parnass@ihu1h.UUCP (Bob Parnass, AJ9S) (10/23/84)
Leaky CATV Equipment Interferes With Scanner User A non-ham scanner friend from Westmont (Illinois) related this tale of grief caused by CATV signals (he is not a CATV subscriber): "In August 1984, a storm dropped several heavy bran- ches onto the cable trunk line in my alley. New York channel 9 appeared on my channel 4. The UHF Atlanta superstation came in on channel 13. Manipulating the tuner controls on my (35 channel) cable ready VCR brought in HBO, Showtime, Cable News Network and other cable services with varying levels of snow and inter- mod. Worse yet, regular Chicago stations now had a ghost caused by the cable retransmission being microwaved around first thus being rebroadcast mil- liseconds behind the direct receptions. Finally, my scanner was being jammed all over the spectrum." "A call to the FCC brought a 'don't disturb my bureau- cratic games, what do you want me to do, be a public servant?' attitude. I called the FAA as they have a remote control sight at nearby Downers Grove/Woodridge in case their system was getting interference. A call to the local cable company office confirmed my suspi- cion that employees were never trained about a closed circuit 'broadcasting'. Besides, a service call was rejected by their computer because I was not a subscri- ber." "I located the regional cable company office in a city it did not serve. From their operator, I found out the name of the Chief Engineer who did not return my call. I sent a certified letter to him citing chapter and paragraph of the FCC regulations. I established my right as a user of the electromagnetic spectrum as a broadcast watcher (scanner owners have no rights as they are not the intended recipient normally) that could not watch non-local stations anymore as well as having regular channels ghosted....... That [registered letter] brought results, a call from the Construction and Repair Chief besides the Chief Engineer." "I had prepared for this by walking several blocks in all directions with a portable scanner to find the point of highest signal strength. The cable company's sweeps were inconclusive because they used a wide band measuring device. Thus, they measured up to 6 MHz of a public safety/business band spectrum. About 100 police and fire departments and 1000 business users masked any meaningful meter reading. After replacing first the connectors, then the 4-drop couple and finally a 500 foot section of trunk cable, the interference cleared up." "A nearby ham continued to suffer interference however. He is a subscriber" and "had added a section of coaxial cable to the cable connecting his TV set with his VCR. That cable purchased at a handy neigh- borhood national electronics chain store.....did not have a 100% shield...." [so it allowed CATV signals to radiate around his own house]. -- =============================================================================== Bob Parnass, Bell Telephone Laboratories - ihnp4!ihu1h!parnass - (312)979-5414
karn@mouton.UUCP (10/23/84)
Regarding leaky CATV systems...I have an item which should appear in QST Hints & Kinks soon about a way of locating it. A 2-meter SSB receiver is about the most sensitive device I know of for detecting CATV leakage. I also found that the doppler shift caused by vehicle motion is quite readily apparent on a mobile SSB transceiver as you drive past the offending spot. Finally! A practical use for all that Relativity Physics you learned in school. Phil