Topband: Verifying integrity of 75 ohm coax.

[Shoppa, Tim]

High pressure contacts, I feel fine getting slathering dielectric grease all over them before making the connection. Examples are like a Battery terminal in a car, or a spade lug under a screw, or the barrel on an F connector. Something you actually apply some amount of force to tighten (even just "tight finger force"). This forces the grease out of the actual metal to metal contact, and at the same time ensures the metal contacts are enclosed in the grease.

But for low pressure contacts, e.g. molex pins, or the center pin on an F connector jack, I think it's best to keep the dielectric grease off the low pressure contacts. Having it in and around a connector boot or shroud that goes around a low pressure contact is fine. A good thing in harsh weather or chemical environment to help keep weather and fumes out. Rubber connector boots last a lot longer with silicone grease on them.

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Jim Garland
Sent: Wednesday, November 20, 2013 9:32 AM
To: 'Tom W8JI'; 'topband'
Subject: Re: Topband: Verifying integrity of 75 ohm coax.

Helpful advice, Tom. Thanks. I've always worried about using silcone grease on connectors. I understand it helps seal the connector, but my fear is that it could interfere with the electrical bond.  On the face of it, getting non-conducting grease on, e.g., the center terminal of an N-connector or
PL259 seems like asking for trouble.
73,
Jim W8ZR

> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Tom
W8JI
> Sent: Tuesday, November 19, 2013 5:26 PM
> To: Bill Wichers; Gary at ka1j.com; Topband at contesting.com
> Subject: Re: Topband: Verifying integrity of 75 ohm coax.
> 
> > Just a suggestion: the T&B Snap'n'seal connectors also have "Seal nuts"
> > which can be bought separately. They're intended to seal out water 
> > from the thread area on the F connector. They are basically a metal 
> > shell
with
> > some threads that captivates an O-ring such that tightening them 
> > against the connector seals the o-ring between the threads and the 
> > F-connector itself. They're intended to be a water seal, but they 
> > also make a pretty decent locknut for an F connector even if you 
> > don't care about the
weather
> > proofing function.
> >
> > The newer CATV splitters, etc, have rubber boots that the male end 
> > seats into. Those also reduce the possibility of loosening but 
> > probably not as much as the seal nuts. If you have a problem with F 
> > connectors loosening over time the seal nuts used as lock nuts might 
> > be worth a try. Note
that
> > the seal nuts will require about 1/8" or so of extra threaded area 
> > on
the
> > female connector compared to using the F connector alone so they 
> > don't work with all female connectors. You need to make sure when 
> > using them that the mail connector still seats properly (i.e. the 
> > coax shouldn't rotate within the threaded ferrule of the male 
> > connector after it's been tightened).
> >
> 
> If the connectors are properly tightened, there is no reason at all to 
> use
a
> lock nut or any locking aids. It is as unnecessary as a lock nut or 
> lock washer on a car lug nut.
> 
> I dealt extensively with F connectors in the 1980's for a company that 
> had dozens of small CATV and MATV systems. They never had problems 
> with
fitting
> getting loose. They had ten's of thousands of F connectors.
> 
> You have to **snug** the connector with a wrench or tool of some type. 
> Be sure the threads are clean and use some light pure silicon or 
> Teflon electrical rated grease. It does not take much pressure, around 
> 10 inch-pounds of torque is enough. With a four inch wrench, that's 
> about 2 pounds of push. DO NOT use the common 30 inch-lb wrenches. 
> They will do as much harm as good. If you do not know what two pounds 
> is to push a wrench, push on a bathroom scale with two fingers and get 
> used to the feel. Then push the same way on a regular 4 or 5 inch wrench.
> 
> The worse tools of all to judge torque are pliers and connector 
> drivers
that
> you spin with your wrist. End wrenches are the easiest to learn, 
> because
you
> can snug with two fingers and really learn the pressure.
> 
> One way to avoid water problems on low frequencies is to flood the
connector
> with a pure silicon grease. Dielectric tune up grease for automobiles 
> is a nearly perfect grease. There are some good Teflon based 
> non-petroleum greases, also. DO NOT use Noalox or any other 
> anti-seize. Noalox is
nothing
> but trouble.
> 
> On higher frequencies, like UHF or higher, you do not want to flood 
> the connector. On lower frequencies, you can just flood it.
> 
> Connectors coming loose is like having connecting rod nuts falling 
> off, or wheel lug nuts falling off. It has nothing at all to do with 
> lock
hardware.
> They all stay on just as well when greased or oiled as they do dry or 
> locked. They only loosen when not tightened properly or when the
mechanical
> connection is seriously abused.
> 
> 73 Tom
> 
> _________________
> Topband Reflector

_________________
Topband Reflector