[TowerTalk] Power limitation for N-Connectors

Ian White GM3SEK gm3sek at ifwtech.co.uk
Wed Apr 19 16:06:06 EDT 2006

Steve Katz wrote:
>I'd say they're wrong.
>Type Ns flashover at >3000V at STP, and that's a lot of voltage.  The center
>pin can handle 6A continuously, probably 12A intermittently.  1500W is 5.48A
>in a 50 Ohm system.  1500W is 273.9V in a 50 Ohm system.
>I don't see the issue.  I've used type Ns at 1500W output power on 70cm for
>eme work, and never had one fail...

There is no problem with correctly assembled N connectors at these power 
levels; but there is a risk of failure if the centre pin is not mated 

This can happen when N connectors with a floating centre pin are used 
with  semi-airspaced cables whose centre conductor is free to move 
inside the cable. A hanging length of cable, and/or some flexing in a 
rotator loop, can sometimes pull the centre pin partly out from its 
socket, causing high resistance (especially at UHF where skin depths are 
smaller) and failures at high power.

The solution is always to use connectors that have a captive centre pin, 
and to take care when installing cables that have a floating centre 

73 from Ian GM3SEK         'In Practice' columnist for RadCom (RSGB)

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