Cigar Box 6 Watt Output Transmitter

In front of my SX101a and HT32 is the little QRP rig and Cigar box power supply,
better known as the  CB-1 and the CB-PS.

The story behind this transmitter may be a little different that you have heard before, but this is how the idea for the CB-1 began.
About two years ago I was back in Potter County, Penn. where I grew up walking around the ten acres I now own when I came across a old dump (landfill) my family had used back in the fifties. In those days I was a teenager and my Dad ran a small TV repair shop. As I looked over the contents I spotted an old RCA TV, one of those that it was cheaper to throw away than fix. Then I looked closer at it and saw that some of the tubes were sill intact and in their sockets. I wondered what tubes were in it and started to look even closer. Then I saw what looked like a 6V6GT (audio output). I reached down and tried to pull it out. When it was free it still had some of the socket attached. Now I had the tube in my hand. What was I going to do with it? Then the idea struck me, "why not see if it still had emission and if so how much?"

All Hams' junk boxes are filled with unknown parts anyway, so I put the tube in my pocket. I kept looking around while I was laughing at myself and trying to figure out what I would do with it if it was good. I then saw an old radio with the wood case all decayed. You guessed it, some of the original tubes were still there. I pulled all of them and stuck them in the pocket along with the 6V6. They were all eight pin and all were metal. One had the partial number on it that looked like it could be a 6C5.

Later that day I was talking with one of my brothers ( I think it was my brother Paul) and told him what I had found. He laughed and asked me what I was going to do with some old tubes that wouldn't work anyway. He went on to tell me that the tubes had been in that dump for almost 40 years and how could any of them be in working order. That sounded like a challenge to me so then I knew if there was any emission at all I was going to build something with them.

During the 250 mile drive back home to Maryland I kept thinking about what I could do with a 6V6. Then I remembered that back when I was a Novice I had tried to build a small transmitter with a 6V6 and could never get it to work. Well that was it! I was going to build a QRP CW transmitter just like that one, but this time it will work with a 40 year old tube from a dump. I remembered that I had started with a cigar box and the coils were wound on hair rollers. It was all coming back to me now. I also remembered how mad my sister and mother had gotten when they found out what I had done with some of their hair rollers.

A couple of days after I was home I tested the filaments (ohm meter) in all the tubes and they were all good. This means there was a low resistance between 7 and 2 in all the tubes. I then set up a test fixture and turned on about half voltage to the filaments. I could see a faint glow in the 6V6 and all the metal ones were drawing current. I left the voltage low for about two or three days. I'm not sure if I had to, but I loved looking at the glow and was afraid if I put full voltage on that it would glow no more.

While this was going on, I found two old cigar boxes that I had been using to store junk box parts in. I found some resistors, caps and two 2.5 MH chokes. This would be enough to start with. But this time I went to the drugstore and bought my own hair rollers. Although Maggi (my XYL)  is very understanding, I was not going to take any chances and use some of her hair rollers. The day I brought the hair rollers home she seemed to wonder if I was changing my life style or what, but she knows that I am a Ham Radio type of guy and to expect almost anything.

The day came when I had to turn up the voltage on the tubes filaments, so with a trembling hand I turned up the voltage and the glow was still there... "HOT DAMN"  There might be a chance I can make this transmitter work! However, I didn't have a tube tester so how was I going to test the tubes for emission?

Looking around the shack for ideas I could use to test the 6V6, I saw an old radio that used a 6V6 in the audio out. Well in desperation I could put my "40 year old dump" 6V6 in there and hope for the best. Well folks, that's what I did and the music from that old Philco never sounded better. I quickly went to work putting the proper holes in the cigar box to the beat of the country and western music from the old Philco with its forty year old audioout 6V6.

It took about two more nights to complete the transmitter but this time it worked. It must have been the hair rollers or something that makes this one work.

The circuit was never put down on paper but someday I will draw a print ( I always say that).  For now I am having too much fun burning a hole on the low end of 40 and 80 meter CW with 6
watts output. I never went back and told my brother what I did with that pocket full of old tubes but one would have to be a Ham to understand.

Below is a picture of the top inside of the Cigar box transmitter.

All parts other than the tubes and coil forms (hair rollers) are from my junk box. The diameter of the hair rollers is 1.25 inches and cost about two dollars at your local drugstore. I used four rollers in all to cover both 80 and 40. In operation (key down), the 6V6 has about 300 volts on the plate and draws about 35 ma of current. The 6C5 that is in the osc. stage is one of the tubes from the old radio in the dump and is a little weak but does the job of driving the 6V6 to full output.


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