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[TowerTalk] connectors

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Subject: [TowerTalk] connectors
From: (Tom Rauch)
Date: Sun, 8 Aug 1999 14:13:13 -0400
> Impedance apart, a properly cabled N connector is safer than any PL-259
> connector already in the HF spectrum, and should be always used starting
> from 50Mhz and above. N connector withstands current and voltage well over
> the amateur legal power, realize better the electrical junction and more
> important keeps it inherently protected. Although the N-connector is not
> rated for such power levels, I've seen no damages occurred to one of it
> (male and female, on antenna side) with >5Kw RF ( applied for days ), in a
> 100MHz  FM broadcast station. Incidentally the antenna was damaged and SWR
> was higher than 1:3. The troubles with N connectors are generally
> connected with bad or improper mountings or by the use of low quality
> devices. This also explains why the good adapters are generally so
> expensive and why changing from a standard to another in a confortable way
> (instead of using the best one) can somethimes lead to have 

My own experience completely disagrees with that. "N" 
connectors, despite all the hoopla about how "good" they are, use 
virtually the same poor size center pins as a BNC connector. There 
is hardly any difference, and if you remove the locking ring from a 
BNC male it actually fits the 50 ohm "N" female.

The standard UHF connector, besides being easier to install, has 
much larger air gap. It withstands far more voltage, despite ratings. 
It has MUCH larger conductor size and contact area, and also has 
more contact pressure. It carries much more current safely.

The N connector has two advantages, and only two. 

1.) Properly installed it has better SWR performance. The female 
part of the UHF has about a half inch long "bump" where 
impedance is 30 ohms or so. The N thus has an advantage ONLY 
over 100 MHz or so, it makes no difference at all below two meters 
unless you have a many connectors in the line.

2.) It is more weather proof when properly assembled. That is an 
advantage if you don't add your own weather proofing.
Other than that, the UHF connector wins hands down by a large 
margin. It has a lower resistive loss connection capable of handling 
much more current and voltage. It is easier to install and remove.

If SWR is ever high (say you grab a wrong antenna at full power), if 
current or voltage is ever high, if the connector ever has water 
ingress, a UHF connector always has less chance of failure. If you 
wouldn't trust a BNC connector, there is not much more reason to 
trust an N connector.

That seems like a lot to give up for an immeasureable SWR 
change and a little weather proofing improvement.

73, Tom W8JI

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