[RFI] CATV Upstream Interference

Raymond LaRue Raymond.LaRue at SkyAngel.com
Fri Aug 28 06:32:53 PDT 2009

This has typically been a problem with end of cable terminations
improperly installed (read not properly torqued), or cheap and/or older
terminations hardware utilized, that is corroded or loose.  Most of the
cable companies in the US have learned to use quality connectors,
torqued to the manufacturers specifications.

Another potential source of RFI is most cable drops into the homes are
only terminated by the TV tuners characteristic return loss which is
optimum only at the channel selected (seldom more than 6 to 10 db RL).
Thus resulting in poor terminations at the other frequencies on line in
the house.  This causes a high SWR on those frequencies back to the
power divider out on the line.  If the divider has a good back match,
much of the reflection is absorbed there.  Once again if there are
poorly torqued or corroded connections, radiation can occur.  

If such problems are repetitious throughout the system, it can be quite
a job localizing the areas needing correction.  

Although it may cost a little more initially, good engineering
practices, hardware and equipment properly installed, can save a lot of
headaches later.  

Ray LaRue, W4BYG
Vice President, Broadcast Engineering
SkyAngel US, LLC

"...Truth eludes us if we do not concentrate with total attention on
it's pursuit"...  Alexander Solzhenitsyn 

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