The trick in assembling N connectors is to make sure you have the shield
wires laid out flat with none overlapping one another. Use a pick to
separate them. Then cut the shield wires to the proper length with a pair of
scissors. The length is critical. Too long and they will jam up. Too short
and they will pull out. If done properly the cable will not turn in the
connector and will last a long time. No solder on the shield!
> -----Original Message-----
> From: firstname.lastname@example.org [mailto:towertalk-
> email@example.com] On Behalf Of Ron Stordahl
> Sent: Wednesday, April 19, 2006 4:31 PM
> To: Ian White GM3SEK
> Cc: firstname.lastname@example.org
> Subject: Re: [TowerTalk] Power limitation for N-Connectors
> 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
> >> pin can handle 6A continuously, probably 12A intermittently. 1500W is
> >> 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
> >> 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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