Brian Reay wrote:
If there is a conductive path before the grease is applied does it matter?

Back in the 50's, it was common practice to smear grease on
automobile battery terminals to keep them from corroding.
--
73, Cecil http://www.qsl.net/w5dxp


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"Cecil Moore" wrote in message
...
Brian Reay wrote:
If there is a conductive path before the grease is applied does it
matter?

Back in the 50's, it was common practice to smear grease on
automobile battery terminals to keep them from corroding.

Still is in the UK. Also I assume in the USA, one of my cars was made in the
USA and came with grease on the terminals.

--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898

"Brian Reay" wrote
"Cecil Moore" wrote in message
...
Brian Reay wrote:
If there is a conductive path before the grease is applied does it
matter?

Back in the 50's, it was common practice to smear grease on
automobile battery terminals to keep them from corroding.

Still is in the UK. Also I assume in the USA, one of my cars was made in
the
USA and came with grease on the terminals.

Guys, the last time I checked, this was not rec.car.battery. We're talking
about antennas and RF, not DC connections to your car battery. Using grease,
even outside the made connection, will eventually penetrate the spaces.
Maybe this doesn't matter to the 50-100w user, but it matters to high power
connections, the most notable of which is lightning.

Jack Painter
Virginia Beach, Virginia

On Sun, 9 Jan 2005 16:35:20 -0500, "Jack Painter"
wrote:

Guys, the last time I checked, this was not rec.car.battery. We're talking
about antennas and RF, not DC connections to your car battery. Using grease,
even outside the made connection, will eventually penetrate the spaces.
Maybe this doesn't matter to the 50-100w user, but it matters to high power
connections, the most notable of which is lightning.

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

"Spike" wrote in message
...
On Sun, 9 Jan 2005 16:35:20 -0500, "Jack Painter"
wrote:

Guys, the last time I checked, this was not rec.car.battery. We're
talking
about antennas and RF, not DC connections to your car battery. Using
grease,
even outside the made connection, will eventually penetrate the spaces.
Maybe this doesn't matter to the 50-100w user, but it matters to high
power
connections, the most notable of which is lightning.

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'....


Plus, of course, the issue isn't so much the power as the current when
thinking of high resistance connections. The cranking current drawn via a
car battery terminal is around 100A. If the grease ingress caused a high
resistance connection, the car wouldn't start. In practice, ungreased
connections tend to 'go high' due to corrosion.



--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898

"Brian Reay" wrote in
:


"Spike" wrote in message
...
On Sun, 9 Jan 2005 16:35:20 -0500, "Jack Painter"
wrote:

Guys, the last time I checked, this was not rec.car.battery. We're
talking about antennas and RF, not DC connections to your car battery.
Using grease, even outside the made connection, will eventually
penetrate the spaces. Maybe this doesn't matter to the 50-100w user,
but it matters to high power connections, the most notable of which
is lightning.

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'....


Plus, of course, the issue isn't so much the power as the current when
thinking of high resistance connections. The cranking current drawn via
a car battery terminal is around 100A. If the grease ingress caused a
high resistance connection, the car wouldn't start. In practice,
ungreased connections tend to 'go high' due to corrosion.




It's not normally grease, it's vaseline, which is conductive. I don't know
how vaseline behaves at RF, though. Maybe not too well?

"Alun" wrote in message
...

Plus, of course, the issue isn't so much the power as the current when
thinking of high resistance connections. The cranking current drawn via
a car battery terminal is around 100A. If the grease ingress caused a
high resistance connection, the car wouldn't start. In practice,
ungreased connections tend to 'go high' due to corrosion.

It's not normally grease, it's vaseline, which is conductive. I don't know
how vaseline behaves at RF, though. Maybe not too well?

If it isn't in the the current path (ie between the mating surfaces) and
also not acting as an unwanted path (eg between the earth clap and the
antenna), does it matter? OK, you may get some local absortion 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.

--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898

On 10 Jan 2005 03:52:38 GMT, Alun wrote:

It's not normally grease, it's vaseline, which is conductive. I don't know
how vaseline behaves at RF, though. Maybe not too well?

What about silicon grease?


Jock.

--

"The graveyards are full of indispensable men."
- Charles de Gaulle (1890-1970)

"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