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by OH6DC
Built in year 2010, this was my first ever building project using vacuum tubes.
The basic design was taken from these sources:
http://nmwilliam.tripod.com/el84.html (by VU3GAO)
http://www.dl9eba.de/qrp1.html (by DL9EBA)
I found an EL86 audio amp tube from an old junked BC radio, as well as a power transformer.
The cabinets are recycled from old PC power supplies.
Click the pictures below to enlarge them.
Looks like a nuclear power plant but is not. The upper box houses the transmitter. I wanted to see (and show) the tube, so I placed it on top. XTAL holder is located in front of it. Power supply with mains switch is in the box below.
Backside view. No cooling fans in cabinets.
Inside of the power supply. The high voltage output is about 240 volts (unloaded). Felt a bit dangerous after all those 12 V projects...
Transmitter opened and upside down. The tube socket is located in the middle. The tank coil was wound around a piece of plastic vitamin tablet tube. It is unknown to me if the remaining vitamin particles increase the coil's Q-value or not.
Real radios glow in the dark!
This red LED indicates plate current when the key is pressed. Power output is about 5 W on 3.5 MHz.
Transmitter schematics (click to enlarge).
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