R: [TowerTalk] connectors

[Maurizio Panicara]

PL259 has been used for many years and it's mostly adequate for
HF amateur use. This can't lead to the statement that N connectors are
the explaination for failures, unless they are improperly used with cables
they were not designed for.

The PL 259 develops one of the electrical contacts through the outer
ring whose tightening has inherently a mechanical and electrical purpose.
This leads to unsafety because of thermal reasons (cold/warm cycles) and
because of oxidation.
The other PL259 contact is soldered to the inner of the coaxial cable
at its edge and this is risky, minimum as a wrong cabled N. Tin excess
might ruin what should be a perfect cylinder. The consequent spreading of
fingers in the female connector dramatically reduce the contact area and
the effective current capability of the connector.
The PL 259 contacts are not inherently weaterproof and if the resistance
of contact rises (oxidation) the heating (Joule)  will be high as the
current capability were times smaller. Smaller current capability leads to
an effective smaller power capability or to irreversible damages to
connectors.
The PL259 "air gaps" (i.e. the space between PL259 and SO 239) are at
risk of humidity and moisture. The dielectric constant in such cases is
rather questionable, in outdoor uses, compared to that of the N.
Allowed continuous power for an N connector is officially hundreds of watts
in the VHF range but PL259 failed repetitively at powers where N connector
had no problems, and well below 100 Mhz.
The N connector can be performed in a short time, comparable to a PL259,
if the process is done not only once in the life, using proper tools (a
right sized Iron-solder, a tool to comb cable shield, proper wrench) and
according to the appropriate cable trimmings.

73,
Mauri I4JMY

P.S. The inner conductor size has little to do with contact resistivity. The
         contact area is what counts. Definitely that of an N connector is
         several times bigger than most of relays used in full legal power
         PAs.


-----Messaggio Originale-----
Da: Tom Rauch <w8ji@contesting.com>
A: Tower Talk (mail list) <towertalk@contesting.com>; <bgkurz@epix.net>;
Maurizio Panicara <i4jmy@iol.it>
Data invio: domenica 8 agosto 1999 20.13
Oggetto: [TowerTalk] connectors


> 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
> w8ji@contesting.com










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