[TowerTalk] Tic Ring problem

[R. Sigismonti]

>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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