In article ,
Ian Jackson wrote:

I have used silicone grease, but WD40 is more-readily available. It also
wets better, and creeps into the hidden nooks and crannies. I give
everything a good dowsing before and after assembly,

Wouldn't that tend to *increase* water infiltration rather than reduce
it?

grin

--
Dave Platt AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

I have used silicone grease, but WD40 is more-readily available. It also
wets better, and creeps into the hidden nooks and crannies. I give
everything a good dowsing before and after assembly,

At one time I thought silicone grease would save wear on N connectors until
I used the spray on wattmeter slugs and found it completely insulated the
shell contact. I since found it caused an SWR hump on N connectors even if
it were just a spot on the threads.

"JB" wrote in message
...

At one time I thought silicone grease would save wear on N
connectors until I used the spray on wattmeter slugs and found it
completely insulated the shell contact. I since found it caused
an SWR hump on N connectors even if it were just a spot on the
threads.

I could see where the thin silicone coating might be an insulator to the
low voltages from the wattmeter slubs, but I find the second statement
exceptionally hard to believe. In type N (and even BNC) connectors, the
threads (or the bayonet connection) are not in the RF path. Look close at
either type of male connector and note that there is a coaxial shield
around the center pin. This shield presses against the inside wall of the
jack providing a continuation of the coaxial line. The threads (or the
bayonet connection) merely provides a sturdy mechanical connection. This
what gives the type N and BNC connectors a constant impedance, and what
makes them far superior to UHF connectors. It also allows the use of a
rubber washer to make the connector waterproof.

In one of my instrumentation applications, I had to use N connectors made
of 304 stainless for corrosion resistance and high temperatures. Ceramic
and glass insulation was used within the connectors. The female jacks were
welded in place and rated to withstand pressures of up to 100 PSIG.
Stainless is quite bad about galling, and these connectors cost plenty, so
a silver paste was used to lubricate the threads. One day, I had to make
an "emergency" repair in the field and did not have the silver paste; so I
used PTFE thread seal tape instead. Going back to my lab, I tested a few
connectors with the thread seal tape using a Tek 1502 time domain
reflectometer. Even with several layers of PTFE tape, I was unable to see
any difference in the impedance through the connector. Since the
application was always less than 200°C, we quit using the silver paste.

--
73, Dr. Barry L. Ornitz WA4VZQ

[transpose digits to reply]

Dr. Barry L. Ornitz wrote:

I could see where the thin silicone coating might be an insulator to the
low voltages from the wattmeter slubs, but I find the second statement
exceptionally hard to believe. In type N (and even BNC) connectors, the
threads (or the bayonet connection) are not in the RF path. Look close
at either type of male connector and note that there is a coaxial shield
around the center pin. This shield presses against the inside wall of
the jack providing a continuation of the coaxial line. The threads (or
the bayonet connection) merely provides a sturdy mechanical connection.
This what gives the type N and BNC connectors a constant impedance, and
what makes them far superior to UHF connectors. It also allows the use
of a rubber washer to make the connector waterproof.

In one of my instrumentation applications, I had to use N connectors
made of 304 stainless for corrosion resistance and high temperatures.
Ceramic and glass insulation was used within the connectors. The female
jacks were welded in place and rated to withstand pressures of up to 100
PSIG. Stainless is quite bad about galling, and these connectors cost
plenty, so a silver paste was used to lubricate the threads. One day, I
had to make an "emergency" repair in the field and did not have the
silver paste; so I used PTFE thread seal tape instead. Going back to my
lab, I tested a few connectors with the thread seal tape using a Tek
1502 time domain reflectometer. Even with several layers of PTFE tape,
I was unable to see any difference in the impedance through the
connector. Since the application was always less than 200°C, we quit
using the silver paste.

And, when tightened threads *are* necessary for electrical contact, oil
or light grease often improves conductivity. Thread pressure is adequate
to squeeze the lubricant out from the contact areas, allowing good
metallic contact. And it prevents oxidation or other corrosion of the
contact surfaces when the contacts are moved or vibrate by excluding
air. This holds true for all contacts properly designed to wipe and
contact with sufficient pressure. Quite a few people incorrectly
attribute this improvement to conductivity or some mystical property of
the lubricant, but its real trick is simply to exclude air.

Roy Lewallen, W7EL

In message tonline,
Roy Lewallen writes




And, when tightened threads *are* necessary for electrical contact, oil
or light grease often improves conductivity. Thread pressure is
adequate to squeeze the lubricant out from the contact areas, allowing
good metallic contact. And it prevents oxidation or other corrosion of
the contact surfaces when the contacts are moved or vibrate by
excluding air. This holds true for all contacts properly designed to
wipe and contact with sufficient pressure. Quite a few people
incorrectly attribute this improvement to conductivity or some mystical
property of the lubricant, but its real trick is simply to exclude air.

Roy Lewallen, W7EL

I would be surprised if a lubricant was sufficiently viscous and had
enough 'body' to act as an insulating layer between two parts of
well-tightened a connector.

However, I have personal experience that Araldite can. This was used to
ensure that a reducing bush (PG11 thread to 5/8"), in the wall of the
housing of a CATV amplifier, remained securely in place. On all four
ports, there was absolutely no continuity between the outers of the
connectors and the housing.
--
Ian

Ian Jackson wrote:

I would be surprised if a lubricant was sufficiently viscous and had
enough 'body' to act as an insulating layer between two parts of
well-tightened a connector.

However, I have personal experience that Araldite can. This was used to
ensure that a reducing bush (PG11 thread to 5/8"), in the wall of the
housing of a CATV amplifier, remained securely in place. On all four
ports, there was absolutely no continuity between the outers of the
connectors and the housing.

Araldite seems to be a trade name for a variety of adhesives. There are
certainly materials other than the oil or light grease I was speaking of
which will interfere with continuity, and some of those adhesives are
apparently in that category. Kids, don't apply epoxy to your relay
contacts. Honey and contact cement might not be too good either.

Roy Lewallen, W7EL

"Roy Lewallen" wrote in message
treetonline...
Ian Jackson wrote:

I would be surprised if a lubricant was sufficiently viscous and had
enough 'body' to act as an insulating layer between two parts of
well-tightened a connector.

However, I have personal experience that Araldite can. This was used to
ensure that a reducing bush (PG11 thread to 5/8"), in the wall of the
housing of a CATV amplifier, remained securely in place. On all four
ports, there was absolutely no continuity between the outers of the
connectors and the housing.

Araldite seems to be a trade name for a variety of adhesives. There are
certainly materials other than the oil or light grease I was speaking of
which will interfere with continuity, and some of those adhesives are
apparently in that category. Kids, don't apply epoxy to your relay
contacts. Honey and contact cement might not be too good either.

Roy Lewallen, W7EL

I used to think that too. Good point about the inner shell, but I wonder if
all N's are created equal. That might have tainted my results. The
experiment was encountered in the process of tuning cavities, duplexers and
other filters with a R2001D. I have used oils before but some will rot the
gasketting. Grease or oils will migrate, but Stainless is a problem about
galling. It was a regular thing to have to clean Silver dust and grunge
from the bulkhead female with a q-tip and Isopropyl. The final answer was
to add a sacrificial N male to female adapter to save wear on the Silver
plating.

I also noticed Coffee doesn't make good contact cleaner either. Even with
plenty of sugar (just trying to help).