, NC          1329km        10mW

I made this recording of Bobik's signal from W1TXT's web receiver; located 245km from my QTH. 


Everybody knows Laika; the original Soviet space dog, but when I read that Bobik ran away several days before her scheduled launch I decided to name my transmitter after her. Smart girl...Bobik!
(BTW, a hastily located replacement was named "ZIB," the Russian acronym for "Substitute for Missing Bobik" (Zamena ischeznuvshemu Bobiku).

Bobik Breadboard Photo

Here's the arrangement used for the above QSOs. The tunnel diodes are soldered to little "Manhattan" carriers.



Package of type-3I201L tunnel diodes
 
The GaAs, type-3I201L tunnel diodes arrived from Mother Russia still sealed in their original factory cellophane.


Data about various diodes
 
Comments

"Hi Mike, Sorry my CW was a bit shakey- I was too excited to send well. Great QSO. I can hardly believe we completed. I had only been listening for less than 2 minutes before calling you!" Dale, W4OP

"Just worked Mike with a 5/6/9 sig to my 5/8/9 -nice and clean sounding....Go get 'em!" Seab, AA1MY

"You're coming in nicely at 559/569, and the European QRM has gone." Charles, W2SH

"Bobik is S9 at 4:12 pm local." Jim, W1PID

"...Mike, I must to little correct you. The dog's name is Bobik (not Bolik)." Oleg, RV3GM  (Tnx Oleg...my goof!)


Homebrew QRP                                                                                                                                                              de AA1TJ