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Friday, July 24, 2020 | History

2 edition of Local oscillator radiation from television receivers. found in the catalog.

Local oscillator radiation from television receivers.

J. Middleton

Local oscillator radiation from television receivers.

by J. Middleton

  • 207 Want to read
  • 7 Currently reading

Published by BBC in London .
Written in English


Edition Notes

SeriesBBC RD -- 1979/21
ID Numbers
Open LibraryOL21000411M

  Applications. Local oscillators are used in the superheterodyne receiver, the most common type of radio receiver circuit. They are also used in many other communications circuits such as modems, cable television set top boxes, frequency division multiplexing systems used in telephone trunklines, microwave relay systems, telemetry systems, atomic clocks, radio telescopes, and military. Televisions -and radio receivers for that matter- are so called super heterodyne receivers. Incoming high frequency signals [the TV channels] are mixed with the TV's internal oscillator [local oscillator] to produce a lower, fixed-frequency signal [the intermediate frequency of Mhz] that is used for further processing [audio/video.

In the Federal Communications Commission established maximum local oscillator radiation levels for all radio and television receivers manufactured for use in the United States. These ceilings are such as to keep the radiation within tolerable limits at a distance of feet, but they do not ensure that it cannot be detected by a sensitive receiver at greater distances. The tuning control on a radio receiver adjusts the local oscillator frequency. If the incoming signals are above the threshold of sensitivity of the receiver and if the receiver is tuned to the frequency of the signal, it will amplify the signal and feed it to circuits that demodulate it, i.e., separate the signal wave itself from the carrier wave.

Local oscillator radiation. It is difficult to keep stray radiation from the local oscillator below the level that a nearby receiver can detect. The receiver's local oscillator can act like a miniature CW transmitter. This means that there can be mutual interference in the operation of two or more superheterodyne receivers in close proximity. (7) Good selectivity and spurious radiation suppression, and easy through CE / Fcc international certification; (8) Good local oscillator radiation suppression, multiple receiver modules to work together (ie, more than single income) and will not interfere with each other, used together does not affect the receiving distance.


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Local oscillator radiation from television receivers by J. Middleton Download PDF EPUB FB2

The local oscillator of a television receiver tuned to channel n can cause interference to a neighbouring receiver tuned to channel n+5. If, in modern receivers, this radiation is significantly.

BBC RD /21 Engineering Research Report The work covered by this report was undertaken by the BBC Research Department for the BBC and the IBA. The local oscillator of a v.h.f. television receiver tends to radiate energy at harmonics of the fundamental oscillator frequency. Some of these harmonics fall within the u.h.f.

Bands IV and V and. A UHF tuner in a TV receiver has two r.f. amplifiers, using three r.f. tuned circuits, ahead of the mixer. The r.f. circuits and the local oscillator are all tuned by varactor diodes.

The tuning range is from − MHz. At these frequencies, the circuit Q s are relatively low, with values of about 30 at MHz. The IF is about 38 MHz. (a). For instance, the cognitive radio might detect the TV receiver local oscillator [9] which acts like a beacon.

Further, the geolocation database schemes provides information for usage in a region. David Large, James Farmer, in Broadband Cable Access Networks, Local Oscillator and Other Interfering Signals from Receivers. Based on measurements made on a sampling of analog production television receivers in and on current FCC regulations for one-way, cable-ready digital receivers, local oscillator signals transmitted out the antenna terminals of receivers may have.

Scope: Spurious radiations from the local oscillator of modern broadcast radio receivers of the superheterodyne type are possible sources of interference with other radio services. In addition, in the case of television broadcast receivers, there may be radiation from sources other than the local oscillator.

This standard describes the potential sources of spurious radiation from frequency. Spurious radiations from the local oscillator of modern broadcast radio receivers of the superheterodyne type are possible sources of interference with other radio services.

In addition, in the case of television broadcast receivers, there may be radiation from sources other than the local oscillator.

This standard describes the potential sources of spurious radiation from frequency. Abstract: Modern broadcast radio receivers of the superheterodyne type are frequently sources of spurious radiation from the local oscillator, which radiation may cause severe interference with other services.

In addition, in the case of television broadcast receivers, there may be radiation of power from other sources beside the local oscillator. Choice of selecting IF 2) Pick-up Due to Local Oscillator Radiation from TV Receivers If the output from the local oscillator of a TV receiver gets coupled to the antenna, it will get radiated and may cause interference in another receiver Here again advantage lies with higher IF frequency, because with higher IF there is a greater separation.

In electronics, a local oscillator (LO) is an electronic oscillator used with a mixer to change the frequency of a signal. This frequency conversion process, also called heterodyning, produces the sum and difference frequencies from the frequency of the local oscillator and frequency of the input sing a signal at a fixed frequency gives a radio receiver improved performance.

The potential interference of spurious, radiation from the local oscillators of direct broadcast satellite (DBS) television receivers to terrestrial 11 GHz microwave radio services is examined. Typical parameters for DBS receivers are identified and used in a computer simulation to calculate the aggregate effect of a large number of units.

The overall effect of the standard is to require that TV receivers must not emit x-radiation above the mR/hr level when tested under adverse operating conditions.

Local Oscillator Radiation from TV and FM Sets Autorzy. Peterson. Treść / Zawartość. Warianty tytułu. Języki publikacji. Abstrakty. Spurious radiation that is generated by any type of superheterodyne type of receiver has presented a mammoth problem to the industry. That is, limits set up by the FCC had to be met by the industry.

(a) Choice of IF and Local Oscillator Frequencies (i) high image rejection ratio, (ii) reduced local oscillator radiation, (iii) ease of detection and (iv) good selectivity at the IF stages.

The local oscillator frequency is kept higher than the channel carrier frequency since this results in a relatively narrow oscillator frequency range. In electronic equipment, an oscillator that (a) usually is used as a source of frequencies for mixing with other frequencies that the equipment is handling, (b) usually is a crystal-controlled fixed-frequency oscillator, though it may be tunable, (c) usually is an inherent part of fiber optic, radar, radio, or television equipment, particularly receivers, and (d) produces output used for many.

Color Television Receiver Block Diagram: Figure shows the block diagram of a Color Television Receiver Block Diagram, but for simplicity the circuits shown in Figure are omitted. Interconnection points are shown on both diagrams, so that there should be no difficulty in reconciling the two figures.

An existing commercial model which employed a balanced oscillator and two preselectors was developed until radiation was below the proposed FCC limit of uv/m. These developments were then successfully applied to a recently designed small package model.

It was not necessary to make any sacrifice of overall tuner performance. The receiver uses superhetrodyne principle as used in radio receivers. In principle an RF amplifier is not necessary and signal could be fed directly to the tuned input circuit of the mixer.

However, the problems of a relatively weak input signal with low signal to noise ratio, local oscillator radiation and image rejection are such, that a. 8 Antenna radiation (local oscillator measurement) Annex A (informative) - General TV test requirements Annex B (informative) - Optional TV antenna-cable input isolation transformer Annex C (informative) - Bibliography.

It is difficult to keep stray radiation from the local oscillator below the level that a nearby receiver can detect. The receiver's local oscillator can act like a low-power CW transmitter. Consequently, there can be mutual interference in the operation of two or more superheterodyne receivers in close proximity.local oscillator (n = 1) it is called fundamental, while if it uses higher harmonics to obtain the IF frequency it is called a.

harmonic. mixer. Harmonic mixing is a cost-effective technique used in the microwave frequency range to operate over an extremely wide bandwidth with a single local oscillator that is tunable only a portion of the.Good local oscillator radiation suppression, multiple receiver module to work with (ie, more than single income) and will not interfere with each other, used together without affecting the receiving distance; Multiple transmission rates, the general module for 2KHz, up to 10KHz;Temperature range: °CReviews: 4.