Today's Topics: Do shielded cables on computers reduce static risk as well as RFI? Shortwave jammers identified - repost ---------------------------------------------------------------------- Date: 5 Dec 89 01:29:34 GMT From: philmtl!philabs!briar.philips.com!rfc@uunet.uu.net (Robert Casey;6282;3.57;$0201) Subject: Do shielded cables on computers reduce static risk as well as RFI? Message-ID: <69679@philabs.Philips.Com> Just wondering, would using shielded cables on your computer help protect it from static discharges from your body during the winter? Assuming that you discharge to the cable. Seems to me that you'd discharge to ground, as there's nothing else exposed, like signal wires, in this case. And you wouldn't blow up some chip that's connected to those wires. Of course, you still could discharge into your keyboard and kill things. Is using shielded cables for this static protection purpose worthwhile? Does it buy me extra protection? 73 de WA2ISE ------------------------------ Date: 5 Dec 89 02:58:10 GMT From: att!cbnewsc!parnass@ucbvax.Berkeley.EDU (Bob Parnass, AJ9S) Subject: Shortwave jammers identified - repost Message-ID: <5227@cbnewsc.ATT.COM> x SHORTWAVE JAMMERS IDENTIFIED by Bob Parnass, AJ9S Until recently, shortwave broadcasters in the United States, the United Kingdom, Israel, and West Germany had long been subjected to intentional interference (jam- ming).1 Who jams shortwave broadcast stations? To answer this question, an intensive investigation was conducted under the auspices of the International Fre- quency Registration Board of the International Telecom- munication Union (ITU). A 318 page report was issued after the investigation, and the highlights will interest radio enthusiasts.2 Jamming Characteristics Foreign language programs, particularly those in languages spoken in Iron Curtain countries, are the pri- mary targets of the jammers. Jamming installations fall into 2 categories: 1. Ground wave jammers are used for localized jamming, directed toward the immediate vicinity (up to 100 km) of the jammer. They are situated close to the people who are to be prevented from hearing the broadcast, and are effective in blanketing high population regions with strong signals. 2. Sky wave jammers are used to prevent people far away from the jammer from hearing the targeted broadcast. The jamming transmitters monitored in this operation were assumed to run 250 KW power and antennas with 10 dB gain. Jammers need not provide a signal with the same field strength as the broadcast signal in order to be disrup- tive to the the targeted transmission. By using appropriate modulation schemes, a jamming signal can obtain 10 to 15 dB relative gain compared to a broadcast signal. Sometimes, several different jamming transmitters are used at the same time to interfere with a single broad- cast frequency. About 90% of the jamming signals observed during the study were accompanied by a 2 charac- ter Morse Code identifier, which presumably allows the offender's field monitoring stations to determine the effectiveness of each jamming transmission. Monitoring Stations Jammers were monitored for two 3 week periods3, in a cooperative effort, by monitoring stations in West Ger- many, the United Kingdom, Norway, Netherlands, Israel, Canada, South Korea, Japan, and the United States. The American locations are FCC field monitoring sites, and employ Wullenweber antenna systems. The Wullenweber system consists of 60 antenna elements (monopoles) spaced around a circle (one every 6 degrees) of 140 meters in diameter. A rotating commutator, called a goniometer, is connected to each element through an appropriate delay line, and samples each element at a rate of several revo- lutions per minute. The idea is that all signals coming from a given direc- tion reach the receiver with the same phase, while those from other directions arrive with random phase.4 The sys- tem has the capability of sampling all or just a portion of the elements on a given pass and forms a visual 360 degree pattern on a CRT screen by comparing the signal strength of opposing elements. The Adcock antenna, employed at many European monitoring stations, consists of two monopole sampling elements, usually about 20 feet apart. The system effectively rotates at about 20 - 30 rpm and may be controlled either manually or automatically. Automatic selection of the antenna rotation averages the signal for each pass. The time averaging continues to average each signal for as long as the device runs freely. Findings Radio Liberty and Radio Free Europe were jammed more than any other broadcaster observed in the operation. For all broadcasters, the Russian language and Polish language broadcasts were consistently jammed. Broadcasts in Czechoslovakian and Bulgarian languages were also fre- quently jammed. The surveillance traced the source of most jamming to the USSR. Other jamming was traced to Poland, E. Germany, Romania, Hungary, Bulgaria, Yugoslavia, and Czechoslo- vakia. ______________________________________________________ | Participating U.S. Monitoring Stations | | | | Location Antenna Type | |_____________________________________________________| | Anchorage, AK fixed monopoles with goniometer| | Belfast, ME fixed monopoles with goniometer| | Douglas, AZ fixed monopoles with goniometer| | Ferndale, WA fixed monopoles with goniometer| | Ft. Lauterdale, FL fixed monopoles with goniometer| | Grand Island, NE rotating Adcock type | | Kingsville, TX fixed monopoles with goniometer| | Laurel, MD fixed monopoles with goniometer| | Livermore, CA fixed monopoles with goniometer| | Powder Springs, GA fixed monopoles with goniometer| | Sabana Seca, PR fixed monopoles with goniometer| | Waipahu, HI fixed monopoles with goniometer| |_____________________________________________________| __________________________________________________________________ | Participating Foreign Monitoring Stations | | | |Location Antenna Type | |________________________________________________________________| |Ottawa, Canada (no bearing information) | |Nedhorst Den Berg, Netherlands 8 element Adcock | |Norway (3 stations) Adcock | |Baldock, U.K. fixed monopoles with goniometer| |Crowsley Park, U.K. (bandwidth measurement only) | |Seoul, S. Korea log periodic | |Osaka, Japan circular array of monopoles | |Tokyo, Japan 8 element Adcock | |Tel Aviv, Israel unknown | |Itzehoe, W. Germany Adcock | |Krefeld, W. Germany Adcock | |Berling, W. Germany Adcock | |Darmstadt, W. Germany Adcock | |Konstanz, W. Germany Adcock | |Munchen, W. Germany Adcock (8-30 MHz only) | |________________________________________________________________| __________________________________________________________ | Jammer Jammer | Jammer Jammer | | cw id Location | cw id Location | |_____________________________|___________________________| | 1D USSR | KV USSR | | 1G USSR | LK Poland/USSR | | 4F USSR | LM E.Germany | | 4N USSR | M5 Yugoslavia | | 7K USSR | MA Poland | | 8L E.Germany | MF E.Germany | | AD USSR | MP Poland | | AG USSR | MS Czechoslovakia | | AN USSR | MU USSR | | AR USSR | MX Poland | | AW USSR | NS USSR | | B1 Poland | P3 Hungary | | BD Poland | PA Poland | | BG Poland/USSR | PB USSR | | BL USSR | PK USSR | | BQ Poland/USSR | PL Poland/USSR | | BR Poland | R6 Bulgaria | | BU USSR | R7 Yugoslavia | | CB USSR | R9 E.Germany/Poland| | D3 Czechoslovakia | RB USSR | | DA USSR | RT USSR | | DG USSR | S5 Czechoslovakia | | DR USSR | ST USSR | | DU USSR | SU USSR | | FA USSR | TK USSR | | FG Poland/USSR | TR Poland/USSR | | FL USSR | TU USSR | | FU Poland/USSR | U7 Czechoslovakia | | G1 USSR | UA USSR | | G3 Bulgaria | UB Romania/USSR | | GI USSR | UN USSR | | GJ USSR | UQ USSR | | GM USSR | US USSR | | GR USSR | VF USSR | | GS USSR | VG USSR | | HM USSR | VN USSR | | HP Czechoslovakia/USSR| VR Poland/USSR | | IG USSR | W1 Czechoslovakia | | IN USSR | WA USSR | | IR USSR | WD USSR | | K3 Hungary | WI USSR | | K7 Bulgaria | WM USSR | | K8 Hungary | WQ Romania/Poland | | KB USSR | Z1 Czechoslovakia | | KD USSR | Z2 Yugoslavia | | KF Czechoslovakia | Z3 Czechoslovakia | | KM USSR | ZM Poland | |_____________________________|___________________________| __________ 1. see "Soviets Switch Jamming From BBC to Radio Liberty", in The Radio Enthusiast, May 1987. 2. Monitoring of Harmful Interference to the HF Broadcasting Service: I. Results of the October 1984 and March/April 1985 Coordinated Monitoring Periods, by M. W. Sowers, G. R. Hand, and C. M. Rush, U.S. Department of Commerce, NTIA, Institute for Telecommunications Sciences. NTIA Report 85-187, December 1985. PB86163011/AS. 3. Jammers were monitored October 1 - 21, 1984 and March 18 - April 7, 1985. 4. Electronics Engineers Handbook, 2nd Edition, pg. 25-89, McGraw-Hill Book Co. -- ============================================================================ Bob Parnass, AJ9S - AT&T Bell Laboratories - att!ihuxz!parnass (708)979-5414 ------------------------------ End of INFO-HAMS Digest V89 Issue #974 **************************************