The Tuna Tin 2 is a simple transmitter originally designed by the legendary author and experimenter Doug DeMaw, W1FB. The TT2 was first published in the May 1976 issue of QST. Doug's intent was to put forth a design for a low cost QRP transmitter that could be duplicated easily using parts obtained locally from Radio Shack.
The original TT2 was built in a tuna fish can and used two transistors, hence the name Tuna Tin 2. It used a crystal oscillator and a power amplifier stage and was capable of producing about 350 milliwatts of 40 meter RF energy.
In 1996, Doug Hendricks, KI6DS (of NorCal fame), started work on building a TT2 transmitter. He soon discovered that some of the parts specified by W1FB back in 1976 were not available any more. He contacted Dave Mecham, W6EMD who agreed to update the design to modern, available parts. KI6DS and W6EMD updated the circuit and designed the round printed circuit board that you see in the photograph above.
Kits for building the Tuna Tin 2 are currently available from the Maine QRP Group. Included in the kits are the circuit board and all board mounted components. They also include a crystal for 7040 KHz . The builder provides the tuna can chassis, the toggle switch plus the antenna and power connectors.
The WØCH Tuna Tin 2 in the photograph was built from the kit worked the first time on power up and produces 250 milliwatts of RF power.
There are a few modifications available to improve the TT2 transmitter. I have added a keying transistor below the circuit board to eliminate chirp.
Another modification that I have made is to use a DPDT toggle switch for T/R switching instead of the specified SPDT switch. One side of the switch is used to transfer the antenna between the transmitter and the receiver. The other side of the switch is used to control the 12 volt power to the amplifier stage. I felt that since the simple design has no SWR protection for the PA transistor, it would not be wise to key the transmitter without a load connected. In the receive position, the 12 volt buss is disconnected from the 2N2222 final amplifier stage. Pressing the key only results in the oscillator turning on, which is useful for spotting purposes.
A third modification was to use a crystal socket made from an integrated circuit (IC) socket.
Finally, I added a Shottky reverse polarity protection diode to the 12 volt power input circuit.
With a good antenna connected, these little transmitters are capable of working clear across the continent. Steve, VE7SL, in British Columbia has completed WAS (Worked All States) using his TT2 on 40 meters. On December 9, 2000 Steve worked Wyoming for his 50th state with the little rig that he is holding. This is the first WAS in history with a Tuna Tin 2 and is an outstanding accomplishment for 400 milliwatts and a single crystal on 40 meters.
I had the pleasure of having a 2-way Tuna Tin 2 QSO with Steve on November 4, 2000. Steve can occasionally be found on 7040.2 KHz looking for QSO's. Give him a call and work a really great operator.
Steve McDonald VE7SL
Tuna Tin 2 links:
Updated April 26, 2004