"The Kaiser's Radio" #55
If I do say so myself, this set is a beauty. It also reminds me of those old German helmets, so I named this one after the Kaiser. I have to thank several of my radio friends for helping me with the parts for this design. Without them, this radio wouldn't have the look that it does.
The coil is made with magnet wire, space wound. There is a tap about 10 turns up and that is where the antenna connects. The detector is tapped at half way up the coil.
Tom Kipgen also made that knob. He is available for custom wood work, if you have that special project that needs them.
The detector stand was provided by Mike Peebles. I haven't made too many catswhisker detector radios. They are a real pain to adjust but otherwise they sure are cool. When I want to do some easy listening, I connect a 1N34A type diode across the detector. Yes, I know I am cheating!
The binding posts were made by Jon Bowers. He sent me these to photograph, and well, I forgot to return them. I had to use them for this project. Nothing else would look so good. Jon sells them. If you are interested, please send him an e-mail.
Check out that little square Faradon capacitor. It is a .001µf that is across the headphones along with a 47k ohm resistor so crystal earphones can be used with this radio.
The variable capacitor is a 365 pf type that is a "SLF" (straight line
frequency) type. These are nice because due to the shape of the capacitor plates,
the stations are more evenly spread over the 180 degree dial rotation.
This set is by no means a high selectivity dx radio. But it looks great and works well for casual listening.
One last thing. This radio is laid out for use by a left handed person, such as myself. (Ah, you knew something was different about me and now you know!) So if you make one of these, put the detector stand on the side of the radio that you are comfy with.
I found with this set, using a crystal earphone, I heard two stations plainly with a third in the background under a stronger station. By changing to my little impedance matching box using a Bogen transformer and sound powered phones, I was able to nearly double the stations heard. The selectivity was much better. So if you can go with the transformer, use it. Even if it is to the crystal earphone. In this case, the sound powered sensitivity was not as important as the selectivity boost by raising the impedance that the detector sees. If you don't want to put in a transformer, I would recommend tapping the coil at half way and connecting the detector at that point.
73 and good crystal DX. Dave - N2DS