Hi Ty!
Thanks for your ideas. I am committed to finding the problem.
I have tried all of the bonding ideas you mentioned. I think N3RS has tried all
of them as well.
I have disconnected the control wiring and there is still terrible harmonic
generated noise. The
problem seems to be exacerbated by the closeness of the two towers. In N3RS's
case it is 127 feet
and 40 into 20 meters. In my case it is 140 feet and 20 into 10 meters.
Turning the rotor by hand also makes the same noise and harmonic issues.
I think the problem may exist in the guide pulleys. They have black (contains
carbon, which is
conductive at radio frequencies) insulating material between the 2 sections of
these rotating
pulleys. 3 of them are used on each ring. The black carbon may set up a diode
which for some
reason bypassing with heavy wire from the boom of the antenna to the tower
cannot fix. These
"pulley diodes" may be the cause of the noise and the terrible harmonic problem
in close
proximity ring rotated antennas.
That is my current hypothesis which also is where N3RS is in his testing.
I will not stop working on this until it is fixed, however we are running out
of places to look.
These problems are always tough the first time!
Any other suggestions???
73!
Tim K3LR
tgstewart@pepco.com wrote:
> Have you tried bonding the ring to the motor as a test? How about the boom
> to the ring as well?
>
> Another thing perhaps worth trying is to isolate both the control wiring
> and/or control box from the rotator.
>
> Have you tried disengaging the motor and turning the ring by hand to see
> what that does?
>
> I cant believe K3LR hasnt solved this problem! :)
>
> 73, Ty K3MM
>
>
> "R. Sigismonti"
> <n3rs@snip.net> To:
> towertalk@contesting.com
> Sent by: cc:
> owner-towertalk@cont Subject: Re: [TowerTalk]
> Tic Ring problem
> esting.com
>
>
> 01/22/2001 02:50 PM
>
>
>
> >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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>
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