From: andy@cmptrc.lonestar.org (Andy Hart)
Newsgroups: alt.cable-tv.re-regulate
Subject: cable signal loss
Summary: description of typical cable signal loss
Keywords: cable signal loss
Date: Sat, 5 Sep 1992 06:14:48 GMT
Distribution: USA
Organization: CompuTrac Inc., Richardson TX


Hope y'all don't mind if I start a new thread. That other one's getting
a little long.


I don't know if this information matters to anyone, but since there have
been several comments regarding hooking up multiple cable devices, here
is some info regarding cable signal loss.   

You can counter the effects of cable signal loss caused by long cable 
lengths and passive components in two ways:  use better cable or a signal
amplifier.  Signal amps are good if you are starting with a low signal
or have runs of a 100 feet or more.  Unfortunately, good ones are expensive.
I, personally, have had no luck with Radio Shack type amps.  Sometimes
they even make it worse.  They don't last either.

The best thing you can do is use good cable with good connections.  Two
different kinds of cable are RG59 and RG6.  RG6 is better, and more expensive.
The following table lists the amount of signal loss thru 100 feet of 
RG59 and RG6 coax cable at different channels.  Note that the amount of 
signal loss is greater at higher frequencies:

CHANNEL   RG59        RG6
  2       2.6 db     1.7 db
  6       3.5 db     1.9 db
  7       4.9 db     2.8 db
 13       5.4 db     3.0 db
 20       8.3 db     4.8 db
 40       9.2 db     5.6 db
 60      10.3 db     6.2 db
 83      11.9 db     6.8 db

 I have some figures for passive cable devices like baluns, splitters, 
 AB Switches, if you're interested.  Most should list the signal loss.

 NOTE:  Please don't take this info to mean you should go rip out your
 cable and replace it.  Usually, the best thing to do if your using 
 lots of splitters and cable runs is to isolate each run and see which 
 one is causing problems.  Look for bad connections first.

 Also, I am NOT a cable expert.  I fix VCRs in my spare time.  This info
 was liberally taken from the book, "Troubleshooting and Repairing VCRs"
 2nd Edition, by Gordon McComb.  It's a common problem to think there's 
 something wrong with a component in your system when LOTS of problems
 are caused by poor cabling. I guess that's why you look silly when 
 you take your VCR or TV in to have it fixed and it works fine at the 
 shop! :)

 You can ALSO have problems if the signal is TOO STRONG, in which case
 you might need a signal attenuator.  This is manifested by ghosts or 
 crosstalk on the channels.  Cable companies are often not too careful
 about how they've got their transmissions "tuned".  Or you might
 be picking up a signal from another source.       

 It's just like debugging a program, tho.  Don't change everything at 
 once.  Change one thing at a time and see how it changes the situation.

 -- andy



-- 
+--------------------------------------------------------------------+
|   Andrew Hart                   |  CompuTrac, Inc.                 |
|   (214) 234-4241                |  222 Municipal Drive             |
|   andy@cmptrc.lonestar.org      |  Richardson, TX  75080           |
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Newsgroups: alt.cable-tv.re-regulate