Re: Best brand coax and F connector for HD cable?

[Roger <GetValidAddress@xxxxxx>]

On 12 Jan 2007 21:11:21 -0800, "G-squared" <stratus46@xxxxxxxxx>
wrote:

>
> Ed Nielsen wrote:
> > From a leading engineer in the CATV industry:  "We did a scientific
> > research for a year on CPD and contact interfaces, the report shows
>us
> > that it is very important to break through the oxide layer to
>prevent a
> > non-linear behavior in contact surfaces. The torque varies with the
>type
> > of plating used on the F-connectors.
> >
> > Finger tight is not tight enough to break through the oxide layer,
>and
> > due to temperature cycles it will loosen up after a while.
>Especially
> > in the neighborhood of the subscribers and RF output of the node it
>is
> > important, (the effect of a loose or bad connection is the biggest
>at
> > those points) to have proper contact interfaces.
> >
> > CPD - This phenomenon, also known as Common Mode Distortion, is
> > generally the result of age and corrosion in the cable plant
>connectors.
> >   This non-linear function is commonly caused by oxidation of metal
> > surfaces, creating a point contact diode.  Should the diode effect
>occur
> > on the ground portion of a connector, common mode distortion and
>ingress
> > are likely.  The effect that this diode phenomenon causes is
>observed as
> > difference products in the return plant, and can be caused by one or
>
> > more faulty connectors.
>
>What you're saying here is what I tell everyone who runs ANY kind of
>signals. The ground is at least as important (I believe more important)
>as the actual signal feed.
>
> > In general, interfering products will be observed at harmonic
>intervals
> > of 6MHz throughout the return plant band.  Sidebands of this will
>tend
> > to raise the apparent noise floor.  Because common mode distortion
>is a
> > non-linear effect, slight variations in the point diode structure
>due to
> > temperature, humidity, wind velocity, etc. have a significant impact
>on
> > the interfering levels observed."
> >
> > Manufacturers and the engineering community in the CATV industry
> > recommend they be tightened to 30-in/lbs.  The best that can be
>achieved
> > by hand is less than 13.
> >
> >
> > CIAO!
> >
> > Ed N.
>
>Everything you say squares with what I have worked with in commercial
>TV. On my outdoors connectors I use clear silicone heatsink (NOT

I use either DC-4 or 5. Having worked for the company that invented
them and I use them in connectors running high power.  However I've
never seen a clear heat sink grease.  Dielectric, yes, but not heat
sink.  The only silicones I have seen for heat sink coupling are rater
thick and white (Mainly Silicon Dioxide in 200 fluid)

>bathtub silicone !! ) grease on the connectors before snugging them up.

There is another family of  Silastic RTVs that are non corrosive for
electronics work, but they are water proof, not moisture proof.  DC-4
and DC-5 compounds work better. Just don't get them on anything you
want to stick something on. <:-))

>The grease prevents oxygen and water from corroding both the center
>conductor and the ground connection. The current antenna is 15 months
>old and doing fine so far. My cable of choice is Belden 1694A though
>their 1505 RG-59 is nearly as good loss-wise as the lesser brands RG-6.
>Yes, we use both types at work from analog NTSC and PAL to digital SDI
>(serial digital) and uncompressed HD SDI.

Our cable company (Charter) seems to be using a compression clamp now.
>
>GG
Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com