[Elecraft] N fittings

[G3VVT at aol.com]

In a message dated 15/02/05 21:20:57 GMT Standard Time,  
rohre at arlut.utexas.edu writes:

My  understanding of the place to place silicon grease is NOT upon the
outside  of the connector, but rather in the interface between male and
female  connectors.  The idea is to exclude moisture pooling on the  insulator
between the center pin and the outer shell  conductor.



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Silicon grease would only be placed on the inside of the connector, but  
enevitably some can be squeezed out, making it's way to the outside  and in the 
process is transferred to your hands. Once that happens  there is no way in the 
world that most tape adhesives or self amalgamating/self  vulcanising tape 
would adhere to the connector or even itself for that matter.  It only takes an 
exceeding small amount and seems impossible to remove by normal  cleaning. This 
would be why Don, W3FPR was wisely advising caution on the amount  of silicon 
grease used.
 
With self amalgamating tape one has to be careful as some  types are said to 
be attacked by UV, though did use one  brand of it in waterproofing CATV 
connectors in the UK for a number of  years without any problems. Applied the self 
amalgamating tape  directly over the connector, then applied a layer of heavy 
duty plastic  tape over the top for mechanical strength and protection.
 
What one uses depends where you live and what the exposure to UV levels  are. 
What could apply in latitudes further away from the equator would not be  
applicable in hotter climates. I lived for many years in the Middle East and  
most types of self amalgamating tape would probably not be usable there due  to 
extremely high levels of UV. Normal plastic tape had a rather short life and  
such things one would use normally in cooler climates such as polypropylene 
rope  and plastic cable ties failed very quickly. The rope was turned to dust in 
the  space of little more than a year and plastic cable ties went brittle and  
snapped. Never managed to source carbon loaded cable ties, though nylon T&B  
Tywraps did last a few more years longer.
 
The only sealant I have seen that seems to stand most situations is the  
fabric/heavy grease type of tape. This is known commonly as Denso tape  in the UK 
and was pretty well standard on professional telecom  installations for 
external connector sealing. Have seen a similar type used  in the Middle East for 
the same type of installation, so presume it must be  resistant to the effects 
of UV. This tape or a very similar type  is also used on small bore natural gas 
lines for joint sealing and  protection, so this could be another source of 
supply. Rather messy to use,  though does give extremely good protection to 
external connectors over many  years.
 
Bob, G3VVT