Interference at the 700 MHz band

Expert Opinion

Expert Opinion
Short LTE articles and opinions by our team of Subject Matter Experts (SMEs)

Interference at the 700 MHz band

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This blog aims at providing some of the (difficult to find) most uncommon sources of interference in the 700 MHz band.

The common sources of interference are:

a) Inter-modulation products: This is typical in all cellular systems. This is due to amplitude modulation of signals containing two or more different frequencies in a system with nonlinearities. This problem is typically solved by separating (vertically) the antennas of the systems involved (if deployed in the same tower).

b) Cellular Jammers: Although illegal in the USA, at the 700 MHz band, several cell jammers have been found in very rare places. Examples of such locations are: 

  • Restaurants and bars (to preclude smokers from smoking close the premises and dropping cigarette butts close to the buildings. The idea is that when smoking, people use their phone to make phone calls or browse the internet),
  • High schools (to prevent students from texting during exams),
  • Churches (priests, pastors, etc.) use them to prevent attendees in their churches or temples people from texting during their sermons.
  • Cars: People have installed cell jammers in cars to prevent people in surrounding cars from texting and/or calling while they drive.

c) Wireless Microphones: Some wireless microphones operating at the 700 MHz emit out of band emissions in that frequency band that interfere some of the bands utilized for LTE. This source of interference is, as the rest, difficult to find as this microphone type is used practically every kind of event!

d) Light bulbs:  A particular model of energy efficient light bulbs produced by LG produce interference at the 700 MHz band. Believe it or not!

Have you spotted another one? Please do let us know… we need to find them.

  • There are some garage door openers that can also cause interference in 700 MHZ band