Vectronics VEC-121K - Manual (Page 29)

VEC-121K Owner's Manual Crystal Radio Set Kit
27
This diagram shows an aerial going between a pole (or tall tree trunk) and
location where the receiver is located. A small length of lead-wire connects the
antenna to the crystal set inside of the house. (Make sure the lead-in wire makes
good electrical connection to the antenna wire!) Note the insulators between the
antenna wire and the supporting structures. A good earth ground is provided by
a short ground rod driven into the earth outside of the window where the crystal
set is located. You may make your own insulators from scraps of 1” plastic pipe,
or small sections of 1” by 6” Lexan
TM or Plexiglas TM . Drill holes at the ends of
the insulators for tie-points for the antenna wire and support rope. Clothesline is
a good way to tie the insulator to the supporting structures.
The antenna wire should not be allowed to touch leaves or rub against branches.
Doing so will affect your reception. Keep your antenna wire away from power
lines.
Finding the elusive ground
Several feet of insulated stranded hookup wire is included in your kit. This is
provided to connect a ground to the crystal set. But, what is a good ground and
how can you make or find one?
Ground rods. Many times a crystal set will work quite well without a ground
connection, especially if a very good antenna is being used. The most effective
ground is a 10 foot ground rod driven into the earth. If you have a TV antenna
on your home, it should be connected to a ground rod for lightning protection. If
it is near your operating position, you may be able to tie a wire between your
crystal set and the TV antenna ground rod. Even four or five feet length of old
copper pipe driven into the earth will do in a pinch! But, be sure you use some
sandpaper to remove any corrosion on the pipe that would prevent making a
good electrical connection to your ground wire lead in.
Water pipe grounds. If you live in an older home that uses metal instead of
plastic plumbing, you have a good ground point at the nearest water pipe or
radiator. Connect a short wire between the crystal set ground and the water pipe.
Remember that the pipe must be free of corrosion or paint to make a good
electrical connection.
Counterpoise grounds. The reason the crystal set needs a ground is because a
single wire antenna is really only one-half of a complete antenna! The ground
makes up for the missing half of the antenna, and gives the wire antenna
something to “work against”. If you have 50 or 60 feet of scrap wire laying
about, you can make what is called a “counterpoise” to serve as a ground for the
crystal set. Simply run the wire out on the ground in a straight line. The wire
needn’t be buried, it will “couple” to the earth due to “stray capacitance”.
Connect one end of the counterpoise wire to the ground Fahnstock on the crystal
set, and you’re in business!