109.275 MHz

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datainmotion

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109.2750 MHz (AM) is a handy frequency to check if you have interfernce you can't otherwise identify the source of.
The reason for this is that cable operators must prevent any signal "leakage" from their cable systems as it may cause interference on a broad portion of the RF spectrum, most notably the assigned aeronautical blocks. Comcast Cable injects an audible tone onto their cables, on 109.275 (Channel 98 or A-2 in cable nomenclature) to detect "leaks" in the Denver Metro cable systems they operate. Other cable operators around the country will have a similar system utilizing frequencies typically between 109 MHz - 116 MHz. The tone Comcast uses sounds like a fast and continuous "woop-woop-woop-woop".

A "leak" can be caused by many things from a loose coaxial connector behind a TV to a cracked jacket on a mainline or feeder cable. As cable TV operates in parallel with a broad part of the RF spectrum (http://www.jneuhaus.com/fccindex/cablech.html#2) they must prevent (per the FCC) any "leaks" from causing interference to over-the-air signals.

With that said, if you are experiencing regular interference that sounds like the buzz of video (tune a capable scanner/receiver to 55.25 MHz AM for an example) on your scanner or HF receiver , try tuning to 109.275 MHz and listen for the Comcast injected tone. If you can hear it, chances are a "leak" may be the culprit. Check all the Cable TV connectors you can access in your residence (don't go climbing any poles or opening utility boxes in the yard) and make sure they are snug on the devices they are connected to and not damaged. If you don't find a problem with them but still are hearing the tone on 109.275, it's worth a call to Comcast to have them come out and check on it. If you live in an apartment/condo/attached townhouse, the leak could be coming from a neighbor's residence.

I realize that our scanners and receivers must accept any interference per the FCC, but helping the cable company find a leak helps them and may eliminate your interference problem at the same time.
 
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Liverdog

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Good info. We should add this to the Wiki, Admins. Perhaps place the frequencies with the cable service provider and location.
 
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datainmotion

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WaveRunner said:
Interesting, I have the noise! Guess I better go looking around.

How many TVs with cable at your place (and don't forget cable modem - if you have one)?

Easiest way to find out if its from a particular connection is to use a handheld scanner and place its antenna near each connection for a moment.
 

WaveRunner

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I have 2 T.V.'s and the cable modem. Thanks for the heads up, now I guess it's time for process of elimination. Test.
 

jeffreyinberthoud

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The Cable Guy

""don't go climbing any poles or opening utility boxes in the yard""

So Jimm
please post anything heard the next few days on us scanner guys falling off ladders and doing ourselves great harm . in strange ways
 
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