Originally Posted by
KG4CGC
If you use galena you only need a piece that is big enough for you to see and handle. Heat up a small piece of metal hot enough to melt some solder and drop the galena on it while keeping the heat on it. Make sure it adheres and there is enough exposed surface on top to find several connecting points or "sweet spots."
The razor blade method also works well. I don't know if it has been mentioned but a safety pin spread open with a piece of #2 pencil lead affixed to it should be used to make touch contact with the blade. The other contact on the blade should be made with wire, washers, a nut and a bolt or a small screw that you can tighten securely.
Whatever method, get creative and get a good contact. The next part are your coils. A variometer consists of two coils that side one inside the other as well as even beside each other if wound for that. The best set ups use matching coils standing side by side and spaced for a balance between sensitivity and selectivity. Use your ears! I've seen this same set up using tapped primary and secondary coils.
Remember on antennas that the more wire you can get out the better. Used television twinlead can be had for cheap if you look in the right venues. One side of course goes to the antenna side of the primary coil and the other lead goes to the ground side. This will work gangbusters. A good quality metal variable capacitor not only works well but looks good too.
Now unless you are going for that total nostalgia look, instead of headphones try an op amp and a speaker. With this op amp you can also tailor your audio response via rotary switches and have it double as an AF filter for different conditions.
Now if you really want to take it further, get into IF mixers and watch your project grow.
