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'[EE]: Silver Conductive Grease'
2010\02\20@225423 by Justin Richards

face picon face
We have an application that involves over 1000 N type connectors
exposed to the elements and from time to time tests indicate that the
phase or attenuation values are outside limits.

Often an investigation reveals that the inner copper conductor has
tarnished/turned black/blue and a clean with some fine sandpaper and a
re tighten returns the connector to a serviceable state.

However, for some of these connectors we find a short time later that
they have once again tarnished and thus we suspect that there must be
moisture in the cable and it is a constant battle repairing these.

Recently someone suggested we use Conductive Silver Grease on the
conductor inner.

I have concerns that perhaps silver may react with the copper, or that
as these connectors withstand extremes in temperature and this may
cause the silver grease to slowly weep and find a way that results in
the dielectric becoming contaminated over time.

The length of these cables are important so if the end was to be
contaminated cutting the cable would present a serious issue.

Anyone had experience using conductive silver grease for this type of
application.

The cable is LDF450 and the connectors are RFS-H15566001 and
temperature ranges from 0 - 50 deg.

The technical data indicates that it is good for this range but mainly
concerned that over time the grease will move especially as the
connectors are unfavorably oriented and exposed to the elements.

Cheers Justin

2010\02\21@001325 by Jonathan Hallameyer

picon face
I wouldnt be putting anything conductive into a RF connector,  we use the
650 heliax (I believe) at work and similar connectors for it.  Murphy says
putting conductive grease into a connector is a bad thing thats going to
happen, not just waiting.   Though I dont know how sensitive your
application is, dielectric grease may be a better choice, or that could
cause problems too.  Our application isnt that sensitive though, we roll the
cable out outside, use a can of air duster to blow out any water/mud that
may have gotten in while we unroll the 6'  diameter roll of cable. No
degreaser/cleaner or anything fancy like that.
-Jon

On Sat, Feb 20, 2010 at 10:54 PM, Justin Richards <spam_OUTjustin.richardsTakeThisOuTspamgmail.com
{Quote hidden}

> -

2010\02\21@003649 by Sean Breheny

face picon face
Hi Justin,

A few questions:

1) What kind of plating is there on these connectors (both the male
and the female, and both on the shield conductors and on the center
conductors)?
2) Have you tried any kind of "boot" on the outside of the mated
connection to prevent moisture entry?
3) Is there any material applied around the area where the cable
enters the connector?
4) Are those temperatures C or F?
5) Is the connector part number you gave for the part on the cable or
the part it mates to? It would be helpful to know both kinds.
6) Do these connections need to be mated/unmated during normal
operation? If so, how often does that happen?
7) When mating the connectors, are they always carefully tightened
(neither too tight or too loose)?
8) Do these experience any kind of vibration or stress on the cables
after mating?
9) How much power is transmitted through these connections? What
frequency range? How much variation in attenuation and phase are you
seeing for failed connections?

It almost sounds to me like the connectors aren't making a proper
gas-tight seal and you are getting normal silver sulfide tarnishing.
Another possibility is that you are actually using incompatible
connectors (like, for example, a gold-plated one on one side and a
tin-plated one on the other) and you are getting incompatible metal
effects, or you are getting fretting corrosion between connections
which can move very slightly over time.

You mention a copper center conductor - I have never seen an N
connector which uses a copper, unplated center pin or any unplated
parts. To what are you referring here?

Sean


On Sat, Feb 20, 2010 at 10:54 PM, Justin Richards
<.....justin.richardsKILLspamspam@spam@gmail.com> wrote:
{Quote hidden}

> -

2010\02\21@013600 by Justin Richards

face picon face
> 1) What kind of plating is there on these connectors (both the male
> and the female, and both on the shield conductors and on the center
> conductors)?

The male side is the LDF450 rigid coax that has been trimmed back and
prepared to take the connector.  The connector has a female side the
takes the LDF450 and male side that has a N type male connector.  The
N-Type male connector interfaces to a female N Type connector
typically on a Balun or Combiner.  The N-Type part of the connectors
always appear fine.  It is the end of the LDF450 with a copper center
conductor that tarnishes (which we have to disassemble the connector
to get at).  The female part of the connector also appears fine.

LDF450 inner conductor is aluminium with a copper coating.  So the
mating surface is copper.
LDF450 shield is copper
Connector female side appears to be aluminium (aluminum) whitish silver
Connector N type side appears to be aluminium (aluminum) whitish silver


> 2) Have you tried any kind of "boot" on the outside of the mated
> connection to prevent moisture entry?

There is no boot but a Orange washer that seals the 2 side of the connector
and a grey SPINNER Plast 2000 is sqeezed in thru a purpose made hole
in the side of the connector to fill the space around the cable and
the inner of the connector.

> 3) Is there any material applied around the area where the cable
> enters the connector?
Yes, as above.

> 4) Are those temperatures C or F?

C

> 5) Is the connector part number you gave for the part on the cable or
> the part it mates to? It would be helpful to know both kinds.
That part number as far as I can tell identifies the connector as a
whole but is made up of 2 halves (6 separable parts:- N Type side,
Cable Side, washer, two cable collars that go around the outer
conductor, 1 collar that goes around the dielectric and 1 M9 grub
screw that fills the entry hole for the Plast 2000.

> 6) Do these connections need to be mated/unmated during normal
> operation? If so, how often does that happen?
No, they should not need to be touched only when our tests fail.

> 7) When mating the connectors, are they always carefully tightened
> (neither too tight or too loose)?

We have a specially made 20Nm torque wrench IAW the connector specs
that is used to tighted the two halves of the connector body.

> 8) Do these experience any kind of vibration or stress on the cables
> after mating?
No stress or vibration.  Except aileron noise (I think thats what it
is called, the noise generated by the wind blowing past the antenna)
and the stress of heating and cooling on the rigid LDF450.

> 9) How much power is transmitted through these connections? What
> frequency range? How much variation in attenuation and phase are you
> seeing for failed connections?
>
HF, receive only power, a small dB variation (I am required to be
ambiguous here)  between similar receive paths will flag a fault.


{Quote hidden}

>> --

2010\02\21@021327 by MCH

flavicon
face
This really sounds like you haven't weatherproofed the connectors
properly. How are you sealing them? Did you use the rubber gaskets that
come with them?

Joe M.

Justin Richards wrote:
{Quote hidden}

2010\02\21@025605 by Justin Richards

face picon face
As mentioned ...

There is no boot but a Orange washer that seals the 2 sides of the connector
and a grey SPINNER Plast 2000 is sqeezed in thru a purpose made hole
in the side of the connector to fill the space around the cable and
the inner of the connector.

The washer you speak of we think is a orange silicon washer and they
are in use and have been injected with Plast 2000.

We suspect that as it took approx 18 months+ to build (this is a large
receive array) that at some stage cable would have been laid but
un-terminated.  It is is easy to consider that at one point in time it
would have rained and contaminated the cable.

This is only a guess.

The cable can not really be replaced because concrete was poured on
top.  I do not know why.  But it was a large reputable company that
was tasked with building the array and laying the numerous cables.

My main concern at the moment is that we are being told to apply this
grease and i need good arguments or evidence where we can clearly show
that this is a very bad idea.

I have mentioned that I believe over time we will do more damage than
good using the grease but we are at at risk of being over ruled unless
I can clearly demonstrate it is bad.

So we are interested in peoples experience using the silver conductive grease.

Cheers Justin


On 21 February 2010 15:12, MCH <EraseMEmchspam_OUTspamTakeThisOuTnb.net> wrote:
{Quote hidden}

2010\02\21@040528 by MCH

flavicon
face
The proper seal on such connectors includes the application of a piece
of heavy heat shrink tubing that has a sealant on the inside. Industry
standard is to supplement even that with a coating of tape and another
layer of protection such as Scotchkote. There is even a certain way the
tape is applied to resist contamination ingress. If these connectors are
outdoors, then they were not properly sealed and that is why you have
water ingress and the resulting corrosion.

As for laying the cable in the elements unprotected, I suspect you are
correct that it was contaminated, and I would not be surprised if your
cable is experiencing corrosion as well.

I would seriously consider contacting the company that installed these
cables and force them to correct the underlying problem, although if you
supplied the cable, they may say you supplied contaminated products.
Regardless, they should replace the connectors and attach and seal them
properly. At this point, it may not solve the problem, as you likely
have water laying in your cable.

I'm a relative newbie to PICS, but I have over 30 years in the radio
communications industry which includes extensive use of this cable. When
these connectors are installed and sealed properly, they should last
decades with no issues, as I have many that are decades old and still
perform to spec. I've also had many customers who have had problems, and
each time it came down to improper installation or improper sealing
(done by other companies - many of them "reputable") - with the
occasional piece of Heliax that suffered from bullet holes or vandalism.

Joe M.

Justin Richards wrote:
{Quote hidden}

>

2010\02\21@050626 by Justin Richards

face picon face
Thanks for your input.

There are so many of these connectors that have been done the same way
and this project represented a significant contract we have all
dismissed the possibility that have been installed incorrectly.

Also they have the silicon seal and the Plast 2000 paste so we figured
they have been installed correctly.

However, i worked for a telco and their rf connectors were more inline
with the way you have described construction.  After seeing these I
kinda assumed that the Telco went over the top but we did not have any
issues.

Interestingly enough they also sported bullet holes.  And I think the
bullets came from the property holders that coax was supplying comms
to.  Go figure.

Some time has passed since these were installed so I am not sure if we
can get them contractors back but I will discuss it.

Thanks again.

Justin

On 21 February 2010 17:04, MCH <RemoveMEmchTakeThisOuTspamnb.net> wrote:
{Quote hidden}

>>

2010\02\21@093332 by Robert A LaBudde

flavicon
face
The grease used to waterproof connections or prevent corrosion
doesn't have to be conductive. Use petroleum jelly, or, if you have
rubber components, use silicone grease.

If you want copperized conductive grease, cylinder head bolt grease works fine.

At 02:12 AM 2/21/2010, MCH wrote:
{Quote hidden}

>

2010\02\21@100714 by Justin Richards

face picon face
My seniors are suggesting that conductive grease will help lower the
high resistance that is a result of the tarnish and will make good the
connector over a long period of time.  I tend to agree in the short
period but have advised against this as I am concerned it will makes
its way into the dielectric and will act as a short circuit.

I want to avoid any grease of any sort because i believe over time it
will   contaminate the dielectric which looks porous and once it is
contaminated it will be very difficult to clean.  This is a harsh
environment, hot, cold, wet, dry and dusty.

We have a lot of these connectors in use 1000's and am concerned that
a lot of damage can be done in a short time if we are careless.

It seems that no one has used conductive grease this way and this goes
someway to supporting my argument.

We have optic fibers that ooze a yucky thick goo over a long period of
time exposed to these conditions.  So it seems clear that grease type
products given time and unfavorable conditions will weep and flow.

My approach is to keep them dry, cleaned and sealed as best we can
without the use of gels, greases etc.  .

Cheers Justin


On 21 February 2010 22:33, Robert A LaBudde <ralEraseMEspam.....lcfltd.com> wrote:
> The grease used to waterproof connections or prevent corrosion
> doesn't have to be conductive. Use petroleum jelly, or, if you have
> rubber components, use silicone grease.
>
> If you want copperized conductive grease, cylinder head bolt grease works fine.
>

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