[BC] about STL dishes and jumpers

[Mike McCarthy]

As a matter of courtesy, I'll generally refrain from calling someone a
!@#$%^&* or their installation !@#$%^&* until I have a better idea of the
circumstances behind it. Sometimes, the invention is of necessity by
default and not by design.

In my wierd STL case, the problem manifested as an improperly installed
male connector breaking the female connector interior apart. Since we had
no connectors available, but did see that the interior of the feed point
was using 7/8" inner/bullet, we bypassed the connector's interior with
3/8" LDF2.  We did that by drilling out the N connector interior and
running the nicely fitting transmission line foam and center through to
the bullet and soldering direct to the bullet. We then simply connected
the N2PNM outer to the remaining N connector shell in a tightly fitting
and impedance friendly manner. No more problem, the connection is
ruggedized, lower VSWR, and performance improved.

Let me offer this anecdote as well on lines. I agree connecting BIG lines
(7/8" and up) direct to the dish is not a good idea. Especially if using N
connectors.  I use a piece of 3/8" (LDF-2) line as my jumper. It's small
and flexible enough that it absorbs vibration easily and yet robust enough
to withstand Midwest weather. I agree with Curt that vibration is a real
killer to connections and hence another reason I resist using N connectors
anymore where I can avoid doing so and not compromise the installation. 
Fortunately, most antennas now offer a DIN connector option.

MM

>> Damn !!   Now I gotta find a dictionary.   ( grrrrrr )
>
>  Me too !
>  I'd NEVER call someone something where I didn't know what the
>  words meant !
>
>  I suppose it's possible to install in such a way that this common
>  failure is less likely, but mechanical theory says, and MY experience
>  bears it out, that any breeze at all will vibrate the tower, the line,
>  the antenna, and not synchronously. The solid outer is the weakest
>  part, so fails first. A soft jumper, just like a motor mount, only needs
>  enough flex to withstand this vibration and not break.
>  Hopefully, it lasts long enough for the jumper to dry out and fail.
>  A failed jumper is much cheaper to replace than the main line !
>
>  I've even seen situations ( though I can't remember why ) where the
>  solid outer HAS failed, but there was enough torque at the connector
>  to maintain a connection of sorts, and the system had not failed.
>  Once disturbed by a climber ( me, of course ) the failure became
>  apparent.
>
>  I suppose it's possible to install in a way that this doesn't happen,
>  without a soft jumper, but I haven't seen it.
>
> --
> Cowboy
>
>