[TowerTalk] connectors
Michael Tope
Michael Tope <w4ef@pacbell.net>
Sun, 30 Jul 2000 20:24:30 -0700
Ty,
The power handling capability of the connector goes
down with the square of the VSWR. For example, at 3:1
VSWR a 10KW connector can fail at only 1100 watts if
its at a sweet spot in the standing wave.
Mike, W4EF
----- Original Message -----
From: "Tyler Stewart" <k3mm@ex-pressnet.com>
To: "Michael Tope" <w4ef@pacbell.net>; "TowerTalk"
<towertalk@contesting.com>
Sent: Sunday, July 30, 2000 5:05 PM
Subject: Re: [TowerTalk] connectors
> As stated by others, UHF connectors are fine up to about 220 Mhz. After
> that, the impedance bump can become noticable.
>
> Also as others have stated, the N connectors are more weatherproof on
their
> own than UHF's.
>
> The big downside to N connectors is that they take a lot more care to
> install correctly. I also like to use some potted shrink tubing over the
> body to cable joint to take some of the twisting strain off the shield
> clamp. Not so important for static installations, but for cables that
get
> moved around a lot, it's a definite plus.
>
> As for power handling, I have to wonder how much power W8JI is running ???
> :)
>
> 73, Ty K3MM
>
> ----- Original Message -----
> From: "Michael Tope" <w4ef@pacbell.net>
> To: "TowerTalk" <towertalk@contesting.com>
> Sent: Sunday, July 30, 2000 7:43 PM
> Subject: Re: [TowerTalk] connectors
>
>
> >
> > I saw some more evidence yesterday that this N stuff
> > is pure marketing hype. My friend Warren and I took
> > apart a non-working Henry 2006 amplifier (6 meter x
> > 3CX800A7) yesterday. While the output connector on
> > the 2006 was a type N, when we took the amplifier
> > apart, we found that the output signal was routed
> > thru a bandpass filter module. Both ends of this
> > filter were fitted with UHF connectors, suggesting
> > that electrical performance wasn't the driving factor
> > in selecting the type N output connector. BTW, our
> > clubs FT-847 which is driving this amp uses a slighly
> > more sensible approach. The HF, 6M, and 2M ouput
> > connectors are all UHF. Only the 70 cm output
> > connector is type N.
> >
> > Mike, W4EF..............
> >
> >
> > Michael C. Tope, W4EF
> >
> > email: W4EF@pacbell.net
> > web: www.dellroy.com
> >
> > ----- Original Message -----
> > From: "Tom Rauch" <w8ji@contesting.com>
> > To: <towertalk@contesting.com>; "Bryan Fields" <kb9mci@qsl.net>
> > Sent: Sunday, July 30, 2000 4:44 AM
> > Subject: Re: [TowerTalk] connectors
> >
> >
> > >
> > > > I think that a N is THE BEST connector to use. The two gaskets give
it
> > > > water resistance that no PL-259 can match. After years of being
> outside
> > > > unprotected the silver may have .006 of a inch of sulfide (i have
> > actually
> > > > mesured this amount!) on it but the inside will be nice and shiny.
> > >
> > > It is more water resistant.
> > >
> > > > Secondly you do not need to heat the whole connector like you have
to
> do
> > > > with a pl-259, this means no melted coax and no impedance bumps b/c
of
> > > > melted dielectric. (i can never put a pl-259 on right the first
time,
> > the
> > > > coax always melts!)
> > >
> > > That's a non-problem if you solder with a big enough iron and pre-
> > > tin, and if you use a good connector.
> > >
> > > On the other hand, the N depends on grabbing the braid with only a
> > > mechanical connection to prevent pulling out. The gaskets "sort-of"
> > > squeeze the jacket, but have no holding power.
> > >
> > > If the cable has a loose braid, or a flexible jacket, the center pin
of
> > > the N will move all around when you pull on the cable.
> > > Mechanically, they are poor connectors for gripping the cable
> > > although they hold all right with thick braid hard jacket cables.
> > >
> > > My biggest gripe is they are low power connectors. They have the
> > > same approximate pin size and air gap as a BNC connector. Not
> > > exactly high-power construction.
> > >
> > > The SWR bump in a PL-259-SO-239 pair is in the 1/2 inch of area
> > > in the SO-239, where the impedance is about 35 ohms or so. 1/2
> > > inch of such a small bump causes almost no change in the system
> > > below a few hundred MHz.
> > >
> > >
> > > >Third, the connector is less noisy b/c the the
> > > > center pin is under pressure from the connector. This is very
> important
> > > > in repeater installations, especially in the duplexer. Many a
> crackling
> > > > noise has been traced to a bad uhf connector on a duplexer.
> > >
> > > At one time I was responsible for about 30 VHF repeaters. I never
> > > saw that problem even one time. Factually, the UHF connector
> > > makes a much better connection than the type "N". Both surface
> > > area and pressure are higher in the UHF connector.
> > >
> > > Now I don't object to "N"s where they are needed, like on SWR
> > > critical upper VHF and UHF systems where power levels are low.
> > > But when I get hardline with N fittings I machine them into good old
> > > UHF style fittings by boring out the center hole and shortening the
> > > threaded area a bit. I then gut a SO-239 and use a brass tube to
> > > solder the center pin to the feedline.
> > >
> > > None of those hard-to-assemble easy-to-pull-apart low-power N
> > > connectors in this fellows station!
> > >
> > >
> > > 73, Tom W8JI
> > > w8ji@contesting.com
> > >
> > > --
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> > > Problems: owner-towertalk@contesting.com
> > >
> >
> >
> > --
> > FAQ on WWW: http://www.contesting.com/FAQ/towertalk
> > Submissions: towertalk@contesting.com
> > Administrative requests: towertalk-REQUEST@contesting.com
> > Problems: owner-towertalk@contesting.com
> >
>
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