Un caz interesant de interferenta RF

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4x1ad
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Un caz interesant de interferenta RF

Mesajde 4x1ad » Mar Aug 09, 2016 8:45 pm

Iata un caz interesant de interferenta RF in care politia a cerut ajutorul radioamatorilor. Totul a inceput cand FCC a refuzat sa se ocupe de reclamatia politiei despre o zona urbana de cateva zeci de metri in care masinile nu pot fi deschise si pornite cu ajutorul brelocului wireless, telefoanele celulare nu mai functioneaza, la fel si alte dispozitive wireless din zona.

TNX ARRL News Bulletin

Amateur Radio Sleuthing Pins Down Source of Strange RF Interference

08/09/2016

Police in Evanston, Illinois, contacted the ARRL Lab, after an apparent interference source began plaguing wireless vehicle key fobs, cell phones, and other wireless electronics. Key fob owners found they could not open or start their vehicles remotely until their vehicles were towed at least a block away, nor were they able to call for help on their cell phones when problems occurred. The police turned to ARRL for help after striking out with the FCC, which told them it considered key fob malfunctions a problem for automakers, although the interference was affecting not just key fobs but cell phones, which are a licensed radio service. ARRL Lab EMC Specialist Mike Gruber, W1MG, believes the FCC should have paid more attention.

“This situation is indicative of what can happen as a result of insufficient FCC enforcement, especially with regard to electrical noise and noncompliant consumer devices,” Gruber said.

Evanston authorities worried that a serious situation could develop if someone were unable to call 911, putting public safety at risk. They also were concerned that the RFI could be intentional and indicate some nefarious or illegal activity. Given the seriousness of this situation, Gruber contacted Central Division Director Kermit Carlson, W9XA, to ask if he could look into the matter.

On June 2, Carlson met with an Evanston police officer, her sergeant, a local business owner, and the local alderman, and he quickly confirmed that the 600 block of Dempster Avenue in Evanston was plagued with an odd RFI problem. Carlson determined that the problem prevailed along a set of eight on-street parallel parking spots in the downtown commercial district of the North Chicago suburb.

Carlson employed a Radar Engineers 240A Noise Signature Receiver and UHF Yagi antenna to survey the affected block. Since key fobs typically operate at around 315 MHz and 433 MHz, he looked on both frequencies. The survey identified several noise sources in the affected block, but in particular a strong signal in the middle of the block. The interference source turned out to be a recently replaced neon sign switching-mode power supply, which was generating a substantial signal within the on-street parking area just across the sidewalk, between 8 and 40 feet from the sign.

The problematic power supply interference also disabled Carlson’s cell phone when he was within a few feet of the device. Carlson anticipated that further investigation would show that the harmful interference could disrupt licensed radio services in close proximity. The troublesome transformer was not replaced, but the building owner agreed to turn off the sign should problems arise.

Carlson called the Evanston case “a particularly alarming example of radio interference,” especially since local authorities considered it a public safety matter. “This situation demonstrates the electromagnetic compatibility problems that are evolving in an atmosphere of noncompliant, unintentional RF-emitting devices,” he said.

A return visit to the area with calibrated antennas and equipment capable of measuring the radiated signal strength with quasi-peak detection is planned for later this year. Since the initial visit, several other instances of unexplained key fob malfunctions have been reported in the Greater Chicago area. — Thanks to Kermit Carlson, W9XA, and Mike Gruber, W1MG
"Daca antena buna nu e, nimic nu e...."

"Radio Amatorii nu trebuie sa fie profesionisti in radio-electronica, dar nici diletanti"

yo2cfs
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Re: Un caz interesant de interferenta RF

Mesajde yo2cfs » Mar Aug 09, 2016 10:45 pm

La neimplicarea FCC chiar nu m`as fi asteptat!
Posibil sa fi fost vorba de ceva neintelegere sau de nerespectarea unor proceduri de reclamare a perturbatiilor.
Pe de alta parte, bravo amatorilor, spiritul lor civic nu se dezminte!
In acelasi timp trebuie sa fac observatia ca de cite ori am apelat la Ancom, Directia Teritoriala Timisoara pentru cazuri de perturbatii au fost de fiecare data disponibili si au cooperat ireprosabil pentru inlaturarea perturbatorilor.
Este vorba de perturbarea unor servicii comerciale licentiate.
Inca o data multumiri celor de la Ancom si pe aceasta cale!

Grig

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yo7mr
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Re: FCC - despre interferenta RF

Mesajde yo7mr » Mie Aug 10, 2016 9:47 am

Salut voios de radioamator !

prin informarea despre cazul prezentat aici, despre felul cum se rezolva sau nu o perturbatie in USA de catre FCC, cred ca noi putem doar sa luam la cunostiinta si sa ne formam cateva pareri, unele favorabile noua, alte negative despre modalitatea de abordare si rezolvare de catre organismele oficial responsabile in regiunea respectiva comparativ cu ce cunoastem noi, in regiunea noastra.
In sensul celor descrise mai sus, va propun sa interpretati paragraful din omologarile FCC pentru echipamentele verificate si agrementate sa functioneze pe teritoriul USA, care mentioneaza in mod expres ca echipamentul omologat trebuie sa ACCEPTE alte interferente ! In concluzie,noi cum " traducem " aceasta ?
cu prietenie, Marian - Targu Jiu.
- Star Trek : space ! ... the last frontier ...
- Ham Radio : space ! ... the first frontier ...
- La toți ni-i greu ! ... dar nu la toți la fel ...

4x1ad
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Re: Un caz interesant de interferenta RF

Mesajde 4x1ad » Mie Aug 10, 2016 11:48 am

@YO7CEG: intentia postarii a fost una pur tehnica. Fara sa cunoastem datele cazului, nu are sens sa disecam problemele birocratiei FCC. Eu am lucrat cu FCC pe linie profesionala (EMC-RFI) multi ani si ii consider o organizatie foarte serioasa dpdv tehnic si legal-administrativ, poate cam inceata dar asa este peste tot cu birocratia administrativa. Oricum, omologarile la care te referi sunt oarecum diferite si se concentreaza pe "Radiated Emissions" si nu pe "Radiated susceptibility". Si e vorba de un anume tip de produse, nu tot ce se fabrica sau se importa trebuie sa aiba eticheta "FCC Part 15 and/or 68". Mai exista si alte agentii federale si organizatii, chiar daca standardele sunt uneori comune. Alta este situatia cu firme mari (exemplu in telecom, Verizon) care au cerintele lor RFI & Safety specifice si extrem de severe (ex. standardele Bell Core) dar care nu sunt obligatorii la nivel federal. Situatia difera in Europa, in tarile care au adoptat cerintele CE de certificare dpdv EMC & Safety.

73 de Morel, 4X1AD ex.YO4BE
"Daca antena buna nu e, nimic nu e...."

"Radio Amatorii nu trebuie sa fie profesionisti in radio-electronica, dar nici diletanti"


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