007 – License to Receive — Dave's #31 Radio
Are you one of those closet crystalsetters? You enjoy the hobby but you wouldn't want your family and friends to know you are receiving radio stations this way? This might be your answer. Disguise your set as some household item, such as a book made out of wood.
I had this box for over a year. I wanted to build a radio inside it but I didn't have the right parts. Then on a recent ebay sale, I ended up with some low profile tuning capacitors. That was all I needed. After staining and splashing some poly on the box I was ready to start.
Since I had success with a recently built tube crystal radio, I wanted to build another. This one uses a 957 acorn tube. These tubes and sockets are available all over the place. The 957 is like the more common 955 tube but with a 1.4 volt filament. This is perfect for my little book radio.
Of particular interest is the spider coil form. The coil form is made from an AOL cd. I have a special spider page describing how to make these. I used some 100/46 litz wire on this coil but 40/44 litz will also work, if you can't find the other. The inside diameter of the coil is 1-3/8 inches. The large winding is 54 turns and the small winding is 5 turns. I got a little fancy by cutting some extra slits in the form for the other winding. This isn't necessary. It is just something that I wanted to try. Later this will be helpful for dual winding coils. The coil hub hole has a grommet and a 1/2 inch piece of wood dowel is screwed to the book cover. This makes a nice looking way to attach the coil to the box.
I used a piece of 1/16 inch styrene sheet as the panel. This panel is attached by using two 5/8 inch tall wood blocks. The bottom edges were sanded down so the bottom of a T-Nut would fit without pushing up the block of wood. Check the picture and you will see what I am writing about. I like the panels on my radios to be easily removed and reattached.
There is a brass link switch on the right side of the panel. This selects between the diode and tube. When the switch is in the tube position, the filament is lit by the AA battery that is on the left side of the panel.
This set is not a high performance radio. Trying to make a super radio is a small package can be difficult. This is another fun project that I wanted to do for a while.
Best wishes and good crystal DX. Dave - N2DS