I will add these both as links to the ARRL Web page on cable TVI:
http://www.arrl.org/tis/info/HTML/catvi/index.html
If you know of good links like this that could be added to our web pages,
let me know. I don't always read every post. :-)
73,
Ed Hare, W1RFI
ARRL Lab
225 Main St
Newington, CT 06111
Tel: 860-594-0318
Internet: w1rfi@arrl.org
Web: http://www.arrl.org/tis
> -----Original Message-----
> From: james.skjervem@hqasc.army.mil
> [mailto:james.skjervem@hqasc.army.mil]
> Sent: Thursday, December 06, 2001 4:08 PM
> To: rfi@contesting.com
> Subject: RE: [RFI] Cable TV Interference
>
>
> All:
>
> Some interesting reading regarding cable TV leakage can be
> found on the Web
> from Communications Technology magazine (a cable industry
> publication, from
> the SCTE that Dale mentioned) in August-December 1999 issues, titled
> "Training: Detecting Signal Leakage", available beginning at
> http://www.cabletoday.com/ct2/archives/0899/ct0899i.htm and
> the July 2000
> issue, titled "Signal Leakage & Harmful Interference, A Ham Radio
> Perspective" available at
> http://www.cabletoday.com/ct2/archives/0700/0700fe4.htm.
>
> Jim, WA7SLD
>
> -----Original Message-----
> From: dgsvetan@rockwellcollins.com
> [mailto:dgsvetan@rockwellcollins.com]
> Sent: Thursday, December 06, 2001 11:50 AM
> To: wb3fsr@home.com; rfi@contesting.com
> Subject: Re: [RFI] Cable TV Interference
>
>
>
> Peter,
>
> I have fought the battle before, in the Chicago suburban
> area, prior to
> coming out here to Iowa.
>
> As a point of interest, I imagine that if you tune your ham
> FM receiver up
> to 149.750, you will hear the audio portion of the channel
> signal. In my
> case, I found that the local cable company (to whose services
> I did not
> subscribe) had the Home Shopping Service on that particular
> channel. (I
> identified the program by listening to the audio portion.)
>
> The interfering signals were 10 over 9 when my yagi was
> pointed toward the
> pedestal near which the obvious leak was occurring. (CATV
> was all buried
> in my neighborhood.) With a groundplane, the sigs were still
> S-7 to S-8.
> The sync pulses made it impossible to monitor repeaters at
> 145.23, .25, and
> .27 MHz. They sometimes caused receive problems at 145.33
> MHz, which was
> the local ESDA repeater freq. In talking with other hams in
> the area at
> that time, I found that this was not an unusual problem.
>
> You appear to at least have gotten some response from the
> cable company. I
> got nowhere with calls, but I think I caught their attention when I
> operated the VHF contest in January, 1998. I ran both SSB
> (only 25 watts
> around 144.2) and FM (50 watts in the region of 146 to 147,
> which is right
> in the passband of that cable channel). The contest started early on
> Saturday afternoon, my time. By late Saturday evening, the
> interference
> was gone. However, it re-appeared 2 days later at the same
> strength. I
> think they temporarily killed the channel in my area, probably due to
> significant overload of the line amp from my sigs (and the
> probable pile of
> irate phone calls from viewers). (Remember, leaks are
> bi-directional. I
> suspected that the leak was at the output end of an amp near my house,
> either a line booster or one feeding signal to most of my
> neighbors to the
> east.. If correct, that means my sigs got onto the cable and
> wiped the
> next amp down the line.)
>
> After several weeks of interference, with the level varying
> in strength,
> the signals finally went away for good. I, of course, had continued
> operating on 2m during the same time. I saw a cable company
> truck in the
> neighborhood once during that time, but he never stopped at
> my house, nor
> did he go into any neighbor's homes. He did, however, wander
> around by the
> pedestals. My guess: the leak was probably at a connector,
> and varied
> with temperature. Tightening the connector was most likely
> the fix. This
> is common in areas with wide seasonal temperature variations.
>
> In your case, the signals seem bad enough to interfere, but
> are not S-meter
> crunchers. The bottom line is that you are licensed to
> radiate, and they
> are not. (In my professional life back in Illinois, I provided signal
> tracking and analysis to some local telco folks who had
> complaints from
> public safety officials that the pilot tone on T-1 carrier,
> which happens
> to be at 1.54 MHz, was interfering with police and fire
> dispatchers. That
> is when I discovered that the pilot tone is generated at 100 times its
> actual frequency - 154.xx MHz - and divided down so as to
> very very stable
> and accurate. Well, in some cases, the 154 MHz fundamental
> got carried
> along by the T-1 lines for hundreds of yards from the central
> office, thus
> wiping out nearby radios tuned to that frequency. Again, the
> Telco was not
> licensed to radiate. The telco engineers were amazed when I tuned my
> mobile ham receiver to 154.xx MHz and drove around the area.
> The pilot
> carrier was copyable as far as 2 blocks from the central
> office with the
> mobile whip.)
>
> My suggestion is that you remind the cable folks of their
> responsibility,
> although they might very well be within allowable limits. In
> that case,
> two thoughts come to mind: 1) Try to minimize antenna aiming in the
> direction of the leak source; 2) transmit and operate
> normally. If they
> experience "intrusion" upon their system by your licensed
> transmitter, I
> suspect they'll be out there to plug the holes sooner or later.
>
> As for obtaining info on CATV specs, there is an organization
> called the
> Society of Cable Television Engineers (SCTE), and I once had some
> communication with them on a matter unrelated to ham rfi. I
> believe they
> are out east, and I am quite certain they have a website.
> Perhaps you can
> get some information from them. Beware however: I suspect
> that, like most
> organizations that issue standards (including the IEEE, UL,
> IEC, etc.),
> there is usually a charge for documents. Typical prices
> range from $25 to
> nearly $100. So, it might be worth checking with them, but
> be prepared.
>
> Good luck.
>
> 73, Dale
> WA9ENA
>
>
>
>
>
> "Peter D. Vouvounas" <wb3fsr@home.com>@contesting.com on 12/06/2001
> 08:20:21 AM
>
> Please respond to <wb3fsr@home.com>
>
> Sent by: rfi-admin@contesting.com
>
>
> To: <rfi@contesting.com>
> cc:
>
> Subject: [RFI] Cable TV Interference
>
>
> Morning ALL,
>
> Can anyone share their thoughts on how best to determine if cable TV
> radiation is within spec...
>
> I am receiving a carrier on 145.250 MHz generally around S7-S9 signal
> strength = approx. 16-17 microvolts at the antenna port. Using a VHF
> collinear on my tower.
>
> I've also been monitoring 121.2625 the cable snifer test
> frequency with my
> spectrum analyzer connected to a VHF yagi (horizontal
> polarization)- Noted
> peaks in at least five directions.
>
> After a bit of prodding I received a call from the Comcast Engineering
> Supervisor stating that they have passed ALL of the fly over
> tests in the
> past with flying colors. He went on to say that they could
> very well be
> within legal limits for cable radiation - due to the
> sensitivity of the
> radio and apparent gain of my antenna system the
> interference signal my be
> normal.
>
> I have two interests one is the interference into my VHF equipment and
> secondly any leaks allowing my high power HF rf into the cable system
> leading to neighborhood TVI issues.
>
> The supervisor did share some others names and numbers to
> work with me. I
> think it's best to be up to speed before I engage them one on one.
>
> Specifically tests & measurements that my be performed by the
> HAM - I have
> no way of knowing how good or poor the cable companies test equipment
> designed, maintained or utilized. In other words I want to
> have my ducks
> in
> a row hihi..
>
> Regards,
>
> PeterV [REN] WB3FSR
>
> p.s. I see a constant carrier at 110.630 MHz that appears to
> have different
> peaks then the ones indicated above. Any idea what this
> signal may be?
> =========================================
> Peter D. Vouvounas Ofc: 732-701-1130
> McLeod USA Cell:732-674-4001
> 98 Meridian Dr.
> Brick, NJ 08724
> Mailto: wb3fsr@home.com
> InterActive 2way: wb3fsr@imcingular.com
> =========================================
>
>
>
>
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