Topband: Verifying integrity of 75 ohm coax.

[Tom W8JI]

> 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