>The problem is not noise caused by the motor. The noise filter at
>the motor does a good
>job, except when the capacitors blow (which has only happened on my
>10 meter tower).
>
>N3RS verified that there is significant noise caused when the ring
>turns, even when turned manually (take the motor off the tower).
Not only is the noise not caused by the motor, it is even there when
there is no motor action at all. We have a very aggravated case of
this noise problem here at N3RS. We have a 3 stack of 20M 5 element
yagis on TIC rings and a 3 element 40M yagi just 127 feet away. When
the 40M yagi is pointed at the 20M TIC rings we get a wideband noise
on 20M that is centered on the harmonic of the 40M signal. The 40M
station has all sorts of filtering and is not the cause of the noise.
This has also been verified by K3WU, who lives less than a mile from
me. He listened to both the fundamental and second harmonic of the
40M signal and it is absolutely clean. The second harmonic was very
weak as well.
Two weeks ago we determined that the noise is not being generated by
anything on the antennas themselves. This was done by shaking the
elements while transmitting on 40M. We also checked all RF
contacts/connections at the same time. We did notice a very strong
correlation between noise generation and gentle rocking of the TIC
rings. We believe that we are getting reasonably substantial
currents in the circuit comprised of the 20M yagi/TIC ring/tower
system. This is induced current from the 40M near field signal.
This current is flowing through a rather poorly connected and
weathered set of surfaces, some of which may be generating the
harmonics.
Noise is also generated when we transmit on 20M and turn the rings at
the same time. The assumption here is that there is current induced
in the rings by the 20M signal itself. This noise can be heard on
other bands as well.
ASAP we plan to insulate the 20M yagis from the ring assembly,
thereby reducing the current that is likely to flow through the
rotating mechanism in the ring. There are several metal-metal
surfaces that are not in good contact at all times in the assembly
and some of the galvanized surface on the rings has become quite
tarnished. We will post any results we get as a result of
introducing the insulation between the ring cradle and the 20M booms.
73's de Sig, N3RS
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