Radio interference by transmitters is quite common in a number of other =
applications. There are several factors that come to mind:
1. The power output of the transmitter leaks into the circuit due to =
proximity i.e. next door to a high power station.
2. The wiring of the circuit suffering the interference be close to the =
wavelength of the transmitting frequency.
3. The lack of shielding in the circuit being interfered with.
4. The harmonics - i.e. multiples or submultiples is a simple term for =
this -  from the transmitter leaking into the circuit.

You can find yourself chasing your tail on this. Here is a suggestion:
1. Shielded cable - but watch out - your shield can act as a receiving =
antenna as well. If you are still suffering try and lift the ground =
connection on one end of the shield. You could have a ground loop =
arrangement. Sometimes you get better results with the ground be =
attached to one end of the circuit. There are decoupling devices to =
prevent ground loops.
2. Ferrite beads are a great help in eliminating interference. You place =
a number of small beads on each wire and the beads act as a filter. If =
you notice on some computer wiring that you will see a drum like device =
on the ends of cables, this is a large ferrite bead. You can also try =
this method.

The worst offender for interference is cheap fluorescent lighting from =
home centers. These buggers can really mess things up. You can try =
grounding the fixture to see what happens but you still notice some =
buzzing. You shop some surplus outlets and might find some Navy surplus =
shielded fluorescent light fixtures and these might help. You can also =
try placing metal mesh over the light to see if this also helps out.








Radio interference by transmitters is =
quite common=20
in a number of other applications. There are several factors that come =
to=20
mind:
1. The power output of the transmitter =
leaks into=20
the circuit due to proximity i.e. next door to a high power=20
station.
2. The wiring of the circuit suffering =
the=20
interference be close to the wavelength of the transmitting=20
frequency.
3. The lack of shielding in the circuit =
being=20
interfered with.
4. The harmonics - i.e. multiples or =
submultiples=20
is a simple term for this -  from the transmitter leaking into the=20
circuit.
 
You can find yourself chasing your tail =
on this.=20
Here is a suggestion:
1. Shielded cable - but watch out - =
your shield can=20
act as a receiving antenna as well. If you are still suffering try and =
lift the=20
ground connection on one end of the shield. You could have a ground loop =

arrangement. Sometimes you get better results with the ground be =
attached to one=20
end of the circuit. There are decoupling devices to prevent ground=20
loops.
2. Ferrite beads are a great help in =
eliminating=20
interference. You place a number of small beads on each wire and the =
beads act=20
as a filter. If you notice on some computer wiring that you will see a =
drum like=20
device on the ends of cables, this is a large ferrite bead. You can also =
try=20
this method.
 
The worst offender for interference is =
cheap=20
fluorescent lighting from home centers. These buggers can really mess =
things up.=20
You can try grounding the fixture to see what happens but you still =
notice some=20
buzzing. You shop some surplus outlets and might find some Navy surplus =
shielded=20
fluorescent light fixtures and these might help. You can also try =
placing metal=20
mesh over the light to see if this also helps out.
 
Jim Santee