Posted by
Bill VanAlstyne W5WVO on
Nov 22, 2006; 2:57am
URL: http://elecraft.85.s1.nabble.com/Fw-RG-213-BNC-connector-tp441088p441090.html
Yup, very true. At HF frequencies, loss is not the issue. (Even at 144 MHz
the loss is not significant if the connectors are mounted/installed
correctly. Above that, at UHF frequencies, things go downhill pretty fast.
That must be why they call 'em UHF connectors. Uh, yeah.)
The REAL problem with traditional PL-259 connectors (besides the need to
weatherproof, but you better weatherproof the N connectors just as well!) is
that they are oftentimes installed badly -- sometimes in such a manner that
they malfunction intermittently. This can cause all sorts of havoc. It
happened to me.
The PL-259s were on either end of a short RG-8/X jumper connecting my rig to
the antenna tuner, and (as I finally figured out) one of them would arc
short whenever the RF voltage reached a certain point. On SSB, that was on
voice peaks, of course. Whenever that would happen, the SWR would soar
instantly, the TX SWR protection circuit would cut in, and the peak would be
clipped off. Sounded just like a transmitter or mic connector problem. Took
me a month to finally swap out that coax jumper, after trying everything
else under the sun. Boy, was I embarrassed, as I had made the durn thing
myself! This is about the time I got deadly serious about learning how to do
these connectors right.
There is much lore, folk wisdom, and mythology about how to properly install
a PL-259 -- much of it bad -- but there is also a lot of really sound advice
out there on the web. I've had the best luck installing it exactly as the
manufacturer specifies. (Gee, imagine that!!) Complying with the specified
cut dimensions is especially important. But you need HEAT CAPACITY, and lots
of it. Other than outdoor water intrusion, the principle cause of PL-259
failure, indoors or out, is poor soldering, and this is often caused by
inadequate soldering iron power. Inadequate soldering iron power leads to
excessive time applying heat, which in turn causes heat to transfer
excessively to the vulnerable inner dielectric and outer jacket material.
You should be using a 100W iron (or larger) with a well-tinned chisel tip
that fits in the "notch" where the solder holes are. You want maximum
contact area. (Others have had good luck with other soldering tools, but
this is what has worked best for me.) I hold the connector body still in a
Vise-Grip, which pulls heat away from the shell of the connector where the
outer jacket contacts it. Solder the connector in the shortest time possible
consistent with correct results -- just long enough to get complete solder
flow with good concave fillets in the solder holes (no balls or blobs).
Quick, efficient soldering will minimize dielectric and jacket heating and
deforming. It is somehow counter-intuitive to many hams that in order to
minimize heat damage to the coax, you need to use more heat. But that's how
it works. :-)
Bill W5WVO
----- Original Message -----
From: "Michael Melland" <
[hidden email]>
To: <
[hidden email]>
Sent: Tuesday, November 21, 2006 12:16 PM
Subject: Re: [Elecraft] Fw: RG-213 BNC connector
> I won't argue that the N connector may be a better choice for any number
of reasons, but don't rush out to change out a PL259 fearing excessive
signal loss... a PL-259 isn't in any way (especially at HF) "High Loss"....
>
> >From the Wirebook IV, pages 3.2 and 3.3.... Alan Bloom, N1AL, used an
HP8753 RF network analyzer to compare losses of UHF vs. N connectors.
>
> Both connectors measured 0 db loss up to 100 MHz.
> At 150 MHz, the N has 0 db loss, the UHF has .01 db loss.
> At 450 MHz, the N has 0 db loss, the UHF has .09 db loss.
>
> Other studies show similar results ...
>
> --
>
> Michael Melland, W9WIS
> Redgranite, WI USA
> "Non Sibi Sed Patriae"
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