"Spike" wrote

Here in the UK I'll think you'll find the lightning conductors have
greased joints.

I always thought it was the origin of the term 'greased lightning'....

(only joking)

--
from
Aero Spike

That is funny. But since this has now become rec.batteries.car (just
kidding):

The reaction from battery acids, air and dirt are minimized with grease. But
mechanics who grease the inside of the cable-clamp and outside of the
battery post *before the connection is made* are not helping the electrical
connection - they're applying preventative maintenance for idiots - who
never clean their battery posts. Conductive paste is much more expensive
than grease. Those who know what they are doing use the former. Conductive
paste is specified in US Lightning protection (NEC-70/NFPA-780), and grease
is not allowed to be used in any mechanical connection there. Back to
antennas for a moment, we all know that grease (or conductive pate) does not
provide waterproofing of any kind. And most of you will accept that grease
is a dialectric, not a conductor. But after making a mechanical joint with
conductive paste (ensuring no air enters the joint, and conductivity remains
per the connected materials), and proper waterproofing is applied, you have
a safe and maintenance-free joint that will last for years. Or it would
anyway, if the same codes didn't require you to expose and mechanically
tighten every such joint once a year. That's why the expensive exothermic
(welding) of all grounding electrode conductor joints becomes a savings in
the long run. Unfortunately that is never practical along rooflines up on
masts and towers. So those mechanical joints must provide as little
impedance as possible, and survival of the equipment depends on this.

Because all transmitter antenna radials automatically become a part of the
lightning protection system, the materials used should be the best you could
afford, not the cheapest you can find. And the connections should likewise
be the best possible. The transmission system will be more efficient, and
safer.

Jack Painter
Virginia Beach, Virginia

Jack Painter wrote:

[...]

Jack is absolutely right about grease being non-conductive! It only
keeps air and moisture out of the areas where the metal is already
touching.

The same is true of the special conductive greases - the particles of
metal provide the conductivity, and the grease only serves to seal
around the contact surfaces.

Let's drive a stake through this stupid urban myth. Vaseline (pure soft
petroleum jelly) is a mixture of hydrocarbons, and is a very close
relative of polyethylene, polypropylene, beeswax and other well-known
insulators.

Still don't believe it?

Creak... stomp stomp stomp... medicine cabinet... jar of Vaseline...
stomp stomp stomp... multimeter... 20 megohm range... test prods... WELL
OF COURSE it's bloody non-conductive!!!!!

Two touching greased surfaces still read 20M until you grind them
together and force the grease out. And unless you DO force two greased
metal surfaces together, they will be almost perfectly insulated from
each other!

[...]

Just one further comment on Jack's posting:

Because all transmitter antenna radials automatically become a part of
the lightning protection system, the materials used should be the best
you could afford, not the cheapest you can find. And the connections
should likewise be the best possible.

In principle that is correct, but heavy-duty radials are not
cost-effective for ham installations, because there are so many of them
(even in a small system). Also, heavy-duty radials are not necessary for
the main purpose, which is RF grounding for normal operation. For a ham
installation, it seems much more realistic to install enough ground rods
to qualify as a lightning ground in their own right (as if there weren't
any radials at all). Then you can treat the radials as being purely for
RF grounding. They will of course contribute to lightning grounding, but
you don't have to rely on them for that purpose.

We're moving house, so I am just about to tear up the radial system here
- and also pull out the 8ft ground rod that goes 5-6ft into groundwater.
The next QTH will have much more space, so this discussion comes at just
the right time.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Sun, 9 Jan 2005 19:55:41 -0500, "Jack Painter"
wrote:

The reaction from battery acids, air and dirt are minimized with grease. But
mechanics who grease the inside of the cable-clamp and outside of the
battery post *before the connection is made* are not helping the electrical
connection - they're applying preventative maintenance for idiots - who
never clean their battery posts. Conductive paste is much more expensive
than grease. Those who know what they are doing use the former.

Jack, many thanks for your informative post, it was certainly an
interesting read, and deserves a response.

I'd like to quote what Brian Reay said in reply to another poster on
this topic. He said "If it isn't in the current path (i.e. between the
mating surfaces) and also not acting as an unwanted path (eg between
the earth clamp and the antenna), does it matter? OK, you may get some
local absorption of RF energy, but how much grease are you going to
use? Not enough to absorb much RF and the mass of grease (or vaseline)
will be far less than other unquantified RF conductors and absorbers
in the vicinity.

You need to look at things like this in the context of the problem."

Now I don't doubt that everyone who has contributed is right in their
own way, but look at the wider problems of the Radio Amateur's
vertical antenna that demand attention. Only having one element, it
has to work against something, which in this case is the ground or
earth. To work with some efficiency it has to make good contact with
said ground or earth, and I did some calculations elsewhere showing in
simple terms how this can vary with the ohmage of the earth path.
Hence the advice about radials wires, cost, corrosion, and all the
other things.

But this antenna has to live outside and cope with wind, rain, snow,
ice, hail, frost, dog pee, etc, the whole nine yards, and this has to
be taken into account in the design and construction phases. What you
wind up with is a compromise, and everyone's choices will likely be
different. I doubt that anyone puts up a vertical antenna designed to
cope with a lightning strike - and very many antenna designs (such as
balanced dipoles) might have either no DC earth path or only a
fortuitous one - or even a 1000 ohm resistor as a static leakage
path....it just doesn't feature as a major topic.

Just to illustrate the point about what is incorporated in antenna
designs, we've had some bad weather here in the UK over the last few
days. One amateur on here had his wire doublet aerial anchored in a
tree, which blew over in the wind. It pulled his aerial along,
together with the length of feeder to his radio. Result was everything
on the shelf was pulled off onto the floor. So although this amateur
had an off-the-shelf design of aerial, he had no snap-line in place
that would have broken when the tree went over. I'll bet there wasn't
much lightning protection either.....

It comes down at the end of the day to the art of the possible. While
a storm-proof, lightning-resistant, non-corroding, highly efficient
vertical antenna could be designed and constructed, it would cost a
fortune, and at the end of the day you'd still have 'only' a vertical
antenna - which anyway is not an all-round solution to working other
amateur stations.

I myself had a vertical antenna for some decades, the earth system of
which was constructed along the lines I mentioned elsewhere. It
withstood everything thrown at it, including the 'great storm' of 1987
with hurricane-force winds. On those occasions when licensed amateurs
used it, there was negligible fall-off in the aerial current over its
life-span, which told me that the earth system was not deteriorating.
In the end the 'maintenance' of this aerial consisted of an occasional
spray of WD40 (shock, horror) - but when finally dismantled, *all* the
mating connections were bright and tight....it served me well and I
don't think I could have asked for more.
--
from
Aero Spike

In message , Spike
writes

but when finally dismantled, *all* the
mating connections were bright and tight....it served me well and I
don't think I could have asked for more.


Remind me, Spike, what precautions you took to ensure all the
connections remained pristine.

--
73
Ian, G3NRW

On Mon, 10 Jan 2005 10:58:43 GMT, news wrote:

In message , Spike
writes

but when finally dismantled, *all* the
mating connections were bright and tight....it served me well and I
don't think I could have asked for more.

Remind me, Spike, what precautions you took to ensure all the
connections remained pristine.

The subject of great debate atm.....chassis grease. Some joints were
overtaped with Lasso tape. All got WD40'd at some time or another....
--
from
Aero Spike