[CW] Power vs BNCs

[Ken Brown]

Hi Ed,

The inside dimensions of BNC connectors are the same as N connectors. 
You can plug a  N male connector into a BNC female, and have a good RF 
connection, although there is no mechanical means of keeping the two 
together when you do that. BNC and N connectors are both much better 
connectors than PL-259/SO-239 "UHF" connectors, in terms of loss and 
constant impedance through the whole coax, male connector, female 
connector, coax again series of transitions. The power limiting using 
BNC connectors is, as you have suggested, most often is determined by 
the limitation due to the type of coax,  not the connectors. There are 
BNC connectors available for RG-8, RG-213 and other large sized coax, 
including heliax and rigid coax.

If you are like most hams, you probably have more equipment with SO-239 
(female "UHF") connectors than any other kind connector. And you have 
more cables with PL-259 (male "UHF") connectors than any other kind. So 
hams generally consider them to be "standard" and everything else to be 
exotic and inconvenient.This is unfortunate, because SO-239/PL-259 are 
some of the worst excuses for RF connectors ever devised. This is 
obvious when checking them on a network analyzer, especially at higher 
frequencies. You can even observe the poor performance with an ohmmeter. 
See what a PL-259/SO-239  sheild resistance measures when the outer 
shell is a half turn loose and you wiggle the connector. Compare this to 
an N connector under the same conditions.

I would not worry about running 1500 watts through a BNC connector, as 
long as it is a quality connector, properly installed on quality coax.

DE N6KB

Ed Tanton wrote:
> I have had, for several years, a very nice Waters 369A Reflectometer. It is
> basically an SWR/power meter, with 2 vertical meters, with a switchable
> maximum FWD Power scale of 200W or 2000W. The thing is: it uses BNC
> connectors. Does anyone have any idea what the deal is? I am under the
> impression that BNC connectors aren't capable of that much. Much less most
> of the cables you would have BNC connectors on. I do understand there are
> some TFE cables that would probably take it, but still it just seems
> improbable. 
>
> While I normally run a great deal less than 1KW, I DO have the capability,
> and was thinking about using it since my old meters had an unfortunate
> accident involving 1/4 inch of kitchen sink/garbage disposal/dishwasher
> 'water' all over them for over a month while I was recovering (DEC 2005)
> from heart surgery. 
>
> Thoughts, comments???
>
> Ed Tanton
>  
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