Jeff Liebermann wrote:

On Sun, 06 Dec 2009 23:11:22 -0500, "Michael A. Terrell"
wrote:

Ingression is external signals getting into the CATV plant. You are
describing radiation' where the signal is lost to being radiated from
the outer conductor, due to poor connections. It is monitored on a
continuous basis on most cable systems using 'Sniffer' or other brands
of monitoring equipment. While the signal is on the video carrier
frequency, it is FM modulated with annoying audio to make it easy to
identify.

Well, the leak or ingress goes both ways. While ingress from ham,
commercial, and broadcast radio xmitters are irritating, the
regulatory requirement is to prevent cable leakage from interfering
with public safety, aircraft, and of course, OTA broadcast. Lots of
nice toys to measure this leakage:
http://www.trilithic.com/Broadband%20Instruments


The idiot manager of one system ordered the wrong midband modulator
that was right in the aircraft band. Rather than admit it, over 10,000
converters had to be modified to tune the new channel. It was used to
add 'The nashville Network' which had just been launched. The system was
in the Cincinnati area where people claimed that they didn't listen to
'**** kicking music'. I tested the mew modulator & c-band equipment for
less than 30 seconds, and after 2 am. We had over 100 phone calls
waiting the next morning, wanting to know when it would be back.



Personally, I prefer visual inspection, a TDR (time domain
reflectometer), signal level measurements, or just a pre-emptive
replacement.

Those are OK if you can shut a system down for repairs. Poor
connections in the trunkline can be detected by reading the voltage drop
between the coax and the amplifier housing, splice block or any other
splice in any powered cable. 60 volts modified sine wave AC @ 30 amps
from a CVT doesn't tolerate much resistance without causing hum
modulation or burning up a connector.

Ummm... the OP is trying to troubleshoot his home installation, not
the trunk line (or cable drop). I think it's a safe bet that he can
unplug his spaghetti without difficulties.


Then it is very unlikely he will have access to a TDR, sniffer or any
other equipment. Even a field strength meter isn't likely.


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