[OKDXA] Lightning Protection For Thrust Bearing

[D C _Mac_ Macdonald]

Hi, Mark.

I think your home brew solution is probably my best option.

I am thinking about using highly flexible welding cable for
the conductor between mast and tower leg.

I wonder how long the connection between the copper cable
and aluminum tower and mast would survive with dissimilar
metals.  Now that I think of it, DX Engineering has interfaces
between copper grounding straps and aluminum or steel towers
that would probably suffice very well.  I already have three of
those to tie ground rods to tower legs (not yet installed.  Two
of those would probably serve well for my purpose.

What do you think?

73 - Mac, K2GKK/5
Since 30 Nov 1953
Oklahoma City, OK
USAF (Retired) 61-81
FAA (Retired) 94-10


________________________________
From: okdxa-bounces at mailman.qth.net <okdxa-bounces at mailman.qth.net> on behalf of Mark Beckwith <dad at megansfamily.net>
Sent: Monday, October 4, 2021 20:06
To: Oklahoma DX Association <okdxa at mailman.qth.net>
Subject: Re: [OKDXA] Lightning Protection For Thrust Bearing

I had not heard of bypassing the thrust bearing as a lightning damage
abatement technique.  I believe this kit is sold to solve the common
problem many hams have where a dirty connection between the mast and the
tower is a source of rectification/mixing/intermod that makes it hard to
copy DX stations.  I think what really matters is shorting across any
pseudo-diode that might be present (i.e. dirt, grease, corrosion).  I
don't think it matters how you do it as long as one end is attached to
the mast and the other end is attached to the tower.  I'm guessing that
would also short out static buildup. If it was me (I have done this once
or twice by making my own) I would go from the mast close to the top of
the tower to the tower close to the top of the tower, and do it in a way
where it didn't mess up when you turned the antenna.  I can see from the
DX Engineering listing, their design does not rely on having this conductor
be "as short as possible" since they appear to provide enough conductor
to go parallel to your coax feedline loop.

I think I made mine with muffler clamps and battery cables.  I'm sure
the DX Engineering one is better.

Come to think of it, a lightning strike would probably also fix any
rectification/mixing/intermod issue  ;-)

73 - Mark N5OT

On 2021-10-04 6:29 PM, D C _Mac_ Macdonald wrote:
> DX Engineering has a by-pass kit to direct
> a lightning strike from the mast above the
> tower top to a location on a tower leg.  This
> kit shows the thrust bearing on a flat plate
> at the top of the tower.  I have my thrust
> bearing mounted down inside the tower about
> 6 feet to carry the load of the mast & antennas
> with the rotator another 6 feet below that which
> carries no dead weight load at all.  This allows
> for the removal and reinstallation of the rotator
> without disturbing the rest of the antenna systems.
>
> Do I need to have a similar system with a shorter
> cable to tie the mast down to a spot on a tower leg?
> The mast has no direct solid connection to the tower
> other than the tube in which the mast rotates.
>
> I believe I could (if necessary) replace the bearing
> by removing the rotator, detaching the bearing from
> its mounting plate, moving that mount plate down
> through the now free mast bottom, and then the
> thrust bearing itself.
>
> Ideas/suggestions welcome.
>
> 73 - Mac, K2GKK/5
> Since 30 Nov 1953
> Oklahoma City, OK
> USAF (Retired) 61-81
> FAA (Retired) 94-10