shack2.art

一个很小和天线计算程序

SUBJECT: Amateur Radio Shack Designs, part 2

GROUNDING:  The ground system to your shack is as important as the
electrical system. But, keep in mind that are two ground systems 
here. First, there is the electrical ground which concerns your power 
system and second, there is the RF ground.  In most Ham Shacks these 
two grounding systems are separate and sometimes by a considerable 
distance in relation to your shack/home.

    The grounding hole in the electrical socket (see figure 1) is NOT 
an RF grounding point!

    Figure 1:             o  <-------- Ground
                         | |
                         ^ ^
                         | |__________ Neutral (Large slot)
                         | 
                         |____________ Hot (Small slot)

    This arrangement may be inverted in you home/shack.  I prefer to 
see where the ground plugs in first being a rather tall individual.
Neutral is basically at ground potential and a meter reading with a 
VOM will show little or no votage potential difference between ground 
and neutral. Ground to hot or neutral to hot will exhibit 115VAC 
(pluss or minus the normal variations from you local power and light 
company).  The reason you DO NOT want to use the electrical ground 
for your radio shack is that there is potential for this ground to 
carry an electrical potential!  Also, this ground can be up to 100 
feet from the socket in a house and up to 600 feet or more in an 
apartment complex! Holy longwire, Batman! And that ground is 
connected to many other people's dwellings!  Holy Bitch and Gripe
from the neighbors, Batman!

              ****************************************

    I have gone to many a ham's homes on RFI problems only to find 
their favorite grounding point is the commercial ground.  I remove it 
and have them run a separate ground.  The RFI goes away.  Please keep 
this in mind.

              ****************************************

    Your RF ground should also be a central point, BUT NOT THE 
COMMERCIAL GROUND!  Single point grounding is the best bet to keep 
RFI under control, provides a point where there is no DC potential, 
and provides the shortest point to ground for the transceivers and 
antennas.  When you consider your shack design, locate the ground 
such that the run is as short as possible.  In apartments, a cold 
water pipe beats no ground at all and beats the commercial ground 
by a mile. Be sure to check that the commercial ground is not the 
cold water pipe also (This I've seen many times, $$ savings during 
construction). 

Grounding Layout: Again, I'll use my shack as the example.
                                                            |
                                                            |  Tower
                                                            |    X
    ---------------------------------------------------------    |
                                |                -----------|----|
                                |              Ground wire  |
                                |                           |
                                |                           |
                                |                           |
                                |                           |
                                |                           |
                                |                           |
                                |                           |
                                |---------------------------|
                                                            |
    The ground Wire is a #6 Copper wire connected to a 10 foot ground 
rod into the water table (Florida water table is 4 ft). The tower is 
also connected to the same ground point.  The ground rod is located 
next to the tower as close as possible outside the cement base.  The 
base is a 1946 design ground distribution system and is electrical 
connected to the ground rod. All equipment from VHF to HF linears are 
connected to the system at on point in the shack and one point in the 
ground.  DC potential is zero.


-WS