Rich Measures wrote:
>
>I have put 14kw pep (1200v-peak) through a N fitting at 7MHz. .
>However, if a Type N center pin looses spring tension there can be
>grief.
Amen, Rich :-)
When they're perfect, N connectors are fine for US legal power up to at
least 432MHz - but as Rich says, the weak point of N connectors is the
inner connection which isn't much bigger than a BNC.
Unfortunately there are too many ways for that connection to go wrong.
Creep of the inner conductor in the cable can either pull the connection
apart (so it arcs) or splay the female contacts out (so either it splits
now, or it arcs later when you re-use the connector). The MIL-style N
connector is even worse because there's no positive axial location for
the inner pin. With big cable the inner pin can easily be forced off-
center, again causing damage to the female part.
The tendency to arc seems to be frequency-dependent. Many people use Ns
with several kW up to 144MHz, but I've had a lot of trouble at 432.
Unfortunately even 7/8in heliax connectors are not immune... and that's
expensive.
>A better connector is the Type-C.. It's like a BNC for RG-213.
>A Type-C fitting has way more contact area than a Type-N.
C connectors are indeed very good, but are not very common (I was lucky
to have a local supply for several years, from scrap nucleonic
testgear). There's also an SC which is like an N, but with a C-size
centre pin, the size it oughta be.
Watch out for 7/16 DIN connectors, which are coming into cellular base
station applications world-wide. They originated in Germany and are
already appearing as surplus here in Europe, in all sizes from 7/8in
heliax down to RG-213. These are serious connectors (7mm inner, 16mm
outer = 50 ohms) which go together with a satisfying clunk. They are
constant impedance, self-centering, have lots of contact area and are
good for any amateur power up to several GHz.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.demon.co.uk/g3sek
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