[TowerTalk] Power limitation for N-Connectors

Ron Stordahl ron.stordahl at digikey.com
Wed Apr 19 16:31:25 EDT 2006

The consensus is that N connectors are fine at 1500 watts up to 30 MHz 
(and probably beyond but my use is 30 MHz or lower).  My problem with 
N-connectors in the past, and it's a distant past, is in assembly..maybe 
I had some bad ones.  And I am from the old school...like to use 
solder.  But if the compression connection for the shield is good enough 
and long lasting..apparently it must be..then fine.

The cable will be LDF5-50A which is foam. 

Is there a certain connector which has a 'captive center pin' as you 

My plan would be to use female connectors on the heliax, then male 
connectors on the more flexible jumpers at the ends, probably short 
length of 213.

Am I on the right path?

Ron Stordahl, N5IN

Ian White GM3SEK wrote:
> 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 
> correctly.
> 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 
> conductor.

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